layout/style/nsRuleNode.cpp
author Gina Yeh <gyeh@mozilla.com>
Wed, 31 Oct 2012 17:33:50 +0800
changeset 112016 de25c9c57c5385b0c23f226aaa3c6a88bf5b2ff3
parent 111838 7bd96dda75f03267736c8e628995c0481014a139
permissions -rw-r--r--
Bug 806296 - Patch 1(v1): Cannot create an encrypted socket, r=echou

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=2 et sw=2 tw=78: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/*
 * a node in the lexicographic tree of rules that match an element,
 * responsible for converting the rules' information into computed style
 */

#include <algorithm>

#include "nsRuleNode.h"
#include "nscore.h"
#include "nsIServiceManager.h"
#include "nsIWidget.h"
#include "nsIPresShell.h"
#include "nsFontMetrics.h"
#include "gfxFont.h"
#include "nsStyleUtil.h"
#include "nsCSSPseudoElements.h"
#include "nsThemeConstants.h"
#include "nsITheme.h"
#include "pldhash.h"
#include "nsStyleContext.h"
#include "nsStyleSet.h"
#include "nsSize.h"
#include "imgIRequest.h"
#include "nsRuleData.h"
#include "nsIStyleRule.h"
#include "nsBidiUtils.h"
#include "nsUnicharUtils.h"
#include "nsStyleStructInlines.h"
#include "nsStyleTransformMatrix.h"
#include "nsCSSKeywords.h"
#include "nsCSSProps.h"
#include "nsTArray.h"
#include "nsContentUtils.h"
#include "CSSCalc.h"
#include "nsPrintfCString.h"

#include "mozilla/Assertions.h"
#include "mozilla/dom/Element.h"
#include "mozilla/Likely.h"
#include "mozilla/LookAndFeel.h"
#include "mozilla/Util.h"

#if defined(_MSC_VER) || defined(__MINGW32__)
#include <malloc.h>
#ifdef _MSC_VER
#define alloca _alloca
#endif
#endif
#ifdef SOLARIS
#include <alloca.h>
#endif

using std::max;
using std::min;
using namespace mozilla;
using namespace mozilla::dom;

#define NS_SET_IMAGE_REQUEST(method_, context_, request_)                   \
  if ((context_)->PresContext()->IsDynamic()) {                               \
    method_(request_);                                                      \
  } else {                                                                  \
    nsCOMPtr<imgIRequest> req = nsContentUtils::GetStaticRequest(request_); \
    method_(req);                                                           \
  }

#define NS_SET_IMAGE_REQUEST_WITH_DOC(method_, context_, requestgetter_)      \
  {                                                                           \
    nsIDocument* doc = (context_)->PresContext()->Document();                 \
    NS_SET_IMAGE_REQUEST(method_, context_, requestgetter_(doc))              \
  }

/*
 * For storage of an |nsRuleNode|'s children in a PLDHashTable.
 */

struct ChildrenHashEntry : public PLDHashEntryHdr {
  // key is |mRuleNode->GetKey()|
  nsRuleNode *mRuleNode;
};

/* static */ PLDHashNumber
nsRuleNode::ChildrenHashHashKey(PLDHashTable *aTable, const void *aKey)
{
  const nsRuleNode::Key *key =
    static_cast<const nsRuleNode::Key*>(aKey);
  // Disagreement on importance and level for the same rule is extremely
  // rare, so hash just on the rule.
  return PL_DHashVoidPtrKeyStub(aTable, key->mRule);
}

/* static */ bool
nsRuleNode::ChildrenHashMatchEntry(PLDHashTable *aTable,
                                   const PLDHashEntryHdr *aHdr,
                                   const void *aKey)
{
  const ChildrenHashEntry *entry =
    static_cast<const ChildrenHashEntry*>(aHdr);
  const nsRuleNode::Key *key =
    static_cast<const nsRuleNode::Key*>(aKey);
  return entry->mRuleNode->GetKey() == *key;
}

/* static */ PLDHashTableOps
nsRuleNode::ChildrenHashOps = {
  // It's probably better to allocate the table itself using malloc and
  // free rather than the pres shell's arena because the table doesn't
  // grow very often and the pres shell's arena doesn't recycle very
  // large size allocations.
  PL_DHashAllocTable,
  PL_DHashFreeTable,
  ChildrenHashHashKey,
  ChildrenHashMatchEntry,
  PL_DHashMoveEntryStub,
  PL_DHashClearEntryStub,
  PL_DHashFinalizeStub,
  NULL
};


// EnsureBlockDisplay:
//  - if the display value (argument) is not a block-type
//    then we set it to a valid block display value
//  - For enforcing the floated/positioned element CSS2 rules
static void EnsureBlockDisplay(uint8_t& display)
{
  // see if the display value is already a block
  switch (display) {
  case NS_STYLE_DISPLAY_NONE :
    // never change display:none *ever*
  case NS_STYLE_DISPLAY_TABLE :
  case NS_STYLE_DISPLAY_BLOCK :
  case NS_STYLE_DISPLAY_LIST_ITEM :
#ifdef MOZ_FLEXBOX
  case NS_STYLE_DISPLAY_FLEX :
#endif // MOZ_FLEXBOX
    // do not muck with these at all - already blocks
    // This is equivalent to nsStyleDisplay::IsBlockOutside.  (XXX Maybe we
    // should just call that?)
    // This needs to match the check done in
    // nsCSSFrameConstructor::FindMathMLData for <math>.
    break;

  case NS_STYLE_DISPLAY_INLINE_TABLE :
    // make inline tables into tables
    display = NS_STYLE_DISPLAY_TABLE;
    break;

#ifdef MOZ_FLEXBOX
  case NS_STYLE_DISPLAY_INLINE_FLEX:
    // make inline flex containers into flex containers
    display = NS_STYLE_DISPLAY_FLEX;
    break;
#endif // MOZ_FLEXBOX

  default :
    // make it a block
    display = NS_STYLE_DISPLAY_BLOCK;
  }
}

static nscoord CalcLengthWith(const nsCSSValue& aValue,
                              nscoord aFontSize,
                              const nsStyleFont* aStyleFont,
                              nsStyleContext* aStyleContext,
                              nsPresContext* aPresContext,
                              bool aUseProvidedRootEmSize,
                              bool aUseUserFontSet,
                              bool& aCanStoreInRuleTree);

struct CalcLengthCalcOps : public css::BasicCoordCalcOps,
                           public css::NumbersAlreadyNormalizedOps
{
  // All of the parameters to CalcLengthWith except aValue.
  const nscoord mFontSize;
  const nsStyleFont* const mStyleFont;
  nsStyleContext* const mStyleContext;
  nsPresContext* const mPresContext;
  const bool mUseProvidedRootEmSize;
  const bool mUseUserFontSet;
  bool& mCanStoreInRuleTree;

  CalcLengthCalcOps(nscoord aFontSize, const nsStyleFont* aStyleFont,
                    nsStyleContext* aStyleContext, nsPresContext* aPresContext,
                    bool aUseProvidedRootEmSize, bool aUseUserFontSet,
                    bool& aCanStoreInRuleTree)
    : mFontSize(aFontSize),
      mStyleFont(aStyleFont),
      mStyleContext(aStyleContext),
      mPresContext(aPresContext),
      mUseProvidedRootEmSize(aUseProvidedRootEmSize),
      mUseUserFontSet(aUseUserFontSet),
      mCanStoreInRuleTree(aCanStoreInRuleTree)
  {
  }

  result_type ComputeLeafValue(const nsCSSValue& aValue)
  {
    return CalcLengthWith(aValue, mFontSize, mStyleFont,
                          mStyleContext, mPresContext, mUseProvidedRootEmSize,
                          mUseUserFontSet, mCanStoreInRuleTree);
  }
};

static inline nscoord ScaleCoord(const nsCSSValue &aValue, float factor)
{
  return NSToCoordRoundWithClamp(aValue.GetFloatValue() * factor);
}

already_AddRefed<nsFontMetrics>
GetMetricsFor(nsPresContext* aPresContext,
              nsStyleContext* aStyleContext,
              const nsStyleFont* aStyleFont,
              nscoord aFontSize, // overrides value from aStyleFont
              bool aUseUserFontSet)
{
  nsFont font = aStyleFont->mFont;
  font.size = aFontSize;
  gfxUserFontSet *fs = nullptr;
  if (aUseUserFontSet) {
    fs = aPresContext->GetUserFontSet();
  }
  nsRefPtr<nsFontMetrics> fm;
  aPresContext->DeviceContext()->GetMetricsFor(font,
                                               aStyleFont->mLanguage,
                                               fs, *getter_AddRefs(fm));
  return fm.forget();
}

static nscoord CalcLengthWith(const nsCSSValue& aValue,
                              nscoord aFontSize,
                              const nsStyleFont* aStyleFont,
                              nsStyleContext* aStyleContext,
                              nsPresContext* aPresContext,
                              bool aUseProvidedRootEmSize,
                              // aUseUserFontSet should always be true
                              // except when called from
                              // CalcLengthWithInitialFont.
                              bool aUseUserFontSet,
                              bool& aCanStoreInRuleTree)
{
  NS_ASSERTION(aValue.IsLengthUnit() || aValue.IsCalcUnit(),
               "not a length or calc unit");
  NS_ASSERTION(aStyleFont || aStyleContext,
               "Must have style data");
  NS_ASSERTION(!aStyleFont || !aStyleContext,
               "Duplicate sources of data");
  NS_ASSERTION(aPresContext, "Must have prescontext");

  if (aValue.IsFixedLengthUnit()) {
    return aValue.GetFixedLength(aPresContext);
  }
  if (aValue.IsPixelLengthUnit()) {
    return aValue.GetPixelLength();
  }
  if (aValue.IsCalcUnit()) {
    // For properties for which lengths are the *only* units accepted in
    // calc(), we can handle calc() here and just compute a final
    // result.  We ensure that we don't get to this code for other
    // properties by not calling CalcLength in those cases:  SetCoord
    // only calls CalcLength for a calc when it is appropriate to do so.
    CalcLengthCalcOps ops(aFontSize, aStyleFont,
                          aStyleContext, aPresContext,
                          aUseProvidedRootEmSize, aUseUserFontSet,
                          aCanStoreInRuleTree);
    return css::ComputeCalc(aValue, ops);
  }
  switch (aValue.GetUnit()) {
    // nsPresContext::SetVisibleArea and
    // nsPresContext::MediaFeatureValuesChanged handle dynamic changes
    // of the basis for viewport units by rebuilding the rule tree and
    // style context tree.  Not caching them in the rule tree wouldn't
    // be sufficient to handle these changes because we also need a way
    // to get rid of cached values in the style context tree without any
    // changes in specified style.  We can either do this by not caching
    // in the rule tree and then throwing away the style context tree
    // for dynamic viewport size changes, or by allowing caching in the
    // rule tree and using the existing rebuild style data path that
    // throws away the style context and the rule tree.
    // Thus we do cache viewport units in the rule tree.  This allows us
    // to benefit from the performance advantages of the rule tree
    // (e.g., faster dynamic changes on other things, like transforms)
    // and allows us not to need an additional code path, in exchange
    // for an increased cost to dynamic changes to the viewport size
    // when viewport units are in use.
    case eCSSUnit_ViewportWidth: {
      aPresContext->SetUsesViewportUnits(true);
      return ScaleCoord(aValue, 0.01f * aPresContext->GetVisibleArea().width);
    }
    case eCSSUnit_ViewportHeight: {
      aPresContext->SetUsesViewportUnits(true);
      return ScaleCoord(aValue, 0.01f * aPresContext->GetVisibleArea().height);
    }
    case eCSSUnit_ViewportMin: {
      aPresContext->SetUsesViewportUnits(true);
      nsSize viewportSize = aPresContext->GetVisibleArea().Size();
      return ScaleCoord(aValue, 0.01f * min(viewportSize.width, viewportSize.height));
    }
    case eCSSUnit_ViewportMax: {
      aPresContext->SetUsesViewportUnits(true);
      nsSize viewportSize = aPresContext->GetVisibleArea().Size();
      return ScaleCoord(aValue, 0.01f * max(viewportSize.width, viewportSize.height));
    }
    // While we could deal with 'rem' units correctly by simply not
    // caching any data that uses them in the rule tree, it's valuable
    // to store them in the rule tree (for faster dynamic changes of
    // other things).  And since the font size of the root element
    // changes rarely, we instead handle dynamic changes to the root
    // element's font size by rebuilding all style data in
    // nsCSSFrameConstructor::RestyleElement.
    case eCSSUnit_RootEM: {
      aPresContext->SetUsesRootEMUnits(true);
      nscoord rootFontSize;

      if (aUseProvidedRootEmSize) {
        // We should use the provided aFontSize as the reference length to
        // scale. This only happens when we are calculating font-size or
        // an equivalent (scriptminsize or CalcLengthWithInitialFont) on
        // the root element, in which case aFontSize is already the
        // value we want.
        rootFontSize = aFontSize;
      } else if (aStyleContext && !aStyleContext->GetParent()) {
        // This is the root element (XXX we don't really know this, but
        // nsRuleNode::SetFont makes the same assumption!), so we should
        // use GetStyleFont on this context to get the root element's
        // font size.
        const nsStyleFont *styleFont =
          aStyleFont ? aStyleFont : aStyleContext->GetStyleFont();
        rootFontSize = styleFont->mFont.size;
      } else {
        // This is not the root element or we are calculating something other
        // than font size, so rem is relative to the root element's font size.
        nsRefPtr<nsStyleContext> rootStyle;
        const nsStyleFont *rootStyleFont =
          aStyleFont ? aStyleFont : aStyleContext->GetStyleFont();
        Element* docElement = aPresContext->Document()->GetRootElement();

        if (docElement) {
          rootStyle = aPresContext->StyleSet()->ResolveStyleFor(docElement,
                                                                nullptr);
          if (rootStyle) {
            rootStyleFont = rootStyle->GetStyleFont();
          }
        }

        rootFontSize = rootStyleFont->mFont.size;
      }

      return ScaleCoord(aValue, float(rootFontSize));
    }
    default:
      // Fall through to the code for units that can't be stored in the
      // rule tree because they depend on font data.
      break;
  }
  // Common code for units that depend on the element's font data and
  // thus can't be stored in the rule tree:
  aCanStoreInRuleTree = false;
  const nsStyleFont *styleFont =
    aStyleFont ? aStyleFont : aStyleContext->GetStyleFont();
  if (aFontSize == -1) {
    // XXX Should this be styleFont->mSize instead to avoid taking minfontsize
    // prefs into account?
    aFontSize = styleFont->mFont.size;
  }
  switch (aValue.GetUnit()) {
    case eCSSUnit_EM: {
      return ScaleCoord(aValue, float(aFontSize));
      // XXX scale against font metrics height instead?
    }
    case eCSSUnit_XHeight: {
      nsRefPtr<nsFontMetrics> fm =
        GetMetricsFor(aPresContext, aStyleContext, styleFont,
                      aFontSize, aUseUserFontSet);
      return ScaleCoord(aValue, float(fm->XHeight()));
    }
    case eCSSUnit_Char: {
      nsRefPtr<nsFontMetrics> fm =
        GetMetricsFor(aPresContext, aStyleContext, styleFont,
                      aFontSize, aUseUserFontSet);
      gfxFloat zeroWidth = (fm->GetThebesFontGroup()->GetFontAt(0)
                            ->GetMetrics().zeroOrAveCharWidth);

      return ScaleCoord(aValue, ceil(aPresContext->AppUnitsPerDevPixel() *
                                     zeroWidth));
    }
    default:
      NS_NOTREACHED("unexpected unit");
      break;
  }
  return 0;
}

/* static */ nscoord
nsRuleNode::CalcLength(const nsCSSValue& aValue,
                       nsStyleContext* aStyleContext,
                       nsPresContext* aPresContext,
                       bool& aCanStoreInRuleTree)
{
  NS_ASSERTION(aStyleContext, "Must have style data");

  return CalcLengthWith(aValue, -1, nullptr,
                        aStyleContext, aPresContext,
                        false, true, aCanStoreInRuleTree);
}

/* Inline helper function to redirect requests to CalcLength. */
static inline nscoord CalcLength(const nsCSSValue& aValue,
                                 nsStyleContext* aStyleContext,
                                 nsPresContext* aPresContext,
                                 bool& aCanStoreInRuleTree)
{
  return nsRuleNode::CalcLength(aValue, aStyleContext,
                                aPresContext, aCanStoreInRuleTree);
}

/* static */ nscoord
nsRuleNode::CalcLengthWithInitialFont(nsPresContext* aPresContext,
                                      const nsCSSValue& aValue)
{
  nsStyleFont defaultFont(aPresContext); // FIXME: best language?
  bool canStoreInRuleTree;
  return CalcLengthWith(aValue, -1, &defaultFont,
                        nullptr, aPresContext,
                        true, false, canStoreInRuleTree);
}

struct LengthPercentPairCalcOps : public css::NumbersAlreadyNormalizedOps
{
  typedef nsRuleNode::ComputedCalc result_type;

  LengthPercentPairCalcOps(nsStyleContext* aContext,
                           nsPresContext* aPresContext,
                           bool& aCanStoreInRuleTree)
    : mContext(aContext),
      mPresContext(aPresContext),
      mCanStoreInRuleTree(aCanStoreInRuleTree),
      mHasPercent(false) {}

  nsStyleContext* mContext;
  nsPresContext* mPresContext;
  bool& mCanStoreInRuleTree;
  bool mHasPercent;

  result_type ComputeLeafValue(const nsCSSValue& aValue)
  {
    if (aValue.GetUnit() == eCSSUnit_Percent) {
      mHasPercent = true;
      return result_type(0, aValue.GetPercentValue());
    }
    return result_type(CalcLength(aValue, mContext, mPresContext,
                                  mCanStoreInRuleTree),
                       0.0f);
  }

  result_type
  MergeAdditive(nsCSSUnit aCalcFunction,
                result_type aValue1, result_type aValue2)
  {
    if (aCalcFunction == eCSSUnit_Calc_Plus) {
      return result_type(NSCoordSaturatingAdd(aValue1.mLength,
                                              aValue2.mLength),
                         aValue1.mPercent + aValue2.mPercent);
    }
    NS_ABORT_IF_FALSE(aCalcFunction == eCSSUnit_Calc_Minus,
                      "min() and max() are not allowed in calc() on "
                      "transform");
    return result_type(NSCoordSaturatingSubtract(aValue1.mLength,
                                                 aValue2.mLength, 0),
                       aValue1.mPercent - aValue2.mPercent);
  }

  result_type
  MergeMultiplicativeL(nsCSSUnit aCalcFunction,
                       float aValue1, result_type aValue2)
  {
    NS_ABORT_IF_FALSE(aCalcFunction == eCSSUnit_Calc_Times_L,
                      "unexpected unit");
    return result_type(NSCoordSaturatingMultiply(aValue2.mLength, aValue1),
                       aValue1 * aValue2.mPercent);
  }

  result_type
  MergeMultiplicativeR(nsCSSUnit aCalcFunction,
                       result_type aValue1, float aValue2)
  {
    NS_ABORT_IF_FALSE(aCalcFunction == eCSSUnit_Calc_Times_R ||
                      aCalcFunction == eCSSUnit_Calc_Divided,
                      "unexpected unit");
    if (aCalcFunction == eCSSUnit_Calc_Divided) {
      aValue2 = 1.0f / aValue2;
    }
    return result_type(NSCoordSaturatingMultiply(aValue1.mLength, aValue2),
                       aValue1.mPercent * aValue2);
  }

};

static void
SpecifiedCalcToComputedCalc(const nsCSSValue& aValue, nsStyleCoord& aCoord, 
                            nsStyleContext* aStyleContext,
                            bool& aCanStoreInRuleTree)
{
  LengthPercentPairCalcOps ops(aStyleContext, aStyleContext->PresContext(),
                               aCanStoreInRuleTree);
  nsRuleNode::ComputedCalc vals = ComputeCalc(aValue, ops);

  nsStyleCoord::Calc *calcObj =
    new (aStyleContext->Alloc(sizeof(nsStyleCoord::Calc))) nsStyleCoord::Calc;
  // Because we use aStyleContext->Alloc(), we have to store the result
  // on the style context and not in the rule tree.
  aCanStoreInRuleTree = false;

  calcObj->mLength = vals.mLength;
  calcObj->mPercent = vals.mPercent;
  calcObj->mHasPercent = ops.mHasPercent;

  aCoord.SetCalcValue(calcObj);
}

/* static */ nsRuleNode::ComputedCalc
nsRuleNode::SpecifiedCalcToComputedCalc(const nsCSSValue& aValue,
                                        nsStyleContext* aStyleContext,
                                        nsPresContext* aPresContext,
                                        bool& aCanStoreInRuleTree)
{
  LengthPercentPairCalcOps ops(aStyleContext, aPresContext,
                               aCanStoreInRuleTree);
  return ComputeCalc(aValue, ops);
}

// This is our public API for handling calc() expressions that involve
// percentages.
/* static */ nscoord
nsRuleNode::ComputeComputedCalc(const nsStyleCoord& aValue,
                                nscoord aPercentageBasis)
{
  nsStyleCoord::Calc *calc = aValue.GetCalcValue();
  return calc->mLength +
         NSToCoordFloorClamped(aPercentageBasis * calc->mPercent);
}

/* static */ nscoord
nsRuleNode::ComputeCoordPercentCalc(const nsStyleCoord& aCoord,
                                    nscoord aPercentageBasis)
{
  switch (aCoord.GetUnit()) {
    case eStyleUnit_Coord:
      return aCoord.GetCoordValue();
    case eStyleUnit_Percent:
      return NSToCoordFloorClamped(aPercentageBasis * aCoord.GetPercentValue());
    case eStyleUnit_Calc:
      return ComputeComputedCalc(aCoord, aPercentageBasis);
    default:
      NS_ABORT_IF_FALSE(false, "unexpected unit");
      return 0;
  }
}

/* Given an enumerated value that represents a box position, converts it to
 * a float representing the percentage of the box it corresponds to.  For
 * example, "center" becomes 0.5f.
 *
 * @param aEnumValue The enumerated value.
 * @return The float percent it corresponds to.
 */
static float
GetFloatFromBoxPosition(int32_t aEnumValue)
{
  switch (aEnumValue) {
  case NS_STYLE_BG_POSITION_LEFT:
  case NS_STYLE_BG_POSITION_TOP:
    return 0.0f;
  case NS_STYLE_BG_POSITION_RIGHT:
  case NS_STYLE_BG_POSITION_BOTTOM:
    return 1.0f;
  default:
    NS_NOTREACHED("unexpected value");
    // fall through
  case NS_STYLE_BG_POSITION_CENTER:
    return 0.5f;
  }
}

#define SETCOORD_NORMAL                 0x01   // N
#define SETCOORD_AUTO                   0x02   // A
#define SETCOORD_INHERIT                0x04   // H
#define SETCOORD_PERCENT                0x08   // P
#define SETCOORD_FACTOR                 0x10   // F
#define SETCOORD_LENGTH                 0x20   // L
#define SETCOORD_INTEGER                0x40   // I
#define SETCOORD_ENUMERATED             0x80   // E
#define SETCOORD_NONE                   0x100  // O
#define SETCOORD_INITIAL_ZERO           0x200
#define SETCOORD_INITIAL_AUTO           0x400
#define SETCOORD_INITIAL_NONE           0x800
#define SETCOORD_INITIAL_NORMAL         0x1000
#define SETCOORD_INITIAL_HALF           0x2000
#define SETCOORD_INITIAL_HUNDRED_PCT    0x00004000
#define SETCOORD_INITIAL_FACTOR_ONE     0x00008000
#define SETCOORD_INITIAL_FACTOR_ZERO    0x00010000
#define SETCOORD_CALC_LENGTH_ONLY       0x00020000
#define SETCOORD_CALC_CLAMP_NONNEGATIVE 0x00040000 // modifier for CALC_LENGTH_ONLY
#define SETCOORD_STORE_CALC             0x00080000
#define SETCOORD_BOX_POSITION           0x00100000 // exclusive with _ENUMERATED

#define SETCOORD_LP     (SETCOORD_LENGTH | SETCOORD_PERCENT)
#define SETCOORD_LH     (SETCOORD_LENGTH | SETCOORD_INHERIT)
#define SETCOORD_AH     (SETCOORD_AUTO | SETCOORD_INHERIT)
#define SETCOORD_LAH    (SETCOORD_AUTO | SETCOORD_LENGTH | SETCOORD_INHERIT)
#define SETCOORD_LPH    (SETCOORD_LP | SETCOORD_INHERIT)
#define SETCOORD_LPAH   (SETCOORD_LP | SETCOORD_AH)
#define SETCOORD_LPEH   (SETCOORD_LP | SETCOORD_ENUMERATED | SETCOORD_INHERIT)
#define SETCOORD_LPAEH  (SETCOORD_LPAH | SETCOORD_ENUMERATED)
#define SETCOORD_LPO    (SETCOORD_LP | SETCOORD_NONE)
#define SETCOORD_LPOH   (SETCOORD_LPH | SETCOORD_NONE)
#define SETCOORD_LPOEH  (SETCOORD_LPOH | SETCOORD_ENUMERATED)
#define SETCOORD_LE     (SETCOORD_LENGTH | SETCOORD_ENUMERATED)
#define SETCOORD_LEH    (SETCOORD_LE | SETCOORD_INHERIT)
#define SETCOORD_IA     (SETCOORD_INTEGER | SETCOORD_AUTO)
#define SETCOORD_LAE    (SETCOORD_LENGTH | SETCOORD_AUTO | SETCOORD_ENUMERATED)

// changes aCoord iff it returns true
static bool SetCoord(const nsCSSValue& aValue, nsStyleCoord& aCoord,
                       const nsStyleCoord& aParentCoord,
                       int32_t aMask, nsStyleContext* aStyleContext,
                       nsPresContext* aPresContext,
                       bool& aCanStoreInRuleTree)
{
  bool result = true;
  if (aValue.GetUnit() == eCSSUnit_Null) {
    result = false;
  }
  else if ((((aMask & SETCOORD_LENGTH) != 0) &&
            aValue.IsLengthUnit()) ||
           (((aMask & SETCOORD_CALC_LENGTH_ONLY) != 0) &&
            aValue.IsCalcUnit())) {
    nscoord len = CalcLength(aValue, aStyleContext, aPresContext,
                             aCanStoreInRuleTree);
    if ((aMask & SETCOORD_CALC_CLAMP_NONNEGATIVE) && len < 0) {
      NS_ASSERTION(aValue.IsCalcUnit(),
                   "parser should have ensured no nonnegative lengths");
      len = 0;
    }
    aCoord.SetCoordValue(len);
  }
  else if (((aMask & SETCOORD_PERCENT) != 0) &&
           (aValue.GetUnit() == eCSSUnit_Percent)) {
    aCoord.SetPercentValue(aValue.GetPercentValue());
  }
  else if (((aMask & SETCOORD_INTEGER) != 0) &&
           (aValue.GetUnit() == eCSSUnit_Integer)) {
    aCoord.SetIntValue(aValue.GetIntValue(), eStyleUnit_Integer);
  }
  else if (((aMask & SETCOORD_ENUMERATED) != 0) &&
           (aValue.GetUnit() == eCSSUnit_Enumerated)) {
    aCoord.SetIntValue(aValue.GetIntValue(), eStyleUnit_Enumerated);
  }
  else if (((aMask & SETCOORD_BOX_POSITION) != 0) &&
           (aValue.GetUnit() == eCSSUnit_Enumerated)) {
    aCoord.SetPercentValue(GetFloatFromBoxPosition(aValue.GetIntValue()));
  }
  else if (((aMask & SETCOORD_AUTO) != 0) &&
           (aValue.GetUnit() == eCSSUnit_Auto)) {
    aCoord.SetAutoValue();
  }
  else if (((aMask & SETCOORD_INHERIT) != 0) &&
           (aValue.GetUnit() == eCSSUnit_Inherit)) {
    aCoord = aParentCoord;  // just inherit value from parent
    aCanStoreInRuleTree = false;
  }
  else if (((aMask & SETCOORD_NORMAL) != 0) &&
           (aValue.GetUnit() == eCSSUnit_Normal)) {
    aCoord.SetNormalValue();
  }
  else if (((aMask & SETCOORD_NONE) != 0) &&
           (aValue.GetUnit() == eCSSUnit_None)) {
    aCoord.SetNoneValue();
  }
  else if (((aMask & SETCOORD_FACTOR) != 0) &&
           (aValue.GetUnit() == eCSSUnit_Number)) {
    aCoord.SetFactorValue(aValue.GetFloatValue());
  }
  else if (((aMask & SETCOORD_STORE_CALC) != 0) &&
           (aValue.IsCalcUnit())) {
    SpecifiedCalcToComputedCalc(aValue, aCoord, aStyleContext,
                                aCanStoreInRuleTree);
  }
  else if (aValue.GetUnit() == eCSSUnit_Initial) {
    if ((aMask & SETCOORD_INITIAL_AUTO) != 0) {
      aCoord.SetAutoValue();
    }
    else if ((aMask & SETCOORD_INITIAL_ZERO) != 0) {
      aCoord.SetCoordValue(0);
    }
    else if ((aMask & SETCOORD_INITIAL_FACTOR_ZERO) != 0) {
      aCoord.SetFactorValue(0.0f);
    }
    else if ((aMask & SETCOORD_INITIAL_NONE) != 0) {
      aCoord.SetNoneValue();
    }
    else if ((aMask & SETCOORD_INITIAL_NORMAL) != 0) {
      aCoord.SetNormalValue();
    }
    else if ((aMask & SETCOORD_INITIAL_HALF) != 0) {
      aCoord.SetPercentValue(0.5f);
    }
    else if ((aMask & SETCOORD_INITIAL_HUNDRED_PCT) != 0) {
      aCoord.SetPercentValue(1.0f);
    }
    else if ((aMask & SETCOORD_INITIAL_FACTOR_ONE) != 0) {
      aCoord.SetFactorValue(1.0f);
    }
    else {
      result = false;  // didn't set anything
    }
  }
  else {
    result = false;  // didn't set anything
  }
  return result;
}

