layout/painting/nsCSSRenderingBorders.cpp
author alwu <alwu@mozilla.com>
Mon, 07 Jan 2019 19:57:48 +0000
changeset 512757 0e229bbdaae5c8fa9f83796c628a4fdf88f057ba
parent 512746 ee870d4a43083769491e0964ae180304542fc10f
child 512983 9dcf694ba4b32bbebc7ae4e88675ddee1c40996a
permissions -rw-r--r--
Bug 1513039 - part5 : log warning when autoplay is blocked. r=cpearce,karlt Wrap 'nsContentUtils::ReportToConsole()' to reduce necessary input parameters and call it when we need to log error or warning message. Show the warning when autoplay is blocked. For web audio, this restores the console messages removed in part4 and also reports the same message when the AudioContext is blocked in the constructor. Differential Revision: https://phabricator.services.mozilla.com/D14330

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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/. */

#include "nsCSSRenderingBorders.h"

#include "gfxUtils.h"
#include "mozilla/ArrayUtils.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/gfx/Helpers.h"
#include "mozilla/gfx/PathHelpers.h"
#include "BorderConsts.h"
#include "DashedCornerFinder.h"
#include "DottedCornerFinder.h"
#include "nsLayoutUtils.h"
#include "nsStyleConsts.h"
#include "nsContentUtils.h"
#include "nsCSSColorUtils.h"
#include "nsCSSRendering.h"
#include "nsCSSRenderingGradients.h"
#include "nsDisplayList.h"
#include "GeckoProfiler.h"
#include "nsExpirationTracker.h"
#include "nsIScriptError.h"
#include "nsClassHashtable.h"
#include "nsPresContext.h"
#include "nsStyleStruct.h"
#include "gfx2DGlue.h"
#include "gfxGradientCache.h"
#include "mozilla/layers/StackingContextHelper.h"
#include "mozilla/layers/RenderRootStateManager.h"
#include "mozilla/layers/WebRenderLayerManager.h"
#include "mozilla/Range.h"
#include <algorithm>

using namespace mozilla;
using namespace mozilla::gfx;
using namespace mozilla::image;

#define MAX_COMPOSITE_BORDER_WIDTH LayoutDeviceIntCoord(10000)

/**
 * nsCSSRendering::PaintBorder
 * nsCSSRendering::PaintOutline
 *   -> DrawBorders
 *
 * DrawBorders
 *   -> Ability to use specialized approach?
 *      |- Draw using specialized function
 *   |- separate corners?
 *   |- dashed side mask
 *   |
 *   -> can border be drawn in 1 pass? (e.g., solid border same color all
 * around)
 *      |- DrawBorderSides with all 4 sides
 *   -> more than 1 pass?
 *      |- for each corner
 *         |- clip to DoCornerClipSubPath
 *         |- for each side adjacent to corner
 *            |- clip to GetSideClipSubPath
 *            |- DrawBorderSides with one side
 *      |- for each side
 *         |- GetSideClipWithoutCornersRect
 *         |- DrawDashedOrDottedSide || DrawBorderSides with one side
 */

static void ComputeBorderCornerDimensions(const Float* aBorderWidths,
                                          const RectCornerRadii& aRadii,
                                          RectCornerRadii* aDimsResult);

// given a side index, get the previous and next side index
#define NEXT_SIDE(_s) mozilla::Side(((_s) + 1) & 3)
#define PREV_SIDE(_s) mozilla::Side(((_s) + 3) & 3)

// given a corner index, get the previous and next corner index
#define NEXT_CORNER(_s) Corner(((_s) + 1) & 3)
#define PREV_CORNER(_s) Corner(((_s) + 3) & 3)

// from the given base color and the background color, turn
// color into a color for the given border pattern style
static Color MakeBorderColor(nscolor aColor,
                             BorderColorStyle aBorderColorStyle);

// Given a line index (an index starting from the outside of the
// border going inwards) and an array of line styles, calculate the
// color that that stripe of the border should be rendered in.
static Color ComputeColorForLine(uint32_t aLineIndex,
                                 const BorderColorStyle* aBorderColorStyle,
                                 uint32_t aBorderColorStyleCount,
                                 nscolor aBorderColor);

// little helper function to check if the array of 4 floats given are
// equal to the given value
static bool CheckFourFloatsEqual(const Float* vals, Float k) {
  return (vals[0] == k && vals[1] == k && vals[2] == k && vals[3] == k);
}

static bool IsZeroSize(const Size& sz) {
  return sz.width == 0.0 || sz.height == 0.0;
}

/* static */ bool nsCSSBorderRenderer::AllCornersZeroSize(
    const RectCornerRadii& corners) {
  return IsZeroSize(corners[eCornerTopLeft]) &&
         IsZeroSize(corners[eCornerTopRight]) &&
         IsZeroSize(corners[eCornerBottomRight]) &&
         IsZeroSize(corners[eCornerBottomLeft]);
}

static mozilla::Side GetHorizontalSide(Corner aCorner) {
  return (aCorner == C_TL || aCorner == C_TR) ? eSideTop : eSideBottom;
}

static mozilla::Side GetVerticalSide(Corner aCorner) {
  return (aCorner == C_TL || aCorner == C_BL) ? eSideLeft : eSideRight;
}

static Corner GetCWCorner(mozilla::Side aSide) {
  return Corner(NEXT_SIDE(aSide));
}

static Corner GetCCWCorner(mozilla::Side aSide) { return Corner(aSide); }

static bool IsSingleSide(int aSides) {
  return aSides == eSideBitsTop || aSides == eSideBitsRight ||
         aSides == eSideBitsBottom || aSides == eSideBitsLeft;
}

static bool IsHorizontalSide(mozilla::Side aSide) {
  return aSide == eSideTop || aSide == eSideBottom;
}

typedef enum {
  // Normal solid square corner.  Will be rectangular, the size of the
  // adjacent sides.  If the corner has a border radius, the corner
  // will always be solid, since we don't do dotted/dashed etc.
  CORNER_NORMAL,

  // Paint the corner in whatever style is not dotted/dashed of the
  // adjacent corners.
  CORNER_SOLID,

  // Paint the corner as a dot, the size of the bigger of the adjacent
  // sides.
  CORNER_DOT
} CornerStyle;

nsCSSBorderRenderer::nsCSSBorderRenderer(
    nsPresContext* aPresContext, const Document* aDocument,
    DrawTarget* aDrawTarget, const Rect& aDirtyRect, Rect& aOuterRect,
    const StyleBorderStyle* aBorderStyles, const Float* aBorderWidths,
    RectCornerRadii& aBorderRadii, const nscolor* aBorderColors,
    bool aBackfaceIsVisible, const Maybe<Rect>& aClipRect)
    : mPresContext(aPresContext),
      mDocument(aDocument),
      mDrawTarget(aDrawTarget),
      mDirtyRect(aDirtyRect),
      mOuterRect(aOuterRect),
      mBorderRadii(aBorderRadii),
      mBackfaceIsVisible(aBackfaceIsVisible),
      mLocalClip(aClipRect) {
  PodCopy(mBorderStyles, aBorderStyles, 4);
  PodCopy(mBorderWidths, aBorderWidths, 4);
  PodCopy(mBorderColors, aBorderColors, 4);
  mInnerRect = mOuterRect;
  mInnerRect.Deflate(Margin(
      mBorderStyles[0] != StyleBorderStyle::None ? mBorderWidths[0] : 0,
      mBorderStyles[1] != StyleBorderStyle::None ? mBorderWidths[1] : 0,
      mBorderStyles[2] != StyleBorderStyle::None ? mBorderWidths[2] : 0,
      mBorderStyles[3] != StyleBorderStyle::None ? mBorderWidths[3] : 0));

  ComputeBorderCornerDimensions(mBorderWidths, mBorderRadii,
                                &mBorderCornerDimensions);

  mOneUnitBorder = CheckFourFloatsEqual(mBorderWidths, 1.0);
  mNoBorderRadius = AllCornersZeroSize(mBorderRadii);
  mAllBordersSameStyle = AreBorderSideFinalStylesSame(eSideBitsAll);
  mAllBordersSameWidth = AllBordersSameWidth();
  mAvoidStroke = false;
}

/* static */ void nsCSSBorderRenderer::ComputeInnerRadii(
    const RectCornerRadii& aRadii, const Float* aBorderSizes,
    RectCornerRadii* aInnerRadiiRet) {
  RectCornerRadii& iRadii = *aInnerRadiiRet;

  iRadii[C_TL].width =
      std::max(0.f, aRadii[C_TL].width - aBorderSizes[eSideLeft]);
  iRadii[C_TL].height =
      std::max(0.f, aRadii[C_TL].height - aBorderSizes[eSideTop]);

  iRadii[C_TR].width =
      std::max(0.f, aRadii[C_TR].width - aBorderSizes[eSideRight]);
  iRadii[C_TR].height =
      std::max(0.f, aRadii[C_TR].height - aBorderSizes[eSideTop]);

  iRadii[C_BR].width =
      std::max(0.f, aRadii[C_BR].width - aBorderSizes[eSideRight]);
  iRadii[C_BR].height =
      std::max(0.f, aRadii[C_BR].height - aBorderSizes[eSideBottom]);

  iRadii[C_BL].width =
      std::max(0.f, aRadii[C_BL].width - aBorderSizes[eSideLeft]);
  iRadii[C_BL].height =
      std::max(0.f, aRadii[C_BL].height - aBorderSizes[eSideBottom]);
}

/* static */ void nsCSSBorderRenderer::ComputeOuterRadii(
    const RectCornerRadii& aRadii, const Float* aBorderSizes,
    RectCornerRadii* aOuterRadiiRet) {
  RectCornerRadii& oRadii = *aOuterRadiiRet;

  // default all corners to sharp corners
  oRadii = RectCornerRadii(0.f);

  // round the edges that have radii > 0.0 to start with
  if (aRadii[C_TL].width > 0.f && aRadii[C_TL].height > 0.f) {
    oRadii[C_TL].width =
        std::max(0.f, aRadii[C_TL].width + aBorderSizes[eSideLeft]);
    oRadii[C_TL].height =
        std::max(0.f, aRadii[C_TL].height + aBorderSizes[eSideTop]);
  }

  if (aRadii[C_TR].width > 0.f && aRadii[C_TR].height > 0.f) {
    oRadii[C_TR].width =
        std::max(0.f, aRadii[C_TR].width + aBorderSizes[eSideRight]);
    oRadii[C_TR].height =
        std::max(0.f, aRadii[C_TR].height + aBorderSizes[eSideTop]);
  }

  if (aRadii[C_BR].width > 0.f && aRadii[C_BR].height > 0.f) {
    oRadii[C_BR].width =
        std::max(0.f, aRadii[C_BR].width + aBorderSizes[eSideRight]);
    oRadii[C_BR].height =
        std::max(0.f, aRadii[C_BR].height + aBorderSizes[eSideBottom]);
  }

  if (aRadii[C_BL].width > 0.f && aRadii[C_BL].height > 0.f) {
    oRadii[C_BL].width =
        std::max(0.f, aRadii[C_BL].width + aBorderSizes[eSideLeft]);
    oRadii[C_BL].height =
        std::max(0.f, aRadii[C_BL].height + aBorderSizes[eSideBottom]);
  }
}