// This inline function offers a shortcut for SetCoord() by refusing to accept
// SETCOORD_LENGTH and SETCOORD_INHERIT masks.
static inline bool SetAbsCoord(const nsCSSValue& aValue,
                                 nsStyleCoord& aCoord,
                                 int32_t aMask)
{
  NS_ABORT_IF_FALSE((aMask & SETCOORD_LH) == 0,
                    "does not handle SETCOORD_LENGTH and SETCOORD_INHERIT");

  // The values of the following variables will never be used; so it does not
  // matter what to set.
  const nsStyleCoord dummyParentCoord;
  nsStyleContext* dummyStyleContext = nullptr;
  nsPresContext* dummyPresContext = nullptr;
  bool dummyCanStoreInRuleTree = true;

  bool rv = SetCoord(aValue, aCoord, dummyParentCoord, aMask,
                       dummyStyleContext, dummyPresContext,
                       dummyCanStoreInRuleTree);
  NS_ABORT_IF_FALSE(dummyCanStoreInRuleTree,
                    "SetCoord() should not modify dummyCanStoreInRuleTree.");

  return rv;
}

/* Given a specified value that might be a pair value, call SetCoord twice,
 * either using each member of the pair, or using the unpaired value twice.
 */
static bool
SetPairCoords(const nsCSSValue& aValue,
              nsStyleCoord& aCoordX, nsStyleCoord& aCoordY,
              const nsStyleCoord& aParentX, const nsStyleCoord& aParentY,
              int32_t aMask, nsStyleContext* aStyleContext,
              nsPresContext* aPresContext, bool& aCanStoreInRuleTree)
{
  const nsCSSValue& valX =
    aValue.GetUnit() == eCSSUnit_Pair ? aValue.GetPairValue().mXValue : aValue;
  const nsCSSValue& valY =
    aValue.GetUnit() == eCSSUnit_Pair ? aValue.GetPairValue().mYValue : aValue;

  bool cX = SetCoord(valX, aCoordX, aParentX, aMask, aStyleContext,
                       aPresContext, aCanStoreInRuleTree);
  mozilla::DebugOnly<bool> cY = SetCoord(valY, aCoordY, aParentY, aMask, 
                       aStyleContext, aPresContext, aCanStoreInRuleTree);
  NS_ABORT_IF_FALSE(cX == cY, "changed one but not the other");
  return cX;
}

static bool SetColor(const nsCSSValue& aValue, const nscolor aParentColor,
                       nsPresContext* aPresContext, nsStyleContext *aContext,
                       nscolor& aResult, bool& aCanStoreInRuleTree)
{
  bool    result = false;
  nsCSSUnit unit = aValue.GetUnit();

  if (eCSSUnit_Color == unit) {
    aResult = aValue.GetColorValue();
    result = true;
  }
  else if (eCSSUnit_Ident == unit) {
    nsAutoString  value;
    aValue.GetStringValue(value);
    nscolor rgba;
    if (NS_ColorNameToRGB(value, &rgba)) {
      aResult = rgba;
      result = true;
    }
  }
  else if (eCSSUnit_EnumColor == unit) {
    int32_t intValue = aValue.GetIntValue();
    if (0 <= intValue) {
      LookAndFeel::ColorID colorID = (LookAndFeel::ColorID) intValue;
      if (NS_SUCCEEDED(LookAndFeel::GetColor(colorID, &aResult))) {
        result = true;
      }
    }
    else {
      aResult = NS_RGB(0, 0, 0);
      result = false;
      switch (intValue) {
        case NS_COLOR_MOZ_HYPERLINKTEXT:
          if (aPresContext) {
            aResult = aPresContext->DefaultLinkColor();
            result = true;
          }
          break;
        case NS_COLOR_MOZ_VISITEDHYPERLINKTEXT:
          if (aPresContext) {
            aResult = aPresContext->DefaultVisitedLinkColor();
            result = true;
          }
          break;
        case NS_COLOR_MOZ_ACTIVEHYPERLINKTEXT:
          if (aPresContext) {
            aResult = aPresContext->DefaultActiveLinkColor();
            result = true;
          }
          break;
        case NS_COLOR_CURRENTCOLOR:
          // The data computed from this can't be shared in the rule tree
          // because they could be used on a node with a different color
          aCanStoreInRuleTree = false;
          if (aContext) {
            aResult = aContext->GetStyleColor()->mColor;
            result = true;
          }
          break;
        case NS_COLOR_MOZ_DEFAULT_COLOR:
          if (aPresContext) {
            aResult = aPresContext->DefaultColor();
            result = true;
          }
          break;
        case NS_COLOR_MOZ_DEFAULT_BACKGROUND_COLOR:
          if (aPresContext) {
            aResult = aPresContext->DefaultBackgroundColor();
            result = true;
          }
          break;
        default:
          NS_NOTREACHED("Should never have an unknown negative colorID.");
          break;
      }
    }
  }
  else if (eCSSUnit_Inherit == unit) {
    aResult = aParentColor;
    result = true;
    aCanStoreInRuleTree = false;
  }
  else if (eCSSUnit_Enumerated == unit &&
           aValue.GetIntValue() == NS_STYLE_COLOR_INHERIT_FROM_BODY) {
    NS_ASSERTION(aPresContext->CompatibilityMode() == eCompatibility_NavQuirks,
                 "Should only get this value in quirks mode");
    // We just grab the color from the prescontext, and rely on the fact that
    // if the body color ever changes all its descendants will get new style
    // contexts (but NOT necessarily new rulenodes).
    aResult = aPresContext->BodyTextColor();
    result = true;
    aCanStoreInRuleTree = false;
  }
  return result;
}

static void SetGradientCoord(const nsCSSValue& aValue, nsPresContext* aPresContext,
                             nsStyleContext* aContext, nsStyleCoord& aResult,
                             bool& aCanStoreInRuleTree)
{
  // OK to pass bad aParentCoord since we're not passing SETCOORD_INHERIT
  if (!SetCoord(aValue, aResult, nsStyleCoord(),
                SETCOORD_LPO | SETCOORD_BOX_POSITION | SETCOORD_STORE_CALC,
                aContext, aPresContext, aCanStoreInRuleTree)) {
    NS_NOTREACHED("unexpected unit for gradient anchor point");
    aResult.SetNoneValue();
  }
}

static void SetGradient(const nsCSSValue& aValue, nsPresContext* aPresContext,
                        nsStyleContext* aContext, nsStyleGradient& aResult,
                        bool& aCanStoreInRuleTree)
{
  NS_ABORT_IF_FALSE(aValue.GetUnit() == eCSSUnit_Gradient,
                    "The given data is not a gradient");

  const nsCSSValueGradient* gradient = aValue.GetGradientValue();

  if (gradient->mIsExplicitSize) {
    SetCoord(gradient->GetRadiusX(), aResult.mRadiusX, nsStyleCoord(),
             SETCOORD_LP | SETCOORD_STORE_CALC,
             aContext, aPresContext, aCanStoreInRuleTree);
    if (gradient->GetRadiusY().GetUnit() != eCSSUnit_None) {
      SetCoord(gradient->GetRadiusY(), aResult.mRadiusY, nsStyleCoord(),
               SETCOORD_LP | SETCOORD_STORE_CALC,
               aContext, aPresContext, aCanStoreInRuleTree);
      aResult.mShape = NS_STYLE_GRADIENT_SHAPE_ELLIPTICAL;
    } else {
      aResult.mRadiusY = aResult.mRadiusX;
      aResult.mShape = NS_STYLE_GRADIENT_SHAPE_CIRCULAR;
    }
    aResult.mSize = NS_STYLE_GRADIENT_SIZE_EXPLICIT_SIZE;
  } else if (gradient->mIsRadial) {
    if (gradient->GetRadialShape().GetUnit() == eCSSUnit_Enumerated) {
      aResult.mShape = gradient->GetRadialShape().GetIntValue();
    } else {
      NS_ASSERTION(gradient->GetRadialShape().GetUnit() == eCSSUnit_None,
                   "bad unit for radial shape");
      aResult.mShape = NS_STYLE_GRADIENT_SHAPE_ELLIPTICAL;
    }
    if (gradient->GetRadialSize().GetUnit() == eCSSUnit_Enumerated) {
      aResult.mSize = gradient->GetRadialSize().GetIntValue();
    } else {
      NS_ASSERTION(gradient->GetRadialSize().GetUnit() == eCSSUnit_None,
                   "bad unit for radial shape");
      aResult.mSize = NS_STYLE_GRADIENT_SIZE_FARTHEST_CORNER;
    }
  } else {
    NS_ASSERTION(gradient->GetRadialShape().GetUnit() == eCSSUnit_None,
                 "bad unit for linear shape");
    NS_ASSERTION(gradient->GetRadialSize().GetUnit() == eCSSUnit_None,
                 "bad unit for linear size");
    aResult.mShape = NS_STYLE_GRADIENT_SHAPE_LINEAR;
    aResult.mSize = NS_STYLE_GRADIENT_SIZE_FARTHEST_CORNER;
  }

  aResult.mLegacySyntax = gradient->mIsLegacySyntax;

  // bg-position
  SetGradientCoord(gradient->mBgPos.mXValue, aPresContext, aContext,
                   aResult.mBgPosX, aCanStoreInRuleTree);

  SetGradientCoord(gradient->mBgPos.mYValue, aPresContext, aContext,
                   aResult.mBgPosY, aCanStoreInRuleTree);

  aResult.mRepeating = gradient->mIsRepeating;

  // angle
  if (gradient->mAngle.IsAngularUnit()) {
    nsStyleUnit unit;
    switch (gradient->mAngle.GetUnit()) {
    case eCSSUnit_Degree: unit = eStyleUnit_Degree; break;
    case eCSSUnit_Grad:   unit = eStyleUnit_Grad; break;
    case eCSSUnit_Radian: unit = eStyleUnit_Radian; break;
    case eCSSUnit_Turn:   unit = eStyleUnit_Turn; break;
    default: NS_NOTREACHED("unrecognized angular unit");
      unit = eStyleUnit_Degree;
    }
    aResult.mAngle.SetAngleValue(gradient->mAngle.GetAngleValue(), unit);
  } else {
    NS_ASSERTION(gradient->mAngle.GetUnit() == eCSSUnit_None,
                 "bad unit for gradient angle");
    aResult.mAngle.SetNoneValue();
  }

  // stops
  for (uint32_t i = 0; i < gradient->mStops.Length(); i++) {
    nsStyleGradientStop stop;
    const nsCSSValueGradientStop &valueStop = gradient->mStops[i];

    if (!SetCoord(valueStop.mLocation, stop.mLocation,
                  nsStyleCoord(), SETCOORD_LPO | SETCOORD_STORE_CALC,
                  aContext, aPresContext, aCanStoreInRuleTree)) {
      NS_NOTREACHED("unexpected unit for gradient stop location");
    }

    // inherit is not a valid color for stops, so we pass in a dummy
    // parent color
    NS_ASSERTION(valueStop.mColor.GetUnit() != eCSSUnit_Inherit,
                 "inherit is not a valid color for gradient stops");
    SetColor(valueStop.mColor, NS_RGB(0, 0, 0), aPresContext,
             aContext, stop.mColor, aCanStoreInRuleTree);

    aResult.mStops.AppendElement(stop);
  }
}

// -moz-image-rect(<uri>, <top>, <right>, <bottom>, <left>)
static void SetStyleImageToImageRect(nsStyleContext* aStyleContext,
                                     const nsCSSValue& aValue,
                                     nsStyleImage& aResult)
{
  NS_ABORT_IF_FALSE(aValue.GetUnit() == eCSSUnit_Function &&
                    aValue.EqualsFunction(eCSSKeyword__moz_image_rect),
                    "the value is not valid -moz-image-rect()");

  nsCSSValue::Array* arr = aValue.GetArrayValue();
  NS_ABORT_IF_FALSE(arr && arr->Count() == 6, "invalid number of arguments");

  // <uri>
  if (arr->Item(1).GetUnit() == eCSSUnit_Image) {
    NS_SET_IMAGE_REQUEST_WITH_DOC(aResult.SetImageData,
                                  aStyleContext,
                                  arr->Item(1).GetImageValue)
  } else {
    NS_WARNING("nsCSSValue::Image::Image() failed?");
  }

  // <top>, <right>, <bottom>, <left>
  nsStyleSides cropRect;
  NS_FOR_CSS_SIDES(side) {
    nsStyleCoord coord;
    const nsCSSValue& val = arr->Item(2 + side);

#ifdef DEBUG
    bool unitOk =
#endif
      SetAbsCoord(val, coord, SETCOORD_FACTOR | SETCOORD_PERCENT);
    NS_ABORT_IF_FALSE(unitOk, "Incorrect data structure created by CSS parser");
    cropRect.Set(side, coord);
  }
  aResult.SetCropRect(&cropRect);
}

static void SetStyleImage(nsStyleContext* aStyleContext,
                          const nsCSSValue& aValue,
                          nsStyleImage& aResult,
                          bool& aCanStoreInRuleTree)
{
  aResult.SetNull();

  switch (aValue.GetUnit()) {
    case eCSSUnit_Image:
      NS_SET_IMAGE_REQUEST_WITH_DOC(aResult.SetImageData,
                                    aStyleContext,
                                    aValue.GetImageValue)
      break;
    case eCSSUnit_Function:
      if (aValue.EqualsFunction(eCSSKeyword__moz_image_rect)) {
        SetStyleImageToImageRect(aStyleContext, aValue, aResult);
      } else {
        NS_NOTREACHED("-moz-image-rect() is the only expected function");
      }
      break;
    case eCSSUnit_Gradient:
    {
      nsStyleGradient* gradient = new nsStyleGradient();
      if (gradient) {
        SetGradient(aValue, aStyleContext->PresContext(), aStyleContext,
                    *gradient, aCanStoreInRuleTree);
        aResult.SetGradientData(gradient);
      }
      break;
    }
    case eCSSUnit_Element:
      aResult.SetElementId(aValue.GetStringBufferValue());
      break;
    case eCSSUnit_None:
      break;
    default:
      // We might have eCSSUnit_URL values for if-visited style
      // contexts, which we can safely treat like 'none'.  Otherwise
      // this is an unexpected unit.
      NS_ASSERTION(aStyleContext->IsStyleIfVisited() &&
                   aValue.GetUnit() == eCSSUnit_URL,
                   "unexpected unit; maybe nsCSSValue::Image::Image() failed?");
      break;
  }
}

// flags for SetDiscrete - align values with SETCOORD_* constants
// where possible

#define SETDSC_NORMAL                 0x01   // N
#define SETDSC_AUTO                   0x02   // A
#define SETDSC_INTEGER                0x40   // I
#define SETDSC_ENUMERATED             0x80   // E
#define SETDSC_NONE                   0x100  // O
#define SETDSC_SYSTEM_FONT            0x2000

// no caller cares whether aField was changed or not
template <typename FieldT,
          typename T1, typename T2, typename T3, typename T4, typename T5>
static void
SetDiscrete(const nsCSSValue& aValue, FieldT & aField,
            bool& aCanStoreInRuleTree, uint32_t aMask,
            FieldT aParentValue,
            T1 aInitialValue,
            T2 aAutoValue,
            T3 aNoneValue,
            T4 aNormalValue,
            T5 aSystemFontValue)
{
  switch (aValue.GetUnit()) {
  case eCSSUnit_Null:
    return;

    // every caller of SetDiscrete provides inherit and initial
    // alternatives, so we don't require them to say so in the mask
  case eCSSUnit_Inherit:
    aCanStoreInRuleTree = false;
    aField = aParentValue;
    return;

  case eCSSUnit_Initial:
    aField = aInitialValue;
    return;

    // every caller provides one or other of these alternatives,
    // but they have to say which
  case eCSSUnit_Enumerated:
    if (aMask & SETDSC_ENUMERATED) {
      aField = aValue.GetIntValue();
      return;
    }
    break;

  case eCSSUnit_Integer:
    if (aMask & SETDSC_INTEGER) {
      aField = aValue.GetIntValue();
      return;
    }
    break;

    // remaining possibilities in descending order of frequency of use
  case eCSSUnit_Auto:
    if (aMask & SETDSC_AUTO) {
      aField = aAutoValue;
      return;
    }
    break;

  case eCSSUnit_None:
    if (aMask & SETDSC_NONE) {
      aField = aNoneValue;
      return;
    }
    break;

  case eCSSUnit_Normal:
    if (aMask & SETDSC_NORMAL) {
      aField = aNormalValue;
      return;
    }
    break;

  case eCSSUnit_System_Font:
    if (aMask & SETDSC_SYSTEM_FONT) {
      aField = aSystemFontValue;
      return;
    }
    break;

  default:
    break;
  }

  NS_NOTREACHED("SetDiscrete: inappropriate unit");
}

// flags for SetFactor
#define SETFCT_POSITIVE 0x01        // assert value is >= 0.0f
#define SETFCT_OPACITY  0x02        // clamp value to [0.0f .. 1.0f]
#define SETFCT_NONE     0x04        // allow _None (uses aInitialValue).

static void
SetFactor(const nsCSSValue& aValue, float& aField, bool& aCanStoreInRuleTree,
          float aParentValue, float aInitialValue, uint32_t aFlags = 0)
{
  switch (aValue.GetUnit()) {
  case eCSSUnit_Null:
    return;

  case eCSSUnit_Number:
    aField = aValue.GetFloatValue();
    if (aFlags & SETFCT_POSITIVE) {
      NS_ASSERTION(aField >= 0.0f, "negative value for positive-only property");
      if (aField < 0.0f)
        aField = 0.0f;
    }
    if (aFlags & SETFCT_OPACITY) {
      if (aField < 0.0f)
        aField = 0.0f;
      if (aField > 1.0f)
        aField = 1.0f;
    }
    return;

  case eCSSUnit_Inherit:
    aCanStoreInRuleTree = false;
    aField = aParentValue;
    return;

  case eCSSUnit_Initial:
    aField = aInitialValue;
    return;

  case eCSSUnit_None:
    if (aFlags & SETFCT_NONE) {
      aField = aInitialValue;
      return;
    }
    break;

  default:
    break;
  }

  NS_NOTREACHED("SetFactor: inappropriate unit");
}

// Overloaded new operator. Initializes the memory to 0 and relies on an arena
// (which comes from the presShell) to perform the allocation.
void*
nsRuleNode::operator new(size_t sz, nsPresContext* aPresContext) CPP_THROW_NEW
{
  // Check the recycle list first.
  return aPresContext->PresShell()->AllocateByObjectID(nsPresArena::nsRuleNode_id, sz);
}

/* static */ PLDHashOperator
nsRuleNode::EnqueueRuleNodeChildren(PLDHashTable *table, PLDHashEntryHdr *hdr,
                                    uint32_t number, void *arg)
{
  ChildrenHashEntry *entry = static_cast<ChildrenHashEntry*>(hdr);
  nsRuleNode ***destroyQueueTail = static_cast<nsRuleNode***>(arg);
  **destroyQueueTail = entry->mRuleNode;
  *destroyQueueTail = &entry->mRuleNode->mNextSibling;
  return PL_DHASH_NEXT;
}

// Overridden to prevent the global delete from being called, since the memory
// came out of an nsIArena instead of the global delete operator's heap.
void
nsRuleNode::DestroyInternal(nsRuleNode ***aDestroyQueueTail)
{
  nsRuleNode *destroyQueue, **destroyQueueTail;
  if (aDestroyQueueTail) {
    destroyQueueTail = *aDestroyQueueTail;
  } else {
    destroyQueue = nullptr;
    destroyQueueTail = &destroyQueue;
  }

  if (ChildrenAreHashed()) {
    PLDHashTable *children = ChildrenHash();
    PL_DHashTableEnumerate(children, EnqueueRuleNodeChildren,
                           &destroyQueueTail);
    *destroyQueueTail = nullptr; // ensure null-termination
    PL_DHashTableDestroy(children);
  } else if (HaveChildren()) {
    *destroyQueueTail = ChildrenList();
    do {
      destroyQueueTail = &(*destroyQueueTail)->mNextSibling;
    } while (*destroyQueueTail);
  }
  mChildren.asVoid = nullptr;

  if (aDestroyQueueTail) {
    // Our caller destroys the queue.
    *aDestroyQueueTail = destroyQueueTail;
  } else {
    // We have to do destroy the queue.  When we destroy each node, it
    // will add its children to the queue.
    while (destroyQueue) {
      nsRuleNode *cur = destroyQueue;
      destroyQueue = destroyQueue->mNextSibling;
      if (!destroyQueue) {
        NS_ASSERTION(destroyQueueTail == &cur->mNextSibling, "mangled list");
        destroyQueueTail = &destroyQueue;
      }
      cur->DestroyInternal(&destroyQueueTail);
    }
  }

  // Destroy ourselves.
  this->~nsRuleNode();

  // Don't let the memory be freed, since it will be recycled
  // instead. Don't call the global operator delete.
  mPresContext->PresShell()->FreeByObjectID(nsPresArena::nsRuleNode_id, this);
}

nsRuleNode* nsRuleNode::CreateRootNode(nsPresContext* aPresContext)
{
  return new (aPresContext)
    nsRuleNode(aPresContext, nullptr, nullptr, 0xff, false);
}

nsRuleNode::nsRuleNode(nsPresContext* aContext, nsRuleNode* aParent,
                       nsIStyleRule* aRule, uint8_t aLevel,
                       bool aIsImportant)
  : mPresContext(aContext),
    mParent(aParent),
    mRule(aRule),
    mDependentBits((uint32_t(aLevel) << NS_RULE_NODE_LEVEL_SHIFT) |
                   (aIsImportant ? NS_RULE_NODE_IS_IMPORTANT : 0)),
    mNoneBits(0),
    mRefCnt(0)
{
  mChildren.asVoid = nullptr;
  MOZ_COUNT_CTOR(nsRuleNode);
  NS_IF_ADDREF(mRule);

  NS_ASSERTION(IsRoot() || GetLevel() == aLevel, "not enough bits");
  NS_ASSERTION(IsRoot() || IsImportantRule() == aIsImportant, "yikes");
  /* If IsRoot(), then aContext->StyleSet() is typically null at this
     point.  In any case, we don't want to treat the root rulenode as
     unused.  */
  if (!IsRoot()) {
    mParent->AddRef();
    aContext->StyleSet()->RuleNodeUnused();
  }

  // nsStyleSet::GetContext depends on there being only one animation
  // rule.
  NS_ABORT_IF_FALSE(IsRoot() || GetLevel() != nsStyleSet::eAnimationSheet ||
                    mParent->IsRoot() ||
                    mParent->GetLevel() != nsStyleSet::eAnimationSheet,
                    "must be only one rule at animation level");
}

nsRuleNode::~nsRuleNode()
{
  MOZ_COUNT_DTOR(nsRuleNode);
  if (mStyleData.mResetData || mStyleData.mInheritedData)
    mStyleData.Destroy(0, mPresContext);
  NS_IF_RELEASE(mRule);
}

nsRuleNode*
nsRuleNode::Transition(nsIStyleRule* aRule, uint8_t aLevel,
                       bool aIsImportantRule)
{
  nsRuleNode* next = nullptr;
  nsRuleNode::Key key(aRule, aLevel, aIsImportantRule);

  if (HaveChildren() && !ChildrenAreHashed()) {
    int32_t numKids = 0;
    nsRuleNode* curr = ChildrenList();
    while (curr && curr->GetKey() != key) {
      curr = curr->mNextSibling;
      ++numKids;
    }
    if (curr)
      next = curr;
    else if (numKids >= kMaxChildrenInList)
      ConvertChildrenToHash();
  }

  if (ChildrenAreHashed()) {
    ChildrenHashEntry *entry = static_cast<ChildrenHashEntry*>
                                          (PL_DHashTableOperate(ChildrenHash(), &key, PL_DHASH_ADD));
    if (!entry) {
      NS_WARNING("out of memory");
      return this;
    }
    if (entry->mRuleNode)
      next = entry->mRuleNode;
    else {
      next = entry->mRuleNode = new (mPresContext)
        nsRuleNode(mPresContext, this, aRule, aLevel, aIsImportantRule);
      if (!next) {
        PL_DHashTableRawRemove(ChildrenHash(), entry);
        NS_WARNING("out of memory");
        return this;
      }
    }
  } else if (!next) {
    // Create the new entry in our list.
    next = new (mPresContext)
      nsRuleNode(mPresContext, this, aRule, aLevel, aIsImportantRule);
    if (!next) {
      NS_WARNING("out of memory");
      return this;
    }
    next->mNextSibling = ChildrenList();
    SetChildrenList(next);
  }

  return next;
}

void
nsRuleNode::ConvertChildrenToHash()
{
  NS_ASSERTION(!ChildrenAreHashed() && HaveChildren(),
               "must have a non-empty list of children");
  PLDHashTable *hash = PL_NewDHashTable(&ChildrenHashOps, nullptr,
                                        sizeof(ChildrenHashEntry),
                                        kMaxChildrenInList * 4);
  if (!hash)
    return;
  for (nsRuleNode* curr = ChildrenList(); curr; curr = curr->mNextSibling) {
    // This will never fail because of the initial size we gave the table.
    ChildrenHashEntry *entry = static_cast<ChildrenHashEntry*>(
      PL_DHashTableOperate(hash, curr->mRule, PL_DHASH_ADD));
    NS_ASSERTION(!entry->mRuleNode, "duplicate entries in list");
    entry->mRuleNode = curr;
  }
  SetChildrenHash(hash);
}

inline void
nsRuleNode::PropagateNoneBit(uint32_t aBit, nsRuleNode* aHighestNode)
{
  nsRuleNode* curr = this;
  for (;;) {
    NS_ASSERTION(!(curr->mNoneBits & aBit), "propagating too far");
    curr->mNoneBits |= aBit;
    if (curr == aHighestNode)
      break;
    curr = curr->mParent;
  }
}

inline void
nsRuleNode::PropagateDependentBit(uint32_t aBit, nsRuleNode* aHighestNode)
{
  for (nsRuleNode* curr = this; curr != aHighestNode; curr = curr->mParent) {
    if (curr->mDependentBits & aBit) {
#ifdef DEBUG
      while (curr != aHighestNode) {
        NS_ASSERTION(curr->mDependentBits & aBit, "bit not set");
        curr = curr->mParent;
      }
#endif
      break;
    }

    curr->mDependentBits |= aBit;
  }
}

/*
 * The following "Check" functions are used for determining what type of
 * sharing can be used for the data on this rule node.  MORE HERE...
 */

/*
 * a callback function that that can revise the result of
 * CheckSpecifiedProperties before finishing; aResult is the current
 * result, and it returns the revised one.
 */
typedef nsRuleNode::RuleDetail
  (* CheckCallbackFn)(const nsRuleData* aRuleData,
                      nsRuleNode::RuleDetail aResult);

/**
 * @param aValue the value being examined
 * @param aSpecifiedCount to be incremented by one if the value is specified
 * @param aInherited to be incremented by one if the value is set to inherit
 */
inline void
ExamineCSSValue(const nsCSSValue& aValue,
                uint32_t& aSpecifiedCount, uint32_t& aInheritedCount)
{
  if (aValue.GetUnit() != eCSSUnit_Null) {
    ++aSpecifiedCount;
    if (aValue.GetUnit() == eCSSUnit_Inherit) {
      ++aInheritedCount;
    }
  }
}

static nsRuleNode::RuleDetail
CheckFontCallback(const nsRuleData* aRuleData,
                  nsRuleNode::RuleDetail aResult)
{
  // em, ex, percent, 'larger', and 'smaller' values on font-size depend
  // on the parent context's font-size
  // Likewise, 'lighter' and 'bolder' values of 'font-weight', and 'wider'
  // and 'narrower' values of 'font-stretch' depend on the parent.
  const nsCSSValue& size = *aRuleData->ValueForFontSize();
  const nsCSSValue& weight = *aRuleData->ValueForFontWeight();
  if (size.IsRelativeLengthUnit() ||
      size.GetUnit() == eCSSUnit_Percent ||
      (size.GetUnit() == eCSSUnit_Enumerated &&
       (size.GetIntValue() == NS_STYLE_FONT_SIZE_SMALLER ||
        size.GetIntValue() == NS_STYLE_FONT_SIZE_LARGER)) ||
      aRuleData->ValueForScriptLevel()->GetUnit() == eCSSUnit_Integer ||
      (weight.GetUnit() == eCSSUnit_Enumerated &&
       (weight.GetIntValue() == NS_STYLE_FONT_WEIGHT_BOLDER ||
        weight.GetIntValue() == NS_STYLE_FONT_WEIGHT_LIGHTER))) {
    NS_ASSERTION(aResult == nsRuleNode::eRulePartialReset ||
                 aResult == nsRuleNode::eRuleFullReset ||
                 aResult == nsRuleNode::eRulePartialMixed ||
                 aResult == nsRuleNode::eRuleFullMixed,
                 "we know we already have a reset-counted property");
    // Promote reset to mixed since we have something that depends on
    // the parent.  But never promote to inherited since that could
    // cause inheritance of the exact value.
    if (aResult == nsRuleNode::eRulePartialReset)
      aResult = nsRuleNode::eRulePartialMixed;
    else if (aResult == nsRuleNode::eRuleFullReset)
      aResult = nsRuleNode::eRuleFullMixed;
  }

  return aResult;
}

static nsRuleNode::RuleDetail
CheckColorCallback(const nsRuleData* aRuleData,
                   nsRuleNode::RuleDetail aResult)
{
  // currentColor values for color require inheritance
  const nsCSSValue* colorValue = aRuleData->ValueForColor();
  if (colorValue->GetUnit() == eCSSUnit_EnumColor &&
      colorValue->GetIntValue() == NS_COLOR_CURRENTCOLOR) {
    NS_ASSERTION(aResult == nsRuleNode::eRuleFullReset,
                 "we should already be counted as full-reset");
    aResult = nsRuleNode::eRuleFullInherited;
  }

  return aResult;
}

static nsRuleNode::RuleDetail
CheckTextCallback(const nsRuleData* aRuleData,
                  nsRuleNode::RuleDetail aResult)
{
  const nsCSSValue* textAlignValue = aRuleData->ValueForTextAlign();
  if (textAlignValue->GetUnit() == eCSSUnit_Enumerated &&
      textAlignValue->GetIntValue() ==
        NS_STYLE_TEXT_ALIGN_MOZ_CENTER_OR_INHERIT) {
    // Promote reset to mixed since we have something that depends on
    // the parent.
    if (aResult == nsRuleNode::eRulePartialReset)
      aResult = nsRuleNode::eRulePartialMixed;
    else if (aResult == nsRuleNode::eRuleFullReset)
      aResult = nsRuleNode::eRuleFullMixed;
  }

  return aResult;
}

#define FLAG_DATA_FOR_PROPERTY(name_, id_, method_, flags_, pref_,          \
                               parsevariant_, kwtable_, stylestructoffset_, \
                               animtype_)                                   \
  flags_,

// The order here must match the enums in *CheckCounter in nsCSSProps.cpp.

static const uint32_t gFontFlags[] = {
#define CSS_PROP_FONT FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_FONT
};

static const uint32_t gDisplayFlags[] = {
#define CSS_PROP_DISPLAY FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_DISPLAY
};

static const uint32_t gVisibilityFlags[] = {
#define CSS_PROP_VISIBILITY FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_VISIBILITY
};

static const uint32_t gMarginFlags[] = {
#define CSS_PROP_MARGIN FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_MARGIN
};

static const uint32_t gBorderFlags[] = {
#define CSS_PROP_BORDER FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_BORDER
};

static const uint32_t gPaddingFlags[] = {
#define CSS_PROP_PADDING FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_PADDING
};

static const uint32_t gOutlineFlags[] = {
#define CSS_PROP_OUTLINE FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_OUTLINE
};

static const uint32_t gListFlags[] = {
#define CSS_PROP_LIST FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_LIST
};

static const uint32_t gColorFlags[] = {
#define CSS_PROP_COLOR FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_COLOR
};

static const uint32_t gBackgroundFlags[] = {
#define CSS_PROP_BACKGROUND FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_BACKGROUND
};

static const uint32_t gPositionFlags[] = {
#define CSS_PROP_POSITION FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_POSITION
};

static const uint32_t gTableFlags[] = {
#define CSS_PROP_TABLE FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_TABLE
};

static const uint32_t gTableBorderFlags[] = {
#define CSS_PROP_TABLEBORDER FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_TABLEBORDER
};

static const uint32_t gContentFlags[] = {
#define CSS_PROP_CONTENT FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_CONTENT
};

static const uint32_t gQuotesFlags[] = {
#define CSS_PROP_QUOTES FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_QUOTES
};

static const uint32_t gTextFlags[] = {
#define CSS_PROP_TEXT FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_TEXT
};

static const uint32_t gTextResetFlags[] = {
#define CSS_PROP_TEXTRESET FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_TEXTRESET
};

static const uint32_t gUserInterfaceFlags[] = {
#define CSS_PROP_USERINTERFACE FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_USERINTERFACE
};

static const uint32_t gUIResetFlags[] = {
#define CSS_PROP_UIRESET FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_UIRESET
};

static const uint32_t gXULFlags[] = {
#define CSS_PROP_XUL FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_XUL
};

static const uint32_t gSVGFlags[] = {
#define CSS_PROP_SVG FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_SVG
};

static const uint32_t gSVGResetFlags[] = {
#define CSS_PROP_SVGRESET FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_SVGRESET
};

static const uint32_t gColumnFlags[] = {
#define CSS_PROP_COLUMN FLAG_DATA_FOR_PROPERTY
#include "nsCSSPropList.h"
#undef CSS_PROP_COLUMN
};

#undef FLAG_DATA_FOR_PROPERTY

static const uint32_t* gFlagsByStruct[] = {

#define STYLE_STRUCT(name, checkdata_cb, ctor_args) \
  g##name##Flags,
#include "nsStyleStructList.h"
#undef STYLE_STRUCT

};

static const CheckCallbackFn gCheckCallbacks[] = {

#define STYLE_STRUCT(name, checkdata_cb, ctor_args) \
  checkdata_cb,
#include "nsStyleStructList.h"
#undef STYLE_STRUCT

};

#ifdef DEBUG
static bool
AreAllMathMLPropertiesUndefined(const nsRuleData* aRuleData)
{
  return
    aRuleData->ValueForScriptLevel()->GetUnit() == eCSSUnit_Null &&
    aRuleData->ValueForScriptSizeMultiplier()->GetUnit() == eCSSUnit_Null &&
    aRuleData->ValueForScriptMinSize()->GetUnit() == eCSSUnit_Null;
}
#endif

inline nsRuleNode::RuleDetail
nsRuleNode::CheckSpecifiedProperties(const nsStyleStructID aSID,
                                     const nsRuleData* aRuleData)
{
  // Build a count of the:
  uint32_t total = 0,      // total number of props in the struct
           specified = 0,  // number that were specified for this node
           inherited = 0;  // number that were 'inherit' (and not
                           //   eCSSUnit_Inherit) for this node

  // See comment in nsRuleData.h above mValueOffsets.
  NS_ABORT_IF_FALSE(aRuleData->mValueOffsets[aSID] == 0,
                    "we assume the value offset is zero instead of adding it");
  for (nsCSSValue *values = aRuleData->mValueStorage,
              *values_end = values + nsCSSProps::PropertyCountInStruct(aSID);
       values != values_end; ++values) {
    ++total;
    ExamineCSSValue(*values, specified, inherited);
  }

#if 0
  printf("CheckSpecifiedProperties: SID=%d total=%d spec=%d inh=%d.\n",
         aSID, total, specified, inherited);
#endif

  NS_ASSERTION(aSID != eStyleStruct_Font ||
               mPresContext->Document()->GetMathMLEnabled() ||
               AreAllMathMLPropertiesUndefined(aRuleData),
               "MathML style property was defined even though MathML is disabled");

  /*
   * Return the most specific information we can: prefer None or Full
   * over Partial, and Reset or Inherited over Mixed, since we can
   * optimize based on the edge cases and not the in-between cases.
   */
  nsRuleNode::RuleDetail result;
  if (inherited == total)
    result = eRuleFullInherited;
  else if (specified == total
           // MathML defines 3 properties in Font that will never be set when
           // MathML is not in use. Therefore if all but three
           // properties have been set, and MathML is not enabled, we can treat
           // this as fully specified. Code in nsMathMLElementFactory will
           // rebuild the rule tree and style data when MathML is first enabled
           // (see nsMathMLElement::BindToTree).
           || (aSID == eStyleStruct_Font && specified + 3 == total &&
               !mPresContext->Document()->GetMathMLEnabled())
          ) {
    if (inherited == 0)
      result = eRuleFullReset;
    else
      result = eRuleFullMixed;
  } else if (specified == 0)
    result = eRuleNone;
  else if (specified == inherited)
    result = eRulePartialInherited;
  else if (inherited == 0)
    result = eRulePartialReset;
  else
    result = eRulePartialMixed;

  CheckCallbackFn cb = gCheckCallbacks[aSID];
  if (cb) {
    result = (*cb)(aRuleData, result);
  }

  return result;
}

// If we need to restrict which properties apply to the style context,
// return the bit to check in nsCSSProp's flags table.  Otherwise,
// return 0.
inline uint32_t
GetPseudoRestriction(nsStyleContext *aContext)
{
  // This needs to match nsStyleSet::WalkRestrictionRule.
  uint32_t pseudoRestriction = 0;
  nsIAtom *pseudoType = aContext->GetPseudo();
  if (pseudoType) {
    if (pseudoType == nsCSSPseudoElements::firstLetter) {
      pseudoRestriction = CSS_PROPERTY_APPLIES_TO_FIRST_LETTER;
    } else if (pseudoType == nsCSSPseudoElements::firstLine) {
      pseudoRestriction = CSS_PROPERTY_APPLIES_TO_FIRST_LINE;
    }
  }
  return pseudoRestriction;
}

static void
UnsetPropertiesWithoutFlags(const nsStyleStructID aSID,
                            nsRuleData* aRuleData,
                            uint32_t aFlags)
{
  NS_ASSERTION(aFlags != 0, "aFlags must be nonzero");

  const uint32_t *flagData = gFlagsByStruct[aSID];

  // See comment in nsRuleData.h above mValueOffsets.
  NS_ABORT_IF_FALSE(aRuleData->mValueOffsets[aSID] == 0,
                    "we assume the value offset is zero instead of adding it");
  nsCSSValue *values = aRuleData->mValueStorage;

  for (size_t i = 0, i_end = nsCSSProps::PropertyCountInStruct(aSID);
       i != i_end; ++i) {
    if ((flagData[i] & aFlags) != aFlags)
      values[i].Reset();
  }
}

/**
 * We allocate arrays of CSS values with alloca.  (These arrays are a
 * fixed size per style struct, but we don't want to waste the
 * allocation and construction/destruction costs of the big structs when
 * we're handling much smaller ones.)  Since the lifetime of an alloca
 * allocation is the life of the calling function, the caller must call
 * alloca.  However, to ensure that constructors and destructors are
 * balanced, we do the constructor and destructor calling from this RAII
 * class, AutoCSSValueArray.
 */
struct AutoCSSValueArray {
  /**
   * aStorage must be the result of alloca(aCount * sizeof(nsCSSValue))
   */
  AutoCSSValueArray(void* aStorage, size_t aCount) {
    NS_ABORT_IF_FALSE(size_t(aStorage) % NS_ALIGNMENT_OF(nsCSSValue) == 0,
                      "bad alignment from alloca");
    mCount = aCount;
    // Don't use placement new[], since it might store extra data
    // for the count (on Windows!).
    mArray = static_cast<nsCSSValue*>(aStorage);
    for (size_t i = 0; i < mCount; ++i) {
      new (mArray + i) nsCSSValue();
    }
  }

  ~AutoCSSValueArray() {
    for (size_t i = 0; i < mCount; ++i) {
      mArray[i].~nsCSSValue();
    }
  }

  nsCSSValue* get() { return mArray; }

private:
  nsCSSValue *mArray;
  size_t mCount;
};

const void*
nsRuleNode::WalkRuleTree(const nsStyleStructID aSID,
                         nsStyleContext* aContext)
{
  // use placement new[] on the result of alloca() to allocate a
  // variable-sized stack array, including execution of constructors,
  // and use an RAII class to run the destructors too.
  size_t nprops = nsCSSProps::PropertyCountInStruct(aSID);
  void* dataStorage = alloca(nprops * sizeof(nsCSSValue));
  AutoCSSValueArray dataArray(dataStorage, nprops);

  nsRuleData ruleData(nsCachedStyleData::GetBitForSID(aSID),
                      dataArray.get(), mPresContext, aContext);
  ruleData.mValueOffsets[aSID] = 0;

  // We start at the most specific rule in the tree.
  void* startStruct = nullptr;

  nsRuleNode* ruleNode = this;
  nsRuleNode* highestNode = nullptr; // The highest node in the rule tree
                                    // that has the same properties
                                    // specified for struct |aSID| as
                                    // |this| does.
  nsRuleNode* rootNode = this; // After the loop below, this will be the
                               // highest node that we've walked without
                               // finding cached data on the rule tree.
                               // If we don't find any cached data, it
                               // will be the root.  (XXX misnamed)
  RuleDetail detail = eRuleNone;
  uint32_t bit = nsCachedStyleData::GetBitForSID(aSID);

  while (ruleNode) {
    // See if this rule node has cached the fact that the remaining
    // nodes along this path specify no data whatsoever.
    if (ruleNode->mNoneBits & bit)
      break;

    // If the dependent bit is set on a rule node for this struct, that
    // means its rule won't have any information to add, so skip it.
    while (ruleNode->mDependentBits & bit) {
      NS_ASSERTION(ruleNode->mStyleData.GetStyleData(aSID) == nullptr,
                   "dependent bit with cached data makes no sense");
      // Climb up to the next rule in the tree (a less specific rule).
      rootNode = ruleNode;
      ruleNode = ruleNode->mParent;
      NS_ASSERTION(!(ruleNode->mNoneBits & bit), "can't have both bits set");
    }

    // Check for cached data after the inner loop above -- otherwise
    // we'll miss it.
    startStruct = ruleNode->mStyleData.GetStyleData(aSID);
    if (startStruct)
      break; // We found a rule with fully specified data.  We don't
             // need to go up the tree any further, since the remainder
             // of this branch has already been computed.

    // Ask the rule to fill in the properties that it specifies.
    nsIStyleRule *rule = ruleNode->mRule;
    if (rule) {
      ruleData.mLevel = ruleNode->GetLevel();
      ruleData.mIsImportantRule = ruleNode->IsImportantRule();
      rule->MapRuleInfoInto(&ruleData);
    }

    // Now we check to see how many properties have been specified by
    // the rules we've examined so far.
    RuleDetail oldDetail = detail;
    detail = CheckSpecifiedProperties(aSID, &ruleData);

    if (oldDetail == eRuleNone && detail != eRuleNone)
      highestNode = ruleNode;

    if (detail == eRuleFullReset ||
        detail == eRuleFullMixed ||
        detail == eRuleFullInherited)
      break; // We don't need to examine any more rules.  All properties
             // have been fully specified.

    // Climb up to the next rule in the tree (a less specific rule).
    rootNode = ruleNode;
    ruleNode = ruleNode->mParent;
  }

  // If needed, unset the properties that don't have a flag that allows
  // them to be set for this style context.  (For example, only some
  // properties apply to :first-line and :first-letter.)
  uint32_t pseudoRestriction = GetPseudoRestriction(aContext);
  if (pseudoRestriction) {
    UnsetPropertiesWithoutFlags(aSID, &ruleData, pseudoRestriction);

    // Recompute |detail| based on the restrictions we just applied.
    // We can adjust |detail| arbitrarily because of the restriction
    // rule added in nsStyleSet::WalkRestrictionRule.
    detail = CheckSpecifiedProperties(aSID, &ruleData);
  }

  NS_ASSERTION(!startStruct || (detail != eRuleFullReset &&
                                detail != eRuleFullMixed &&
                                detail != eRuleFullInherited),
               "can't have start struct and be fully specified");

  bool isReset = nsCachedStyleData::IsReset(aSID);
  if (!highestNode)
    highestNode = rootNode;

  if (!ruleData.mCanStoreInRuleTree)
    detail = eRulePartialMixed; // Treat as though some data is specified to avoid
                                // the optimizations and force data computation.

  if (detail == eRuleNone && startStruct && !ruleData.mPostResolveCallback) {
    // We specified absolutely no rule information, but a parent rule in the tree
    // specified all the rule information.  We set a bit along the branch from our
    // node in the tree to the node that specified the data that tells nodes on that
    // branch that they never need to examine their rules for this particular struct type
    // ever again.
    PropagateDependentBit(bit, ruleNode);
    return startStruct;
  }
  // FIXME Do we need to check for mPostResolveCallback?
  if ((!startStruct && !isReset &&
       (detail == eRuleNone || detail == eRulePartialInherited)) ||
      detail == eRuleFullInherited) {
    // We specified no non-inherited information and neither did any of
    // our parent rules.

    // We set a bit along the branch from the highest node (ruleNode)
    // down to our node (this) indicating that no non-inherited data was
    // specified.  This bit is guaranteed to be set already on the path
    // from the highest node to the root node in the case where
    // (detail == eRuleNone), which is the most common case here.
    // We must check |!isReset| because the Compute*Data functions for
    // reset structs wouldn't handle none bits correctly.
    if (highestNode != this && !isReset)
      PropagateNoneBit(bit, highestNode);

    // All information must necessarily be inherited from our parent style context.
    // In the absence of any computed data in the rule tree and with
    // no rules specified that didn't have values of 'inherit', we should check our parent.
    nsStyleContext* parentContext = aContext->GetParent();
    if (isReset) {
      /* Reset structs don't inherit from first-line. */
      /* See similar code in COMPUTE_START_RESET */
      while (parentContext &&
             parentContext->GetPseudo() == nsCSSPseudoElements::firstLine) {
        parentContext = parentContext->GetParent();
      }
    }
    if (parentContext) {
      // We have a parent, and so we should just inherit from the parent.
      // Set the inherit bits on our context.  These bits tell the style context that
      // it never has to go back to the rule tree for data.  Instead the style context tree
      // should be walked to find the data.
      const void* parentStruct = parentContext->GetStyleData(aSID);
      aContext->AddStyleBit(bit); // makes const_cast OK.
      aContext->SetStyle(aSID, const_cast<void*>(parentStruct));
      return parentStruct;
    }
    else
      // We are the root.  In the case of fonts, the default values just
      // come from the pres context.
      return SetDefaultOnRoot(aSID, aContext);
  }

  // We need to compute the data from the information that the rules specified.
  const void* res;
#define STYLE_STRUCT_TEST aSID
#define STYLE_STRUCT(name, checkdata_cb, ctor_args)                           \
  res = Compute##name##Data(startStruct, &ruleData, aContext,                 \
                            highestNode, detail, ruleData.mCanStoreInRuleTree);
#include "nsStyleStructList.h"
#undef STYLE_STRUCT
#undef STYLE_STRUCT_TEST

  // If we have a post-resolve callback, handle that now.
  if (ruleData.mPostResolveCallback && (MOZ_LIKELY(res != nullptr)))
    (*ruleData.mPostResolveCallback)(const_cast<void*>(res), &ruleData);

  // Now return the result.
  return res;
}

const void*
nsRuleNode::SetDefaultOnRoot(const nsStyleStructID aSID, nsStyleContext* aContext)
{
  switch (aSID) {
    case eStyleStruct_Font:
    {
      nsStyleFont* fontData = new (mPresContext) nsStyleFont(mPresContext);
      if (MOZ_LIKELY(fontData != nullptr)) {
        nscoord minimumFontSize = mPresContext->MinFontSize(fontData->mLanguage);

        if (minimumFontSize > 0 && !mPresContext->IsChrome()) {
          fontData->mFont.size = NS_MAX(fontData->mSize, minimumFontSize);
        }
        else {
          fontData->mFont.size = fontData->mSize;
        }
        aContext->SetStyle(eStyleStruct_Font, fontData);
      }
      return fontData;
    }
    case eStyleStruct_Display:
    {
      nsStyleDisplay* disp = new (mPresContext) nsStyleDisplay();
      if (MOZ_LIKELY(disp != nullptr)) {
        aContext->SetStyle(eStyleStruct_Display, disp);
      }
      return disp;
    }
    case eStyleStruct_Visibility:
    {
      nsStyleVisibility* vis = new (mPresContext) nsStyleVisibility(mPresContext);
      if (MOZ_LIKELY(vis != nullptr)) {
        aContext->SetStyle(eStyleStruct_Visibility, vis);
      }
      return vis;
    }
    case eStyleStruct_Text:
    {
      nsStyleText* text = new (mPresContext) nsStyleText();
      if (MOZ_LIKELY(text != nullptr)) {
        aContext->SetStyle(eStyleStruct_Text, text);
      }
      return text;
    }
    case eStyleStruct_TextReset:
    {
      nsStyleTextReset* text = new (mPresContext) nsStyleTextReset();
      if (MOZ_LIKELY(text != nullptr)) {
        aContext->SetStyle(eStyleStruct_TextReset, text);
      }
      return text;
    }
    case eStyleStruct_Color:
    {
      nsStyleColor* color = new (mPresContext) nsStyleColor(mPresContext);
      if (MOZ_LIKELY(color != nullptr)) {
        aContext->SetStyle(eStyleStruct_Color, color);
      }
      return color;
    }
    case eStyleStruct_Background:
    {
      nsStyleBackground* bg = new (mPresContext) nsStyleBackground();
      if (MOZ_LIKELY(bg != nullptr)) {
        aContext->SetStyle(eStyleStruct_Background, bg);
      }
      return bg;
    }
    case eStyleStruct_Margin:
    {
      nsStyleMargin* margin = new (mPresContext) nsStyleMargin();
      if (MOZ_LIKELY(margin != nullptr)) {
        aContext->SetStyle(eStyleStruct_Margin, margin);
      }
      return margin;
    }
    case eStyleStruct_Border:
    {
      nsStyleBorder* border = new (mPresContext) nsStyleBorder(mPresContext);
      if (MOZ_LIKELY(border != nullptr)) {
        aContext->SetStyle(eStyleStruct_Border, border);
      }
      return border;
    }
    case eStyleStruct_Padding:
    {
      nsStylePadding* padding = new (mPresContext) nsStylePadding();
      if (MOZ_LIKELY(padding != nullptr)) {
        aContext->SetStyle(eStyleStruct_Padding, padding);
      }
      return padding;
    }
    case eStyleStruct_Outline:
    {
      nsStyleOutline* outline = new (mPresContext) nsStyleOutline(mPresContext);
      if (MOZ_LIKELY(outline != nullptr)) {
        aContext->SetStyle(eStyleStruct_Outline, outline);
      }
      return outline;
    }
    case eStyleStruct_List:
    {
      nsStyleList* list = new (mPresContext) nsStyleList();
      if (MOZ_LIKELY(list != nullptr)) {
        aContext->SetStyle(eStyleStruct_List, list);
      }
      return list;
    }
    case eStyleStruct_Position:
    {
      nsStylePosition* pos = new (mPresContext) nsStylePosition();
      if (MOZ_LIKELY(pos != nullptr)) {
        aContext->SetStyle(eStyleStruct_Position, pos);
      }
      return pos;
    }
    case eStyleStruct_Table:
    {
      nsStyleTable* table = new (mPresContext) nsStyleTable();
      if (MOZ_LIKELY(table != nullptr)) {
        aContext->SetStyle(eStyleStruct_Table, table);
      }
      return table;
    }
    case eStyleStruct_TableBorder:
    {
      nsStyleTableBorder* table = new (mPresContext) nsStyleTableBorder(mPresContext);
      if (MOZ_LIKELY(table != nullptr)) {
        aContext->SetStyle(eStyleStruct_TableBorder, table);
      }
      return table;
    }
    case eStyleStruct_Content:
    {
      nsStyleContent* content = new (mPresContext) nsStyleContent();
      if (MOZ_LIKELY(content != nullptr)) {
        aContext->SetStyle(eStyleStruct_Content, content);
      }
      return content;
    }
    case eStyleStruct_Quotes:
    {
      nsStyleQuotes* quotes = new (mPresContext) nsStyleQuotes();
      if (MOZ_LIKELY(quotes != nullptr)) {
        aContext->SetStyle(eStyleStruct_Quotes, quotes);
      }
      return quotes;
    }
    case eStyleStruct_UserInterface:
    {
      nsStyleUserInterface* ui = new (mPresContext) nsStyleUserInterface();
      if (MOZ_LIKELY(ui != nullptr)) {
        aContext->SetStyle(eStyleStruct_UserInterface, ui);
      }
      return ui;
    }
    case eStyleStruct_UIReset:
    {
      nsStyleUIReset* ui = new (mPresContext) nsStyleUIReset();
      if (MOZ_LIKELY(ui != nullptr)) {
        aContext->SetStyle(eStyleStruct_UIReset, ui);
      }
      return ui;
    }

    case eStyleStruct_XUL:
    {
      nsStyleXUL* xul = new (mPresContext) nsStyleXUL();
      if (MOZ_LIKELY(xul != nullptr)) {
        aContext->SetStyle(eStyleStruct_XUL, xul);
      }
      return xul;
    }

    case eStyleStruct_Column:
    {
      nsStyleColumn* column = new (mPresContext) nsStyleColumn(mPresContext);
      if (MOZ_LIKELY(column != nullptr)) {
        aContext->SetStyle(eStyleStruct_Column, column);
      }
      return column;
    }

    case eStyleStruct_SVG:
    {
      nsStyleSVG* svg = new (mPresContext) nsStyleSVG();
      if (MOZ_LIKELY(svg != nullptr)) {
        aContext->SetStyle(eStyleStruct_SVG, svg);
      }
      return svg;
    }

    case eStyleStruct_SVGReset:
    {
      nsStyleSVGReset* svgReset = new (mPresContext) nsStyleSVGReset();
      if (MOZ_LIKELY(svgReset != nullptr)) {
        aContext->SetStyle(eStyleStruct_SVGReset, svgReset);
      }
      return svgReset;
    }
    default:
      /*
       * unhandled case: nsStyleStructID_Length.
       * last item of nsStyleStructID, to know its length.
       */
      return nullptr;
  }
  return nullptr;
}

/*
 * This function handles cascading of *-left or *-right box properties
 * against *-start (which is L for LTR and R for RTL) or *-end (which is
 * R for LTR and L for RTL).
 *
 * Cascading these properties correctly is hard because we need to
 * cascade two properties as one, but which two properties depends on a
 * third property ('direction').  We solve this by treating each of
 * these properties (say, 'margin-start') as a shorthand that sets a
 * property containing the value of the property specified
 * ('margin-start-value') and sets a pair of properties
 * ('margin-left-ltr-source' and 'margin-right-rtl-source') saying which
 * of the properties we use.  Thus, when we want to compute the value of
 * 'margin-left' when 'direction' is 'ltr', we look at the value of
 * 'margin-left-ltr-source', which tells us whether to use the highest
 * 'margin-left' in the cascade or the highest 'margin-start'.
 *
 * Finally, since we can compute the normal (*-left and *-right)
 * properties in a loop, this function works by modifying the data we
 * will use in that loop (which the caller must copy from the const
 * input).
 */
void
nsRuleNode::AdjustLogicalBoxProp(nsStyleContext* aContext,
                                 const nsCSSValue& aLTRSource,
                                 const nsCSSValue& aRTLSource,
                                 const nsCSSValue& aLTRLogicalValue,
                                 const nsCSSValue& aRTLLogicalValue,
                                 mozilla::css::Side aSide,
                                 nsCSSRect& aValueRect,
                                 bool& aCanStoreInRuleTree)
{
  bool LTRlogical = aLTRSource.GetUnit() == eCSSUnit_Enumerated &&
                      aLTRSource.GetIntValue() == NS_BOXPROP_SOURCE_LOGICAL;
  bool RTLlogical = aRTLSource.GetUnit() == eCSSUnit_Enumerated &&
                      aRTLSource.GetIntValue() == NS_BOXPROP_SOURCE_LOGICAL;
  if (LTRlogical || RTLlogical) {
    // We can't cache anything on the rule tree if we use any data from
    // the style context, since data cached in the rule tree could be
    // used with a style context with a different value.
    aCanStoreInRuleTree = false;
    uint8_t dir = aContext->GetStyleVisibility()->mDirection;

    if (dir == NS_STYLE_DIRECTION_LTR) {
      if (LTRlogical)
        aValueRect.*(nsCSSRect::sides[aSide]) = aLTRLogicalValue;
    } else {
      if (RTLlogical)
        aValueRect.*(nsCSSRect::sides[aSide]) = aRTLLogicalValue;
    }
  } else if (aLTRLogicalValue.GetUnit() == eCSSUnit_Inherit ||
             aRTLLogicalValue.GetUnit() == eCSSUnit_Inherit) {
    // It actually is valid to store this in the ruletree, since
    // LTRlogical and RTLlogical are both false, but doing that will
    // trigger asserts.  Silence those.
    aCanStoreInRuleTree = false;
  }
}