/*static*/ void ComputeBorderCornerDimensions(const Float* aBorderWidths,
                                              const RectCornerRadii& aRadii,
                                              RectCornerRadii* aDimsRet) {
  Float leftWidth = aBorderWidths[eSideLeft];
  Float topWidth = aBorderWidths[eSideTop];
  Float rightWidth = aBorderWidths[eSideRight];
  Float bottomWidth = aBorderWidths[eSideBottom];

  if (nsCSSBorderRenderer::AllCornersZeroSize(aRadii)) {
    // These will always be in pixel units from CSS
    (*aDimsRet)[C_TL] = Size(leftWidth, topWidth);
    (*aDimsRet)[C_TR] = Size(rightWidth, topWidth);
    (*aDimsRet)[C_BR] = Size(rightWidth, bottomWidth);
    (*aDimsRet)[C_BL] = Size(leftWidth, bottomWidth);
  } else {
    // Always round up to whole pixels for the corners; it's safe to
    // make the corners bigger than necessary, and this way we ensure
    // that we avoid seams.
    (*aDimsRet)[C_TL] = Size(ceil(std::max(leftWidth, aRadii[C_TL].width)),
                             ceil(std::max(topWidth, aRadii[C_TL].height)));
    (*aDimsRet)[C_TR] = Size(ceil(std::max(rightWidth, aRadii[C_TR].width)),
                             ceil(std::max(topWidth, aRadii[C_TR].height)));
    (*aDimsRet)[C_BR] = Size(ceil(std::max(rightWidth, aRadii[C_BR].width)),
                             ceil(std::max(bottomWidth, aRadii[C_BR].height)));
    (*aDimsRet)[C_BL] = Size(ceil(std::max(leftWidth, aRadii[C_BL].width)),
                             ceil(std::max(bottomWidth, aRadii[C_BL].height)));
  }
}

bool nsCSSBorderRenderer::AreBorderSideFinalStylesSame(uint8_t aSides) {
  NS_ASSERTION(aSides != 0 && (aSides & ~eSideBitsAll) == 0,
               "AreBorderSidesSame: invalid whichSides!");

  /* First check if the specified styles and colors are the same for all sides
   */
  int firstStyle = 0;
  NS_FOR_CSS_SIDES(i) {
    if (firstStyle == i) {
      if (((1 << i) & aSides) == 0) firstStyle++;
      continue;
    }

    if (((1 << i) & aSides) == 0) {
      continue;
    }

    if (mBorderStyles[firstStyle] != mBorderStyles[i] ||
        mBorderColors[firstStyle] != mBorderColors[i]) {
      return false;
    }
  }

  /* Then if it's one of the two-tone styles and we're not
   * just comparing the TL or BR sides */
  switch (mBorderStyles[firstStyle]) {
    case StyleBorderStyle::Groove:
    case StyleBorderStyle::Ridge:
    case StyleBorderStyle::Inset:
    case StyleBorderStyle::Outset:
      return ((aSides & ~(eSideBitsTop | eSideBitsLeft)) == 0 ||
              (aSides & ~(eSideBitsBottom | eSideBitsRight)) == 0);
    default:
      return true;
  }
}

bool nsCSSBorderRenderer::IsSolidCornerStyle(StyleBorderStyle aStyle,
                                             Corner aCorner) {
  switch (aStyle) {
    case StyleBorderStyle::Solid:
      return true;

    case StyleBorderStyle::Inset:
    case StyleBorderStyle::Outset:
      return (aCorner == eCornerTopLeft || aCorner == eCornerBottomRight);

    case StyleBorderStyle::Groove:
    case StyleBorderStyle::Ridge:
      return mOneUnitBorder &&
             (aCorner == eCornerTopLeft || aCorner == eCornerBottomRight);

    case StyleBorderStyle::Double:
      return mOneUnitBorder;

    default:
      return false;
  }
}

bool nsCSSBorderRenderer::IsCornerMergeable(Corner aCorner) {
  // Corner between dotted borders with same width and small radii is
  // merged into single dot.
  //
  //  widthH / 2.0
  // |<---------->|
  // |            |
  // |radius.width|
  // |<--->|      |
  // |     |      |
  // |    _+------+------------+-----
  // |  /      ###|###         |
  // |/    #######|#######     |
  // +   #########|#########   |
  // |  ##########|##########  |
  // | ###########|########### |
  // | ###########|########### |
  // |############|############|
  // +------------+############|
  // |#########################|
  // | ####################### |
  // | ####################### |
  // |  #####################  |
  // |   ###################   |
  // |     ###############     |
  // |         #######         |
  // +-------------------------+----
  // |                         |
  // |                         |
  mozilla::Side sideH(GetHorizontalSide(aCorner));
  mozilla::Side sideV(GetVerticalSide(aCorner));
  StyleBorderStyle styleH = mBorderStyles[sideH];
  StyleBorderStyle styleV = mBorderStyles[sideV];
  if (styleH != styleV || styleH != StyleBorderStyle::Dotted) {
    return false;
  }

  Float widthH = mBorderWidths[sideH];
  Float widthV = mBorderWidths[sideV];
  if (widthH != widthV) {
    return false;
  }

  Size radius = mBorderRadii[aCorner];
  return IsZeroSize(radius) ||
         (radius.width < widthH / 2.0f && radius.height < widthH / 2.0f);
}

BorderColorStyle nsCSSBorderRenderer::BorderColorStyleForSolidCorner(
    StyleBorderStyle aStyle, Corner aCorner) {
  // note that this function assumes that the corner is already solid,
  // as per the earlier function
  switch (aStyle) {
    case StyleBorderStyle::Solid:
    case StyleBorderStyle::Double:
      return BorderColorStyleSolid;

    case StyleBorderStyle::Inset:
    case StyleBorderStyle::Groove:
      if (aCorner == eCornerTopLeft)
        return BorderColorStyleDark;
      else if (aCorner == eCornerBottomRight)
        return BorderColorStyleLight;
      break;

    case StyleBorderStyle::Outset:
    case StyleBorderStyle::Ridge:
      if (aCorner == eCornerTopLeft)
        return BorderColorStyleLight;
      else if (aCorner == eCornerBottomRight)
        return BorderColorStyleDark;
      break;
    default:
      return BorderColorStyleNone;
  }

  return BorderColorStyleNone;
}

Rect nsCSSBorderRenderer::GetCornerRect(Corner aCorner) {
  Point offset(0.f, 0.f);

  if (aCorner == C_TR || aCorner == C_BR)
    offset.x = mOuterRect.Width() - mBorderCornerDimensions[aCorner].width;
  if (aCorner == C_BR || aCorner == C_BL)
    offset.y = mOuterRect.Height() - mBorderCornerDimensions[aCorner].height;

  return Rect(mOuterRect.TopLeft() + offset, mBorderCornerDimensions[aCorner]);
}

Rect nsCSSBorderRenderer::GetSideClipWithoutCornersRect(mozilla::Side aSide) {
  Point offset(0.f, 0.f);

  // The offset from the outside rect to the start of this side's
  // box.  For the top and bottom sides, the height of the box
  // must be the border height; the x start must take into account
  // the corner size (which may be bigger than the right or left
  // side's width).  The same applies to the right and left sides.
  if (aSide == eSideTop) {
    offset.x = mBorderCornerDimensions[C_TL].width;
  } else if (aSide == eSideRight) {
    offset.x = mOuterRect.Width() - mBorderWidths[eSideRight];
    offset.y = mBorderCornerDimensions[C_TR].height;
  } else if (aSide == eSideBottom) {
    offset.x = mBorderCornerDimensions[C_BL].width;
    offset.y = mOuterRect.Height() - mBorderWidths[eSideBottom];
  } else if (aSide == eSideLeft) {
    offset.y = mBorderCornerDimensions[C_TL].height;
  }

  // The sum of the width & height of the corners adjacent to the
  // side.  This relies on the relationship between side indexing and
  // corner indexing; that is, 0 == SIDE_TOP and 0 == CORNER_TOP_LEFT,
  // with both proceeding clockwise.
  Size sideCornerSum = mBorderCornerDimensions[GetCCWCorner(aSide)] +
                       mBorderCornerDimensions[GetCWCorner(aSide)];
  Rect rect(mOuterRect.TopLeft() + offset, mOuterRect.Size() - sideCornerSum);

  if (IsHorizontalSide(aSide))
    rect.height = mBorderWidths[aSide];
  else
    rect.width = mBorderWidths[aSide];

  return rect;
}

// The side border type and the adjacent border types are
// examined and one of the different types of clipping (listed
// below) is selected.

typedef enum {
  // clip to the trapezoid formed by the corners of the
  // inner and outer rectangles for the given side
  //
  // +---------------
  // |\%%%%%%%%%%%%%%
  // |  \%%%%%%%%%%%%
  // |   \%%%%%%%%%%%
  // |     \%%%%%%%%%
  // |      +--------
  // |      |
  // |      |
  SIDE_CLIP_TRAPEZOID,

  // clip to the trapezoid formed by the outer rectangle
  // corners and the center of the region, making sure
  // that diagonal lines all go directly from the outside
  // corner to the inside corner, but that they then continue on
  // to the middle.
  //
  // This is needed for correctly clipping rounded borders,
  // which might extend past the SIDE_CLIP_TRAPEZOID trap.
  //
  // +-------__--+---
  //  \%%%%_-%%%%%%%%
  //    \+-%%%%%%%%%%
  //    / \%%%%%%%%%%
  //   /   \%%%%%%%%%
  //  |     +%%_-+---
  // |        +%%%%%%
  // |       / \%%%%%
  // +      +    \%%%
  // |      |      +-
  SIDE_CLIP_TRAPEZOID_FULL,

  // clip to the rectangle formed by the given side including corner.
  // This is used by the non-dotted side next to dotted side.
  //
  // +---------------
  // |%%%%%%%%%%%%%%%
  // |%%%%%%%%%%%%%%%
  // |%%%%%%%%%%%%%%%
  // |%%%%%%%%%%%%%%%
  // +------+--------
  // |      |
  // |      |
  SIDE_CLIP_RECTANGLE_CORNER,

  // clip to the rectangle formed by the given side excluding corner.
  // This is used by the dotted side next to non-dotted side.
  //
  // +------+--------
  // |      |%%%%%%%%
  // |      |%%%%%%%%
  // |      |%%%%%%%%
  // |      |%%%%%%%%
  // |      +--------
  // |      |
  // |      |
  SIDE_CLIP_RECTANGLE_NO_CORNER,
} SideClipType;

// Given three points, p0, p1, and midPoint, move p1 further in to the
// rectangle (of which aMidPoint is the center) so that it reaches the
// closer of the horizontal or vertical lines intersecting the midpoint,
// while maintaing the slope of the line.  If p0 and p1 are the same,
// just move p1 to midPoint (since there's no slope to maintain).
// FIXME: Extending only to the midpoint isn't actually sufficient for
// boxes with asymmetric radii.
static void MaybeMoveToMidPoint(Point& aP0, Point& aP1,
                                const Point& aMidPoint) {
  Point ps = aP1 - aP0;

  if (ps.x == 0.0) {
    if (ps.y == 0.0) {
      aP1 = aMidPoint;
    } else {
      aP1.y = aMidPoint.y;
    }
  } else {
    if (ps.y == 0.0) {
      aP1.x = aMidPoint.x;
    } else {
      Float k =
          std::min((aMidPoint.x - aP0.x) / ps.x, (aMidPoint.y - aP0.y) / ps.y);
      aP1 = aP0 + ps * k;
    }
  }
}

already_AddRefed<Path> nsCSSBorderRenderer::GetSideClipSubPath(
    mozilla::Side aSide) {
  // the clip proceeds clockwise from the top left corner;
  // so "start" in each case is the start of the region from that side.
  //
  // the final path will be formed like:
  // s0 ------- e0
  // |         /
  // s1 ----- e1
  //
  // that is, the second point will always be on the inside

  Point start[2];
  Point end[2];

#define IS_DOTTED(_s) ((_s) == StyleBorderStyle::Dotted)
  bool isDotted = IS_DOTTED(mBorderStyles[aSide]);
  bool startIsDotted = IS_DOTTED(mBorderStyles[PREV_SIDE(aSide)]);
  bool endIsDotted = IS_DOTTED(mBorderStyles[NEXT_SIDE(aSide)]);
#undef IS_DOTTED