/**
 * Begin an nsRuleNode::Compute*Data function for an inherited struct.
 *
 * @param type_ The nsStyle* type this function computes.
 * @param ctorargs_ The arguments used for the default nsStyle* constructor.
 * @param data_ Variable (declared here) holding the result of this
 *              function.
 * @param parentdata_ Variable (declared here) holding the parent style
 *                    context's data for this struct.
 */
#define COMPUTE_START_INHERITED(type_, ctorargs_, data_, parentdata_)         \
  NS_ASSERTION(aRuleDetail != eRuleFullInherited,                             \
               "should not have bothered calling Compute*Data");              \
                                                                              \
  nsStyleContext* parentContext = aContext->GetParent();                      \
                                                                              \
  nsStyle##type_* data_ = nullptr;                                             \
  const nsStyle##type_* parentdata_ = nullptr;                                 \
  bool canStoreInRuleTree = aCanStoreInRuleTree;                            \
                                                                              \
  /* If |canStoreInRuleTree| might be true by the time we're done, we */      \
  /* can't call parentContext->GetStyle##type_() since it could recur into */ \
  /* setting the same struct on the same rule node, causing a leak. */        \
  if (parentContext && aRuleDetail != eRuleFullReset &&                       \
      (!aStartStruct || (aRuleDetail != eRulePartialReset &&                  \
                         aRuleDetail != eRuleNone)))                          \
    parentdata_ = parentContext->GetStyle##type_();                           \
  if (aStartStruct)                                                           \
    /* We only need to compute the delta between this computed data and */    \
    /* our computed data. */                                                  \
    data_ = new (mPresContext)                                                \
            nsStyle##type_(*static_cast<nsStyle##type_*>(aStartStruct));      \
  else {                                                                      \
    if (aRuleDetail != eRuleFullMixed && aRuleDetail != eRuleFullReset) {     \
      /* No question. We will have to inherit. Go ahead and init */           \
      /* with inherited vals from parent. */                                  \
      canStoreInRuleTree = false;                                          \
      if (parentdata_)                                                        \
        data_ = new (mPresContext) nsStyle##type_(*parentdata_);              \
      else                                                                    \
        data_ = new (mPresContext) nsStyle##type_ ctorargs_;                  \
    }                                                                         \
    else                                                                      \
      data_ = new (mPresContext) nsStyle##type_ ctorargs_;                    \
  }                                                                           \
                                                                              \
  if (MOZ_UNLIKELY(!data_))                                                   \
    return nullptr;  /* Out Of Memory */                                      \
  if (!parentdata_)                                                           \
    parentdata_ = data_;

/**
 * Begin an nsRuleNode::Compute*Data function for a reset struct.
 *
 * @param type_ The nsStyle* type this function computes.
 * @param ctorargs_ The arguments used for the default nsStyle* constructor.
 * @param data_ Variable (declared here) holding the result of this
 *              function.
 * @param parentdata_ Variable (declared here) holding the parent style
 *                    context's data for this struct.
 */
#define COMPUTE_START_RESET(type_, ctorargs_, data_, parentdata_)             \
  NS_ASSERTION(aRuleDetail != eRuleFullInherited,                             \
               "should not have bothered calling Compute*Data");              \
                                                                              \
  nsStyleContext* parentContext = aContext->GetParent();                      \
  /* Reset structs don't inherit from first-line */                           \
  /* See similar code in WalkRuleTree */                                      \
  while (parentContext &&                                                     \
         parentContext->GetPseudo() == nsCSSPseudoElements::firstLine) {      \
    parentContext = parentContext->GetParent();                               \
  }                                                                           \
                                                                              \
  nsStyle##type_* data_;                                                      \
  if (aStartStruct)                                                           \
    /* We only need to compute the delta between this computed data and */    \
    /* our computed data. */                                                  \
    data_ = new (mPresContext)                                                \
            nsStyle##type_(*static_cast<nsStyle##type_*>(aStartStruct));      \
  else                                                                        \
    data_ = new (mPresContext) nsStyle##type_ ctorargs_;                      \
                                                                              \
  if (MOZ_UNLIKELY(!data_))                                                   \
    return nullptr;  /* Out Of Memory */                                      \
                                                                              \
  /* If |canStoreInRuleTree| might be true by the time we're done, we */      \
  /* can't call parentContext->GetStyle##type_() since it could recur into */ \
  /* setting the same struct on the same rule node, causing a leak. */        \
  const nsStyle##type_* parentdata_ = data_;                                  \
  if (parentContext &&                                                        \
      aRuleDetail != eRuleFullReset &&                                        \
      aRuleDetail != eRulePartialReset &&                                     \
      aRuleDetail != eRuleNone)                                               \
    parentdata_ = parentContext->GetStyle##type_();                           \
  bool canStoreInRuleTree = aCanStoreInRuleTree;

/**
 * Begin an nsRuleNode::Compute*Data function for an inherited struct.
 *
 * @param type_ The nsStyle* type this function computes.
 * @param data_ Variable holding the result of this function.
 */
#define COMPUTE_END_INHERITED(type_, data_)                                   \
  NS_POSTCONDITION(!canStoreInRuleTree || aRuleDetail == eRuleFullReset ||    \
                   (aStartStruct && aRuleDetail == eRulePartialReset),        \
                   "canStoreInRuleTree must be false for inherited structs "  \
                   "unless all properties have been specified with values "   \
                   "other than inherit");                                     \
  if (canStoreInRuleTree) {                                                   \
    /* We were fully specified and can therefore be cached right on the */    \
    /* rule node. */                                                          \
    if (!aHighestNode->mStyleData.mInheritedData) {                           \
      aHighestNode->mStyleData.mInheritedData =                               \
        new (mPresContext) nsInheritedStyleData;                              \
      if (MOZ_UNLIKELY(!aHighestNode->mStyleData.mInheritedData)) {           \
        data_->Destroy(mPresContext);                                         \
        return nullptr;                                                       \
      }                                                                       \
    }                                                                         \
    NS_ASSERTION(!aHighestNode->mStyleData.mInheritedData->                   \
                   mStyleStructs[eStyleStruct_##type_],                       \
                 "Going to leak style data");                                 \
    aHighestNode->mStyleData.mInheritedData->                                 \
      mStyleStructs[eStyleStruct_##type_] = data_;                            \
    /* Propagate the bit down. */                                             \
    PropagateDependentBit(NS_STYLE_INHERIT_BIT(type_), aHighestNode);         \
    /* Tell the style context that it doesn't own the data */                 \
    aContext->                                                                \
      AddStyleBit(nsCachedStyleData::GetBitForSID(eStyleStruct_##type_));     \
  }                                                                           \
  /* Always cache inherited data on the style context */                      \
  aContext->SetStyle##type_(data_);                                           \
                                                                              \
  return data_;

/**
 * Begin an nsRuleNode::Compute*Data function for a reset struct.
 *
 * @param type_ The nsStyle* type this function computes.
 * @param data_ Variable holding the result of this function.
 */
#define COMPUTE_END_RESET(type_, data_)                                       \
  NS_POSTCONDITION(!canStoreInRuleTree ||                                     \
                   aRuleDetail == eRuleNone ||                                \
                   aRuleDetail == eRulePartialReset ||                        \
                   aRuleDetail == eRuleFullReset,                             \
                   "canStoreInRuleTree must be false for reset structs "      \
                   "if any properties were specified as inherit");            \
  if (!canStoreInRuleTree)                                                    \
    /* We can't be cached in the rule node.  We have to be put right */       \
    /* on the style context. */                                               \
    aContext->SetStyle(eStyleStruct_##type_, data_);                          \
  else {                                                                      \
    /* We were fully specified and can therefore be cached right on the */    \
    /* rule node. */                                                          \
    if (!aHighestNode->mStyleData.mResetData) {                               \
      aHighestNode->mStyleData.mResetData =                                   \
        new (mPresContext) nsResetStyleData;                                  \
      if (MOZ_UNLIKELY(!aHighestNode->mStyleData.mResetData)) {               \
        data_->Destroy(mPresContext);                                         \
        return nullptr;                                                       \
      }                                                                       \
    }                                                                         \
    NS_ASSERTION(!aHighestNode->mStyleData.mResetData->                       \
                   mStyleStructs[eStyleStruct_##type_],                       \
                 "Going to leak style data");                                 \
    aHighestNode->mStyleData.mResetData->                                     \
      mStyleStructs[eStyleStruct_##type_] = data_;                            \
    /* Propagate the bit down. */                                             \
    PropagateDependentBit(NS_STYLE_INHERIT_BIT(type_), aHighestNode);         \
  }                                                                           \
                                                                              \
  return data_;

// This function figures out how much scaling should be suppressed to
// satisfy scriptminsize. This is our attempt to implement
// http://www.w3.org/TR/MathML2/chapter3.html#id.3.3.4.2.2
// This is called after mScriptLevel, mScriptMinSize and mScriptSizeMultiplier
// have been set in aFont.
//
// Here are the invariants we enforce:
// 1) A decrease in size must not reduce the size below minscriptsize.
// 2) An increase in size must not increase the size above the size we would
// have if minscriptsize had not been applied anywhere.
// 3) The scriptlevel-induced size change must between 1.0 and the parent's
// scriptsizemultiplier^(new script level - old script level), as close to the
// latter as possible subject to constraints 1 and 2.
static nscoord
ComputeScriptLevelSize(const nsStyleFont* aFont, const nsStyleFont* aParentFont,
                       nsPresContext* aPresContext, nscoord* aUnconstrainedSize)
{
  int32_t scriptLevelChange =
    aFont->mScriptLevel - aParentFont->mScriptLevel;
  if (scriptLevelChange == 0) {
    *aUnconstrainedSize = aParentFont->mScriptUnconstrainedSize;
    // Constraint #3 says that we cannot change size, and #1 and #2 are always
    // satisfied with no change. It's important this be fast because it covers
    // all non-MathML content.
    return aParentFont->mSize;
  }

  // Compute actual value of minScriptSize
  nscoord minScriptSize =
    nsStyleFont::ZoomText(aPresContext, aParentFont->mScriptMinSize);

  double scriptLevelScale =
    pow(aParentFont->mScriptSizeMultiplier, scriptLevelChange);
  // Compute the size we would have had if minscriptsize had never been
  // applied, also prevent overflow (bug 413274)
  *aUnconstrainedSize =
    NSToCoordRound(NS_MIN(aParentFont->mScriptUnconstrainedSize*scriptLevelScale,
                          double(nscoord_MAX)));
  // Compute the size we could get via scriptlevel change
  nscoord scriptLevelSize =
    NSToCoordRound(NS_MIN(aParentFont->mSize*scriptLevelScale,
                          double(nscoord_MAX)));
  if (scriptLevelScale <= 1.0) {
    if (aParentFont->mSize <= minScriptSize) {
      // We can't decrease the font size at all, so just stick to no change
      // (authors are allowed to explicitly set the font size smaller than
      // minscriptsize)
      return aParentFont->mSize;
    }
    // We can decrease, so apply constraint #1
    return NS_MAX(minScriptSize, scriptLevelSize);
  } else {
    // scriptminsize can only make sizes larger than the unconstrained size
    NS_ASSERTION(*aUnconstrainedSize <= scriptLevelSize, "How can this ever happen?");
    // Apply constraint #2
    return NS_MIN(scriptLevelSize, NS_MAX(*aUnconstrainedSize, minScriptSize));
  }
}


/* static */ nscoord
nsRuleNode::CalcFontPointSize(int32_t aHTMLSize, int32_t aBasePointSize,
                              nsPresContext* aPresContext,
                              nsFontSizeType aFontSizeType)
{
#define sFontSizeTableMin  9 
#define sFontSizeTableMax 16 

// This table seems to be the one used by MacIE5. We hope its adoption in Mozilla
// and eventually in WinIE5.5 will help to establish a standard rendering across
// platforms and browsers. For now, it is used only in Strict mode. More can be read
// in the document written by Todd Farhner at:
// http://style.verso.com/font_size_intervals/altintervals.html
//
  static int32_t sStrictFontSizeTable[sFontSizeTableMax - sFontSizeTableMin + 1][8] =
  {
      { 9,    9,     9,     9,    11,    14,    18,    27},
      { 9,    9,     9,    10,    12,    15,    20,    30},
      { 9,    9,    10,    11,    13,    17,    22,    33},
      { 9,    9,    10,    12,    14,    18,    24,    36},
      { 9,   10,    12,    13,    16,    20,    26,    39},
      { 9,   10,    12,    14,    17,    21,    28,    42},
      { 9,   10,    13,    15,    18,    23,    30,    45},
      { 9,   10,    13,    16,    18,    24,    32,    48}
  };
// HTML       1      2      3      4      5      6      7
// CSS  xxs   xs     s      m      l     xl     xxl
//                          |
//                      user pref
//
//------------------------------------------------------------
//
// This table gives us compatibility with WinNav4 for the default fonts only.
// In WinNav4, the default fonts were:
//
//     Times/12pt ==   Times/16px at 96ppi
//   Courier/10pt == Courier/13px at 96ppi
//
// The 2 lines below marked "anchored" have the exact pixel sizes used by
// WinNav4 for Times/12pt and Courier/10pt at 96ppi. As you can see, the
// HTML size 3 (user pref) for those 2 anchored lines is 13px and 16px.
//
// All values other than the anchored values were filled in by hand, never
// going below 9px, and maintaining a "diagonal" relationship. See for
// example the 13s -- they follow a diagonal line through the table.
//
  static int32_t sQuirksFontSizeTable[sFontSizeTableMax - sFontSizeTableMin + 1][8] =
  {
      { 9,    9,     9,     9,    11,    14,    18,    28 },
      { 9,    9,     9,    10,    12,    15,    20,    31 },
      { 9,    9,     9,    11,    13,    17,    22,    34 },
      { 9,    9,    10,    12,    14,    18,    24,    37 },
      { 9,    9,    10,    13,    16,    20,    26,    40 }, // anchored (13)
      { 9,    9,    11,    14,    17,    21,    28,    42 },
      { 9,   10,    12,    15,    17,    23,    30,    45 },
      { 9,   10,    13,    16,    18,    24,    32,    48 }  // anchored (16)
  };
// HTML       1      2      3      4      5      6      7
// CSS  xxs   xs     s      m      l     xl     xxl
//                          |
//                      user pref

#if 0
//
// These are the exact pixel values used by WinIE5 at 96ppi.
//
      { ?,    8,    11,    12,    13,    16,    21,    32 }, // smallest
      { ?,    9,    12,    13,    16,    21,    27,    40 }, // smaller
      { ?,   10,    13,    16,    18,    24,    32,    48 }, // medium
      { ?,   13,    16,    19,    21,    27,    37,    ?? }, // larger
      { ?,   16,    19,    21,    24,    32,    43,    ?? }  // largest
//
// HTML       1      2      3      4      5      6      7
// CSS  ?     ?      ?      ?      ?      ?      ?      ?
//
// (CSS not tested yet.)
//
#endif

  static int32_t sFontSizeFactors[8] = { 60,75,89,100,120,150,200,300 };

  static int32_t sCSSColumns[7]  = {0, 1, 2, 3, 4, 5, 6}; // xxs...xxl
  static int32_t sHTMLColumns[7] = {1, 2, 3, 4, 5, 6, 7}; // 1...7

  double dFontSize;

  if (aFontSizeType == eFontSize_HTML) {
    aHTMLSize--;    // input as 1-7
  }

  if (aHTMLSize < 0)
    aHTMLSize = 0;
  else if (aHTMLSize > 6)
    aHTMLSize = 6;

  int32_t* column;
  switch (aFontSizeType)
  {
    case eFontSize_HTML: column = sHTMLColumns; break;
    case eFontSize_CSS:  column = sCSSColumns;  break;
  }

  // Make special call specifically for fonts (needed PrintPreview)
  int32_t fontSize = nsPresContext::AppUnitsToIntCSSPixels(aBasePointSize);

  if ((fontSize >= sFontSizeTableMin) && (fontSize <= sFontSizeTableMax))
  {
    int32_t row = fontSize - sFontSizeTableMin;

    if (aPresContext->CompatibilityMode() == eCompatibility_NavQuirks) {
      dFontSize = nsPresContext::CSSPixelsToAppUnits(sQuirksFontSizeTable[row][column[aHTMLSize]]);
    } else {
      dFontSize = nsPresContext::CSSPixelsToAppUnits(sStrictFontSizeTable[row][column[aHTMLSize]]);
    }
  }
  else
  {
    int32_t factor = sFontSizeFactors[column[aHTMLSize]];
    dFontSize = (factor * aBasePointSize) / 100;
  }


  if (1.0 < dFontSize) {
    return (nscoord)dFontSize;
  }
  return (nscoord)1;
}


//------------------------------------------------------------------------------
//
//------------------------------------------------------------------------------

/* static */ nscoord
nsRuleNode::FindNextSmallerFontSize(nscoord aFontSize, int32_t aBasePointSize, 
                                    nsPresContext* aPresContext,
                                    nsFontSizeType aFontSizeType)
{
  int32_t index;
  int32_t indexMin;
  int32_t indexMax;
  float relativePosition;
  nscoord smallerSize;
  nscoord indexFontSize = aFontSize; // XXX initialize to quell a spurious gcc3.2 warning
  nscoord smallestIndexFontSize;
  nscoord largestIndexFontSize;
  nscoord smallerIndexFontSize;
  nscoord largerIndexFontSize;

  nscoord onePx = nsPresContext::CSSPixelsToAppUnits(1);

  if (aFontSizeType == eFontSize_HTML) {
    indexMin = 1;
    indexMax = 7;
  } else {
    indexMin = 0;
    indexMax = 6;
  }
  
  smallestIndexFontSize = CalcFontPointSize(indexMin, aBasePointSize, aPresContext, aFontSizeType);
  largestIndexFontSize = CalcFontPointSize(indexMax, aBasePointSize, aPresContext, aFontSizeType); 
  if (aFontSize > smallestIndexFontSize) {
    if (aFontSize < NSToCoordRound(float(largestIndexFontSize) * 1.5)) { // smaller will be in HTML table
      // find largest index smaller than current
      for (index = indexMax; index >= indexMin; index--) {
        indexFontSize = CalcFontPointSize(index, aBasePointSize, aPresContext, aFontSizeType);
        if (indexFontSize < aFontSize)
          break;
      } 
      // set up points beyond table for interpolation purposes
      if (indexFontSize == smallestIndexFontSize) {
        smallerIndexFontSize = indexFontSize - onePx;
        largerIndexFontSize = CalcFontPointSize(index+1, aBasePointSize, aPresContext, aFontSizeType);
      } else if (indexFontSize == largestIndexFontSize) {
        smallerIndexFontSize = CalcFontPointSize(index-1, aBasePointSize, aPresContext, aFontSizeType);
        largerIndexFontSize = NSToCoordRound(float(largestIndexFontSize) * 1.5);
      } else {
        smallerIndexFontSize = CalcFontPointSize(index-1, aBasePointSize, aPresContext, aFontSizeType);
        largerIndexFontSize = CalcFontPointSize(index+1, aBasePointSize, aPresContext, aFontSizeType);
      }
      // compute the relative position of the parent size between the two closest indexed sizes
      relativePosition = float(aFontSize - indexFontSize) / float(largerIndexFontSize - indexFontSize);            
      // set the new size to have the same relative position between the next smallest two indexed sizes
      smallerSize = smallerIndexFontSize + NSToCoordRound(relativePosition * (indexFontSize - smallerIndexFontSize));      
    }
    else {  // larger than HTML table, drop by 33%
      smallerSize = NSToCoordRound(float(aFontSize) / 1.5);
    }
  }
  else { // smaller than HTML table, drop by 1px
    smallerSize = NS_MAX(aFontSize - onePx, onePx);
  }
  return smallerSize;
}

//------------------------------------------------------------------------------
//
//------------------------------------------------------------------------------

/* static */ nscoord
nsRuleNode::FindNextLargerFontSize(nscoord aFontSize, int32_t aBasePointSize, 
                                   nsPresContext* aPresContext,
                                   nsFontSizeType aFontSizeType)
{
  int32_t index;
  int32_t indexMin;
  int32_t indexMax;
  float relativePosition;
  nscoord adjustment;
  nscoord largerSize;
  nscoord indexFontSize = aFontSize; // XXX initialize to quell a spurious gcc3.2 warning
  nscoord smallestIndexFontSize;
  nscoord largestIndexFontSize;
  nscoord smallerIndexFontSize;
  nscoord largerIndexFontSize;

  nscoord onePx = nsPresContext::CSSPixelsToAppUnits(1);

  if (aFontSizeType == eFontSize_HTML) {
    indexMin = 1;
    indexMax = 7;
  } else {
    indexMin = 0;
    indexMax = 6;
  }
  
  smallestIndexFontSize = CalcFontPointSize(indexMin, aBasePointSize, aPresContext, aFontSizeType);
  largestIndexFontSize = CalcFontPointSize(indexMax, aBasePointSize, aPresContext, aFontSizeType); 
  if (aFontSize > (smallestIndexFontSize - onePx)) {
    if (aFontSize < largestIndexFontSize) { // larger will be in HTML table
      // find smallest index larger than current
      for (index = indexMin; index <= indexMax; index++) { 
        indexFontSize = CalcFontPointSize(index, aBasePointSize, aPresContext, aFontSizeType);
        if (indexFontSize > aFontSize)
          break;
      }
      // set up points beyond table for interpolation purposes
      if (indexFontSize == smallestIndexFontSize) {
        smallerIndexFontSize = indexFontSize - onePx;
        largerIndexFontSize = CalcFontPointSize(index+1, aBasePointSize, aPresContext, aFontSizeType);
      } else if (indexFontSize == largestIndexFontSize) {
        smallerIndexFontSize = CalcFontPointSize(index-1, aBasePointSize, aPresContext, aFontSizeType);
        largerIndexFontSize = NSCoordSaturatingMultiply(largestIndexFontSize, 1.5);
      } else {
        smallerIndexFontSize = CalcFontPointSize(index-1, aBasePointSize, aPresContext, aFontSizeType);
        largerIndexFontSize = CalcFontPointSize(index+1, aBasePointSize, aPresContext, aFontSizeType);
      }
      // compute the relative position of the parent size between the two closest indexed sizes
      relativePosition = float(aFontSize - smallerIndexFontSize) / float(indexFontSize - smallerIndexFontSize);
      // set the new size to have the same relative position between the next largest two indexed sizes
      adjustment = NSCoordSaturatingNonnegativeMultiply(largerIndexFontSize - indexFontSize, relativePosition);
      largerSize = NSCoordSaturatingAdd(indexFontSize, adjustment);
    }
    else {  // larger than HTML table, increase by 50%
      largerSize = NSCoordSaturatingMultiply(aFontSize, 1.5);
    }
  }
  else { // smaller than HTML table, increase by 1px
    largerSize = NSCoordSaturatingAdd(aFontSize, onePx);
  }
  return largerSize;
}

struct SetFontSizeCalcOps : public css::BasicCoordCalcOps,
                            public css::NumbersAlreadyNormalizedOps
{
  // The parameters beyond aValue that we need for CalcLengthWith.
  const nscoord mParentSize;
  const nsStyleFont* const mParentFont;
  nsPresContext* const mPresContext;
  const bool mAtRoot;
  bool& mCanStoreInRuleTree;

  SetFontSizeCalcOps(nscoord aParentSize, const nsStyleFont* aParentFont,
                     nsPresContext* aPresContext, bool aAtRoot,
                     bool& aCanStoreInRuleTree)
    : mParentSize(aParentSize),
      mParentFont(aParentFont),
      mPresContext(aPresContext),
      mAtRoot(aAtRoot),
      mCanStoreInRuleTree(aCanStoreInRuleTree)
  {
  }

  result_type ComputeLeafValue(const nsCSSValue& aValue)
  {
    nscoord size;
    if (aValue.IsLengthUnit()) {
      // Note that font-based length units use the parent's size
      // unadjusted for scriptlevel changes. A scriptlevel change
      // between us and the parent is simply ignored.
      size = CalcLengthWith(aValue, mParentSize,
                            mParentFont,
                            nullptr, mPresContext, mAtRoot,
                            true, mCanStoreInRuleTree);
      if (!aValue.IsRelativeLengthUnit()) {
        size = nsStyleFont::ZoomText(mPresContext, size);
      }
    }
    else if (eCSSUnit_Percent == aValue.GetUnit()) {
      mCanStoreInRuleTree = false;
      // Note that % units use the parent's size unadjusted for scriptlevel
      // changes. A scriptlevel change between us and the parent is simply
      // ignored.
      // aValue.GetPercentValue() may be negative for, e.g., calc(-50%)
      size = NSCoordSaturatingMultiply(mParentSize, aValue.GetPercentValue());
    } else {
      NS_ABORT_IF_FALSE(false, "unexpected value");
      size = mParentSize;
    }

    return size;
  }
};

/* static */ void
nsRuleNode::SetFontSize(nsPresContext* aPresContext,
                        const nsRuleData* aRuleData,
                        const nsStyleFont* aFont,
                        const nsStyleFont* aParentFont,
                        nscoord* aSize,
                        const nsFont& aSystemFont,
                        nscoord aParentSize,
                        nscoord aScriptLevelAdjustedParentSize,
                        bool aUsedStartStruct,
                        bool aAtRoot,
                        bool& aCanStoreInRuleTree)
{
  bool zoom = false;
  int32_t baseSize = (int32_t) aPresContext->
    GetDefaultFont(aFont->mGenericID, aFont->mLanguage)->size;
  const nsCSSValue* sizeValue = aRuleData->ValueForFontSize();
  if (eCSSUnit_Enumerated == sizeValue->GetUnit()) {
    int32_t value = sizeValue->GetIntValue();

    zoom = true;
    if ((NS_STYLE_FONT_SIZE_XXSMALL <= value) &&
        (value <= NS_STYLE_FONT_SIZE_XXLARGE)) {
      *aSize = CalcFontPointSize(value, baseSize,
                       aPresContext, eFontSize_CSS);
    }
    else if (NS_STYLE_FONT_SIZE_XXXLARGE == value) {
      // <font size="7"> is not specified in CSS, so we don't use eFontSize_CSS.
      *aSize = CalcFontPointSize(value, baseSize, aPresContext);
    }
    else if (NS_STYLE_FONT_SIZE_LARGER  == value ||
             NS_STYLE_FONT_SIZE_SMALLER == value) {
      aCanStoreInRuleTree = false;

      // Un-zoom so we use the tables correctly.  We'll then rezoom due
      // to the |zoom = true| above.
      // Note that relative units here use the parent's size unadjusted
      // for scriptlevel changes. A scriptlevel change between us and the parent
      // is simply ignored.
      nscoord parentSize =
        nsStyleFont::UnZoomText(aPresContext, aParentSize);

      if (NS_STYLE_FONT_SIZE_LARGER == value) {
        *aSize = FindNextLargerFontSize(parentSize,
                         baseSize, aPresContext, eFontSize_CSS);

        NS_ASSERTION(*aSize >= parentSize,
                     "FindNextLargerFontSize failed");
      }
      else {
        *aSize = FindNextSmallerFontSize(parentSize,
                         baseSize, aPresContext, eFontSize_CSS);
        NS_ASSERTION(*aSize < parentSize ||
                     parentSize <= nsPresContext::CSSPixelsToAppUnits(1),
                     "FindNextSmallerFontSize failed");
      }
    } else {
      NS_NOTREACHED("unexpected value");
    }
  }
  else if (sizeValue->IsLengthUnit() ||
           sizeValue->GetUnit() == eCSSUnit_Percent ||
           sizeValue->IsCalcUnit()) {
    SetFontSizeCalcOps ops(aParentSize, aParentFont,
                           aPresContext, aAtRoot, aCanStoreInRuleTree);
    *aSize = css::ComputeCalc(*sizeValue, ops);
    if (*aSize < 0) {
      NS_ABORT_IF_FALSE(sizeValue->IsCalcUnit(),
                        "negative lengths and percents should be rejected "
                        "by parser");
      *aSize = 0;
    }
    // Zoom is handled inside the calc ops when needed.
    zoom = false;
  }
  else if (eCSSUnit_System_Font == sizeValue->GetUnit()) {
    // this becomes our cascading size
    *aSize = aSystemFont.size;
    zoom = true;
  }
  else if (eCSSUnit_Inherit == sizeValue->GetUnit()) {
    aCanStoreInRuleTree = false;
    // We apply scriptlevel change for this case, because the default is
    // to inherit and we don't want explicit "inherit" to differ from the
    // default.
    *aSize = aScriptLevelAdjustedParentSize;
    zoom = false;
  }
  else if (eCSSUnit_Initial == sizeValue->GetUnit()) {
    // The initial value is 'medium', which has magical sizing based on
    // the generic font family, so do that here too.
    *aSize = baseSize;
    zoom = true;
  } else {
    NS_ASSERTION(eCSSUnit_Null == sizeValue->GetUnit(),
                 "What kind of font-size value is this?");
    // if aUsedStartStruct is true, then every single property in the
    // font struct is being set all at once. This means scriptlevel is not
    // going to have any influence on the font size; there is no need to
    // do anything here.
    if (!aUsedStartStruct && aParentSize != aScriptLevelAdjustedParentSize) {
      // There was no rule affecting the size but the size has been
      // affected by the parent's size via scriptlevel change. So we cannot
      // store the data in the rule tree.
      aCanStoreInRuleTree = false;
      *aSize = aScriptLevelAdjustedParentSize;
    }
  }

  // We want to zoom the cascaded size so that em-based measurements,
  // line-heights, etc., work.
  if (zoom) {
    *aSize = nsStyleFont::ZoomText(aPresContext, *aSize);
  }
}

static int8_t ClampTo8Bit(int32_t aValue) {
  if (aValue < -128)
    return -128;
  if (aValue > 127)
    return 127;
  return int8_t(aValue);
}

/* static */ void
nsRuleNode::SetFont(nsPresContext* aPresContext, nsStyleContext* aContext,
                    uint8_t aGenericFontID, const nsRuleData* aRuleData,
                    const nsStyleFont* aParentFont,
                    nsStyleFont* aFont, bool aUsedStartStruct,
                    bool& aCanStoreInRuleTree)
{
  bool atRoot = !aContext->GetParent();

  // mLanguage must be set before before any of the CalcLengthWith calls
  // (direct calls or calls via SetFontSize) for the cases where |aParentFont|
  // is the same as |aFont|.
  //
  // -x-lang: string, inherit
  // This is not a real CSS property, it is an HTML attribute mapped to CSS.
  const nsCSSValue* langValue = aRuleData->ValueForLang();
  if (eCSSUnit_Ident == langValue->GetUnit()) {
    nsAutoString lang;
    langValue->GetStringValue(lang);

    nsContentUtils::ASCIIToLower(lang);
    aFont->mLanguage = do_GetAtom(lang);
    aFont->mExplicitLanguage = true;
  }

  const nsFont* defaultVariableFont =
    aPresContext->GetDefaultFont(kPresContext_DefaultVariableFont_ID,
                                 aFont->mLanguage);

  // -moz-system-font: enum (never inherit!)
  MOZ_STATIC_ASSERT(
    NS_STYLE_FONT_CAPTION        == LookAndFeel::eFont_Caption &&
    NS_STYLE_FONT_ICON           == LookAndFeel::eFont_Icon &&
    NS_STYLE_FONT_MENU           == LookAndFeel::eFont_Menu &&
    NS_STYLE_FONT_MESSAGE_BOX    == LookAndFeel::eFont_MessageBox &&
    NS_STYLE_FONT_SMALL_CAPTION  == LookAndFeel::eFont_SmallCaption &&
    NS_STYLE_FONT_STATUS_BAR     == LookAndFeel::eFont_StatusBar &&
    NS_STYLE_FONT_WINDOW         == LookAndFeel::eFont_Window &&
    NS_STYLE_FONT_DOCUMENT       == LookAndFeel::eFont_Document &&
    NS_STYLE_FONT_WORKSPACE      == LookAndFeel::eFont_Workspace &&
    NS_STYLE_FONT_DESKTOP        == LookAndFeel::eFont_Desktop &&
    NS_STYLE_FONT_INFO           == LookAndFeel::eFont_Info &&
    NS_STYLE_FONT_DIALOG         == LookAndFeel::eFont_Dialog &&
    NS_STYLE_FONT_BUTTON         == LookAndFeel::eFont_Button &&
    NS_STYLE_FONT_PULL_DOWN_MENU == LookAndFeel::eFont_PullDownMenu &&
    NS_STYLE_FONT_LIST           == LookAndFeel::eFont_List &&
    NS_STYLE_FONT_FIELD          == LookAndFeel::eFont_Field,
    "LookAndFeel.h system-font constants out of sync with nsStyleConsts.h");

  // Fall back to defaultVariableFont.
  nsFont systemFont = *defaultVariableFont;
  const nsCSSValue* systemFontValue = aRuleData->ValueForSystemFont();
  if (eCSSUnit_Enumerated == systemFontValue->GetUnit()) {
    gfxFontStyle fontStyle;
    LookAndFeel::FontID fontID =
      (LookAndFeel::FontID)systemFontValue->GetIntValue();
    float devPerCSS =
      (float)nsPresContext::AppUnitsPerCSSPixel() /
      aPresContext->DeviceContext()->UnscaledAppUnitsPerDevPixel();
    if (LookAndFeel::GetFont(fontID, systemFont.name, fontStyle, devPerCSS)) {
      systemFont.style = fontStyle.style;
      systemFont.systemFont = fontStyle.systemFont;
      systemFont.variant = NS_FONT_VARIANT_NORMAL;
      systemFont.weight = fontStyle.weight;
      systemFont.stretch = fontStyle.stretch;
      systemFont.decorations = NS_FONT_DECORATION_NONE;
      systemFont.size = NSFloatPixelsToAppUnits(fontStyle.size,
                                                aPresContext->DeviceContext()->
                                                UnscaledAppUnitsPerDevPixel());
      //systemFont.langGroup = fontStyle.langGroup;
      systemFont.sizeAdjust = fontStyle.sizeAdjust;

#ifdef XP_WIN
      // XXXldb This platform-specific stuff should be in the
      // LookAndFeel implementation, not here.
      // XXXzw Should we even still *have* this code?  It looks to be making
      // old, probably obsolete assumptions.