  SideClipType startType = SIDE_CLIP_TRAPEZOID;
  SideClipType endType = SIDE_CLIP_TRAPEZOID;

  if (!IsZeroSize(mBorderRadii[GetCCWCorner(aSide)])) {
    startType = SIDE_CLIP_TRAPEZOID_FULL;
  } else if (startIsDotted && !isDotted) {
    startType = SIDE_CLIP_RECTANGLE_CORNER;
  } else if (!startIsDotted && isDotted) {
    startType = SIDE_CLIP_RECTANGLE_NO_CORNER;
  }

  if (!IsZeroSize(mBorderRadii[GetCWCorner(aSide)])) {
    endType = SIDE_CLIP_TRAPEZOID_FULL;
  } else if (endIsDotted && !isDotted) {
    endType = SIDE_CLIP_RECTANGLE_CORNER;
  } else if (!endIsDotted && isDotted) {
    endType = SIDE_CLIP_RECTANGLE_NO_CORNER;
  }

  Point midPoint = mInnerRect.Center();

  start[0] = mOuterRect.CCWCorner(aSide);
  start[1] = mInnerRect.CCWCorner(aSide);

  end[0] = mOuterRect.CWCorner(aSide);
  end[1] = mInnerRect.CWCorner(aSide);

  if (startType == SIDE_CLIP_TRAPEZOID_FULL) {
    MaybeMoveToMidPoint(start[0], start[1], midPoint);
  } else if (startType == SIDE_CLIP_RECTANGLE_CORNER) {
    if (IsHorizontalSide(aSide)) {
      start[1] =
          Point(mOuterRect.CCWCorner(aSide).x, mInnerRect.CCWCorner(aSide).y);
    } else {
      start[1] =
          Point(mInnerRect.CCWCorner(aSide).x, mOuterRect.CCWCorner(aSide).y);
    }
  } else if (startType == SIDE_CLIP_RECTANGLE_NO_CORNER) {
    if (IsHorizontalSide(aSide)) {
      start[0] =
          Point(mInnerRect.CCWCorner(aSide).x, mOuterRect.CCWCorner(aSide).y);
    } else {
      start[0] =
          Point(mOuterRect.CCWCorner(aSide).x, mInnerRect.CCWCorner(aSide).y);
    }
  }

  if (endType == SIDE_CLIP_TRAPEZOID_FULL) {
    MaybeMoveToMidPoint(end[0], end[1], midPoint);
  } else if (endType == SIDE_CLIP_RECTANGLE_CORNER) {
    if (IsHorizontalSide(aSide)) {
      end[1] =
          Point(mOuterRect.CWCorner(aSide).x, mInnerRect.CWCorner(aSide).y);
    } else {
      end[1] =
          Point(mInnerRect.CWCorner(aSide).x, mOuterRect.CWCorner(aSide).y);
    }
  } else if (endType == SIDE_CLIP_RECTANGLE_NO_CORNER) {
    if (IsHorizontalSide(aSide)) {
      end[0] =
          Point(mInnerRect.CWCorner(aSide).x, mOuterRect.CWCorner(aSide).y);
    } else {
      end[0] =
          Point(mOuterRect.CWCorner(aSide).x, mInnerRect.CWCorner(aSide).y);
    }
  }

  RefPtr<PathBuilder> builder = mDrawTarget->CreatePathBuilder();
  builder->MoveTo(start[0]);
  builder->LineTo(end[0]);
  builder->LineTo(end[1]);
  builder->LineTo(start[1]);
  builder->Close();
  return builder->Finish();
}

Point nsCSSBorderRenderer::GetStraightBorderPoint(mozilla::Side aSide,
                                                  Corner aCorner,
                                                  bool* aIsUnfilled,
                                                  Float aDotOffset) {
  // Calculate the end point of the side for dashed/dotted border, that is also
  // the end point of the corner curve.  The point is specified by aSide and
  // aCorner. (e.g. eSideTop and C_TL means the left end of border-top)
  //
  //
  //  aCorner        aSide
  //         +--------------------
  //         |
  //         |
  //         |         +----------
  //         |    the end point
  //         |
  //         |         +----------
  //         |         |
  //         |         |
  //         |         |
  //
  // The position of the point depends on the border-style, border-width, and
  // border-radius of the side, corner, and the adjacent side beyond the corner,
  // to make those sides (and corner) interact well.
  //
  // If the style of aSide is dotted and the dot at the point should be
  // unfilled, true is stored to *aIsUnfilled, otherwise false is stored.

  const Float signsList[4][2] = {
      {+1.0f, +1.0f}, {-1.0f, +1.0f}, {-1.0f, -1.0f}, {+1.0f, -1.0f}};
  const Float(&signs)[2] = signsList[aCorner];

  *aIsUnfilled = false;

  Point P = mOuterRect.AtCorner(aCorner);
  StyleBorderStyle style = mBorderStyles[aSide];
  Float borderWidth = mBorderWidths[aSide];
  Size dim = mBorderCornerDimensions[aCorner];
  bool isHorizontal = IsHorizontalSide(aSide);
  //
  //    aCorner      aSide
  //           +--------------
  //           |
  //           |   +----------
  //           |   |
  // otherSide |   |
  //           |   |
  mozilla::Side otherSide = ((uint8_t)aSide == (uint8_t)aCorner)
                                ? PREV_SIDE(aSide)
                                : NEXT_SIDE(aSide);
  StyleBorderStyle otherStyle = mBorderStyles[otherSide];
  Float otherBorderWidth = mBorderWidths[otherSide];
  Size radius = mBorderRadii[aCorner];
  if (IsZeroSize(radius)) {
    radius.width = 0.0f;
    radius.height = 0.0f;
  }
  if (style == StyleBorderStyle::Dotted) {
    // Offset the dot's location along the side toward the corner by a
    // multiple of its width.
    if (isHorizontal) {
      P.x -= signs[0] * aDotOffset * borderWidth;
    } else {
      P.y -= signs[1] * aDotOffset * borderWidth;
    }
  }
  if (style == StyleBorderStyle::Dotted &&
      otherStyle == StyleBorderStyle::Dotted) {
    if (borderWidth == otherBorderWidth) {
      if (radius.width < borderWidth / 2.0f &&
          radius.height < borderWidth / 2.0f) {
        // Two dots are merged into one and placed at the corner.
        //
        //  borderWidth / 2.0
        // |<---------->|
        // |            |
        // |radius.width|
        // |<--->|      |
        // |     |      |
        // |    _+------+------------+-----
        // |  /      ###|###         |
        // |/    #######|#######     |
        // +   #########|#########   |
        // |  ##########|##########  |
        // | ###########|########### |
        // | ###########|########### |
        // |############|############|
        // +------------+############|
        // |########### P ###########|
        // | ####################### |
        // | ####################### |
        // |  #####################  |
        // |   ###################   |
        // |     ###############     |
        // |         #######         |
        // +-------------------------+----
        // |                         |
        // |                         |
        P.x += signs[0] * borderWidth / 2.0f;
        P.y += signs[1] * borderWidth / 2.0f;
      } else {
        // Two dots are drawn separately.
        //
        //    borderWidth * 1.5
        //   |<------------>|
        //   |              |
        //   |radius.width  |
        //   |<----->|      |
        //   |       |      |
        //   |    _--+-+----+---
        //   |  _-     |  ##|##
        //   | /       | ###|###
        //   |/        |####|####
        //   |         |####+####
        //   |         |### P ###
        //   +         | ###|###
        //   |         |  ##|##
        //   +---------+----+---
        //   |  #####  |
        //   | ####### |
        //   |#########|
        //   +----+----+
        //   |#########|
        //   | ####### |
        //   |  #####  |
        //   |         |
        //
        // There should be enough gap between 2 dots even if radius.width is
        // small but larger than borderWidth / 2.0.  borderWidth * 1.5 is the
        // value that there's imaginally unfilled dot at the corner.  The
        // unfilled dot may overflow from the outer curve, but filled dots
        // doesn't, so this could be acceptable solution at least for now.
        // We may have to find better model/value.
        //
        //    imaginally unfilled dot at the corner
        //        |
        //        v    +----+---
        //      *****  |  ##|##
        //     ******* | ###|###
        //    *********|####|####
        //    *********|####+####
        //    *********|### P ###
        //     ******* | ###|###
        //      *****  |  ##|##
        //   +---------+----+---
        //   |  #####  |
        //   | ####### |
        //   |#########|
        //   +----+----+
        //   |#########|
        //   | ####### |
        //   |  #####  |
        //   |         |
        Float minimum = borderWidth * 1.5f;
        if (isHorizontal) {
          P.x += signs[0] * std::max(radius.width, minimum);
          P.y += signs[1] * borderWidth / 2.0f;
        } else {
          P.x += signs[0] * borderWidth / 2.0f;
          P.y += signs[1] * std::max(radius.height, minimum);
        }
      }

      return P;
    }

    if (borderWidth < otherBorderWidth) {
      // This side is smaller than other side, other side draws the corner.
      //
      //  otherBorderWidth + borderWidth / 2.0
      // |<---------->|
      // |            |
      // +---------+--+--------
      // |  #####  | *|*  ###
      // | ####### |**|**#####
      // |#########|**+**##+##
      // |####+####|* P *#####
      // |#########| ***  ###
      // | ####### +-----------
      // |  #####  |  ^
      // |         |  |
      // |         | first dot is not filled
      // |         |
      //
      //      radius.width
      // |<----------------->|
      // |                   |
      // |             ___---+-------------
      // |         __--     #|#       ###
      // |       _-        ##|##     #####
      // |     /           ##+##     ##+##
      // |   /             # P #     #####
      // |  |               #|#       ###
      // | |             __--+-------------
      // ||            _-    ^
      // ||           /      |
      // |           /      first dot is filled
      // |          |
      // |          |
      // |  #####  |
      // | ####### |
      // |#########|
      // +----+----+
      // |#########|
      // | ####### |
      // |  #####  |
      Float minimum = otherBorderWidth + borderWidth / 2.0f;
      if (isHorizontal) {
        if (radius.width < minimum) {
          *aIsUnfilled = true;
          P.x += signs[0] * minimum;
        } else {
          P.x += signs[0] * radius.width;
        }
        P.y += signs[1] * borderWidth / 2.0f;
      } else {
        P.x += signs[0] * borderWidth / 2.0f;
        if (radius.height < minimum) {
          *aIsUnfilled = true;
          P.y += signs[1] * minimum;
        } else {
          P.y += signs[1] * radius.height;
        }
      }

      return P;
    }

    // This side is larger than other side, this side draws the corner.
    //
    //  borderWidth / 2.0
    // |<-->|
    // |    |
    // +----+---------------------
    // |  ##|##           #####
    // | ###|###         #######
    // |####|####       #########
    // |####+####       ####+####
    // |### P ###       #########
    // | #######         #######
    // |  #####           #####
    // +-----+---------------------
    // | *** |
    // |*****|
    // |**+**| <-- first dot in other side is not filled
    // |*****|
    // | *** |
    // | ### |
    // |#####|
    // |##+##|
    // |#####|
    // | ### |
    // |     |
    if (isHorizontal) {
      P.x += signs[0] * std::max(radius.width, borderWidth / 2.0f);
      P.y += signs[1] * borderWidth / 2.0f;
    } else {
      P.x += signs[0] * borderWidth / 2.0f;
      P.y += signs[1] * std::max(radius.height, borderWidth / 2.0f);
    }
    return P;
  }

  if (style == StyleBorderStyle::Dotted) {
    // If only this side is dotted, other side draws the corner.
    //
    //  otherBorderWidth + borderWidth / 2.0
    // |<------->|
    // |         |
    // +------+--+--------
    // |##  ##| *|*  ###
    // |##  ##|**|**#####
    // |##  ##|**+**##+##
    // |##  ##|* P *#####
    // |##  ##| ***  ###
    // |##  ##+-----------
    // |##  ##|  ^
    // |##  ##|  |
    // |##  ##| first dot is not filled
    // |##  ##|
    //
    //      radius.width
    // |<----------------->|
    // |                   |
    // |             ___---+-------------
    // |         __--     #|#       ###
    // |       _-        ##|##     #####
    // |     /           ##+##     ##+##
    // |   /             # P #     #####
    // |  |               #|#       ###
    // | |             __--+-------------
    // ||            _-    ^
    // ||          /       |
    // |         /        first dot is filled
    // |        |
    // |       |
    // |      |
    // |      |
    // |      |
    // +------+
    // |##  ##|
    // |##  ##|
    // |##  ##|
    Float minimum = otherBorderWidth + borderWidth / 2.0f;
    if (isHorizontal) {
      if (radius.width < minimum) {
        *aIsUnfilled = true;
        P.x += signs[0] * minimum;
      } else {
        P.x += signs[0] * radius.width;
      }
      P.y += signs[1] * borderWidth / 2.0f;
    } else {
      P.x += signs[0] * borderWidth / 2.0f;
      if (radius.height < minimum) {
        *aIsUnfilled = true;
        P.y += signs[1] * minimum;
      } else {
        P.y += signs[1] * radius.height;
      }
    }
    return P;
  }

  if (otherStyle == StyleBorderStyle::Dotted && IsZeroSize(radius)) {
    // If other side is dotted and radius=0, draw side to the end of corner.
    //
    //   +-------------------------------
    //   |##########          ##########
    // P +##########          ##########
    //   |##########          ##########
    //   +-----+-------------------------
    //   | *** |
    //   |*****|
    //   |**+**| <-- first dot in other side is not filled
    //   |*****|
    //   | *** |
    //   | ### |
    //   |#####|
    //   |##+##|
    //   |#####|
    //   | ### |
    //   |     |
    if (isHorizontal) {
      P.y += signs[1] * borderWidth / 2.0f;
    } else {
      P.x += signs[0] * borderWidth / 2.0f;
    }
    return P;
  }