      // As far as I can tell the system default fonts and sizes
      // on MS-Windows for Buttons, Listboxes/Comboxes and Text Fields are
      // all pre-determined and cannot be changed by either the control panel
      // or programmtically.
      switch (fontID) {
        // Fields (text fields)
        // Button and Selects (listboxes/comboboxes)
        //    We use whatever font is defined by the system. Which it appears
        //    (and the assumption is) it is always a proportional font. Then we
        //    always use 2 points smaller than what the browser has defined as
        //    the default proportional font.
      case LookAndFeel::eFont_Field:
      case LookAndFeel::eFont_Button:
      case LookAndFeel::eFont_List:
        // Assumption: system defined font is proportional
        systemFont.size =
          NS_MAX(defaultVariableFont->size -
                 nsPresContext::CSSPointsToAppUnits(2), 0);
        break;
      }
#endif
    }
  }

  // font-family: string list, enum, inherit
  const nsCSSValue* familyValue = aRuleData->ValueForFontFamily();
  NS_ASSERTION(eCSSUnit_Enumerated != familyValue->GetUnit(),
               "system fonts should not be in mFamily anymore");
  if (eCSSUnit_Families == familyValue->GetUnit()) {
    // set the correct font if we are using DocumentFonts OR we are overriding for XUL
    // MJA: bug 31816
    if (aGenericFontID == kGenericFont_NONE) {
      // only bother appending fallback fonts if this isn't a fallback generic font itself
      if (!aFont->mFont.name.IsEmpty())
        aFont->mFont.name.Append((PRUnichar)',');
      // defaultVariableFont.name should always be "serif" or "sans-serif".
      aFont->mFont.name.Append(defaultVariableFont->name);
    }
    aFont->mFont.systemFont = false;
    // Technically this is redundant with the code below, but it's good
    // to have since we'll still want it once we get rid of
    // SetGenericFont (bug 380915).
    aFont->mGenericID = aGenericFontID;
  }
  else if (eCSSUnit_System_Font == familyValue->GetUnit()) {
    aFont->mFont.name = systemFont.name;
    aFont->mFont.systemFont = true;
    aFont->mGenericID = kGenericFont_NONE;
  }
  else if (eCSSUnit_Inherit == familyValue->GetUnit()) {
    aCanStoreInRuleTree = false;
    aFont->mFont.name = aParentFont->mFont.name;
    aFont->mFont.systemFont = aParentFont->mFont.systemFont;
    aFont->mGenericID = aParentFont->mGenericID;
  }
  else if (eCSSUnit_Initial == familyValue->GetUnit()) {
    aFont->mFont.name = defaultVariableFont->name;
    aFont->mFont.systemFont = defaultVariableFont->systemFont;
    aFont->mGenericID = kGenericFont_NONE;
  }

  // When we're in the loop in SetGenericFont, we must ensure that we
  // always keep aFont->mFlags set to the correct generic.  But we have
  // to be careful not to touch it when we're called directly from
  // ComputeFontData, because we could have a start struct.
  if (aGenericFontID != kGenericFont_NONE) {
    aFont->mGenericID = aGenericFontID;
  }

  // font-style: enum, inherit, initial, -moz-system-font
  SetDiscrete(*aRuleData->ValueForFontStyle(),
              aFont->mFont.style, aCanStoreInRuleTree,
              SETDSC_ENUMERATED | SETDSC_SYSTEM_FONT,
              aParentFont->mFont.style,
              defaultVariableFont->style,
              0, 0, 0, systemFont.style);

  // font-variant: enum, inherit, initial, -moz-system-font
  SetDiscrete(*aRuleData->ValueForFontVariant(),
              aFont->mFont.variant, aCanStoreInRuleTree,
              SETDSC_ENUMERATED | SETDSC_SYSTEM_FONT,
              aParentFont->mFont.variant,
              defaultVariableFont->variant,
              0, 0, 0, systemFont.variant);

  // font-weight: int, enum, inherit, initial, -moz-system-font
  // special handling for enum
  const nsCSSValue* weightValue = aRuleData->ValueForFontWeight();
  if (eCSSUnit_Enumerated == weightValue->GetUnit()) {
    int32_t value = weightValue->GetIntValue();
    switch (value) {
      case NS_STYLE_FONT_WEIGHT_NORMAL:
      case NS_STYLE_FONT_WEIGHT_BOLD:
        aFont->mFont.weight = value;
        break;
      case NS_STYLE_FONT_WEIGHT_BOLDER: {
        aCanStoreInRuleTree = false;
        int32_t inheritedValue = aParentFont->mFont.weight;
        if (inheritedValue <= 300) {
          aFont->mFont.weight = 400;
        } else if (inheritedValue <= 500) {
          aFont->mFont.weight = 700;
        } else {
          aFont->mFont.weight = 900;
        }
        break;
      }
      case NS_STYLE_FONT_WEIGHT_LIGHTER: {
        aCanStoreInRuleTree = false;
        int32_t inheritedValue = aParentFont->mFont.weight;
        if (inheritedValue < 600) {
          aFont->mFont.weight = 100;
        } else if (inheritedValue < 800) {
          aFont->mFont.weight = 400;
        } else {
          aFont->mFont.weight = 700;
        }
        break;
      }
    }
  } else
    SetDiscrete(*weightValue, aFont->mFont.weight, aCanStoreInRuleTree,
                SETDSC_INTEGER | SETDSC_SYSTEM_FONT,
                aParentFont->mFont.weight,
                defaultVariableFont->weight,
                0, 0, 0, systemFont.weight);

  // font-stretch: enum, inherit, initial, -moz-system-font
  SetDiscrete(*aRuleData->ValueForFontStretch(),
              aFont->mFont.stretch, aCanStoreInRuleTree,
              SETDSC_SYSTEM_FONT | SETDSC_ENUMERATED,
              aParentFont->mFont.stretch,
              defaultVariableFont->stretch,
              0, 0, 0, systemFont.stretch);

  // Compute scriptlevel, scriptminsize and scriptsizemultiplier now so
  // they're available for font-size computation.

  // -moz-script-min-size: length
  const nsCSSValue* scriptMinSizeValue = aRuleData->ValueForScriptMinSize();
  if (scriptMinSizeValue->IsLengthUnit()) {
    // scriptminsize in font units (em, ex) has to be interpreted relative
    // to the parent font, or the size definitions are circular and we
    //
    aFont->mScriptMinSize =
      CalcLengthWith(*scriptMinSizeValue, aParentFont->mSize,
                     aParentFont,
                     nullptr, aPresContext, atRoot, true,
                     aCanStoreInRuleTree);
  }

  // -moz-script-size-multiplier: factor, inherit, initial
  SetFactor(*aRuleData->ValueForScriptSizeMultiplier(),
            aFont->mScriptSizeMultiplier,
            aCanStoreInRuleTree, aParentFont->mScriptSizeMultiplier,
            NS_MATHML_DEFAULT_SCRIPT_SIZE_MULTIPLIER,
            SETFCT_POSITIVE);

  // -moz-script-level: integer, number, inherit
  const nsCSSValue* scriptLevelValue = aRuleData->ValueForScriptLevel();
  if (eCSSUnit_Integer == scriptLevelValue->GetUnit()) {
    // "relative"
    aFont->mScriptLevel = ClampTo8Bit(aParentFont->mScriptLevel + scriptLevelValue->GetIntValue());
  }
  else if (eCSSUnit_Number == scriptLevelValue->GetUnit()) {
    // "absolute"
    aFont->mScriptLevel = ClampTo8Bit(int32_t(scriptLevelValue->GetFloatValue()));
  }
  else if (eCSSUnit_Inherit == scriptLevelValue->GetUnit()) {
    aCanStoreInRuleTree = false;
    aFont->mScriptLevel = aParentFont->mScriptLevel;
  }
  else if (eCSSUnit_Initial == scriptLevelValue->GetUnit()) {
    aFont->mScriptLevel = 0;
  }

  // font-feature-settings
  const nsCSSValue* featureSettingsValue =
    aRuleData->ValueForFontFeatureSettings();

  switch (featureSettingsValue->GetUnit()) {
  case eCSSUnit_Null:
    break;

  case eCSSUnit_Normal:
  case eCSSUnit_Initial:
    aFont->mFont.fontFeatureSettings.Clear();
    break;

  case eCSSUnit_Inherit:
    aCanStoreInRuleTree = false;
    aFont->mFont.fontFeatureSettings = aParentFont->mFont.fontFeatureSettings;
    break;

  case eCSSUnit_System_Font:
    aFont->mFont.fontFeatureSettings = systemFont.fontFeatureSettings;
    break;

  case eCSSUnit_PairList:
  case eCSSUnit_PairListDep:
    ComputeFontFeatures(featureSettingsValue->GetPairListValue(),
                        aFont->mFont.fontFeatureSettings);
    break;

  default:
    NS_ABORT_IF_FALSE(false, "unexpected value unit");
    break;
  }

  // font-language-override
  const nsCSSValue* languageOverrideValue =
    aRuleData->ValueForFontLanguageOverride();
  if (eCSSUnit_Inherit == languageOverrideValue->GetUnit()) {
    aCanStoreInRuleTree = false;
    aFont->mFont.languageOverride = aParentFont->mFont.languageOverride;
  } else if (eCSSUnit_Normal == languageOverrideValue->GetUnit() ||
             eCSSUnit_Initial == languageOverrideValue->GetUnit()) {
    aFont->mFont.languageOverride.Truncate();
  } else if (eCSSUnit_System_Font == languageOverrideValue->GetUnit()) {
    aFont->mFont.languageOverride = systemFont.languageOverride;
  } else if (eCSSUnit_String == languageOverrideValue->GetUnit()) {
    languageOverrideValue->GetStringValue(aFont->mFont.languageOverride);
  }

  // font-size: enum, length, percent, inherit
  nscoord scriptLevelAdjustedParentSize = aParentFont->mSize;
  nscoord scriptLevelAdjustedUnconstrainedParentSize;
  scriptLevelAdjustedParentSize =
    ComputeScriptLevelSize(aFont, aParentFont, aPresContext,
                           &scriptLevelAdjustedUnconstrainedParentSize);
  NS_ASSERTION(!aUsedStartStruct || aFont->mScriptUnconstrainedSize == aFont->mSize,
               "If we have a start struct, we should have reset everything coming in here");
  SetFontSize(aPresContext, aRuleData, aFont, aParentFont,
              &aFont->mSize,
              systemFont, aParentFont->mSize, scriptLevelAdjustedParentSize,
              aUsedStartStruct, atRoot, aCanStoreInRuleTree);
  if (aParentFont->mSize == aParentFont->mScriptUnconstrainedSize &&
      scriptLevelAdjustedParentSize == scriptLevelAdjustedUnconstrainedParentSize) {
    // Fast path: we have not been affected by scriptminsize so we don't
    // need to call SetFontSize again to compute the
    // scriptminsize-unconstrained size. This is OK even if we have a
    // start struct, because if we have a start struct then 'font-size'
    // was specified and so scriptminsize has no effect.
    aFont->mScriptUnconstrainedSize = aFont->mSize;
  } else {
    SetFontSize(aPresContext, aRuleData, aFont, aParentFont,
                &aFont->mScriptUnconstrainedSize,
                systemFont, aParentFont->mScriptUnconstrainedSize,
                scriptLevelAdjustedUnconstrainedParentSize,
                aUsedStartStruct, atRoot, aCanStoreInRuleTree);
  }
  NS_ASSERTION(aFont->mScriptUnconstrainedSize <= aFont->mSize,
               "scriptminsize should never be making things bigger");

  nscoord fontSize = aFont->mSize;

  // enforce the user' specified minimum font-size on the value that we expose
  // (but don't change font-size:0, since that would unhide hidden text)
  if (fontSize > 0) {
    nscoord minFontSize = aPresContext->MinFontSize(aFont->mLanguage);
    if (minFontSize < 0) {
      minFontSize = 0;
    }
    if (fontSize < minFontSize && !aPresContext->IsChrome()) {
      // override the minimum font-size constraint
      fontSize = minFontSize;
    }
  }
  aFont->mFont.size = fontSize;

  // font-size-adjust: number, none, inherit, initial, -moz-system-font
  const nsCSSValue* sizeAdjustValue = aRuleData->ValueForFontSizeAdjust();
  if (eCSSUnit_System_Font == sizeAdjustValue->GetUnit()) {
    aFont->mFont.sizeAdjust = systemFont.sizeAdjust;
  } else
    SetFactor(*sizeAdjustValue, aFont->mFont.sizeAdjust,
              aCanStoreInRuleTree, aParentFont->mFont.sizeAdjust, 0.0f,
              SETFCT_NONE);
}

/* static */ void
nsRuleNode::ComputeFontFeatures(const nsCSSValuePairList *aFeaturesList,
                                nsTArray<gfxFontFeature>& aFeatureSettings)
{
  aFeatureSettings.Clear();
  for (const nsCSSValuePairList* p = aFeaturesList; p; p = p->mNext) {
    gfxFontFeature feat = {0, 0};

    NS_ABORT_IF_FALSE(aFeaturesList->mXValue.GetUnit() == eCSSUnit_String,
                      "unexpected value unit");

    // tag is a 4-byte ASCII sequence
    nsAutoString tag;
    p->mXValue.GetStringValue(tag);
    if (tag.Length() != 4) {
      continue;
    }
    // parsing validates that these are ASCII chars
    // tags are always big-endian
    feat.mTag = (tag[0] << 24) | (tag[1] << 16) | (tag[2] << 8)  | tag[3];

    // value
    NS_ASSERTION(p->mYValue.GetUnit() == eCSSUnit_Integer,
                 "should have found an integer unit");
    feat.mValue = p->mYValue.GetIntValue();

    aFeatureSettings.AppendElement(feat);
  }
}

// This should die (bug 380915).
//
// SetGenericFont:
//  - backtrack to an ancestor with the same generic font name (possibly
//    up to the root where default values come from the presentation context)
//  - re-apply cascading rules from there without caching intermediate values
/* static */ void
nsRuleNode::SetGenericFont(nsPresContext* aPresContext,
                           nsStyleContext* aContext,
                           uint8_t aGenericFontID,
                           nsStyleFont* aFont)
{
  // walk up the contexts until a context with the desired generic font
  nsAutoTArray<nsStyleContext*, 8> contextPath;
  contextPath.AppendElement(aContext);
  nsStyleContext* higherContext = aContext->GetParent();
  while (higherContext) {
    if (higherContext->GetStyleFont()->mGenericID == aGenericFontID) {
      // done walking up the higher contexts
      break;
    }
    contextPath.AppendElement(higherContext);
    higherContext = higherContext->GetParent();
  }

  // re-apply the cascading rules, starting from the higher context

  // If we stopped earlier because we reached the root of the style tree,
  // we will start with the default generic font from the presentation
  // context. Otherwise we start with the higher context.
  const nsFont* defaultFont =
    aPresContext->GetDefaultFont(aGenericFontID, aFont->mLanguage);
  nsStyleFont parentFont(*defaultFont, aPresContext);
  if (higherContext) {
    const nsStyleFont* tmpFont = higherContext->GetStyleFont();
    parentFont = *tmpFont;
  }
  *aFont = parentFont;

  bool dummy;
  uint32_t fontBit = nsCachedStyleData::GetBitForSID(eStyleStruct_Font);

  // use placement new[] on the result of alloca() to allocate a
  // variable-sized stack array, including execution of constructors,
  // and use an RAII class to run the destructors too.
  size_t nprops = nsCSSProps::PropertyCountInStruct(eStyleStruct_Font);
  void* dataStorage = alloca(nprops * sizeof(nsCSSValue));

  for (int32_t i = contextPath.Length() - 1; i >= 0; --i) {
    nsStyleContext* context = contextPath[i];
    AutoCSSValueArray dataArray(dataStorage, nprops);

    nsRuleData ruleData(NS_STYLE_INHERIT_BIT(Font), dataArray.get(),
                        aPresContext, context);
    ruleData.mValueOffsets[eStyleStruct_Font] = 0;

    // Trimmed down version of ::WalkRuleTree() to re-apply the style rules
    // Note that we *do* need to do this for our own data, since what is
    // in |fontData| in ComputeFontData is only for the rules below
    // aStartStruct.
    for (nsRuleNode* ruleNode = context->GetRuleNode(); ruleNode;
         ruleNode = ruleNode->GetParent()) {
      if (ruleNode->mNoneBits & fontBit)
        // no more font rules on this branch, get out
        break;

      nsIStyleRule *rule = ruleNode->GetRule();
      if (rule) {
        ruleData.mLevel = ruleNode->GetLevel();
        ruleData.mIsImportantRule = ruleNode->IsImportantRule();
        rule->MapRuleInfoInto(&ruleData);
      }
    }

    // Compute the delta from the information that the rules specified

    // Avoid unnecessary operations in SetFont().  But we care if it's
    // the final value that we're computing.
    if (i != 0)
      ruleData.ValueForFontFamily()->Reset();

    nsRuleNode::SetFont(aPresContext, context,
                        aGenericFontID, &ruleData, &parentFont, aFont,
                        false, dummy);

    // XXX Not sure if we need to do this here
    // If we have a post-resolve callback, handle that now.
    if (ruleData.mPostResolveCallback)
      (ruleData.mPostResolveCallback)(aFont, &ruleData);

    parentFont = *aFont;
  }
}

static bool ExtractGeneric(const nsString& aFamily, bool aGeneric,
                             void *aData)
{
  nsAutoString *data = static_cast<nsAutoString*>(aData);

  if (aGeneric) {
    *data = aFamily;
    return false; // stop enumeration
  }
  return true;
}

const void*
nsRuleNode::ComputeFontData(void* aStartStruct,
                            const nsRuleData* aRuleData,
                            nsStyleContext* aContext,
                            nsRuleNode* aHighestNode,
                            const RuleDetail aRuleDetail,
                            const bool aCanStoreInRuleTree)
{
  COMPUTE_START_INHERITED(Font, (mPresContext), font, parentFont)

  // NOTE:  The |aRuleDetail| passed in is a little bit conservative due
  // to the -moz-system-font property.  We really don't need to consider
  // it here in determining whether to cache in the rule tree.  However,
  // we do need to consider it in WalkRuleTree when deciding whether to
  // walk further up the tree.  So this means that when the font struct
  // is fully specified using *longhand* properties (excluding
  // -moz-system-font), we won't cache in the rule tree even though we
  // could.  However, it's pretty unlikely authors will do that
  // (although there is a pretty good chance they'll fully specify it
  // using the 'font' shorthand).

  bool useDocumentFonts =
    mPresContext->GetCachedBoolPref(kPresContext_UseDocumentFonts);

  // See if we are in the chrome
  // We only need to know this to determine if we have to use the
  // document fonts (overriding the useDocumentFonts flag).
  if (!useDocumentFonts && mPresContext->IsChrome()) {
    // if we are not using document fonts, but this is a XUL document,
    // then we use the document fonts anyway
    useDocumentFonts = true;
  }

  // Figure out if we are a generic font
  uint8_t generic = kGenericFont_NONE;
  // XXXldb What if we would have had a string if we hadn't been doing
  // the optimization with a non-null aStartStruct?
  const nsCSSValue* familyValue = aRuleData->ValueForFontFamily();
  if (eCSSUnit_Families == familyValue->GetUnit()) {
    familyValue->GetStringValue(font->mFont.name);
    // XXXldb Do we want to extract the generic for this if it's not only a
    // generic?
    nsFont::GetGenericID(font->mFont.name, &generic);

    // If we aren't allowed to use document fonts, then we are only entitled
    // to use the user's default variable-width font and fixed-width font
    if (!useDocumentFonts) {
      // Extract the generic from the specified font family...
      nsAutoString genericName;
      if (!font->mFont.EnumerateFamilies(ExtractGeneric, &genericName)) {
        // The specified font had a generic family.
        font->mFont.name = genericName;
        nsFont::GetGenericID(genericName, &generic);

        // ... and only use it if it's -moz-fixed or monospace
        if (generic != kGenericFont_moz_fixed &&
            generic != kGenericFont_monospace) {
          font->mFont.name.Truncate();
          generic = kGenericFont_NONE;
        }
      } else {
        // The specified font did not have a generic family.
        font->mFont.name.Truncate();
        generic = kGenericFont_NONE;
      }
    }
  }

  // Now compute our font struct
  if (generic == kGenericFont_NONE) {
    // continue the normal processing
    nsRuleNode::SetFont(mPresContext, aContext, generic,
                        aRuleData, parentFont, font,
                        aStartStruct != nullptr, canStoreInRuleTree);
  }
  else {
    // re-calculate the font as a generic font
    canStoreInRuleTree = false;
    nsRuleNode::SetGenericFont(mPresContext, aContext, generic,
                               font);
  }

  COMPUTE_END_INHERITED(Font, font)
}

template <typename T>
inline uint32_t ListLength(const T* aList)
{
  uint32_t len = 0;
  while (aList) {
    len++;
    aList = aList->mNext;
  }
  return len;
}



already_AddRefed<nsCSSShadowArray>
nsRuleNode::GetShadowData(const nsCSSValueList* aList,
                          nsStyleContext* aContext,
                          bool aIsBoxShadow,
                          bool& canStoreInRuleTree)
{
  uint32_t arrayLength = ListLength(aList);

  NS_ABORT_IF_FALSE(arrayLength > 0,
                    "Non-null text-shadow list, yet we counted 0 items.");
  nsCSSShadowArray* shadowList = new(arrayLength) nsCSSShadowArray(arrayLength);

  if (!shadowList)
    return nullptr;

  nsStyleCoord tempCoord;
  bool unitOK;
  for (nsCSSShadowItem* item = shadowList->ShadowAt(0);
       aList;
       aList = aList->mNext, ++item) {
    NS_ABORT_IF_FALSE(aList->mValue.GetUnit() == eCSSUnit_Array,
                      "expecting a plain array value");
    nsCSSValue::Array *arr = aList->mValue.GetArrayValue();
    // OK to pass bad aParentCoord since we're not passing SETCOORD_INHERIT
    unitOK = SetCoord(arr->Item(0), tempCoord, nsStyleCoord(),
                      SETCOORD_LENGTH | SETCOORD_CALC_LENGTH_ONLY,
                      aContext, mPresContext, canStoreInRuleTree);
    NS_ASSERTION(unitOK, "unexpected unit");
    item->mXOffset = tempCoord.GetCoordValue();

    unitOK = SetCoord(arr->Item(1), tempCoord, nsStyleCoord(),
                      SETCOORD_LENGTH | SETCOORD_CALC_LENGTH_ONLY,
                      aContext, mPresContext, canStoreInRuleTree);
    NS_ASSERTION(unitOK, "unexpected unit");
    item->mYOffset = tempCoord.GetCoordValue();

    // Blur radius is optional in the current box-shadow spec
    if (arr->Item(2).GetUnit() != eCSSUnit_Null) {
      unitOK = SetCoord(arr->Item(2), tempCoord, nsStyleCoord(),
                        SETCOORD_LENGTH | SETCOORD_CALC_LENGTH_ONLY |
                          SETCOORD_CALC_CLAMP_NONNEGATIVE,
                        aContext, mPresContext, canStoreInRuleTree);
      NS_ASSERTION(unitOK, "unexpected unit");
      item->mRadius = tempCoord.GetCoordValue();
    } else {
      item->mRadius = 0;
    }

    // Find the spread radius
    if (aIsBoxShadow && arr->Item(3).GetUnit() != eCSSUnit_Null) {
      unitOK = SetCoord(arr->Item(3), tempCoord, nsStyleCoord(),
                        SETCOORD_LENGTH | SETCOORD_CALC_LENGTH_ONLY,
                        aContext, mPresContext, canStoreInRuleTree);
      NS_ASSERTION(unitOK, "unexpected unit");
      item->mSpread = tempCoord.GetCoordValue();
    } else {
      item->mSpread = 0;
    }

    if (arr->Item(4).GetUnit() != eCSSUnit_Null) {
      item->mHasColor = true;
      // 2nd argument can be bogus since inherit is not a valid color
      unitOK = SetColor(arr->Item(4), 0, mPresContext, aContext, item->mColor,
                        canStoreInRuleTree);
      NS_ASSERTION(unitOK, "unexpected unit");
    }

    if (aIsBoxShadow && arr->Item(5).GetUnit() == eCSSUnit_Enumerated) {
      NS_ASSERTION(arr->Item(5).GetIntValue() == NS_STYLE_BOX_SHADOW_INSET,
                   "invalid keyword type for box shadow");
      item->mInset = true;
    } else {
      item->mInset = false;
    }
  }

  NS_ADDREF(shadowList);
  return shadowList;
}

const void*
nsRuleNode::ComputeTextData(void* aStartStruct,
                            const nsRuleData* aRuleData,
                            nsStyleContext* aContext,
                            nsRuleNode* aHighestNode,
                            const RuleDetail aRuleDetail,
                            const bool aCanStoreInRuleTree)
{
  COMPUTE_START_INHERITED(Text, (), text, parentText)

  // tab-size: integer, inherit
  SetDiscrete(*aRuleData->ValueForTabSize(),
              text->mTabSize, canStoreInRuleTree,
              SETDSC_INTEGER, parentText->mTabSize,
              NS_STYLE_TABSIZE_INITIAL, 0, 0, 0, 0);

  // letter-spacing: normal, length, inherit
  SetCoord(*aRuleData->ValueForLetterSpacing(),
           text->mLetterSpacing, parentText->mLetterSpacing,
           SETCOORD_LH | SETCOORD_NORMAL | SETCOORD_INITIAL_NORMAL |
             SETCOORD_CALC_LENGTH_ONLY,
           aContext, mPresContext, canStoreInRuleTree);