  // Other cases.
  //
  //  dim.width
  // |<----------------->|
  // |                   |
  // |             ___---+------------------
  // |         __--      |#######        ###
  // |       _-        P +#######        ###
  // |     /             |#######        ###
  // |   /          __---+------------------
  // |  |       __--
  // | |       /
  // ||      /
  // ||     |
  // |     |
  // |    |
  // |   |
  // |   |
  // +-+-+
  // |###|
  // |###|
  // |###|
  // |###|
  // |###|
  // |   |
  // |   |
  if (isHorizontal) {
    P.x += signs[0] * dim.width;
    P.y += signs[1] * borderWidth / 2.0f;
  } else {
    P.x += signs[0] * borderWidth / 2.0f;
    P.y += signs[1] * dim.height;
  }

  return P;
}

void nsCSSBorderRenderer::GetOuterAndInnerBezier(Bezier* aOuterBezier,
                                                 Bezier* aInnerBezier,
                                                 Corner aCorner) {
  // Return bezier control points for outer and inner curve for given corner.
  //
  //               ___---+ outer curve
  //           __--      |
  //         _-          |
  //       /             |
  //     /               |
  //    |                |
  //   |             __--+ inner curve
  //  |            _-
  //  |           /
  // |           /
  // |          |
  // |          |
  // |         |
  // |         |
  // |         |
  // +---------+

  mozilla::Side sideH(GetHorizontalSide(aCorner));
  mozilla::Side sideV(GetVerticalSide(aCorner));

  Size outerCornerSize(ceil(mBorderRadii[aCorner].width),
                       ceil(mBorderRadii[aCorner].height));
  Size innerCornerSize(
      ceil(std::max(0.0f, mBorderRadii[aCorner].width - mBorderWidths[sideV])),
      ceil(
          std::max(0.0f, mBorderRadii[aCorner].height - mBorderWidths[sideH])));

  GetBezierPointsForCorner(aOuterBezier, aCorner, mOuterRect.AtCorner(aCorner),
                           outerCornerSize);

  GetBezierPointsForCorner(aInnerBezier, aCorner, mInnerRect.AtCorner(aCorner),
                           innerCornerSize);
}

void nsCSSBorderRenderer::FillSolidBorder(const Rect& aOuterRect,
                                          const Rect& aInnerRect,
                                          const RectCornerRadii& aBorderRadii,
                                          const Float* aBorderSizes, int aSides,
                                          const ColorPattern& aColor) {
  // Note that this function is allowed to draw more than just the
  // requested sides.

  // If we have a border radius, do full rounded rectangles
  // and fill, regardless of what sides we're asked to draw.
  if (!AllCornersZeroSize(aBorderRadii)) {
    RefPtr<PathBuilder> builder = mDrawTarget->CreatePathBuilder();

    RectCornerRadii innerRadii;
    ComputeInnerRadii(aBorderRadii, aBorderSizes, &innerRadii);

    // do the outer border
    AppendRoundedRectToPath(builder, aOuterRect, aBorderRadii, true);

    // then do the inner border CCW
    AppendRoundedRectToPath(builder, aInnerRect, innerRadii, false);

    RefPtr<Path> path = builder->Finish();

    mDrawTarget->Fill(path, aColor);
    return;
  }

  // If we're asked to draw all sides of an equal-sized border,
  // stroking is fastest.  This is a fairly common path, but partial
  // sides is probably second in the list -- there are a bunch of
  // common border styles, such as inset and outset, that are
  // top-left/bottom-right split.
  if (aSides == eSideBitsAll &&
      CheckFourFloatsEqual(aBorderSizes, aBorderSizes[0]) && !mAvoidStroke) {
    Float strokeWidth = aBorderSizes[0];
    Rect r(aOuterRect);
    r.Deflate(strokeWidth / 2.f);
    mDrawTarget->StrokeRect(r, aColor, StrokeOptions(strokeWidth));
    return;
  }

  // Otherwise, we have unequal sized borders or we're only
  // drawing some sides; create rectangles for each side
  // and fill them.

  Rect r[4];

  // compute base rects for each side
  if (aSides & eSideBitsTop) {
    r[eSideTop] = Rect(aOuterRect.X(), aOuterRect.Y(), aOuterRect.Width(),
                       aBorderSizes[eSideTop]);
  }

  if (aSides & eSideBitsBottom) {
    r[eSideBottom] =
        Rect(aOuterRect.X(), aOuterRect.YMost() - aBorderSizes[eSideBottom],
             aOuterRect.Width(), aBorderSizes[eSideBottom]);
  }

  if (aSides & eSideBitsLeft) {
    r[eSideLeft] = Rect(aOuterRect.X(), aOuterRect.Y(), aBorderSizes[eSideLeft],
                        aOuterRect.Height());
  }

  if (aSides & eSideBitsRight) {
    r[eSideRight] =
        Rect(aOuterRect.XMost() - aBorderSizes[eSideRight], aOuterRect.Y(),
             aBorderSizes[eSideRight], aOuterRect.Height());
  }

  // If two sides meet at a corner that we're rendering, then
  // make sure that we adjust one of the sides to avoid overlap.
  // This is especially important in the case of colors with
  // an alpha channel.

  if ((aSides & (eSideBitsTop | eSideBitsLeft)) ==
      (eSideBitsTop | eSideBitsLeft)) {
    // adjust the left's top down a bit
    r[eSideLeft].y += aBorderSizes[eSideTop];
    r[eSideLeft].height -= aBorderSizes[eSideTop];
  }

  if ((aSides & (eSideBitsTop | eSideBitsRight)) ==
      (eSideBitsTop | eSideBitsRight)) {
    // adjust the top's left a bit
    r[eSideTop].width -= aBorderSizes[eSideRight];
  }

  if ((aSides & (eSideBitsBottom | eSideBitsRight)) ==
      (eSideBitsBottom | eSideBitsRight)) {
    // adjust the right's bottom a bit
    r[eSideRight].height -= aBorderSizes[eSideBottom];
  }

  if ((aSides & (eSideBitsBottom | eSideBitsLeft)) ==
      (eSideBitsBottom | eSideBitsLeft)) {
    // adjust the bottom's left a bit
    r[eSideBottom].x += aBorderSizes[eSideLeft];
    r[eSideBottom].width -= aBorderSizes[eSideLeft];
  }

  // Filling these one by one is faster than filling them all at once.
  for (uint32_t i = 0; i < 4; i++) {
    if (aSides & (1 << i)) {
      MaybeSnapToDevicePixels(r[i], *mDrawTarget, true);
      mDrawTarget->FillRect(r[i], aColor);
    }
  }
}

Color MakeBorderColor(nscolor aColor, BorderColorStyle aBorderColorStyle) {
  nscolor colors[2];
  int k = 0;

  switch (aBorderColorStyle) {
    case BorderColorStyleNone:
      return Color(0.f, 0.f, 0.f, 0.f);  // transparent black

    case BorderColorStyleLight:
      k = 1;
      MOZ_FALLTHROUGH;
    case BorderColorStyleDark:
      NS_GetSpecial3DColors(colors, aColor);
      return Color::FromABGR(colors[k]);

    case BorderColorStyleSolid:
    default:
      return Color::FromABGR(aColor);
  }
}

Color ComputeColorForLine(uint32_t aLineIndex,
                          const BorderColorStyle* aBorderColorStyle,
                          uint32_t aBorderColorStyleCount,
                          nscolor aBorderColor) {
  NS_ASSERTION(aLineIndex < aBorderColorStyleCount, "Invalid lineIndex given");

  return MakeBorderColor(aBorderColor, aBorderColorStyle[aLineIndex]);
}

void nsCSSBorderRenderer::DrawBorderSides(int aSides) {
  if (aSides == 0 || (aSides & ~eSideBitsAll) != 0) {
    NS_WARNING("DrawBorderSides: invalid sides!");
    return;
  }

  StyleBorderStyle borderRenderStyle = StyleBorderStyle::None;
  nscolor borderRenderColor;

  uint32_t borderColorStyleCount = 0;
  BorderColorStyle borderColorStyleTopLeft[3], borderColorStyleBottomRight[3];
  BorderColorStyle* borderColorStyle = nullptr;

  NS_FOR_CSS_SIDES(i) {
    if ((aSides & (1 << i)) == 0) continue;
    borderRenderStyle = mBorderStyles[i];
    borderRenderColor = mBorderColors[i];
    break;
  }

  if (borderRenderStyle == StyleBorderStyle::None ||
      borderRenderStyle == StyleBorderStyle::Hidden)
    return;

  if (borderRenderStyle == StyleBorderStyle::Dashed ||
      borderRenderStyle == StyleBorderStyle::Dotted) {
    // Draw each corner separately, with the given side's color.
    if (aSides & eSideBitsTop) {
      DrawDashedOrDottedCorner(eSideTop, C_TL);
    } else if (aSides & eSideBitsLeft) {
      DrawDashedOrDottedCorner(eSideLeft, C_TL);
    }

    if (aSides & eSideBitsTop) {
      DrawDashedOrDottedCorner(eSideTop, C_TR);
    } else if (aSides & eSideBitsRight) {
      DrawDashedOrDottedCorner(eSideRight, C_TR);
    }

    if (aSides & eSideBitsBottom) {
      DrawDashedOrDottedCorner(eSideBottom, C_BL);
    } else if (aSides & eSideBitsLeft) {
      DrawDashedOrDottedCorner(eSideLeft, C_BL);
    }

    if (aSides & eSideBitsBottom) {
      DrawDashedOrDottedCorner(eSideBottom, C_BR);
    } else if (aSides & eSideBitsRight) {
      DrawDashedOrDottedCorner(eSideRight, C_BR);
    }
    return;
  }