  // text-shadow: none, list, inherit, initial
  const nsCSSValue* textShadowValue = aRuleData->ValueForTextShadow();
  if (textShadowValue->GetUnit() != eCSSUnit_Null) {
    text->mTextShadow = nullptr;

    // Don't need to handle none/initial explicitly: The above assignment
    // takes care of that
    if (textShadowValue->GetUnit() == eCSSUnit_Inherit) {
      canStoreInRuleTree = false;
      text->mTextShadow = parentText->mTextShadow;
    } else if (textShadowValue->GetUnit() == eCSSUnit_List ||
               textShadowValue->GetUnit() == eCSSUnit_ListDep) {
      // List of arrays
      text->mTextShadow = GetShadowData(textShadowValue->GetListValue(),
                                        aContext, false, canStoreInRuleTree);
    }
  }

  // line-height: normal, number, length, percent, inherit
  const nsCSSValue* lineHeightValue = aRuleData->ValueForLineHeight();
  if (eCSSUnit_Percent == lineHeightValue->GetUnit()) {
    canStoreInRuleTree = false;
    // Use |mFont.size| to pick up minimum font size.
    text->mLineHeight.SetCoordValue(
        NSToCoordRound(float(aContext->GetStyleFont()->mFont.size) *
                       lineHeightValue->GetPercentValue()));
  }
  else if (eCSSUnit_Initial == lineHeightValue->GetUnit() ||
           eCSSUnit_System_Font == lineHeightValue->GetUnit()) {
    text->mLineHeight.SetNormalValue();
  }
  else {
    SetCoord(*lineHeightValue, text->mLineHeight, parentText->mLineHeight,
             SETCOORD_LEH | SETCOORD_FACTOR | SETCOORD_NORMAL,
             aContext, mPresContext, canStoreInRuleTree);
    if (lineHeightValue->IsLengthUnit() &&
        !lineHeightValue->IsRelativeLengthUnit()) {
      nscoord lh = nsStyleFont::ZoomText(mPresContext,
                                         text->mLineHeight.GetCoordValue());

      canStoreInRuleTree = false;
      const nsStyleFont *font = aContext->GetStyleFont();
      nscoord minimumFontSize = mPresContext->MinFontSize(font->mLanguage);

      if (minimumFontSize > 0 && !mPresContext->IsChrome()) {
        if (font->mSize != 0) {
          lh = nscoord(float(lh) * float(font->mFont.size) / float(font->mSize));
        } else {
          lh = minimumFontSize;
        }
      }
      text->mLineHeight.SetCoordValue(lh);
    }
  }


  // text-align: enum, string, inherit, initial
  const nsCSSValue* textAlignValue = aRuleData->ValueForTextAlign();
  if (eCSSUnit_String == textAlignValue->GetUnit()) {
    NS_NOTYETIMPLEMENTED("align string");
  } else if (eCSSUnit_Enumerated == textAlignValue->GetUnit() &&
             NS_STYLE_TEXT_ALIGN_MOZ_CENTER_OR_INHERIT ==
               textAlignValue->GetIntValue()) {
    canStoreInRuleTree = false;
    uint8_t parentAlign = parentText->mTextAlign;
    text->mTextAlign = (NS_STYLE_TEXT_ALIGN_DEFAULT == parentAlign) ?
      NS_STYLE_TEXT_ALIGN_CENTER : parentAlign;
  } else
    SetDiscrete(*textAlignValue, text->mTextAlign, canStoreInRuleTree,
                SETDSC_ENUMERATED, parentText->mTextAlign,
                NS_STYLE_TEXT_ALIGN_DEFAULT,
                0, 0, 0, 0);

  // text-align-last: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForTextAlignLast(), text->mTextAlignLast,
              canStoreInRuleTree, SETDSC_ENUMERATED, parentText->mTextAlignLast,
              NS_STYLE_TEXT_ALIGN_AUTO, 0, 0, 0, 0);

  // text-indent: length, percent, calc, inherit, initial
  SetCoord(*aRuleData->ValueForTextIndent(), text->mTextIndent, parentText->mTextIndent,
           SETCOORD_LPH | SETCOORD_INITIAL_ZERO | SETCOORD_STORE_CALC,
           aContext, mPresContext, canStoreInRuleTree);

  // text-transform: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForTextTransform(), text->mTextTransform, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentText->mTextTransform,
              NS_STYLE_TEXT_TRANSFORM_NONE, 0, 0, 0, 0);

  // white-space: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForWhiteSpace(), text->mWhiteSpace, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentText->mWhiteSpace,
              NS_STYLE_WHITESPACE_NORMAL, 0, 0, 0, 0);

  // word-break: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForWordBreak(), text->mWordBreak, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentText->mWordBreak,
              NS_STYLE_WORDBREAK_NORMAL, 0, 0, 0, 0);

  // word-spacing: normal, length, inherit
  nsStyleCoord tempCoord;
  const nsCSSValue* wordSpacingValue = aRuleData->ValueForWordSpacing();
  if (SetCoord(*wordSpacingValue, tempCoord,
               nsStyleCoord(parentText->mWordSpacing,
                            nsStyleCoord::CoordConstructor),
               SETCOORD_LH | SETCOORD_NORMAL | SETCOORD_INITIAL_NORMAL |
                 SETCOORD_CALC_LENGTH_ONLY,
               aContext, mPresContext, canStoreInRuleTree)) {
    if (tempCoord.GetUnit() == eStyleUnit_Coord) {
      text->mWordSpacing = tempCoord.GetCoordValue();
    } else if (tempCoord.GetUnit() == eStyleUnit_Normal) {
      text->mWordSpacing = 0;
    } else {
      NS_NOTREACHED("unexpected unit");
    }
  } else {
    NS_ASSERTION(wordSpacingValue->GetUnit() == eCSSUnit_Null,
                 "unexpected unit");
  }

  // word-wrap: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForWordWrap(), text->mWordWrap, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentText->mWordWrap,
              NS_STYLE_WORDWRAP_NORMAL, 0, 0, 0, 0);

  // hyphens: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForHyphens(), text->mHyphens, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentText->mHyphens,
              NS_STYLE_HYPHENS_MANUAL, 0, 0, 0, 0);

  // text-size-adjust: none, auto, inherit, initial
  SetDiscrete(*aRuleData->ValueForTextSizeAdjust(), text->mTextSizeAdjust,
              canStoreInRuleTree, SETDSC_NONE | SETDSC_AUTO,
              parentText->mTextSizeAdjust,
              NS_STYLE_TEXT_SIZE_ADJUST_AUTO, // initial value
              NS_STYLE_TEXT_SIZE_ADJUST_AUTO, // auto value
              NS_STYLE_TEXT_SIZE_ADJUST_NONE, // none value
              0, 0);

  COMPUTE_END_INHERITED(Text, text)
}

const void*
nsRuleNode::ComputeTextResetData(void* aStartStruct,
                                 const nsRuleData* aRuleData,
                                 nsStyleContext* aContext,
                                 nsRuleNode* aHighestNode,
                                 const RuleDetail aRuleDetail,
                                 const bool aCanStoreInRuleTree)
{
  COMPUTE_START_RESET(TextReset, (), text, parentText)

  // vertical-align: enum, length, percent, calc, inherit
  const nsCSSValue* verticalAlignValue = aRuleData->ValueForVerticalAlign();
  if (!SetCoord(*verticalAlignValue, text->mVerticalAlign,
                parentText->mVerticalAlign,
                SETCOORD_LPH | SETCOORD_ENUMERATED | SETCOORD_STORE_CALC,
                aContext, mPresContext, canStoreInRuleTree)) {
    if (eCSSUnit_Initial == verticalAlignValue->GetUnit()) {
      text->mVerticalAlign.SetIntValue(NS_STYLE_VERTICAL_ALIGN_BASELINE,
                                       eStyleUnit_Enumerated);
    }
  }

  // text-blink: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForTextBlink(), text->mTextBlink,
              canStoreInRuleTree, SETDSC_ENUMERATED, parentText->mTextBlink,
              NS_STYLE_TEXT_BLINK_NONE, 0, 0, 0, 0);

  // text-decoration-line: enum (bit field), inherit, initial
  const nsCSSValue* decorationLineValue =
    aRuleData->ValueForTextDecorationLine();
  if (eCSSUnit_Enumerated == decorationLineValue->GetUnit()) {
    int32_t td = decorationLineValue->GetIntValue();
    text->mTextDecorationLine = td;
    if (td & NS_STYLE_TEXT_DECORATION_LINE_PREF_ANCHORS) {
      bool underlineLinks =
        mPresContext->GetCachedBoolPref(kPresContext_UnderlineLinks);
      if (underlineLinks) {
        text->mTextDecorationLine |= NS_STYLE_TEXT_DECORATION_LINE_UNDERLINE;
      }
      else {
        text->mTextDecorationLine &= ~NS_STYLE_TEXT_DECORATION_LINE_UNDERLINE;
      }
    }
  } else if (eCSSUnit_Inherit == decorationLineValue->GetUnit()) {
    canStoreInRuleTree = false;
    text->mTextDecorationLine = parentText->mTextDecorationLine;
  } else if (eCSSUnit_Initial == decorationLineValue->GetUnit()) {
    text->mTextDecorationLine = NS_STYLE_TEXT_DECORATION_LINE_NONE;
  }

  // text-decoration-color: color, string, enum, inherit, initial
  const nsCSSValue* decorationColorValue =
    aRuleData->ValueForTextDecorationColor();
  nscolor decorationColor;
  if (eCSSUnit_Inherit == decorationColorValue->GetUnit()) {
    canStoreInRuleTree = false;
    if (parentContext) {
      bool isForeground;
      parentText->GetDecorationColor(decorationColor, isForeground);
      if (isForeground) {
        text->SetDecorationColor(parentContext->GetStyleColor()->mColor);
      } else {
        text->SetDecorationColor(decorationColor);
      }
    } else {
      text->SetDecorationColorToForeground();
    }
  }
  else if (eCSSUnit_EnumColor == decorationColorValue->GetUnit() &&
           decorationColorValue->GetIntValue() == NS_COLOR_CURRENTCOLOR) {
    text->SetDecorationColorToForeground();
  }
  else if (SetColor(*decorationColorValue, 0, mPresContext, aContext,
                    decorationColor, canStoreInRuleTree)) {
    text->SetDecorationColor(decorationColor);
  }
  else if (eCSSUnit_Initial == decorationColorValue->GetUnit() ||
           eCSSUnit_Enumerated == decorationColorValue->GetUnit()) {
    NS_ABORT_IF_FALSE(eCSSUnit_Enumerated != decorationColorValue->GetUnit() ||
                      decorationColorValue->GetIntValue() ==
                        NS_STYLE_COLOR_MOZ_USE_TEXT_COLOR,
                      "unexpected enumerated value");
    text->SetDecorationColorToForeground();
  }

  // text-decoration-style: enum, inherit, initial
  const nsCSSValue* decorationStyleValue =
    aRuleData->ValueForTextDecorationStyle();
  if (eCSSUnit_Enumerated == decorationStyleValue->GetUnit()) {
    text->SetDecorationStyle(decorationStyleValue->GetIntValue());
  } else if (eCSSUnit_Inherit == decorationStyleValue->GetUnit()) {
    text->SetDecorationStyle(parentText->GetDecorationStyle());
    canStoreInRuleTree = false;
  } else if (eCSSUnit_Initial == decorationStyleValue->GetUnit()) {
    text->SetDecorationStyle(NS_STYLE_TEXT_DECORATION_STYLE_SOLID);
  }

  // text-overflow: enum, string, pair(enum|string), inherit, initial
  const nsCSSValue* textOverflowValue =
    aRuleData->ValueForTextOverflow();
  if (eCSSUnit_Initial == textOverflowValue->GetUnit()) {
    text->mTextOverflow = nsStyleTextOverflow();
  } else if (eCSSUnit_Inherit == textOverflowValue->GetUnit()) {
    canStoreInRuleTree = false;
    text->mTextOverflow = parentText->mTextOverflow;
  } else if (eCSSUnit_Enumerated == textOverflowValue->GetUnit()) {
    // A single enumerated value.
    SetDiscrete(*textOverflowValue, text->mTextOverflow.mRight.mType,
                canStoreInRuleTree,
                SETDSC_ENUMERATED, parentText->mTextOverflow.mRight.mType,
                NS_STYLE_TEXT_OVERFLOW_CLIP, 0, 0, 0, 0);
    text->mTextOverflow.mRight.mString.Truncate();
    text->mTextOverflow.mLeft.mType = NS_STYLE_TEXT_OVERFLOW_CLIP;
    text->mTextOverflow.mLeft.mString.Truncate();
    text->mTextOverflow.mLogicalDirections = true;
  } else if (eCSSUnit_String == textOverflowValue->GetUnit()) {
    // A single string value.
    text->mTextOverflow.mRight.mType = NS_STYLE_TEXT_OVERFLOW_STRING;
    textOverflowValue->GetStringValue(text->mTextOverflow.mRight.mString);
    text->mTextOverflow.mLeft.mType = NS_STYLE_TEXT_OVERFLOW_CLIP;
    text->mTextOverflow.mLeft.mString.Truncate();
    text->mTextOverflow.mLogicalDirections = true;
  } else if (eCSSUnit_Pair == textOverflowValue->GetUnit()) {
    // Two values were specified.
    text->mTextOverflow.mLogicalDirections = false;
    const nsCSSValuePair& textOverflowValue =
      aRuleData->ValueForTextOverflow()->GetPairValue();

    const nsCSSValue *textOverflowLeftValue = &textOverflowValue.mXValue;
    if (eCSSUnit_Enumerated == textOverflowLeftValue->GetUnit()) {
      SetDiscrete(*textOverflowLeftValue, text->mTextOverflow.mLeft.mType,
                  canStoreInRuleTree,
                  SETDSC_ENUMERATED, parentText->mTextOverflow.mLeft.mType,
                  NS_STYLE_TEXT_OVERFLOW_CLIP, 0, 0, 0, 0);
      text->mTextOverflow.mLeft.mString.Truncate();
    } else if (eCSSUnit_String == textOverflowLeftValue->GetUnit()) {
      textOverflowLeftValue->GetStringValue(text->mTextOverflow.mLeft.mString);
      text->mTextOverflow.mLeft.mType = NS_STYLE_TEXT_OVERFLOW_STRING;
    }

    const nsCSSValue *textOverflowRightValue = &textOverflowValue.mYValue;
    if (eCSSUnit_Enumerated == textOverflowRightValue->GetUnit()) {
      SetDiscrete(*textOverflowRightValue, text->mTextOverflow.mRight.mType,
                  canStoreInRuleTree,
                  SETDSC_ENUMERATED, parentText->mTextOverflow.mRight.mType,
                  NS_STYLE_TEXT_OVERFLOW_CLIP, 0, 0, 0, 0);
      text->mTextOverflow.mRight.mString.Truncate();
    } else if (eCSSUnit_String == textOverflowRightValue->GetUnit()) {
      textOverflowRightValue->GetStringValue(text->mTextOverflow.mRight.mString);
      text->mTextOverflow.mRight.mType = NS_STYLE_TEXT_OVERFLOW_STRING;
    }
  }

  // unicode-bidi: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForUnicodeBidi(), text->mUnicodeBidi, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentText->mUnicodeBidi,
              NS_STYLE_UNICODE_BIDI_NORMAL, 0, 0, 0, 0);

  COMPUTE_END_RESET(TextReset, text)
}

const void*
nsRuleNode::ComputeUserInterfaceData(void* aStartStruct,
                                     const nsRuleData* aRuleData,
                                     nsStyleContext* aContext,
                                     nsRuleNode* aHighestNode,
                                     const RuleDetail aRuleDetail,
                                     const bool aCanStoreInRuleTree)
{
  COMPUTE_START_INHERITED(UserInterface, (), ui, parentUI)

  // cursor: enum, url, inherit
  const nsCSSValue* cursorValue = aRuleData->ValueForCursor();
  nsCSSUnit cursorUnit = cursorValue->GetUnit();
  if (cursorUnit != eCSSUnit_Null) {
    delete [] ui->mCursorArray;
    ui->mCursorArray = nullptr;
    ui->mCursorArrayLength = 0;

    if (cursorUnit == eCSSUnit_Inherit) {
      canStoreInRuleTree = false;
      ui->mCursor = parentUI->mCursor;
      ui->CopyCursorArrayFrom(*parentUI);
    }
    else if (cursorUnit == eCSSUnit_Initial) {
      ui->mCursor = NS_STYLE_CURSOR_AUTO;
    }
    else {
      // The parser will never create a list that is *all* URL values --
      // that's invalid.
      NS_ABORT_IF_FALSE(cursorUnit == eCSSUnit_List ||
                        cursorUnit == eCSSUnit_ListDep,
                        nsPrintfCString("unrecognized cursor unit %d",
                                        cursorUnit).get());
      const nsCSSValueList* list = cursorValue->GetListValue();
      const nsCSSValueList* list2 = list;
      nsIDocument* doc = aContext->PresContext()->Document();
      uint32_t arrayLength = 0;
      for ( ; list->mValue.GetUnit() == eCSSUnit_Array; list = list->mNext)
        if (list->mValue.GetArrayValue()->Item(0).GetImageValue(doc))
          ++arrayLength;

      if (arrayLength != 0) {
        ui->mCursorArray = new nsCursorImage[arrayLength];
        if (ui->mCursorArray) {
          ui->mCursorArrayLength = arrayLength;

          for (nsCursorImage *item = ui->mCursorArray;
               list2->mValue.GetUnit() == eCSSUnit_Array;
               list2 = list2->mNext) {
            nsCSSValue::Array *arr = list2->mValue.GetArrayValue();
            imgIRequest *req = arr->Item(0).GetImageValue(doc);
            if (req) {
              item->SetImage(req);
              if (arr->Item(1).GetUnit() != eCSSUnit_Null) {
                item->mHaveHotspot = true;
                item->mHotspotX = arr->Item(1).GetFloatValue(),
                item->mHotspotY = arr->Item(2).GetFloatValue();
              }
              ++item;
            }
          }
        }
      }

      NS_ASSERTION(list, "Must have non-array value at the end");
      NS_ASSERTION(list->mValue.GetUnit() == eCSSUnit_Enumerated,
                   "Unexpected fallback value at end of cursor list");
      ui->mCursor = list->mValue.GetIntValue();
    }
  }

  // user-input: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForUserInput(),
              ui->mUserInput, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentUI->mUserInput,
              NS_STYLE_USER_INPUT_AUTO, 0, 0, 0, 0);

  // user-modify: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForUserModify(),
              ui->mUserModify, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentUI->mUserModify,
              NS_STYLE_USER_MODIFY_READ_ONLY,
              0, 0, 0, 0);

  // user-focus: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForUserFocus(),
              ui->mUserFocus, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentUI->mUserFocus,
              NS_STYLE_USER_FOCUS_NONE, 0, 0, 0, 0);

  COMPUTE_END_INHERITED(UserInterface, ui)
}

const void*
nsRuleNode::ComputeUIResetData(void* aStartStruct,
                               const nsRuleData* aRuleData,
                               nsStyleContext* aContext,
                               nsRuleNode* aHighestNode,
                               const RuleDetail aRuleDetail,
                               const bool aCanStoreInRuleTree)
{
  COMPUTE_START_RESET(UIReset, (), ui, parentUI)

  // user-select: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForUserSelect(),
              ui->mUserSelect, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentUI->mUserSelect,
              NS_STYLE_USER_SELECT_AUTO, 0, 0, 0, 0);

  // ime-mode: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForImeMode(),
              ui->mIMEMode, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentUI->mIMEMode,
              NS_STYLE_IME_MODE_AUTO, 0, 0, 0, 0);

  // force-broken-image-icons: integer, inherit, initial
  SetDiscrete(*aRuleData->ValueForForceBrokenImageIcon(),
              ui->mForceBrokenImageIcon,
              canStoreInRuleTree,
              SETDSC_INTEGER,
              parentUI->mForceBrokenImageIcon,
              0, 0, 0, 0, 0);

  // -moz-window-shadow: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForWindowShadow(),
              ui->mWindowShadow, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentUI->mWindowShadow,
              NS_STYLE_WINDOW_SHADOW_DEFAULT, 0, 0, 0, 0);

  COMPUTE_END_RESET(UIReset, ui)
}

// Information about each transition or animation property that is
// constant.
struct TransitionPropInfo {
  nsCSSProperty property;
  // Location of the count of the property's computed value.
  uint32_t nsStyleDisplay::* sdCount;
};

// Each property's index in this array must match its index in the
// mutable array |transitionPropData| below.
static const TransitionPropInfo transitionPropInfo[4] = {
  { eCSSProperty_transition_delay,
    &nsStyleDisplay::mTransitionDelayCount },
  { eCSSProperty_transition_duration,
    &nsStyleDisplay::mTransitionDurationCount },
  { eCSSProperty_transition_property,
    &nsStyleDisplay::mTransitionPropertyCount },
  { eCSSProperty_transition_timing_function,
    &nsStyleDisplay::mTransitionTimingFunctionCount },
};

// Each property's index in this array must match its index in the
// mutable array |animationPropData| below.
static const TransitionPropInfo animationPropInfo[8] = {
  { eCSSProperty_animation_delay,
    &nsStyleDisplay::mAnimationDelayCount },
  { eCSSProperty_animation_duration,
    &nsStyleDisplay::mAnimationDurationCount },
  { eCSSProperty_animation_name,
    &nsStyleDisplay::mAnimationNameCount },
  { eCSSProperty_animation_timing_function,
    &nsStyleDisplay::mAnimationTimingFunctionCount },
  { eCSSProperty_animation_direction,
    &nsStyleDisplay::mAnimationDirectionCount },
  { eCSSProperty_animation_fill_mode,
    &nsStyleDisplay::mAnimationFillModeCount },
  { eCSSProperty_animation_play_state,
    &nsStyleDisplay::mAnimationPlayStateCount },
  { eCSSProperty_animation_iteration_count,
    &nsStyleDisplay::mAnimationIterationCountCount },
};

// Information about each transition or animation property that changes
// during ComputeDisplayData.
struct TransitionPropData {
  const nsCSSValueList *list;
  nsCSSUnit unit;
  uint32_t num;
};

static uint32_t
CountTransitionProps(const TransitionPropInfo* aInfo,
                     TransitionPropData* aData,
                     size_t aLength,
                     nsStyleDisplay* aDisplay,
                     const nsStyleDisplay* aParentDisplay,
                     const nsRuleData* aRuleData,
                     bool& aCanStoreInRuleTree)
{
  // The four transition properties or eight animation properties are
  // stored in nsCSSDisplay in a single array for all properties.  The
  // number of transitions is equal to the number of items in the
  // longest property's value.  Properties that have fewer values than
  // the longest are filled in by repeating the list.  However, this
  // repetition does not extend the computed value of that particular
  // property (for purposes of inheritance, or, in our code, for when
  // other properties are overridden by a more specific rule).

  // But actually, since the spec isn't clear yet, we'll fully compute
  // all of them (so we can switch easily later), but only care about
  // the ones up to the number of items for 'transition-property', per
  // http://lists.w3.org/Archives/Public/www-style/2009Aug/0109.html .

  // Transitions are difficult to handle correctly because of this.  For
  // example, we need to handle scenarios such as:
  //  * a more general rule specifies transition-property: a, b, c;
  //  * a more specific rule overrides as transition-property: d;
  //
  // If only the general rule applied, we would fill in the extra
  // properties (duration, delay, etc) with initial values to create 3
  // fully-specified transitions.  But when the more specific rule
  // applies, we should only create a single transition.  In order to do
  // this we need to remember which properties were explicitly specified
  // and which ones were just filled in with initial values to get a
  // fully-specified transition, which we do by remembering the number
  // of values for each property.

  uint32_t numTransitions = 0;
  for (size_t i = 0; i < aLength; ++i) {
    const TransitionPropInfo& info = aInfo[i];
    TransitionPropData& data = aData[i];

    // cache whether any of the properties are specified as 'inherit' so
    // we can use it below

    const nsCSSValue& value = *aRuleData->ValueFor(info.property);
    data.unit = value.GetUnit();
    data.list = (value.GetUnit() == eCSSUnit_List ||
                 value.GetUnit() == eCSSUnit_ListDep)
                  ? value.GetListValue() : nullptr;

    // General algorithm to determine how many total transitions we need
    // to build.  For each property:
    //  - if there is no value specified in for the property in
    //    displayData, use the values from the start struct, but only if
    //    they were explicitly specified
    //  - if there is a value specified for the property in displayData:
    //    - if the value is 'inherit', count the number of values for
    //      that property are specified by the parent, but only those
    //      that were explicitly specified
    //    - otherwise, count the number of values specified in displayData


    // calculate number of elements
    if (data.unit == eCSSUnit_Inherit) {
      data.num = aParentDisplay->*(info.sdCount);
      aCanStoreInRuleTree = false;
    } else if (data.list) {
      data.num = ListLength(data.list);
    } else {
      data.num = aDisplay->*(info.sdCount);
    }
    if (data.num > numTransitions)
      numTransitions = data.num;
  }

  return numTransitions;
}

static void
ComputeTimingFunction(const nsCSSValue& aValue, nsTimingFunction& aResult)
{
  switch (aValue.GetUnit()) {
    case eCSSUnit_Enumerated:
      aResult = nsTimingFunction(aValue.GetIntValue());
      break;
    case eCSSUnit_Cubic_Bezier:
      {
        nsCSSValue::Array* array = aValue.GetArrayValue();
        NS_ASSERTION(array && array->Count() == 4,
                     "Need 4 control points");
        aResult = nsTimingFunction(array->Item(0).GetFloatValue(),
                                   array->Item(1).GetFloatValue(),
                                   array->Item(2).GetFloatValue(),
                                   array->Item(3).GetFloatValue());
      }
      break;
    case eCSSUnit_Steps:
      {
        nsCSSValue::Array* array = aValue.GetArrayValue();
        NS_ASSERTION(array && array->Count() == 2,
                     "Need 2 items");
        NS_ASSERTION(array->Item(0).GetUnit() == eCSSUnit_Integer,
                     "unexpected first value");
        NS_ASSERTION(array->Item(1).GetUnit() == eCSSUnit_Enumerated &&
                     (array->Item(1).GetIntValue() ==
                       NS_STYLE_TRANSITION_TIMING_FUNCTION_STEP_START ||
                      array->Item(1).GetIntValue() ==
                       NS_STYLE_TRANSITION_TIMING_FUNCTION_STEP_END),
                     "unexpected second value");
        nsTimingFunction::Type type =
          (array->Item(1).GetIntValue() ==
            NS_STYLE_TRANSITION_TIMING_FUNCTION_STEP_END)
            ? nsTimingFunction::StepEnd : nsTimingFunction::StepStart;
        aResult = nsTimingFunction(type, array->Item(0).GetIntValue());
      }
      break;
    default:
      NS_NOTREACHED("Invalid transition property unit");
  }
}

const void*
nsRuleNode::ComputeDisplayData(void* aStartStruct,
                               const nsRuleData* aRuleData,
                               nsStyleContext* aContext,
                               nsRuleNode* aHighestNode,
                               const RuleDetail aRuleDetail,
                               const bool aCanStoreInRuleTree)
{
  COMPUTE_START_RESET(Display, (), display, parentDisplay)

  // We may have ended up with aStartStruct's values of mDisplay and
  // mFloats, but those may not be correct if our style data overrides
  // its position or float properties.  Reset to mOriginalDisplay and
  // mOriginalFloats; it if turns out we still need the display/floats
  // adjustments we'll do them below.
  display->mDisplay = display->mOriginalDisplay;
  display->mFloats = display->mOriginalFloats;

  // Each property's index in this array must match its index in the
  // const array |transitionPropInfo| above.
  TransitionPropData transitionPropData[4];
  TransitionPropData& delay = transitionPropData[0];
  TransitionPropData& duration = transitionPropData[1];
  TransitionPropData& property = transitionPropData[2];
  TransitionPropData& timingFunction = transitionPropData[3];

#define FOR_ALL_TRANSITION_PROPS(var_) \
                                      for (uint32_t var_ = 0; var_ < 4; ++var_)