  // The borderColorStyle array goes from the outer to the inner style.
  //
  // If the border width is 1, we need to change the borderRenderStyle
  // a bit to make sure that we get the right colors -- e.g. 'ridge'
  // with a 1px border needs to look like solid, not like 'outset'.
  if (mOneUnitBorder && (borderRenderStyle == StyleBorderStyle::Ridge ||
                         borderRenderStyle == StyleBorderStyle::Groove ||
                         borderRenderStyle == StyleBorderStyle::Double))
    borderRenderStyle = StyleBorderStyle::Solid;

  switch (borderRenderStyle) {
    case StyleBorderStyle::Solid:
      borderColorStyleTopLeft[0] = BorderColorStyleSolid;

      borderColorStyleBottomRight[0] = BorderColorStyleSolid;

      borderColorStyleCount = 1;
      break;

    case StyleBorderStyle::Groove:
      borderColorStyleTopLeft[0] = BorderColorStyleDark;
      borderColorStyleTopLeft[1] = BorderColorStyleLight;

      borderColorStyleBottomRight[0] = BorderColorStyleLight;
      borderColorStyleBottomRight[1] = BorderColorStyleDark;

      borderColorStyleCount = 2;
      break;

    case StyleBorderStyle::Ridge:
      borderColorStyleTopLeft[0] = BorderColorStyleLight;
      borderColorStyleTopLeft[1] = BorderColorStyleDark;

      borderColorStyleBottomRight[0] = BorderColorStyleDark;
      borderColorStyleBottomRight[1] = BorderColorStyleLight;

      borderColorStyleCount = 2;
      break;

    case StyleBorderStyle::Double:
      borderColorStyleTopLeft[0] = BorderColorStyleSolid;
      borderColorStyleTopLeft[1] = BorderColorStyleNone;
      borderColorStyleTopLeft[2] = BorderColorStyleSolid;

      borderColorStyleBottomRight[0] = BorderColorStyleSolid;
      borderColorStyleBottomRight[1] = BorderColorStyleNone;
      borderColorStyleBottomRight[2] = BorderColorStyleSolid;

      borderColorStyleCount = 3;
      break;

    case StyleBorderStyle::Inset:
      borderColorStyleTopLeft[0] = BorderColorStyleDark;
      borderColorStyleBottomRight[0] = BorderColorStyleLight;

      borderColorStyleCount = 1;
      break;

    case StyleBorderStyle::Outset:
      borderColorStyleTopLeft[0] = BorderColorStyleLight;
      borderColorStyleBottomRight[0] = BorderColorStyleDark;

      borderColorStyleCount = 1;
      break;

    default:
      MOZ_ASSERT_UNREACHABLE("Unhandled border style!!");
      break;
  }

  // The only way to get to here is by having a
  // borderColorStyleCount < 1 or > 3; this should never happen,
  // since -moz-border-colors doesn't get handled here.
  NS_ASSERTION(borderColorStyleCount > 0 && borderColorStyleCount < 4,
               "Non-border-colors case with borderColorStyleCount < 1 or > 3; "
               "what happened?");

  // The caller should never give us anything with a mix
  // of TL/BR if the border style would require a
  // TL/BR split.
  if (aSides & (eSideBitsBottom | eSideBitsRight))
    borderColorStyle = borderColorStyleBottomRight;
  else
    borderColorStyle = borderColorStyleTopLeft;

  // Distribute the border across the available space.
  Float borderWidths[3][4];

  if (borderColorStyleCount == 1) {
    NS_FOR_CSS_SIDES(i) { borderWidths[0][i] = mBorderWidths[i]; }
  } else if (borderColorStyleCount == 2) {
    // with 2 color styles, any extra pixel goes to the outside
    NS_FOR_CSS_SIDES(i) {
      borderWidths[0][i] =
          int32_t(mBorderWidths[i]) / 2 + int32_t(mBorderWidths[i]) % 2;
      borderWidths[1][i] = int32_t(mBorderWidths[i]) / 2;
    }
  } else if (borderColorStyleCount == 3) {
    // with 3 color styles, any extra pixel (or lack of extra pixel)
    // goes to the middle
    NS_FOR_CSS_SIDES(i) {
      if (mBorderWidths[i] == 1.0) {
        borderWidths[0][i] = 1.f;
        borderWidths[1][i] = borderWidths[2][i] = 0.f;
      } else {
        int32_t rest = int32_t(mBorderWidths[i]) % 3;
        borderWidths[0][i] = borderWidths[2][i] = borderWidths[1][i] =
            (int32_t(mBorderWidths[i]) - rest) / 3;

        if (rest == 1) {
          borderWidths[1][i] += 1.f;
        } else if (rest == 2) {
          borderWidths[0][i] += 1.f;
          borderWidths[2][i] += 1.f;
        }
      }
    }
  }

  // make a copy that we can modify
  RectCornerRadii radii = mBorderRadii;

  Rect soRect(mOuterRect);
  Rect siRect(mOuterRect);

  // If adjacent side is dotted and radius=0, draw side to the end of corner.
  //
  // +--------------------------------
  // |################################
  // |
  // |################################
  // +-----+--------------------------
  // |     |
  // |     |
  // |     |
  // |     |
  // |     |
  // | ### |
  // |#####|
  // |#####|
  // |#####|
  // | ### |
  // |     |
  bool noMarginTop = false;
  bool noMarginRight = false;
  bool noMarginBottom = false;
  bool noMarginLeft = false;

  // If there is at least one dotted side, every side is rendered separately.
  if (IsSingleSide(aSides)) {
    if (aSides == eSideBitsTop) {
      if (mBorderStyles[eSideRight] == StyleBorderStyle::Dotted &&
          IsZeroSize(mBorderRadii[C_TR])) {
        noMarginRight = true;
      }
      if (mBorderStyles[eSideLeft] == StyleBorderStyle::Dotted &&
          IsZeroSize(mBorderRadii[C_TL])) {
        noMarginLeft = true;
      }
    } else if (aSides == eSideBitsRight) {
      if (mBorderStyles[eSideTop] == StyleBorderStyle::Dotted &&
          IsZeroSize(mBorderRadii[C_TR])) {
        noMarginTop = true;
      }
      if (mBorderStyles[eSideBottom] == StyleBorderStyle::Dotted &&
          IsZeroSize(mBorderRadii[C_BR])) {
        noMarginBottom = true;
      }
    } else if (aSides == eSideBitsBottom) {
      if (mBorderStyles[eSideRight] == StyleBorderStyle::Dotted &&
          IsZeroSize(mBorderRadii[C_BR])) {
        noMarginRight = true;
      }
      if (mBorderStyles[eSideLeft] == StyleBorderStyle::Dotted &&
          IsZeroSize(mBorderRadii[C_BL])) {
        noMarginLeft = true;
      }
    } else {
      if (mBorderStyles[eSideTop] == StyleBorderStyle::Dotted &&
          IsZeroSize(mBorderRadii[C_TL])) {
        noMarginTop = true;
      }
      if (mBorderStyles[eSideBottom] == StyleBorderStyle::Dotted &&
          IsZeroSize(mBorderRadii[C_BL])) {
        noMarginBottom = true;
      }
    }
  }

  for (unsigned int i = 0; i < borderColorStyleCount; i++) {
    // walk siRect inwards at the start of the loop to get the
    // correct inner rect.
    //
    // If noMarginTop is false:
    //   --------------------+
    //                      /|
    //                     / |
    //                    L  |
    //   ----------------+   |
    //                   |   |
    //                   |   |
    //
    // If noMarginTop is true:
    //   ----------------+<--+
    //                   |   |
    //                   |   |
    //                   |   |
    //                   |   |
    //                   |   |
    //                   |   |
    siRect.Deflate(Margin(noMarginTop ? 0 : borderWidths[i][0],
                          noMarginRight ? 0 : borderWidths[i][1],
                          noMarginBottom ? 0 : borderWidths[i][2],
                          noMarginLeft ? 0 : borderWidths[i][3]));

    if (borderColorStyle[i] != BorderColorStyleNone) {
      Color c = ComputeColorForLine(i, borderColorStyle, borderColorStyleCount,
                                    borderRenderColor);
      ColorPattern color(ToDeviceColor(c));

      FillSolidBorder(soRect, siRect, radii, borderWidths[i], aSides, color);
    }

    ComputeInnerRadii(radii, borderWidths[i], &radii);

    // And now soRect is the same as siRect, for the next line in.
    soRect = siRect;
  }
}

void nsCSSBorderRenderer::SetupDashedOptions(StrokeOptions* aStrokeOptions,
                                             Float aDash[2],
                                             mozilla::Side aSide,
                                             Float aBorderLength,
                                             bool isCorner) {
  MOZ_ASSERT(mBorderStyles[aSide] == StyleBorderStyle::Dashed ||
                 mBorderStyles[aSide] == StyleBorderStyle::Dotted,
             "Style should be dashed or dotted.");

  StyleBorderStyle style = mBorderStyles[aSide];
  Float borderWidth = mBorderWidths[aSide];

  // Dashed line starts and ends with half segment in most case.
  //
  // __--+---+---+---+---+---+---+---+---+--__
  //     |###|   |   |###|###|   |   |###|
  //     |###|   |   |###|###|   |   |###|
  //     |###|   |   |###|###|   |   |###|
  // __--+---+---+---+---+---+---+---+---+--__
  //
  // If radius=0 and other side is either dotted or 0-width, it starts or ends
  // with full segment.
  //
  // +---+---+---+---+---+---+---+---+---+---+
  // |###|###|   |   |###|###|   |   |###|###|
  // |###|###|   |   |###|###|   |   |###|###|
  // |###|###|   |   |###|###|   |   |###|###|
  // +---++--+---+---+---+---+---+---+--++---+
  // |    |                             |    |
  // |    |                             |    |
  // |    |                             |    |
  // |    |                             |    |
  // | ## |                             | ## |
  // |####|                             |####|
  // |####|                             |####|
  // | ## |                             | ## |
  // |    |                             |    |
  bool fullStart = false, fullEnd = false;
  Float halfDash;
  if (style == StyleBorderStyle::Dashed) {
    // If either end of the side is not connecting onto a corner then we want a
    // full dash at that end.
    //
    // Note that in the case that a corner is empty, either the adjacent side
    // has zero width, or else DrawBorders() set the corner to be empty
    // (it does that if the adjacent side has zero length and the border widths
    // of this and the adjacent sides are thin enough that the corner will be
    // insignificantly small).

    if (mBorderRadii[GetCCWCorner(aSide)].IsEmpty() &&
        (mBorderCornerDimensions[GetCCWCorner(aSide)].IsEmpty() ||
         mBorderStyles[PREV_SIDE(aSide)] == StyleBorderStyle::Dotted ||
         // XXX why this <=1 check?
         borderWidth <= 1.0f)) {
      fullStart = true;
    }

    if (mBorderRadii[GetCWCorner(aSide)].IsEmpty() &&
        (mBorderCornerDimensions[GetCWCorner(aSide)].IsEmpty() ||
         mBorderStyles[NEXT_SIDE(aSide)] == StyleBorderStyle::Dotted)) {
      fullEnd = true;
    }

    halfDash = borderWidth * DOT_LENGTH * DASH_LENGTH / 2.0f;
  } else {
    halfDash = borderWidth * DOT_LENGTH / 2.0f;
  }

  if (style == StyleBorderStyle::Dashed && aBorderLength > 0.0f) {
    // The number of half segments, with maximum dash length.
    int32_t count = floor(aBorderLength / halfDash);
    Float minHalfDash = borderWidth * DOT_LENGTH / 2.0f;

    if (fullStart && fullEnd) {
      // count should be 4n + 2
      //
      //   1 +       4       +        4      + 1
      //
      // |   |               |               |   |
      // +---+---+---+---+---+---+---+---+---+---+
      // |###|###|   |   |###|###|   |   |###|###|
      // |###|###|   |   |###|###|   |   |###|###|
      // |###|###|   |   |###|###|   |   |###|###|
      // +---+---+---+---+---+---+---+---+---+---+