  // CSS Transitions
  uint32_t numTransitions =
    CountTransitionProps(transitionPropInfo, transitionPropData,
                         ArrayLength(transitionPropData),
                         display, parentDisplay, aRuleData,
                         canStoreInRuleTree);

  if (!display->mTransitions.SetLength(numTransitions)) {
    NS_WARNING("failed to allocate transitions array");
    display->mTransitions.SetLength(1);
    NS_ABORT_IF_FALSE(display->mTransitions.Length() == 1,
                      "could not allocate using auto array buffer");
    numTransitions = 1;
    FOR_ALL_TRANSITION_PROPS(p) {
      TransitionPropData& d = transitionPropData[p];

      d.num = 1;
    }
  }

  FOR_ALL_TRANSITION_PROPS(p) {
    const TransitionPropInfo& i = transitionPropInfo[p];
    TransitionPropData& d = transitionPropData[p];

    display->*(i.sdCount) = d.num;
  }

  // Fill in the transitions we just allocated with the appropriate values.
  for (uint32_t i = 0; i < numTransitions; ++i) {
    nsTransition *transition = &display->mTransitions[i];

    if (i >= delay.num) {
      transition->SetDelay(display->mTransitions[i % delay.num].GetDelay());
    } else if (delay.unit == eCSSUnit_Inherit) {
      // FIXME (Bug 522599) (for all transition properties): write a test that
      // detects when this was wrong for i >= delay.num if parent had
      // count for this property not equal to length
      NS_ABORT_IF_FALSE(i < parentDisplay->mTransitionDelayCount,
                        "delay.num computed incorrectly");
      NS_ABORT_IF_FALSE(!canStoreInRuleTree,
                        "should have made canStoreInRuleTree false above");
      transition->SetDelay(parentDisplay->mTransitions[i].GetDelay());
    } else if (delay.unit == eCSSUnit_Initial) {
      transition->SetDelay(0.0);
    } else if (delay.list) {
      switch (delay.list->mValue.GetUnit()) {
        case eCSSUnit_Seconds:
          transition->SetDelay(PR_MSEC_PER_SEC *
                               delay.list->mValue.GetFloatValue());
          break;
        case eCSSUnit_Milliseconds:
          transition->SetDelay(delay.list->mValue.GetFloatValue());
          break;
        default:
          NS_NOTREACHED("Invalid delay unit");
      }
    }

    if (i >= duration.num) {
      transition->SetDuration(
        display->mTransitions[i % duration.num].GetDuration());
    } else if (duration.unit == eCSSUnit_Inherit) {
      NS_ABORT_IF_FALSE(i < parentDisplay->mTransitionDurationCount,
                        "duration.num computed incorrectly");
      NS_ABORT_IF_FALSE(!canStoreInRuleTree,
                        "should have made canStoreInRuleTree false above");
      transition->SetDuration(parentDisplay->mTransitions[i].GetDuration());
    } else if (duration.unit == eCSSUnit_Initial) {
      transition->SetDuration(0.0);
    } else if (duration.list) {
      switch (duration.list->mValue.GetUnit()) {
        case eCSSUnit_Seconds:
          transition->SetDuration(PR_MSEC_PER_SEC *
                                  duration.list->mValue.GetFloatValue());
          break;
        case eCSSUnit_Milliseconds:
          transition->SetDuration(duration.list->mValue.GetFloatValue());
          break;
        default:
          NS_NOTREACHED("Invalid duration unit");
      }
    }

    if (i >= property.num) {
      transition->CopyPropertyFrom(display->mTransitions[i % property.num]);
    } else if (property.unit == eCSSUnit_Inherit) {
      NS_ABORT_IF_FALSE(i < parentDisplay->mTransitionPropertyCount,
                        "property.num computed incorrectly");
      NS_ABORT_IF_FALSE(!canStoreInRuleTree,
                        "should have made canStoreInRuleTree false above");
      transition->CopyPropertyFrom(parentDisplay->mTransitions[i]);
    } else if (property.unit == eCSSUnit_Initial ||
               property.unit == eCSSUnit_All) {
      transition->SetProperty(eCSSPropertyExtra_all_properties);
    } else if (property.unit == eCSSUnit_None) {
      transition->SetProperty(eCSSPropertyExtra_no_properties);
    } else if (property.list) {
      NS_ABORT_IF_FALSE(property.list->mValue.GetUnit() == eCSSUnit_Ident,
                        nsPrintfCString("Invalid transition property unit %d",
                                        property.list->mValue.GetUnit()).get());

      nsDependentString
        propertyStr(property.list->mValue.GetStringBufferValue());
      nsCSSProperty prop = nsCSSProps::LookupProperty(propertyStr,
                                                      nsCSSProps::eEnabled);
      if (prop == eCSSProperty_UNKNOWN) {
        transition->SetUnknownProperty(propertyStr);
      } else {
        transition->SetProperty(prop);
      }
    }

    if (i >= timingFunction.num) {
      transition->SetTimingFunction(
        display->mTransitions[i % timingFunction.num].GetTimingFunction());
    } else if (timingFunction.unit == eCSSUnit_Inherit) {
      NS_ABORT_IF_FALSE(i < parentDisplay->mTransitionTimingFunctionCount,
                        "timingFunction.num computed incorrectly");
      NS_ABORT_IF_FALSE(!canStoreInRuleTree,
                        "should have made canStoreInRuleTree false above");
      transition->SetTimingFunction(
        parentDisplay->mTransitions[i].GetTimingFunction());
    } else if (timingFunction.unit == eCSSUnit_Initial) {
      transition->SetTimingFunction(
        nsTimingFunction(NS_STYLE_TRANSITION_TIMING_FUNCTION_EASE));
    } else if (timingFunction.list) {
      ComputeTimingFunction(timingFunction.list->mValue,
                            transition->TimingFunctionSlot());
    }

    FOR_ALL_TRANSITION_PROPS(p) {
      const TransitionPropInfo& info = transitionPropInfo[p];
      TransitionPropData& d = transitionPropData[p];

      // if we're at the end of the list, start at the beginning and repeat
      // until we're out of transitions to populate
      if (d.list) {
        d.list = d.list->mNext ? d.list->mNext :
          aRuleData->ValueFor(info.property)->GetListValue();
      }
    }
  }

  // Each property's index in this array must match its index in the
  // const array |animationPropInfo| above.
  TransitionPropData animationPropData[8];
  TransitionPropData& animDelay = animationPropData[0];
  TransitionPropData& animDuration = animationPropData[1];
  TransitionPropData& animName = animationPropData[2];
  TransitionPropData& animTimingFunction = animationPropData[3];
  TransitionPropData& animDirection = animationPropData[4];
  TransitionPropData& animFillMode = animationPropData[5];
  TransitionPropData& animPlayState = animationPropData[6];
  TransitionPropData& animIterationCount = animationPropData[7];

#define FOR_ALL_ANIMATION_PROPS(var_) \
    for (uint32_t var_ = 0; var_ < 8; ++var_)

  // CSS Animations.

  uint32_t numAnimations =
    CountTransitionProps(animationPropInfo, animationPropData,
                         ArrayLength(animationPropData),
                         display, parentDisplay, aRuleData,
                         canStoreInRuleTree);

  if (!display->mAnimations.SetLength(numAnimations)) {
    NS_WARNING("failed to allocate animations array");
    display->mAnimations.SetLength(1);
    NS_ABORT_IF_FALSE(display->mAnimations.Length() == 1,
                      "could not allocate using auto array buffer");
    numAnimations = 1;
    FOR_ALL_ANIMATION_PROPS(p) {
      TransitionPropData& d = animationPropData[p];

      d.num = 1;
    }
  }

  FOR_ALL_ANIMATION_PROPS(p) {
    const TransitionPropInfo& i = animationPropInfo[p];
    TransitionPropData& d = animationPropData[p];

    display->*(i.sdCount) = d.num;
  }

  // Fill in the animations we just allocated with the appropriate values.
  for (uint32_t i = 0; i < numAnimations; ++i) {
    nsAnimation *animation = &display->mAnimations[i];

    if (i >= animDelay.num) {
      animation->SetDelay(display->mAnimations[i % animDelay.num].GetDelay());
    } else if (animDelay.unit == eCSSUnit_Inherit) {
      // FIXME (Bug 522599) (for all animation properties): write a test that
      // detects when this was wrong for i >= animDelay.num if parent had
      // count for this property not equal to length
      NS_ABORT_IF_FALSE(i < parentDisplay->mAnimationDelayCount,
                        "animDelay.num computed incorrectly");
      NS_ABORT_IF_FALSE(!canStoreInRuleTree,
                        "should have made canStoreInRuleTree false above");
      animation->SetDelay(parentDisplay->mAnimations[i].GetDelay());
    } else if (animDelay.unit == eCSSUnit_Initial) {
      animation->SetDelay(0.0);
    } else if (animDelay.list) {
      switch (animDelay.list->mValue.GetUnit()) {
        case eCSSUnit_Seconds:
          animation->SetDelay(PR_MSEC_PER_SEC *
                              animDelay.list->mValue.GetFloatValue());
          break;
        case eCSSUnit_Milliseconds:
          animation->SetDelay(animDelay.list->mValue.GetFloatValue());
          break;
        default:
          NS_NOTREACHED("Invalid delay unit");
      }
    }

    if (i >= animDuration.num) {
      animation->SetDuration(
        display->mAnimations[i % animDuration.num].GetDuration());
    } else if (animDuration.unit == eCSSUnit_Inherit) {
      NS_ABORT_IF_FALSE(i < parentDisplay->mAnimationDurationCount,
                        "animDuration.num computed incorrectly");
      NS_ABORT_IF_FALSE(!canStoreInRuleTree,
                        "should have made canStoreInRuleTree false above");
      animation->SetDuration(parentDisplay->mAnimations[i].GetDuration());
    } else if (animDuration.unit == eCSSUnit_Initial) {
      animation->SetDuration(0.0);
    } else if (animDuration.list) {
      switch (animDuration.list->mValue.GetUnit()) {
        case eCSSUnit_Seconds:
          animation->SetDuration(PR_MSEC_PER_SEC *
                                 animDuration.list->mValue.GetFloatValue());
          break;
        case eCSSUnit_Milliseconds:
          animation->SetDuration(animDuration.list->mValue.GetFloatValue());
          break;
        default:
          NS_NOTREACHED("Invalid duration unit");
      }
    }

    if (i >= animName.num) {
      animation->SetName(display->mAnimations[i % animName.num].GetName());
    } else if (animName.unit == eCSSUnit_Inherit) {
      NS_ABORT_IF_FALSE(i < parentDisplay->mAnimationNameCount,
                        "animName.num computed incorrectly");
      NS_ABORT_IF_FALSE(!canStoreInRuleTree,
                        "should have made canStoreInRuleTree false above");
      animation->SetName(parentDisplay->mAnimations[i].GetName());
    } else if (animName.unit == eCSSUnit_Initial) {
      animation->SetName(EmptyString());
    } else if (animName.list) {
      switch (animName.list->mValue.GetUnit()) {
        case eCSSUnit_Ident: {
          nsDependentString
            nameStr(animName.list->mValue.GetStringBufferValue());
          animation->SetName(nameStr);
          break;
        }
        case eCSSUnit_None: {
          animation->SetName(EmptyString());
          break;
        }
        default:
          NS_ABORT_IF_FALSE(false,
            nsPrintfCString("Invalid animation-name unit %d",
                                animName.list->mValue.GetUnit()).get());
      }
    }

    if (i >= animTimingFunction.num) {
      animation->SetTimingFunction(
        display->mAnimations[i % animTimingFunction.num].GetTimingFunction());
    } else if (animTimingFunction.unit == eCSSUnit_Inherit) {
      NS_ABORT_IF_FALSE(i < parentDisplay->mAnimationTimingFunctionCount,
                        "animTimingFunction.num computed incorrectly");
      NS_ABORT_IF_FALSE(!canStoreInRuleTree,
                        "should have made canStoreInRuleTree false above");
      animation->SetTimingFunction(
        parentDisplay->mAnimations[i].GetTimingFunction());
    } else if (animTimingFunction.unit == eCSSUnit_Initial) {
      animation->SetTimingFunction(
        nsTimingFunction(NS_STYLE_TRANSITION_TIMING_FUNCTION_EASE));
    } else if (animTimingFunction.list) {
      ComputeTimingFunction(animTimingFunction.list->mValue,
                            animation->TimingFunctionSlot());
    }

    if (i >= animDirection.num) {
      animation->SetDirection(display->mAnimations[i % animDirection.num].GetDirection());
    } else if (animDirection.unit == eCSSUnit_Inherit) {
      NS_ABORT_IF_FALSE(i < parentDisplay->mAnimationDirectionCount,
                        "animDirection.num computed incorrectly");
      NS_ABORT_IF_FALSE(!canStoreInRuleTree,
                        "should have made canStoreInRuleTree false above");
      animation->SetDirection(parentDisplay->mAnimations[i].GetDirection());
    } else if (animDirection.unit == eCSSUnit_Initial) {
      animation->SetDirection(NS_STYLE_ANIMATION_DIRECTION_NORMAL);
    } else if (animDirection.list) {
      NS_ABORT_IF_FALSE(animDirection.list->mValue.GetUnit() == eCSSUnit_Enumerated,
                        nsPrintfCString("Invalid animation-direction unit %d",
                                        animDirection.list->mValue.GetUnit()).get());

      animation->SetDirection(animDirection.list->mValue.GetIntValue());
    }

    if (i >= animFillMode.num) {
      animation->SetFillMode(display->mAnimations[i % animFillMode.num].GetFillMode());
    } else if (animFillMode.unit == eCSSUnit_Inherit) {
      NS_ABORT_IF_FALSE(i < parentDisplay->mAnimationFillModeCount,
                        "animFillMode.num computed incorrectly");
      NS_ABORT_IF_FALSE(!canStoreInRuleTree,
                        "should have made canStoreInRuleTree false above");
      animation->SetFillMode(parentDisplay->mAnimations[i].GetFillMode());
    } else if (animFillMode.unit == eCSSUnit_Initial) {
      animation->SetFillMode(NS_STYLE_ANIMATION_FILL_MODE_NONE);
    } else if (animFillMode.list) {
      NS_ABORT_IF_FALSE(animFillMode.list->mValue.GetUnit() == eCSSUnit_Enumerated,
                        nsPrintfCString("Invalid animation-fill-mode unit %d",
                                        animFillMode.list->mValue.GetUnit()).get());

      animation->SetFillMode(animFillMode.list->mValue.GetIntValue());
    }

    if (i >= animPlayState.num) {
      animation->SetPlayState(display->mAnimations[i % animPlayState.num].GetPlayState());
    } else if (animPlayState.unit == eCSSUnit_Inherit) {
      NS_ABORT_IF_FALSE(i < parentDisplay->mAnimationPlayStateCount,
                        "animPlayState.num computed incorrectly");
      NS_ABORT_IF_FALSE(!canStoreInRuleTree,
                        "should have made canStoreInRuleTree false above");
      animation->SetPlayState(parentDisplay->mAnimations[i].GetPlayState());
    } else if (animPlayState.unit == eCSSUnit_Initial) {
      animation->SetPlayState(NS_STYLE_ANIMATION_PLAY_STATE_RUNNING);
    } else if (animPlayState.list) {
      NS_ABORT_IF_FALSE(animPlayState.list->mValue.GetUnit() == eCSSUnit_Enumerated,
                        nsPrintfCString("Invalid animation-play-state unit %d",
                                        animPlayState.list->mValue.GetUnit()).get());

      animation->SetPlayState(animPlayState.list->mValue.GetIntValue());
    }

    if (i >= animIterationCount.num) {
      animation->SetIterationCount(display->mAnimations[i % animIterationCount.num].GetIterationCount());
    } else if (animIterationCount.unit == eCSSUnit_Inherit) {
      NS_ABORT_IF_FALSE(i < parentDisplay->mAnimationIterationCountCount,
                        "animIterationCount.num computed incorrectly");
      NS_ABORT_IF_FALSE(!canStoreInRuleTree,
                        "should have made canStoreInRuleTree false above");
      animation->SetIterationCount(parentDisplay->mAnimations[i].GetIterationCount());
    } else if (animIterationCount.unit == eCSSUnit_Initial) {
      animation->SetIterationCount(1.0f);
    } else if (animIterationCount.list) {
      switch(animIterationCount.list->mValue.GetUnit()) {
        case eCSSUnit_Enumerated:
          NS_ABORT_IF_FALSE(animIterationCount.list->mValue.GetIntValue() ==
                              NS_STYLE_ANIMATION_ITERATION_COUNT_INFINITE,
                            "unexpected value");
          animation->SetIterationCount(NS_IEEEPositiveInfinity());
          break;
        case eCSSUnit_Number:
          animation->SetIterationCount(
            animIterationCount.list->mValue.GetFloatValue());
          break;
        default:
          NS_ABORT_IF_FALSE(false,
                            "unexpected animation-iteration-count unit");
      }
    }

    FOR_ALL_ANIMATION_PROPS(p) {
      const TransitionPropInfo& info = animationPropInfo[p];
      TransitionPropData& d = animationPropData[p];

      // if we're at the end of the list, start at the beginning and repeat
      // until we're out of animations to populate
      if (d.list) {
        d.list = d.list->mNext ? d.list->mNext :
          aRuleData->ValueFor(info.property)->GetListValue();
      }
    }
  }

  // opacity: factor, inherit, initial
  SetFactor(*aRuleData->ValueForOpacity(), display->mOpacity, canStoreInRuleTree,
            parentDisplay->mOpacity, 1.0f, SETFCT_OPACITY);

  // display: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForDisplay(), display->mDisplay, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentDisplay->mDisplay,
              NS_STYLE_DISPLAY_INLINE, 0, 0, 0, 0);
  // Backup original display value for calculation of a hypothetical
  // box (CSS2 10.6.4/10.6.5), in addition to getting our style data right later.
  // See nsHTMLReflowState::CalculateHypotheticalBox
  display->mOriginalDisplay = display->mDisplay;

  // appearance: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForAppearance(),
              display->mAppearance, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentDisplay->mAppearance,
              NS_THEME_NONE, 0, 0, 0, 0);

  // binding: url, none, inherit
  const nsCSSValue* bindingValue = aRuleData->ValueForBinding();
  if (eCSSUnit_URL == bindingValue->GetUnit()) {
    mozilla::css::URLValue* url = bindingValue->GetURLStructValue();
    NS_ASSERTION(url, "What's going on here?");

    if (MOZ_LIKELY(url->GetURI())) {
      display->mBinding = url;
    } else {
      display->mBinding = nullptr;
    }
  }
  else if (eCSSUnit_None == bindingValue->GetUnit() ||
           eCSSUnit_Initial == bindingValue->GetUnit()) {
    display->mBinding = nullptr;
  }
  else if (eCSSUnit_Inherit == bindingValue->GetUnit()) {
    canStoreInRuleTree = false;
    display->mBinding = parentDisplay->mBinding;
  }

  // position: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForPosition(), display->mPosition, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentDisplay->mPosition,
              NS_STYLE_POSITION_STATIC, 0, 0, 0, 0);

  // clear: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForClear(), display->mBreakType, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentDisplay->mBreakType,
              NS_STYLE_CLEAR_NONE, 0, 0, 0, 0);

  // temp fix for bug 24000
  // Map 'auto' and 'avoid' to false, and 'always', 'left', and
  // 'right' to true.
  // "A conforming user agent may interpret the values 'left' and
  // 'right' as 'always'." - CSS2.1, section 13.3.1
  const nsCSSValue* breakBeforeValue = aRuleData->ValueForPageBreakBefore();
  if (eCSSUnit_Enumerated == breakBeforeValue->GetUnit()) {
    display->mBreakBefore =
      (NS_STYLE_PAGE_BREAK_AVOID != breakBeforeValue->GetIntValue() &&
       NS_STYLE_PAGE_BREAK_AUTO  != breakBeforeValue->GetIntValue());
  }
  else if (eCSSUnit_Initial == breakBeforeValue->GetUnit()) {
    display->mBreakBefore = false;
  }
  else if (eCSSUnit_Inherit == breakBeforeValue->GetUnit()) {
    canStoreInRuleTree = false;
    display->mBreakBefore = parentDisplay->mBreakBefore;
  }

  const nsCSSValue* breakAfterValue = aRuleData->ValueForPageBreakAfter();
  if (eCSSUnit_Enumerated == breakAfterValue->GetUnit()) {
    display->mBreakAfter =
      (NS_STYLE_PAGE_BREAK_AVOID != breakAfterValue->GetIntValue() &&
       NS_STYLE_PAGE_BREAK_AUTO  != breakAfterValue->GetIntValue());
  }
  else if (eCSSUnit_Initial == breakAfterValue->GetUnit()) {
    display->mBreakAfter = false;
  }
  else if (eCSSUnit_Inherit == breakAfterValue->GetUnit()) {
    canStoreInRuleTree = false;
    display->mBreakAfter = parentDisplay->mBreakAfter;
  }
  // end temp fix

  // float: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForCssFloat(),
              display->mFloats, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentDisplay->mFloats,
              NS_STYLE_FLOAT_NONE, 0, 0, 0, 0);
  // Save mFloats in mOriginalFloats in case we need it later
  display->mOriginalFloats = display->mFloats;

  // overflow-x: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForOverflowX(),
              display->mOverflowX, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentDisplay->mOverflowX,
              NS_STYLE_OVERFLOW_VISIBLE, 0, 0, 0, 0);

  // overflow-y: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForOverflowY(),
              display->mOverflowY, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentDisplay->mOverflowY,
              NS_STYLE_OVERFLOW_VISIBLE, 0, 0, 0, 0);

  // CSS3 overflow-x and overflow-y require some fixup as well in some
  // cases.  NS_STYLE_OVERFLOW_VISIBLE and NS_STYLE_OVERFLOW_CLIP are
  // meaningful only when used in both dimensions.
  if (display->mOverflowX != display->mOverflowY &&
      (display->mOverflowX == NS_STYLE_OVERFLOW_VISIBLE ||
       display->mOverflowX == NS_STYLE_OVERFLOW_CLIP ||
       display->mOverflowY == NS_STYLE_OVERFLOW_VISIBLE ||
       display->mOverflowY == NS_STYLE_OVERFLOW_CLIP)) {
    // We can't store in the rule tree since a more specific rule might
    // change these conditions.
    canStoreInRuleTree = false;

    // NS_STYLE_OVERFLOW_CLIP is a deprecated value, so if it's specified
    // in only one dimension, convert it to NS_STYLE_OVERFLOW_HIDDEN.
    if (display->mOverflowX == NS_STYLE_OVERFLOW_CLIP)
      display->mOverflowX = NS_STYLE_OVERFLOW_HIDDEN;
    if (display->mOverflowY == NS_STYLE_OVERFLOW_CLIP)
      display->mOverflowY = NS_STYLE_OVERFLOW_HIDDEN;

    // If 'visible' is specified but doesn't match the other dimension, it
    // turns into 'auto'.
    if (display->mOverflowX == NS_STYLE_OVERFLOW_VISIBLE)
      display->mOverflowX = NS_STYLE_OVERFLOW_AUTO;
    if (display->mOverflowY == NS_STYLE_OVERFLOW_VISIBLE)
      display->mOverflowY = NS_STYLE_OVERFLOW_AUTO;
  }

  SetDiscrete(*aRuleData->ValueForResize(), display->mResize, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentDisplay->mResize,
              NS_STYLE_RESIZE_NONE, 0, 0, 0, 0);

  // clip property: length, auto, inherit
  const nsCSSValue* clipValue = aRuleData->ValueForClip();
  switch (clipValue->GetUnit()) {
  case eCSSUnit_Inherit:
    canStoreInRuleTree = false;
    display->mClipFlags = parentDisplay->mClipFlags;
    display->mClip = parentDisplay->mClip;
    break;

  case eCSSUnit_Initial:
  case eCSSUnit_Auto:
    display->mClipFlags = NS_STYLE_CLIP_AUTO;
    display->mClip.SetRect(0,0,0,0);
    break;

  case eCSSUnit_Null:
    break;

  case eCSSUnit_Rect: {
    const nsCSSRect& clipRect = clipValue->GetRectValue();

    display->mClipFlags = NS_STYLE_CLIP_RECT;

    if (clipRect.mTop.GetUnit() == eCSSUnit_Auto) {
      display->mClip.y = 0;
      display->mClipFlags |= NS_STYLE_CLIP_TOP_AUTO;
    }
    else if (clipRect.mTop.IsLengthUnit()) {
      display->mClip.y = CalcLength(clipRect.mTop, aContext,
                                    mPresContext, canStoreInRuleTree);
    }

    if (clipRect.mBottom.GetUnit() == eCSSUnit_Auto) {
      // Setting to NS_MAXSIZE for the 'auto' case ensures that
      // the clip rect is nonempty. It is important that mClip be
      // nonempty if the actual clip rect could be nonempty.
      display->mClip.height = NS_MAXSIZE;
      display->mClipFlags |= NS_STYLE_CLIP_BOTTOM_AUTO;
    }
    else if (clipRect.mBottom.IsLengthUnit()) {
      display->mClip.height = CalcLength(clipRect.mBottom, aContext,
                                         mPresContext, canStoreInRuleTree) -
                              display->mClip.y;
    }

    if (clipRect.mLeft.GetUnit() == eCSSUnit_Auto) {
      display->mClip.x = 0;
      display->mClipFlags |= NS_STYLE_CLIP_LEFT_AUTO;
    }
    else if (clipRect.mLeft.IsLengthUnit()) {
      display->mClip.x = CalcLength(clipRect.mLeft, aContext,
                                    mPresContext, canStoreInRuleTree);
    }

    if (clipRect.mRight.GetUnit() == eCSSUnit_Auto) {
      // Setting to NS_MAXSIZE for the 'auto' case ensures that
      // the clip rect is nonempty. It is important that mClip be
      // nonempty if the actual clip rect could be nonempty.
      display->mClip.width = NS_MAXSIZE;
      display->mClipFlags |= NS_STYLE_CLIP_RIGHT_AUTO;
    }
    else if (clipRect.mRight.IsLengthUnit()) {
      display->mClip.width = CalcLength(clipRect.mRight, aContext,
                                        mPresContext, canStoreInRuleTree) -
                             display->mClip.x;
    }
    break;
  }

  default:
    NS_ABORT_IF_FALSE(false, "unrecognized clip unit");
  }

  if (display->mDisplay != NS_STYLE_DISPLAY_NONE) {
    // CSS2 9.7 specifies display type corrections dealing with 'float'
    // and 'position'.  Since generated content can't be floated or
    // positioned, we can deal with it here.

    if (nsCSSPseudoElements::firstLetter == aContext->GetPseudo()) {
      // a non-floating first-letter must be inline
      // XXX this fix can go away once bug 103189 is fixed correctly
      // Note that we reset mOriginalDisplay to enforce the invariant that it equals mDisplay if we're not positioned or floating.
      display->mOriginalDisplay = display->mDisplay = NS_STYLE_DISPLAY_INLINE;

      // We can't cache the data in the rule tree since if a more specific
      // rule has 'float: left' we'll end up with the wrong 'display'
      // property.
      canStoreInRuleTree = false;
    }

    if (display->IsAbsolutelyPositionedStyle()) {
      // 1) if position is 'absolute' or 'fixed' then display must be
      // block-level and float must be 'none'
      EnsureBlockDisplay(display->mDisplay);
      display->mFloats = NS_STYLE_FLOAT_NONE;

      // Note that it's OK to cache this struct in the ruletree
      // because it's fine as-is for any style context that points to
      // it directly, and any use of it as aStartStruct (e.g. if a
      // more specific rule sets "position: static") will use
      // mOriginalDisplay and mOriginalFloats, which we have carefully
      // not changed.
    } else if (display->mFloats != NS_STYLE_FLOAT_NONE) {
      // 2) if float is not none, and display is not none, then we must
      // set a block-level 'display' type per CSS2.1 section 9.7.
      EnsureBlockDisplay(display->mDisplay);

      // Note that it's OK to cache this struct in the ruletree
      // because it's fine as-is for any style context that points to
      // it directly, and any use of it as aStartStruct (e.g. if a
      // more specific rule sets "float: none") will use
      // mOriginalDisplay, which we have carefully not changed.
    }

  }

  /* Convert the nsCSSValueList into an nsTArray<nsTransformFunction *>. */
  const nsCSSValue* transformValue = aRuleData->ValueForTransform();
  switch (transformValue->GetUnit()) {
  case eCSSUnit_Null:
    break;

  case eCSSUnit_Initial:
  case eCSSUnit_None:
    display->mSpecifiedTransform = nullptr;
    break;

  case eCSSUnit_Inherit:
    display->mSpecifiedTransform = parentDisplay->mSpecifiedTransform;
    canStoreInRuleTree = false;
    break;

  case eCSSUnit_List:
  case eCSSUnit_ListDep: {
    const nsCSSValueList* head = transformValue->GetListValue();
    // can get a _None in here from transform animation
    if (head->mValue.GetUnit() == eCSSUnit_None) {
      NS_ABORT_IF_FALSE(head->mNext == nullptr, "none must be alone");
      display->mSpecifiedTransform = nullptr;
    } else {
      display->mSpecifiedTransform = head; // weak pointer, owned by rule
    }
    break;
  }

  default:
    NS_ABORT_IF_FALSE(false, "unrecognized transform unit");
  }

  /* Convert -moz-transform-origin. */
  const nsCSSValue* transformOriginValue =
    aRuleData->ValueForTransformOrigin();
  if (transformOriginValue->GetUnit() != eCSSUnit_Null) {
    const nsCSSValue& valX =
      transformOriginValue->GetUnit() == eCSSUnit_Triplet ?
        transformOriginValue->GetTripletValue().mXValue : *transformOriginValue;
    const nsCSSValue& valY =
      transformOriginValue->GetUnit() == eCSSUnit_Triplet ?
        transformOriginValue->GetTripletValue().mYValue : *transformOriginValue;
    const nsCSSValue& valZ =
      transformOriginValue->GetUnit() == eCSSUnit_Triplet ?
        transformOriginValue->GetTripletValue().mZValue : *transformOriginValue;

    mozilla::DebugOnly<bool> cX =
       SetCoord(valX, display->mTransformOrigin[0],
                parentDisplay->mTransformOrigin[0],
                SETCOORD_LPH | SETCOORD_INITIAL_HALF |
                  SETCOORD_BOX_POSITION | SETCOORD_STORE_CALC,
                aContext, mPresContext, canStoreInRuleTree);

     mozilla::DebugOnly<bool> cY =
       SetCoord(valY, display->mTransformOrigin[1],
                parentDisplay->mTransformOrigin[1],
                SETCOORD_LPH | SETCOORD_INITIAL_HALF |
                  SETCOORD_BOX_POSITION | SETCOORD_STORE_CALC,
                aContext, mPresContext, canStoreInRuleTree);

     if (valZ.GetUnit() == eCSSUnit_Null) {
       // Null for the z component means a 0 translation, not
       // unspecified, as we have already checked the triplet
       // value for Null.
       display->mTransformOrigin[2].SetCoordValue(0);
     } else {
       mozilla::DebugOnly<bool> cZ =
         SetCoord(valZ, display->mTransformOrigin[2],
                  parentDisplay->mTransformOrigin[2],
                  SETCOORD_LH | SETCOORD_INITIAL_ZERO | SETCOORD_STORE_CALC,
                  aContext, mPresContext, canStoreInRuleTree);
       NS_ABORT_IF_FALSE(cY == cZ, "changed one but not the other");
     }
     NS_ABORT_IF_FALSE(cX == cY, "changed one but not the other");
     NS_ASSERTION(cX, "Malformed -moz-transform-origin parse!");
  }

  const nsCSSValue* perspectiveOriginValue =
    aRuleData->ValueForPerspectiveOrigin();
  if (perspectiveOriginValue->GetUnit() != eCSSUnit_Null) {
    mozilla::DebugOnly<bool> result =
      SetPairCoords(*perspectiveOriginValue,
                    display->mPerspectiveOrigin[0],
                    display->mPerspectiveOrigin[1],
                    parentDisplay->mPerspectiveOrigin[0],
                    parentDisplay->mPerspectiveOrigin[1],
                    SETCOORD_LPH | SETCOORD_INITIAL_HALF |
                    SETCOORD_BOX_POSITION | SETCOORD_STORE_CALC,
                    aContext, mPresContext, canStoreInRuleTree);
    NS_ASSERTION(result, "Malformed -moz-perspective-origin parse!");
  }

  SetCoord(*aRuleData->ValueForPerspective(), 
           display->mChildPerspective, parentDisplay->mChildPerspective,
           SETCOORD_LAH | SETCOORD_INITIAL_ZERO | SETCOORD_NONE,
           aContext, mPresContext, canStoreInRuleTree);

  SetDiscrete(*aRuleData->ValueForBackfaceVisibility(),
              display->mBackfaceVisibility, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentDisplay->mBackfaceVisibility,
              NS_STYLE_BACKFACE_VISIBILITY_VISIBLE, 0, 0, 0, 0);

  // transform-style: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForTransformStyle(),
              display->mTransformStyle, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentDisplay->mTransformStyle,
              NS_STYLE_TRANSFORM_STYLE_FLAT, 0, 0, 0, 0);

  // orient: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForOrient(),
              display->mOrient, canStoreInRuleTree,
              SETDSC_ENUMERATED, parentDisplay->mOrient,
              NS_STYLE_ORIENT_HORIZONTAL, 0, 0, 0, 0);

  COMPUTE_END_RESET(Display, display)
}

const void*
nsRuleNode::ComputeVisibilityData(void* aStartStruct,
                                  const nsRuleData* aRuleData,
                                  nsStyleContext* aContext,
                                  nsRuleNode* aHighestNode,
                                  const RuleDetail aRuleDetail,
                                  const bool aCanStoreInRuleTree)
{
  COMPUTE_START_INHERITED(Visibility, (mPresContext),
                          visibility, parentVisibility)

  // IMPORTANT: No properties in this struct have lengths in them.  We
  // depend on this since CalcLengthWith can call GetStyleVisibility()
  // to get the language for resolving fonts!