      // If border is too short, draw solid line.
      if (aBorderLength < 6.0f * minHalfDash) return;

      if (count % 4 == 0) {
        count += 2;
      } else if (count % 4 == 1) {
        count += 1;
      } else if (count % 4 == 3) {
        count += 3;
      }
    } else if (fullStart || fullEnd) {
      // count should be 4n + 1
      //
      //   1 +       4       +        4
      //
      // |   |               |               |
      // +---+---+---+---+---+---+---+---+---+
      // |###|###|   |   |###|###|   |   |###|
      // |###|###|   |   |###|###|   |   |###|
      // |###|###|   |   |###|###|   |   |###|
      // +---+---+---+---+---+---+---+---+---+
      //
      //         4       +        4      + 1
      //
      // |               |               |   |
      // +---+---+---+---+---+---+---+---+---+
      // |###|   |   |###|###|   |   |###|###|
      // |###|   |   |###|###|   |   |###|###|
      // |###|   |   |###|###|   |   |###|###|
      // +---+---+---+---+---+---+---+---+---+

      // If border is too short, draw solid line.
      if (aBorderLength < 5.0f * minHalfDash) return;

      if (count % 4 == 0) {
        count += 1;
      } else if (count % 4 == 2) {
        count += 3;
      } else if (count % 4 == 3) {
        count += 2;
      }
    } else {
      // count should be 4n
      //
      //         4       +        4
      //
      // |               |               |
      // +---+---+---+---+---+---+---+---+
      // |###|   |   |###|###|   |   |###|
      // |###|   |   |###|###|   |   |###|
      // |###|   |   |###|###|   |   |###|
      // +---+---+---+---+---+---+---+---+

      // If border is too short, draw solid line.
      if (aBorderLength < 4.0f * minHalfDash) return;

      if (count % 4 == 1) {
        count += 3;
      } else if (count % 4 == 2) {
        count += 2;
      } else if (count % 4 == 3) {
        count += 1;
      }
    }
    halfDash = aBorderLength / count;
  }

  Float fullDash = halfDash * 2.0f;

  aDash[0] = fullDash;
  aDash[1] = fullDash;

  if (style == StyleBorderStyle::Dashed && fullDash > 1.0f) {
    if (!fullStart) {
      // Draw half segments on both ends.
      aStrokeOptions->mDashOffset = halfDash;
    }
  } else if (style != StyleBorderStyle::Dotted && isCorner) {
    // If side ends with filled full segment, corner should start with unfilled
    // full segment. Not needed for dotted corners, as they overlap one dot with
    // the side's end.
    //
    //     corner            side
    //   ------------>|<---------------------------
    //                |
    //          __+---+---+---+---+---+---+---+---+
    //       _+-  |   |###|###|   |   |###|###|   |
    //     /##|   |   |###|###|   |   |###|###|   |
    //    +####|   |  |###|###|   |   |###|###|   |
    //   /#\####| _+--+---+---+---+---+---+---+---+
    //  |####\##+-
    //  |#####+-
    //  +--###/
    //  |  --+
    aStrokeOptions->mDashOffset = fullDash;
  }

  aStrokeOptions->mDashPattern = aDash;
  aStrokeOptions->mDashLength = 2;

  PrintAsFormatString("dash: %f %f\n", aDash[0], aDash[1]);
}

static Float GetBorderLength(mozilla::Side aSide, const Point& aStart,
                             const Point& aEnd) {
  if (aSide == eSideTop) {
    return aEnd.x - aStart.x;
  }
  if (aSide == eSideRight) {
    return aEnd.y - aStart.y;
  }
  if (aSide == eSideBottom) {
    return aStart.x - aEnd.x;
  }
  return aStart.y - aEnd.y;
}

void nsCSSBorderRenderer::DrawDashedOrDottedSide(mozilla::Side aSide) {
  // Draw dashed/dotted side with following approach.
  //
  // dashed side
  //   Draw dashed line along the side, with appropriate dash length and gap
  //   to make the side symmetric as far as possible.  Dash length equals to
  //   the gap, and the ratio of the dash length to border-width is the maximum
  //   value in in [1, 3] range.
  //   In most case, line ends with half segment, to joint with corner easily.
  //   If adjacent side is dotted or 0px and border-radius for the corner
  //   between them is 0, the line ends with full segment.
  //   (see comment for GetStraightBorderPoint for more detail)
  //
  // dotted side
  //   If border-width <= 2.0, draw 1:1 dashed line.
  //   Otherwise, draw circles along the side, with appropriate gap that makes
  //   the side symmetric as far as possible.  The ratio of the gap to
  //   border-width is the maximum value in [0.5, 1] range in most case.
  //   if the side is too short and there's only 2 dots, it can be more smaller.
  //   If there's no space to place 2 dots at the side, draw single dot at the
  //   middle of the side.
  //   In most case, line ends with filled dot, to joint with corner easily,
  //   If adjacent side is dotted with larger border-width, or other style,
  //   the line ends with unfilled dot.
  //   (see comment for GetStraightBorderPoint for more detail)

  NS_ASSERTION(mBorderStyles[aSide] == StyleBorderStyle::Dashed ||
                   mBorderStyles[aSide] == StyleBorderStyle::Dotted,
               "Style should be dashed or dotted.");

  Float borderWidth = mBorderWidths[aSide];
  if (borderWidth == 0.0f) {
    return;
  }

  if (mBorderStyles[aSide] == StyleBorderStyle::Dotted && borderWidth > 2.0f) {
    DrawDottedSideSlow(aSide);
    return;
  }

  nscolor borderColor = mBorderColors[aSide];
  bool ignored;
  // Get the start and end points of the side, ensuring that any dot origins get
  // pushed outward to account for stroking.
  Point start =
      GetStraightBorderPoint(aSide, GetCCWCorner(aSide), &ignored, 0.5f);
  Point end = GetStraightBorderPoint(aSide, GetCWCorner(aSide), &ignored, 0.5f);
  if (borderWidth < 2.0f) {
    // Round start to draw dot on each pixel.
    if (IsHorizontalSide(aSide)) {
      start.x = round(start.x);
    } else {
      start.y = round(start.y);
    }
  }

  Float borderLength = GetBorderLength(aSide, start, end);
  if (borderLength < 0.0f) {
    return;
  }

  StrokeOptions strokeOptions(borderWidth);
  Float dash[2];
  SetupDashedOptions(&strokeOptions, dash, aSide, borderLength, false);

  // For dotted sides that can merge with their prior dotted sides, advance the
  // dash offset to measure the distance around the combined path. This prevents
  // two dots from bunching together at a corner.
  mozilla::Side mergeSide = aSide;
  while (IsCornerMergeable(GetCCWCorner(mergeSide))) {
    mergeSide = PREV_SIDE(mergeSide);
    // If we looped all the way around, measure starting at the top side, since
    // we need to pick a fixed location to start measuring distance from still.
    if (mergeSide == aSide) {
      mergeSide = eSideTop;
      break;
    }
  }
  while (mergeSide != aSide) {
    // Measure the length of the merged side starting from a possibly
    // unmergeable corner up to the merged corner. A merged corner effectively
    // has no border radius, so we can just use the cheaper AtCorner to find the
    // end point.
    Float mergeLength =
        GetBorderLength(mergeSide,
                        GetStraightBorderPoint(
                            mergeSide, GetCCWCorner(mergeSide), &ignored, 0.5f),
                        mOuterRect.AtCorner(GetCWCorner(mergeSide)));
    // Add in the merged side length. Also offset the dash progress by an extra
    // dot's width to avoid drawing a dot that would overdraw where the merged
    // side would have ended in a gap, i.e. O_O_
    //                                    O
    strokeOptions.mDashOffset += mergeLength + borderWidth;
    mergeSide = NEXT_SIDE(mergeSide);
  }

  DrawOptions drawOptions;
  if (mBorderStyles[aSide] == StyleBorderStyle::Dotted) {
    drawOptions.mAntialiasMode = AntialiasMode::NONE;
  }

  mDrawTarget->StrokeLine(start, end, ColorPattern(ToDeviceColor(borderColor)),
                          strokeOptions, drawOptions);
}

void nsCSSBorderRenderer::DrawDottedSideSlow(mozilla::Side aSide) {
  // Draw each circles separately for dotted with borderWidth > 2.0.
  // Dashed line with CapStyle::ROUND doesn't render perfect circles.

  NS_ASSERTION(mBorderStyles[aSide] == StyleBorderStyle::Dotted,
               "Style should be dotted.");

  Float borderWidth = mBorderWidths[aSide];
  if (borderWidth == 0.0f) {
    return;
  }

  nscolor borderColor = mBorderColors[aSide];
  bool isStartUnfilled, isEndUnfilled;
  Point start =
      GetStraightBorderPoint(aSide, GetCCWCorner(aSide), &isStartUnfilled);
  Point end = GetStraightBorderPoint(aSide, GetCWCorner(aSide), &isEndUnfilled);
  enum {
    // Corner is not mergeable.
    NO_MERGE,

    // Corner between different colors.
    // Two dots are merged into one, and both side draw half dot.
    MERGE_HALF,

    // Corner between same colors, CCW corner of the side.
    // Two dots are merged into one, and this side draw entire dot.
    //
    // MERGE_ALL               MERGE_NONE
    //   |                       |
    //   v                       v
    // +-----------------------+----+
    // | ##      ##      ##    | ## |
    // |####    ####    ####   |####|
    // |####    ####    ####   |####|
    // | ##      ##      ##    | ## |
    // +----+------------------+    |
    // |    |                  |    |
    // |    |                  |    |
    // |    |                  |    |
    // | ## |                  | ## |
    // |####|                  |####|
    MERGE_ALL,

    // Corner between same colors, CW corner of the side.
    // Two dots are merged into one, and this side doesn't draw dot.
    MERGE_NONE
  } mergeStart = NO_MERGE,
    mergeEnd = NO_MERGE;

  if (IsCornerMergeable(GetCCWCorner(aSide))) {
    if (borderColor == mBorderColors[PREV_SIDE(aSide)]) {
      mergeStart = MERGE_ALL;
    } else {
      mergeStart = MERGE_HALF;
    }
  }

  if (IsCornerMergeable(GetCWCorner(aSide))) {
    if (borderColor == mBorderColors[NEXT_SIDE(aSide)]) {
      mergeEnd = MERGE_NONE;
    } else {
      mergeEnd = MERGE_HALF;
    }
  }

  Float borderLength = GetBorderLength(aSide, start, end);
  if (borderLength < 0.0f) {
    if (isStartUnfilled || isEndUnfilled) {
      return;
    }
    borderLength = 0.0f;
    start = end = (start + end) / 2.0f;
  }

  Float dotWidth = borderWidth * DOT_LENGTH;
  Float radius = borderWidth / 2.0f;
  if (borderLength < dotWidth) {
    // If dots on start and end may overlap, draw a dot at the middle of them.
    //
    //     ___---+-------+---___
    // __--      | ##### |      --__
    //          #|#######|#
    //         ##|#######|##
    //        ###|#######|###
    //        ###+###+###+###
    //         start ## end #
    //         ##|#######|##
    //          #|#######|#
    //           | ##### |
    //       __--+-------+--__
    //     _-                 -_
    //
    // If that circle overflows from outer rect, do not draw it.
    //
    //           +-------+
    //           | ##### |
    //          #|#######|#
    //         ##|#######|##
    //        ###|#######|###
    //        ###|###+###|###
    //        ###|#######|###
    //         ##|#######|##
    //          #|#######|#
    //           | ##### |
    //           +--+-+--+
    //           |  | |  |
    //           |  | |  |
    if (!mOuterRect.Contains(Rect(start.x - radius, start.y - radius,
                                  borderWidth, borderWidth))) {
      return;
    }

    if (isStartUnfilled || isEndUnfilled) {
      return;
    }

    Point P = (start + end) / 2;
    RefPtr<PathBuilder> builder = mDrawTarget->CreatePathBuilder();
    builder->MoveTo(Point(P.x + radius, P.y));
    builder->Arc(P, radius, 0.0f, Float(2.0 * M_PI));
    RefPtr<Path> path = builder->Finish();
    mDrawTarget->Fill(path, ColorPattern(ToDeviceColor(borderColor)));
    return;
  }

  if (mergeStart == MERGE_HALF || mergeEnd == MERGE_HALF) {
    // MERGE_HALF
    //               Eo
    //   -------+----+
    //        ##### /
    //       ######/
    //      ######/
    //      ####+
    //      ##/ end
    //       /
    //      /
    //   --+
    //     Ei
    //
    // other (NO_MERGE, MERGE_ALL, MERGE_NONE)
    //               Eo
    //   ------------+
    //        #####  |
    //       ####### |
    //      #########|
    //      ####+####|
    //      ## end ##|
    //       ####### |
    //        #####  |
    //   ------------+
    //               Ei