  // direction: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForDirection(), visibility->mDirection,
              canStoreInRuleTree,
              SETDSC_ENUMERATED, parentVisibility->mDirection,
              (GET_BIDI_OPTION_DIRECTION(mPresContext->GetBidi())
               == IBMBIDI_TEXTDIRECTION_RTL)
              ? NS_STYLE_DIRECTION_RTL : NS_STYLE_DIRECTION_LTR,
              0, 0, 0, 0);

  // visibility: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForVisibility(), visibility->mVisible,
              canStoreInRuleTree,
              SETDSC_ENUMERATED, parentVisibility->mVisible,
              NS_STYLE_VISIBILITY_VISIBLE, 0, 0, 0, 0);

  // pointer-events: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForPointerEvents(), visibility->mPointerEvents,
              canStoreInRuleTree,
              SETDSC_ENUMERATED, parentVisibility->mPointerEvents,
              NS_STYLE_POINTER_EVENTS_AUTO, 0, 0, 0, 0);

  COMPUTE_END_INHERITED(Visibility, visibility)
}

const void*
nsRuleNode::ComputeColorData(void* aStartStruct,
                             const nsRuleData* aRuleData,
                             nsStyleContext* aContext,
                             nsRuleNode* aHighestNode,
                             const RuleDetail aRuleDetail,
                             const bool aCanStoreInRuleTree)
{
  COMPUTE_START_INHERITED(Color, (mPresContext), color, parentColor)

  // color: color, string, inherit
  // Special case for currentColor.  According to CSS3, setting color to 'currentColor'
  // should behave as if it is inherited
  const nsCSSValue* colorValue = aRuleData->ValueForColor();
  if (colorValue->GetUnit() == eCSSUnit_EnumColor &&
      colorValue->GetIntValue() == NS_COLOR_CURRENTCOLOR) {
    color->mColor = parentColor->mColor;
    canStoreInRuleTree = false;
  }
  else if (colorValue->GetUnit() == eCSSUnit_Initial) {
    color->mColor = mPresContext->DefaultColor();
  }
  else {
    SetColor(*colorValue, parentColor->mColor, mPresContext, aContext,
             color->mColor, canStoreInRuleTree);
  }

  COMPUTE_END_INHERITED(Color, color)
}

// information about how to compute values for background-* properties
template <class SpecifiedValueItem>
struct InitialInheritLocationFor {
};

template <>
struct InitialInheritLocationFor<nsCSSValueList> {
  static nsCSSValue nsCSSValueList::* Location() {
    return &nsCSSValueList::mValue;
  }
};

template <>
struct InitialInheritLocationFor<nsCSSValuePairList> {
  static nsCSSValue nsCSSValuePairList::* Location() {
    return &nsCSSValuePairList::mXValue;
  }
};

template <class SpecifiedValueItem, class ComputedValueItem>
struct BackgroundItemComputer {
};

template <>
struct BackgroundItemComputer<nsCSSValueList, uint8_t>
{
  static void ComputeValue(nsStyleContext* aStyleContext,
                           const nsCSSValueList* aSpecifiedValue,
                           uint8_t& aComputedValue,
                           bool& aCanStoreInRuleTree)
  {
    SetDiscrete(aSpecifiedValue->mValue, aComputedValue, aCanStoreInRuleTree,
                SETDSC_ENUMERATED, uint8_t(0), 0, 0, 0, 0, 0);
  }
};

template <>
struct BackgroundItemComputer<nsCSSValuePairList, nsStyleBackground::Repeat>
{
  static void ComputeValue(nsStyleContext* aStyleContext,
                           const nsCSSValuePairList* aSpecifiedValue,
                           nsStyleBackground::Repeat& aComputedValue,
                           bool& aCanStoreInRuleTree)
  {
    NS_ASSERTION(aSpecifiedValue->mXValue.GetUnit() == eCSSUnit_Enumerated &&
                 (aSpecifiedValue->mYValue.GetUnit() == eCSSUnit_Enumerated ||
                  aSpecifiedValue->mYValue.GetUnit() == eCSSUnit_Null),
                 "Invalid unit");
    
    bool hasContraction = true;
    uint8_t value = aSpecifiedValue->mXValue.GetIntValue();
    switch (value) {
    case NS_STYLE_BG_REPEAT_REPEAT_X:
      aComputedValue.mXRepeat = NS_STYLE_BG_REPEAT_REPEAT;
      aComputedValue.mYRepeat = NS_STYLE_BG_REPEAT_NO_REPEAT;
      break;
    case NS_STYLE_BG_REPEAT_REPEAT_Y:
      aComputedValue.mXRepeat = NS_STYLE_BG_REPEAT_NO_REPEAT;
      aComputedValue.mYRepeat = NS_STYLE_BG_REPEAT_REPEAT;
      break;
    default:
      aComputedValue.mXRepeat = value;
      hasContraction = false;
      break;
    }
    
    if (hasContraction) {
      NS_ASSERTION(aSpecifiedValue->mYValue.GetUnit() == eCSSUnit_Null,
                   "Invalid unit.");
      return;
    }
    
    switch (aSpecifiedValue->mYValue.GetUnit()) {
    case eCSSUnit_Null:
      aComputedValue.mYRepeat = aComputedValue.mXRepeat;
      break;
    case eCSSUnit_Enumerated:
      value = aSpecifiedValue->mYValue.GetIntValue();
      NS_ASSERTION(value == NS_STYLE_BG_REPEAT_NO_REPEAT ||
                   value == NS_STYLE_BG_REPEAT_REPEAT, "Unexpected value");
      aComputedValue.mYRepeat = value;
      break;
    default:
      NS_NOTREACHED("Unexpected CSS value");
      break;
    }
  }
};

template <>
struct BackgroundItemComputer<nsCSSValueList, nsStyleImage>
{
  static void ComputeValue(nsStyleContext* aStyleContext,
                           const nsCSSValueList* aSpecifiedValue,
                           nsStyleImage& aComputedValue,
                           bool& aCanStoreInRuleTree)
  {
    SetStyleImage(aStyleContext, aSpecifiedValue->mValue, aComputedValue,
                  aCanStoreInRuleTree);
  }
};

/* Helper function for
 * BackgroundItemComputer<nsCSSValue, nsStyleBackground::Position>
 * It computes a single PositionCoord from an nsCSSValue object
 * (contained in a list).
 */
typedef nsStyleBackground::Position::PositionCoord PositionCoord;
static void
ComputeBackgroundPositionCoord(nsStyleContext* aStyleContext,
                               const nsCSSValue& aEdge,
                               const nsCSSValue& aOffset,
                               PositionCoord* aResult,
                               bool& aCanStoreInRuleTree)
{
  if (eCSSUnit_Percent == aOffset.GetUnit()) {
    aResult->mLength = 0;
    aResult->mPercent = aOffset.GetPercentValue();
    aResult->mHasPercent = true;
  } else if (aOffset.IsLengthUnit()) {
    aResult->mLength = CalcLength(aOffset, aStyleContext,
                                  aStyleContext->PresContext(),
                                  aCanStoreInRuleTree);
    aResult->mPercent = 0.0f;
    aResult->mHasPercent = false;
  } else if (aOffset.IsCalcUnit()) {
    LengthPercentPairCalcOps ops(aStyleContext,
                                 aStyleContext->PresContext(),
                                 aCanStoreInRuleTree);
    nsRuleNode::ComputedCalc vals = ComputeCalc(aOffset, ops);
    aResult->mLength = vals.mLength;
    aResult->mPercent = vals.mPercent;
    aResult->mHasPercent = ops.mHasPercent;
  } else {
    aResult->mLength = 0;
    aResult->mPercent = 0.0f;
    aResult->mHasPercent = false;
    NS_ASSERTION(aOffset.GetUnit() == eCSSUnit_Null, "unexpected unit");
  }

  if (eCSSUnit_Enumerated == aEdge.GetUnit()) {
    int sign;
    if (aEdge.GetIntValue() & (NS_STYLE_BG_POSITION_BOTTOM |
                               NS_STYLE_BG_POSITION_RIGHT)) {
      sign = -1;
    } else {
      sign = 1;
    }
    aResult->mPercent = GetFloatFromBoxPosition(aEdge.GetIntValue()) +
                        sign * aResult->mPercent;
    aResult->mLength = sign * aResult->mLength;
    aResult->mHasPercent = true;
  } else {
    NS_ASSERTION(eCSSUnit_Null == aEdge.GetUnit(), "unexpected unit");
  }
}

template <>
struct BackgroundItemComputer<nsCSSValueList, nsStyleBackground::Position>
{
  static void ComputeValue(nsStyleContext* aStyleContext,
                           const nsCSSValueList* aSpecifiedValue,
                           nsStyleBackground::Position& aComputedValue,
                           bool& aCanStoreInRuleTree)
  {
    NS_ASSERTION(aSpecifiedValue->mValue.GetUnit() == eCSSUnit_Array, "bg-position not an array");

    nsRefPtr<nsCSSValue::Array> bgPositionArray =
                                  aSpecifiedValue->mValue.GetArrayValue();
    const nsCSSValue &xEdge   = bgPositionArray->Item(0);
    const nsCSSValue &xOffset = bgPositionArray->Item(1);
    const nsCSSValue &yEdge   = bgPositionArray->Item(2);
    const nsCSSValue &yOffset = bgPositionArray->Item(3);

    NS_ASSERTION((eCSSUnit_Enumerated == xEdge.GetUnit()  ||
                  eCSSUnit_Null       == xEdge.GetUnit()) &&
                 (eCSSUnit_Enumerated == yEdge.GetUnit()  ||
                  eCSSUnit_Null       == yEdge.GetUnit()) &&
                  eCSSUnit_Enumerated != xOffset.GetUnit()  &&
                  eCSSUnit_Enumerated != yOffset.GetUnit(),
                  "Invalid background position");

    ComputeBackgroundPositionCoord(aStyleContext, xEdge, xOffset,
                                   &aComputedValue.mXPosition,
                                   aCanStoreInRuleTree);

    ComputeBackgroundPositionCoord(aStyleContext, yEdge, yOffset,
                                   &aComputedValue.mYPosition,
                                   aCanStoreInRuleTree);
  }
};


struct BackgroundSizeAxis {
  nsCSSValue nsCSSValuePairList::* specified;
  nsStyleBackground::Size::Dimension nsStyleBackground::Size::* result;
  uint8_t nsStyleBackground::Size::* type;
};

static const BackgroundSizeAxis gBGSizeAxes[] = {
  { &nsCSSValuePairList::mXValue,
    &nsStyleBackground::Size::mWidth,
    &nsStyleBackground::Size::mWidthType },
  { &nsCSSValuePairList::mYValue,
    &nsStyleBackground::Size::mHeight,
    &nsStyleBackground::Size::mHeightType }
};

template <>
struct BackgroundItemComputer<nsCSSValuePairList, nsStyleBackground::Size>
{
  static void ComputeValue(nsStyleContext* aStyleContext,
                           const nsCSSValuePairList* aSpecifiedValue,
                           nsStyleBackground::Size& aComputedValue,
                           bool& aCanStoreInRuleTree)
  {
    nsStyleBackground::Size &size = aComputedValue;
    for (const BackgroundSizeAxis *axis = gBGSizeAxes,
                        *axis_end = ArrayEnd(gBGSizeAxes);
         axis < axis_end; ++axis) {
      const nsCSSValue &specified = aSpecifiedValue->*(axis->specified);
      if (eCSSUnit_Auto == specified.GetUnit()) {
        size.*(axis->type) = nsStyleBackground::Size::eAuto;
      }
      else if (eCSSUnit_Enumerated == specified.GetUnit()) {
        MOZ_STATIC_ASSERT(nsStyleBackground::Size::eContain ==
                          NS_STYLE_BG_SIZE_CONTAIN &&
                          nsStyleBackground::Size::eCover ==
                          NS_STYLE_BG_SIZE_COVER,
                          "background size constants out of sync");
        NS_ABORT_IF_FALSE(specified.GetIntValue() == NS_STYLE_BG_SIZE_CONTAIN ||
                          specified.GetIntValue() == NS_STYLE_BG_SIZE_COVER,
                          "invalid enumerated value for size coordinate");
        size.*(axis->type) = specified.GetIntValue();
      }
      else if (eCSSUnit_Null == specified.GetUnit()) {
        NS_ABORT_IF_FALSE(axis == gBGSizeAxes + 1,
                          "null allowed only as height value, and only "
                          "for contain/cover/initial/inherit");
#ifdef DEBUG
        {
          const nsCSSValue &widthValue = aSpecifiedValue->mXValue;
          NS_ABORT_IF_FALSE(widthValue.GetUnit() != eCSSUnit_Inherit &&
                            widthValue.GetUnit() != eCSSUnit_Initial,
                            "initial/inherit should already have been handled");
          NS_ABORT_IF_FALSE(widthValue.GetUnit() == eCSSUnit_Enumerated &&
                            (widthValue.GetIntValue() == NS_STYLE_BG_SIZE_CONTAIN ||
                             widthValue.GetIntValue() == NS_STYLE_BG_SIZE_COVER),
                            "null height value not corresponding to allowable "
                            "non-null width value");
        }
#endif
        size.*(axis->type) = size.mWidthType;
      }
      else if (eCSSUnit_Percent == specified.GetUnit()) {
        (size.*(axis->result)).mLength = 0;
        (size.*(axis->result)).mPercent = specified.GetPercentValue();
        (size.*(axis->result)).mHasPercent = true;
        size.*(axis->type) = nsStyleBackground::Size::eLengthPercentage;
      }
      else if (specified.IsLengthUnit()) {
        (size.*(axis->result)).mLength =
          CalcLength(specified, aStyleContext, aStyleContext->PresContext(),
                     aCanStoreInRuleTree);
        (size.*(axis->result)).mPercent = 0.0f;
        (size.*(axis->result)).mHasPercent = false;
        size.*(axis->type) = nsStyleBackground::Size::eLengthPercentage;
      } else {
        NS_ABORT_IF_FALSE(specified.IsCalcUnit(), "unexpected unit");
        LengthPercentPairCalcOps ops(aStyleContext,
                                     aStyleContext->PresContext(),
                                     aCanStoreInRuleTree);
        nsRuleNode::ComputedCalc vals = ComputeCalc(specified, ops);
        (size.*(axis->result)).mLength = vals.mLength;
        (size.*(axis->result)).mPercent = vals.mPercent;
        (size.*(axis->result)).mHasPercent = ops.mHasPercent;
        size.*(axis->type) = nsStyleBackground::Size::eLengthPercentage;
      }
    }

    NS_ABORT_IF_FALSE(size.mWidthType < nsStyleBackground::Size::eDimensionType_COUNT,
                      "bad width type");
    NS_ABORT_IF_FALSE(size.mHeightType < nsStyleBackground::Size::eDimensionType_COUNT,
                      "bad height type");
    NS_ABORT_IF_FALSE((size.mWidthType != nsStyleBackground::Size::eContain &&
                       size.mWidthType != nsStyleBackground::Size::eCover) ||
                      size.mWidthType == size.mHeightType,
                      "contain/cover apply to both dimensions or to neither");
  }
};

template <class ComputedValueItem>
static void
SetBackgroundList(nsStyleContext* aStyleContext,
                  const nsCSSValue& aValue,
                  nsAutoTArray< nsStyleBackground::Layer, 1> &aLayers,
                  const nsAutoTArray<nsStyleBackground::Layer, 1> &aParentLayers,
                  ComputedValueItem nsStyleBackground::Layer::* aResultLocation,
                  ComputedValueItem aInitialValue,
                  uint32_t aParentItemCount,
                  uint32_t& aItemCount,
                  uint32_t& aMaxItemCount,
                  bool& aRebuild,
                  bool& aCanStoreInRuleTree)
{
  switch (aValue.GetUnit()) {
  case eCSSUnit_Null:
    break;

  case eCSSUnit_Inherit:
    aRebuild = true;
    aCanStoreInRuleTree = false;
    if (!aLayers.EnsureLengthAtLeast(aParentItemCount)) {
      NS_WARNING("out of memory");
      aParentItemCount = aLayers.Length();
    }
    aItemCount = aParentItemCount;
    for (uint32_t i = 0; i < aParentItemCount; ++i) {
      aLayers[i].*aResultLocation = aParentLayers[i].*aResultLocation;
    }
    break;

  case eCSSUnit_Initial:
    aRebuild = true;
    aItemCount = 1;
    aLayers[0].*aResultLocation = aInitialValue;
    break;

  case eCSSUnit_List:
  case eCSSUnit_ListDep: {
    aRebuild = true;
    aItemCount = 0;
    const nsCSSValueList* item = aValue.GetListValue();
    do {
      NS_ASSERTION(item->mValue.GetUnit() != eCSSUnit_Null &&
                   item->mValue.GetUnit() != eCSSUnit_Inherit &&
                   item->mValue.GetUnit() != eCSSUnit_Initial,
                   "unexpected unit");
      ++aItemCount;
      if (!aLayers.EnsureLengthAtLeast(aItemCount)) {
        NS_WARNING("out of memory");
        --aItemCount;
        break;
      }
      BackgroundItemComputer<nsCSSValueList, ComputedValueItem>
        ::ComputeValue(aStyleContext, item,
                       aLayers[aItemCount-1].*aResultLocation,
                       aCanStoreInRuleTree);
      item = item->mNext;
    } while (item);
    break;
  }

  default:
    NS_ABORT_IF_FALSE(false,
                      nsPrintfCString("unexpected unit %d",
                                      aValue.GetUnit()).get());
  }

  if (aItemCount > aMaxItemCount)
    aMaxItemCount = aItemCount;
}

template <class ComputedValueItem>
static void
SetBackgroundPairList(nsStyleContext* aStyleContext,
                      const nsCSSValue& aValue,
                      nsAutoTArray< nsStyleBackground::Layer, 1> &aLayers,
                      const nsAutoTArray<nsStyleBackground::Layer, 1>
                                                                 &aParentLayers,
                      ComputedValueItem nsStyleBackground::Layer::*
                                                                aResultLocation,
                      ComputedValueItem aInitialValue,
                      uint32_t aParentItemCount,
                      uint32_t& aItemCount,
                      uint32_t& aMaxItemCount,
                      bool& aRebuild,
                      bool& aCanStoreInRuleTree)
{
  switch (aValue.GetUnit()) {
  case eCSSUnit_Null:
    break;

  case eCSSUnit_Inherit:
    aRebuild = true;
    aCanStoreInRuleTree = false;
    if (!aLayers.EnsureLengthAtLeast(aParentItemCount)) {
      NS_WARNING("out of memory");
      aParentItemCount = aLayers.Length();
    }
    aItemCount = aParentItemCount;
    for (uint32_t i = 0; i < aParentItemCount; ++i) {
      aLayers[i].*aResultLocation = aParentLayers[i].*aResultLocation;
    }
    break;

  case eCSSUnit_Initial:
    aRebuild = true;
    aItemCount = 1;
    aLayers[0].*aResultLocation = aInitialValue;
    break;

  case eCSSUnit_PairList:
  case eCSSUnit_PairListDep: {
    aRebuild = true;
    aItemCount = 0;
    const nsCSSValuePairList* item = aValue.GetPairListValue();
    do {
      NS_ASSERTION(item->mXValue.GetUnit() != eCSSUnit_Inherit &&
                   item->mXValue.GetUnit() != eCSSUnit_Initial &&
                   item->mYValue.GetUnit() != eCSSUnit_Inherit &&
                   item->mYValue.GetUnit() != eCSSUnit_Initial,
                   "unexpected unit");
      ++aItemCount;
      if (!aLayers.EnsureLengthAtLeast(aItemCount)) {
        NS_WARNING("out of memory");
        --aItemCount;
        break;
      }
      BackgroundItemComputer<nsCSSValuePairList, ComputedValueItem>
        ::ComputeValue(aStyleContext, item,
                       aLayers[aItemCount-1].*aResultLocation,
                       aCanStoreInRuleTree);
      item = item->mNext;
    } while (item);
    break;
  }

  default:
    NS_ABORT_IF_FALSE(false,
                      nsPrintfCString("unexpected unit %d",
                                      aValue.GetUnit()).get());
  }

  if (aItemCount > aMaxItemCount)
    aMaxItemCount = aItemCount;
}

template <class ComputedValueItem>
static void
FillBackgroundList(nsAutoTArray< nsStyleBackground::Layer, 1> &aLayers,
    ComputedValueItem nsStyleBackground::Layer::* aResultLocation,
    uint32_t aItemCount, uint32_t aFillCount)
{
  NS_PRECONDITION(aFillCount <= aLayers.Length(), "unexpected array length");
  for (uint32_t sourceLayer = 0, destLayer = aItemCount;
       destLayer < aFillCount;
       ++sourceLayer, ++destLayer) {
    aLayers[destLayer].*aResultLocation =
      aLayers[sourceLayer].*aResultLocation;
  }
}

const void*
nsRuleNode::ComputeBackgroundData(void* aStartStruct,
                                  const nsRuleData* aRuleData,
                                  nsStyleContext* aContext,
                                  nsRuleNode* aHighestNode,
                                  const RuleDetail aRuleDetail,
                                  const bool aCanStoreInRuleTree)
{
  COMPUTE_START_RESET(Background, (), bg, parentBG)

  // background-color: color, string, inherit
  const nsCSSValue* backColorValue = aRuleData->ValueForBackgroundColor();
  if (eCSSUnit_Initial == backColorValue->GetUnit()) {
    bg->mBackgroundColor = NS_RGBA(0, 0, 0, 0);
  } else if (!SetColor(*backColorValue, parentBG->mBackgroundColor,
                       mPresContext, aContext, bg->mBackgroundColor,
                       canStoreInRuleTree)) {
    NS_ASSERTION(eCSSUnit_Null == backColorValue->GetUnit(),
                 "unexpected color unit");
  }

  uint32_t maxItemCount = 1;
  bool rebuild = false;

  // background-image: url (stored as image), none, inherit [list]
  nsStyleImage initialImage;
  SetBackgroundList(aContext, *aRuleData->ValueForBackgroundImage(),
                    bg->mLayers,
                    parentBG->mLayers, &nsStyleBackground::Layer::mImage,
                    initialImage, parentBG->mImageCount, bg->mImageCount,
                    maxItemCount, rebuild, canStoreInRuleTree);

  // background-repeat: enum, inherit, initial [pair list]
  nsStyleBackground::Repeat initialRepeat;
  initialRepeat.SetInitialValues();
  SetBackgroundPairList(aContext, *aRuleData->ValueForBackgroundRepeat(),
                        bg->mLayers,
                        parentBG->mLayers, &nsStyleBackground::Layer::mRepeat,
                        initialRepeat, parentBG->mRepeatCount,
                        bg->mRepeatCount, maxItemCount, rebuild, 
                        canStoreInRuleTree);

  // background-attachment: enum, inherit, initial [list]
  SetBackgroundList(aContext, *aRuleData->ValueForBackgroundAttachment(),
                    bg->mLayers, parentBG->mLayers,
                    &nsStyleBackground::Layer::mAttachment,
                    uint8_t(NS_STYLE_BG_ATTACHMENT_SCROLL),
                    parentBG->mAttachmentCount,
                    bg->mAttachmentCount, maxItemCount, rebuild,
                    canStoreInRuleTree);

  // background-clip: enum, inherit, initial [list]
  SetBackgroundList(aContext, *aRuleData->ValueForBackgroundClip(),
                    bg->mLayers,
                    parentBG->mLayers, &nsStyleBackground::Layer::mClip,
                    uint8_t(NS_STYLE_BG_CLIP_BORDER), parentBG->mClipCount,
                    bg->mClipCount, maxItemCount, rebuild, canStoreInRuleTree);

  // background-inline-policy: enum, inherit, initial
  SetDiscrete(*aRuleData->ValueForBackgroundInlinePolicy(),
              bg->mBackgroundInlinePolicy,
              canStoreInRuleTree, SETDSC_ENUMERATED,
              parentBG->mBackgroundInlinePolicy,
              NS_STYLE_BG_INLINE_POLICY_CONTINUOUS, 0, 0, 0, 0);

  // background-origin: enum, inherit, initial [list]
  SetBackgroundList(aContext, *aRuleData->ValueForBackgroundOrigin(),
                    bg->mLayers,
                    parentBG->mLayers, &nsStyleBackground::Layer::mOrigin,
                    uint8_t(NS_STYLE_BG_ORIGIN_PADDING), parentBG->mOriginCount,
                    bg->mOriginCount, maxItemCount, rebuild,
                    canStoreInRuleTree);

  // background-position: enum, length, percent (flags), inherit [pair list]
  nsStyleBackground::Position initialPosition;
  initialPosition.SetInitialValues();
  SetBackgroundList(aContext, *aRuleData->ValueForBackgroundPosition(),
                    bg->mLayers,
                    parentBG->mLayers, &nsStyleBackground::Layer::mPosition,
                    initialPosition, parentBG->mPositionCount,
                    bg->mPositionCount, maxItemCount, rebuild,
                    canStoreInRuleTree);

  // background-size: enum, length, auto, inherit, initial [pair list]
  nsStyleBackground::Size initialSize;
  initialSize.SetInitialValues();
  SetBackgroundPairList(aContext, *aRuleData->ValueForBackgroundSize(),
                        bg->mLayers,
                        parentBG->mLayers, &nsStyleBackground::Layer::mSize,
                        initialSize, parentBG->mSizeCount,
                        bg->mSizeCount, maxItemCount, rebuild,
                        canStoreInRuleTree);

  if (rebuild) {
    // Delete any extra items.  We need to keep layers in which any
    // property was specified.
    bg->mLayers.TruncateLength(maxItemCount);

    uint32_t fillCount = bg->mImageCount;
    FillBackgroundList(bg->mLayers, &nsStyleBackground::Layer::mImage,
                       bg->mImageCount, fillCount);
    FillBackgroundList(bg->mLayers,