    Point I(0.0f, 0.0f), J(0.0f, 0.0f);
    if (aSide == eSideTop) {
      I.x = 1.0f;
      J.y = 1.0f;
    } else if (aSide == eSideRight) {
      I.y = 1.0f;
      J.x = -1.0f;
    } else if (aSide == eSideBottom) {
      I.x = -1.0f;
      J.y = -1.0f;
    } else if (aSide == eSideLeft) {
      I.y = -1.0f;
      J.x = 1.0f;
    }

    Point So, Si, Eo, Ei;

    So = (start + (-I + -J) * borderWidth / 2.0f);
    Si = (mergeStart == MERGE_HALF) ? (start + (I + J) * borderWidth / 2.0f)
                                    : (start + (-I + J) * borderWidth / 2.0f);
    Eo = (end + (I - J) * borderWidth / 2.0f);
    Ei = (mergeEnd == MERGE_HALF) ? (end + (-I + J) * borderWidth / 2.0f)
                                  : (end + (I + J) * borderWidth / 2.0f);

    RefPtr<PathBuilder> builder = mDrawTarget->CreatePathBuilder();
    builder->MoveTo(So);
    builder->LineTo(Eo);
    builder->LineTo(Ei);
    builder->LineTo(Si);
    builder->Close();
    RefPtr<Path> path = builder->Finish();

    mDrawTarget->PushClip(path);
  }

  size_t count = round(borderLength / dotWidth);
  if (isStartUnfilled == isEndUnfilled) {
    // Split into 2n segments.
    if (count % 2) {
      count++;
    }
  } else {
    // Split into 2n+1 segments.
    if (count % 2 == 0) {
      count++;
    }
  }

  // A: radius == borderWidth / 2.0
  // B: borderLength / count == borderWidth * (1 - overlap)
  //
  //   A      B         B        B        B     A
  // |<-->|<------>|<------>|<------>|<------>|<-->|
  // |    |        |        |        |        |    |
  // +----+--------+--------+--------+--------+----+
  // |  ##|##    **|**    ##|##    **|**    ##|##  |
  // | ###|###  ***|***  ###|###  ***|***  ###|### |
  // |####|####****|****####|####****|****####|####|
  // |####+####****+****####+####****+****####+####|
  // |# start #****|****####|####****|****## end ##|
  // | ###|###  ***|***  ###|###  ***|***  ###|### |
  // |  ##|##    **|**    ##|##    **|**    ##|##  |
  // +----+----+---+--------+--------+---+----+----+
  // |         |                         |         |
  // |         |                         |         |

  // If isStartUnfilled is true, draw dots on 2j+1 points, if not, draw dots on
  // 2j points.
  size_t from = isStartUnfilled ? 1 : 0;

  // If mergeEnd == MERGE_NONE, last dot is drawn by next side.
  size_t to = count;
  if (mergeEnd == MERGE_NONE) {
    if (to > 2) {
      to -= 2;
    } else {
      to = 0;
    }
  }

  Point fromP = (start * (count - from) + end * from) / count;
  Point toP = (start * (count - to) + end * to) / count;
  // Extend dirty rect to avoid clipping pixel for anti-aliasing.
  const Float AA_MARGIN = 2.0f;

  if (aSide == eSideTop) {
    // Tweak |from| and |to| to fit into |mDirtyRect + radius margin|,
    // to render only paths that may overlap mDirtyRect.
    //
    //                mDirtyRect + radius margin
    //              +--+---------------------+--+
    //              |                           |
    //              |         mDirtyRect        |
    //              +  +---------------------+  +
    // from   ===>  |from                    to |   <===  to
    //    +-----+-----+-----+-----+-----+-----+-----+-----+
    //   ###        |###         ###         ###|        ###
    //  #####       #####       #####       #####       #####
    //  #####       #####       #####       #####       #####
    //  #####       #####       #####       #####       #####
    //   ###        |###         ###         ###|        ###
    //              |  |                     |  |
    //              +  +---------------------+  +
    //              |                           |
    //              |                           |
    //              +--+---------------------+--+

    Float left = mDirtyRect.x - radius - AA_MARGIN;
    if (fromP.x < left) {
      size_t tmp = ceil(count * (left - start.x) / (end.x - start.x));
      if (tmp > from) {
        // We increment by 2, so odd/even should match between before/after.
        if ((tmp & 1) != (from & 1)) {
          from = tmp - 1;
        } else {
          from = tmp;
        }
      }
    }
    Float right = mDirtyRect.x + mDirtyRect.width + radius + AA_MARGIN;
    if (toP.x > right) {
      size_t tmp = floor(count * (right - start.x) / (end.x - start.x));
      if (tmp < to) {
        if ((tmp & 1) != (to & 1)) {
          to = tmp + 1;
        } else {
          to = tmp;
        }
      }
    }
  } else if (aSide == eSideRight) {
    Float top = mDirtyRect.y - radius - AA_MARGIN;
    if (fromP.y < top) {
      size_t tmp = ceil(count * (top - start.y) / (end.y - start.y));
      if (tmp > from) {
        if ((tmp & 1) != (from & 1)) {
          from = tmp - 1;
        } else {
          from = tmp;
        }
      }
    }
    Float bottom = mDirtyRect.y + mDirtyRect.height + radius + AA_MARGIN;
    if (toP.y > bottom) {
      size_t tmp = floor(count * (bottom - start.y) / (end.y - start.y));
      if (tmp < to) {
        if ((tmp & 1) != (to & 1)) {
          to = tmp + 1;
        } else {
          to = tmp;
        }
      }
    }
  } else if (aSide == eSideBottom) {
    Float right = mDirtyRect.x + mDirtyRect.width + radius + AA_MARGIN;
    if (fromP.x > right) {
      size_t tmp = ceil(count * (right - start.x) / (end.x - start.x));
      if (tmp > from) {
        if ((tmp & 1) != (from & 1)) {
          from = tmp - 1;
        } else {
          from = tmp;
        }
      }
    }
    Float left = mDirtyRect.x - radius - AA_MARGIN;
    if (toP.x < left) {
      size_t tmp = floor(count * (left - start.x) / (end.x - start.x));
      if (tmp < to) {
        if ((tmp & 1) != (to & 1)) {
          to = tmp + 1;
        } else {
          to = tmp;
        }
      }
    }
  } else if (aSide == eSideLeft) {
    Float bottom = mDirtyRect.y + mDirtyRect.height + radius + AA_MARGIN;
    if (fromP.y > bottom) {
      size_t tmp = ceil(count * (bottom - start.y) / (end.y - start.y));
      if (tmp > from) {
        if ((tmp & 1) != (from & 1)) {
          from = tmp - 1;
        } else {
          from = tmp;
        }
      }
    }
    Float top = mDirtyRect.y - radius - AA_MARGIN;
    if (toP.y < top) {
      size_t tmp = floor(count * (top - start.y) / (end.y - start.y));
      if (tmp < to) {
        if ((tmp & 1) != (to & 1)) {
          to = tmp + 1;
        } else {
          to = tmp;
        }
      }
    }
  }

  RefPtr<PathBuilder> builder = mDrawTarget->CreatePathBuilder();
  size_t segmentCount = 0;
  for (size_t i = from; i <= to; i += 2) {
    if (segmentCount > BORDER_SEGMENT_COUNT_MAX) {
      RefPtr<Path> path = builder->Finish();
      mDrawTarget->Fill(path, ColorPattern(ToDeviceColor(borderColor)));
      builder = mDrawTarget->CreatePathBuilder();
      segmentCount = 0;
    }

    Point P = (start * (count - i) + end * i) / count;
    builder->MoveTo(Point(P.x + radius, P.y));
    builder->Arc(P, radius, 0.0f, Float(2.0 * M_PI));
    segmentCount++;
  }
  RefPtr<Path> path = builder->Finish();
  mDrawTarget->Fill(path, ColorPattern(ToDeviceColor(borderColor)));

  if (mergeStart == MERGE_HALF || mergeEnd == MERGE_HALF) {
    mDrawTarget->PopClip();
  }
}

void nsCSSBorderRenderer::DrawDashedOrDottedCorner(mozilla::Side aSide,
                                                   Corner aCorner) {
  // Draw dashed/dotted corner with following approach.
  //
  // dashed corner
  //   If both side has same border-width and border-width <= 2.0, draw dashed
  //   line along the corner, with appropriate dash length and gap to make the
  //   corner symmetric as far as possible.  Dash length equals to the gap, and
  //   the ratio of the dash length to border-width is the maximum value in in
  //   [1, 3] range.
  //   Otherwise, draw dashed segments along the corner, keeping same dash
  //   length ratio to border-width at that point.
  //   (see DashedCornerFinder.h for more detail)
  //   Line ends with half segments, to joint with both side easily.
  //
  // dotted corner
  //   If both side has same border-width and border-width <= 2.0, draw 1:1
  //   dashed line along the corner.
  //   Otherwise Draw circles along the corner, with appropriate gap that makes
  //   the corner symmetric as far as possible.  The size of the circle may
  //   change along the corner, that is tangent to the outer curver and the
  //   inner curve.  The ratio of the gap to circle diameter is the maximum
  //   value in [0.5, 1] range.
  //   (see DottedCornerFinder.h for more detail)
  //   Corner ends with filled dots but those dots are drawn by
  //   DrawDashedOrDottedSide.  So this may draw no circles if there's no space
  //   between 2 dots at both ends.

  NS_ASSERTION(mBorderStyles[aSide] == StyleBorderStyle::Dashed ||
                   mBorderStyles[aSide] == StyleBorderStyle::Dotted,
               "Style should be dashed or dotted.");

  if (IsCornerMergeable(aCorner)) {
    // DrawDashedOrDottedSide will draw corner.
    return;
  }

  mozilla::Side sideH(GetHorizontalSide(aCorner));
  mozilla::Side sideV(GetVerticalSide(aCorner));
  Float borderWidthH = mBorderWidths[sideH];
  Float borderWidthV = mBorderWidths[sideV];
  if (borderWidthH == 0.0f && borderWidthV == 0.0f) {
    return;
  }

  StyleBorderStyle styleH = mBorderStyles[sideH];
  StyleBorderStyle styleV = mBorderStyles[sideV];

  // Corner between dotted and others with radius=0 is drawn by side.
  if (IsZeroSize(mBorderRadii[aCorner]) &&
      (styleV == StyleBorderStyle::Dotted ||
       styleH == StyleBorderStyle::Dotted)) {
    return;
  }

  Float maxRadius =
      std::max(mBorderRadii[aCorner].width, mBorderRadii[aCorner].height);
  if (maxRadius > BORDER_DOTTED_CORNER_MAX_RADIUS) {
    DrawFallbackSolidCorner(aSide, aCorner);
    return;
  }

  if (borderWidthH != borderWidthV || borderWidthH > 2.0f) {
    StyleBorderStyle style = mBorderStyles[aSide];
    if (style == StyleBorderStyle::Dotted) {
      DrawDottedCornerSlow(aSide, aCorner);
    } else {
      DrawDashedCornerSlow(aSide, aCorner);
    }
    return;
  }

  nscolor borderColor = mBorderColors[aSide];
  Point points[4];
  bool ignored;
  // Get the start and end points of the corner arc, ensuring that any dot
  // origins get pushed backwards towards the edges of the corner rect to
  // account for stroking.
  points[0] = GetStraightBorderPoint(sideH, aCorner, &ignored, -0.5f);
  points[3] = GetStraightBorderPoint(sideV, aCorner, &ignored, -0.5f);
  // Round points to draw dot on each pixel.
  if (borderWidthH < 2.0f) {
    points[0].x = round(points[0].x);
  }
  if (borderWidthV < 2.0f) {
    points[3].y = round(points[3].y);
  }
  points[1] = points[0];
  points[1].x += kKappaFactor * (points[3].x - points[0].x);
  points[2] = points[3];
  points[2].y += kKappaFactor * (points[0].y - points[3].y);

  Float len = GetQuarterEllipticArcLength(fabs(points[0].x - points[3].x),
                                          fabs(points[0].y - points[3].y));

  Float dash[2];
  StrokeOptions strokeOptions(borderWidthH);
  SetupDashedOptions(&strokeOptions, dash, aSide, len, true);

  RefPtr<PathBuilder> builder = mDrawTarget->CreatePathBuilder();
  builder->MoveTo(points[0]);
  builder->BezierTo(points[1], points[2], points[3]);
  RefPtr<Path> path = builder->Finish();
  mDrawTarget->Stroke(path, ColorPattern(ToDeviceColor(borderColor)),
                      strokeOptions);
}

void nsCSSBorderRenderer::DrawDottedCornerSlow(mozilla::Side aSide,
                                               Corner aCorner) {
  NS_ASSERTION(mBorderStyles[aSide] == StyleBorderStyle::Dotted,
               "Style should be dotted.");

  mozilla::Side sideH(GetHorizontalSide(aCorner));
  mozilla::Side sideV(GetVerticalSide(aCorner));
  Float R0 = mBorderWidths[sideH] / 2.0f;
  Float Rn = mBorderWidths[sideV] / 2.0f;
  if (R0 == 0.0f && Rn == 0.0f) {
    return;
  }

  nscolor borderColor = mBorderColors[aSide];
  Bezier outerBezier;
  Bezier innerBezier;
  GetOuterAndInnerBezier(&outerBezier, &innerBezier, aCorner);

  bool ignored;
  Point C0 = GetStraightBorderPoint(sideH, aCorner, &ignored);
  Point Cn = GetStraightBorderPoint(sideV, aCorner, &ignored);
  DottedCornerFinder finder(outerBezier, innerBezier, aCorner,
                            mBorderRadii[aCorner].width,
                            mBorderRadii[aCorner].height, C0, R0, Cn, Rn,
                            mBorderCornerDimensions[aCorner]);

  RefPtr<PathBuilder> builder = mDrawTarget->CreatePathBuilder();
  size_t segmentCount = 0;
  const Float AA_MARGIN = 2.0f;
  Rect marginedDirtyRect = mDirtyRect;
  marginedDirtyRect.Inflate(std::max(R0, Rn) + AA_MARGIN);
  bool entered = false;
  while (finder.HasMore()) {
    if (segmentCount > BORDER_SEGMENT_COUNT_MAX) {
      RefPtr<Path> path = builder->Finish();
      mDrawTarget->Fill(path, ColorPattern(ToDeviceColor(borderColor)));
      builder = mDrawTarget->CreatePathBuilder();
      segmentCount = 0;
    }

    DottedCornerFinder::Result result = finder.Next();

    if (marginedDirtyRect.Contains(result.C) && result.r > 0) {
      entered = true;
      builder->MoveTo(Point(result.C.x + result.r, result.C.y));
      builder->Arc(result.C, result.r, 0, Float(2.0 * M_PI));
      segmentCount++;
    } else if (entered) {
      break;
    }
  }
  RefPtr<Path> path = builder->Finish();
  mDrawTarget->Fill(path, ColorPattern(ToDeviceColor(borderColor)));
}

static inline bool DashedPathOverlapsRect(Rect& pathRect,
                                          const Rect& marginedDirtyRect,
                                          DashedCornerFinder::Result& result) {
  // Calculate a rect that contains all control points of the |result| path,
  // and check if it intersects with |marginedDirtyRect|.
  pathRect.SetRect(result.outerSectionBezier.mPoints[0].x,
                   result.outerSectionBezier.mPoints[0].y, 0, 0);
  pathRect.ExpandToEnclose(result.outerSectionBezier.mPoints[1]);
  pathRect.ExpandToEnclose(result.outerSectionBezier.mPoints[2]);
  pathRect.ExpandToEnclose(result.outerSectionBezier.mPoints[3]);
  pathRect.ExpandToEnclose(result.innerSectionBezier.mPoints[0]);
  pathRect.ExpandToEnclose(result.innerSectionBezier.mPoints[1]);
  pathRect.ExpandToEnclose(result.innerSectionBezier.mPoints[2]);
  pathRect.ExpandToEnclose(result.innerSectionBezier.mPoints[3]);

  return pathRect.Intersects(marginedDirtyRect);
}

void nsCSSBorderRenderer::DrawDashedCornerSlow(mozilla::Side aSide,
                                               Corner aCorner) {
  NS_ASSERTION(mBorderStyles[aSide] == StyleBorderStyle::Dashed,
               "Style should be dashed.");

  mozilla::Side sideH(GetHorizontalSide(aCorner));
  mozilla::Side sideV(GetVerticalSide(aCorner));
  Float borderWidthH = mBorderWidths[sideH];
  Float borderWidthV = mBorderWidths[sideV];
  if (borderWidthH == 0.0f && borderWidthV == 0.0f) {
    return;
  }

  nscolor borderColor = mBorderColors[aSide];
  Bezier outerBezier;
  Bezier innerBezier;
  GetOuterAndInnerBezier(&outerBezier, &innerBezier, aCorner);

  DashedCornerFinder finder(outerBezier, innerBezier, borderWidthH,
                            borderWidthV, mBorderCornerDimensions[aCorner]);

  RefPtr<PathBuilder> builder = mDrawTarget->CreatePathBuilder();
  size_t segmentCount = 0;
  const Float AA_MARGIN = 2.0f;
  Rect marginedDirtyRect = mDirtyRect;
  marginedDirtyRect.Inflate(AA_MARGIN);
  Rect pathRect;
  bool entered = false;
  while (finder.HasMore()) {
    if (segmentCount > BORDER_SEGMENT_COUNT_MAX) {
      RefPtr<Path> path = builder->Finish();
      mDrawTarget->Fill(path, ColorPattern(ToDeviceColor(borderColor)));
      builder = mDrawTarget->CreatePathBuilder();
      segmentCount = 0;
    }

    DashedCornerFinder::Result result = finder.Next();

    if (DashedPathOverlapsRect(pathRect, marginedDirtyRect, result)) {
      entered = true;
      builder->MoveTo(result.outerSectionBezier.mPoints[0]);
      builder->BezierTo(result.outerSectionBezier.mPoints[1],
                        result.outerSectionBezier.mPoints[2],
                        result.outerSectionBezier.mPoints[3]);
      builder->LineTo(result.innerSectionBezier.mPoints[3]);
      builder->BezierTo(result.innerSectionBezier.mPoints[2],
                        result.innerSectionBezier.mPoints[1],
                        result.innerSectionBezier.mPoints[0]);
      builder->LineTo(result.outerSectionBezier.mPoints[0]);
      segmentCount++;
    } else if (entered) {
      break;
    }
  }

  if (outerBezier.mPoints[0].x != innerBezier.mPoints[0].x) {
    // Fill gap before the first section.
    //
    //     outnerPoint[0]
    //         |
    //         v
    //        _+-----------+--
    //      /   \##########|
    //    /      \#########|
    //   +        \########|
    //   |\         \######|
    //   |  \        \#####|
    //   |    \       \####|
    //   |      \       \##|
    //   |        \      \#|
    //   |          \     \|
    //   |            \  _-+--
    //   +--------------+  ^
    //   |              |  |
    //   |              |  innerPoint[0]
    //   |              |
    builder->MoveTo(outerBezier.mPoints[0]);
    builder->LineTo(innerBezier.mPoints[0]);
    builder->LineTo(Point(innerBezier.mPoints[0].x, outerBezier.mPoints[0].y));
    builder->LineTo(outerBezier.mPoints[0]);
  }

  if (outerBezier.mPoints[3].y != innerBezier.mPoints[3].y) {
    // Fill gap after the last section.
    //
    // outnerPoint[3]
    //   |
    //   |
    //   |    _+-----------+--
    //   |  /   \          |
    //   v/      \         |
    //   +        \        |
    //   |\         \      |
    //   |##\        \     |
    //   |####\       \    |
    //   |######\       \  |
    //   |########\      \ |
    //   |##########\     \|
    //   |############\  _-+--
    //   +--------------+<-- innerPoint[3]
    //   |              |
    //   |              |
    //   |              |
    builder->MoveTo(outerBezier.mPoints[3]);
    builder->LineTo(innerBezier.mPoints[3]);
    builder->LineTo(Point(outerBezier.mPoints[3].x, innerBezier.mPoints[3].y));
    builder->LineTo(outerBezier.mPoints[3]);
  }

  RefPtr<Path> path = builder->Finish();
  mDrawTarget->Fill(path, ColorPattern(ToDeviceColor(borderColor)));
}

void nsCSSBorderRenderer::DrawFallbackSolidCorner(mozilla::Side aSide,
                                                  Corner aCorner) {
  // Render too large dashed or dotted corner with solid style, to avoid hangup
  // inside DashedCornerFinder and DottedCornerFinder.

  NS_ASSERTION(mBorderStyles[aSide] == StyleBorderStyle::Dashed ||
                   mBorderStyles[aSide] == StyleBorderStyle::Dotted,
               "Style should be dashed or dotted.");

  nscolor borderColor = mBorderColors[aSide];
  Bezier outerBezier;
  Bezier innerBezier;
  GetOuterAndInnerBezier(&outerBezier, &innerBezier, aCorner);

  RefPtr<PathBuilder> builder = mDrawTarget->CreatePathBuilder();

  builder->MoveTo(outerBezier.mPoints[0]);
  builder->BezierTo(outerBezier.mPoints[1], outerBezier.mPoints[2],
                    outerBezier.mPoints[3]);
  builder->LineTo(innerBezier.mPoints[3]);
  builder->BezierTo(innerBezier.mPoints[2], innerBezier.mPoints[1],
                    innerBezier.mPoints[0]);
  builder->LineTo(outerBezier.mPoints[0]);

  RefPtr<Path> path = builder->Finish();
  mDrawTarget->Fill(path, ColorPattern(ToDeviceColor(borderColor)));

  if (mDocument) {
    if (!mPresContext->HasWarnedAboutTooLargeDashedOrDottedRadius()) {
      mPresContext->SetHasWarnedAboutTooLargeDashedOrDottedRadius();
      nsContentUtils::ReportToConsole(
          nsIScriptError::warningFlag, NS_LITERAL_CSTRING("CSS"), mDocument,
          nsContentUtils::eCSS_PROPERTIES,
          mBorderStyles[aSide] == StyleBorderStyle::Dashed
              ? "TooLargeDashedRadius"
              : "TooLargeDottedRadius");
    }
  }
}

bool nsCSSBorderRenderer::AllBordersSameWidth() {
  if (mBorderWidths[0] == mBorderWidths[1] &&
      mBorderWidths[0] == mBorderWidths[2] &&
      mBorderWidths[0] == mBorderWidths[3]) {
    return true;
  }

  return false;
}

bool nsCSSBorderRenderer::AllBordersSolid() {
  NS_FOR_CSS_SIDES(i) {
    if (mBorderStyles[i] == StyleBorderStyle::Solid ||
        mBorderStyles[i] == StyleBorderStyle::None ||
        mBorderStyles[i] == StyleBorderStyle::Hidden) {
      continue;
    }
    return false;
  }

  return true;
}

static bool IsVisible(StyleBorderStyle aStyle) {
  if (aStyle != StyleBorderStyle::None && aStyle != StyleBorderStyle::Hidden) {
    return true;
  }
  return false;
}

struct twoFloats {
  Float a, b;

  twoFloats operator*(const Size& aSize) const {
    return {a * aSize.width, b * aSize.height};
  }

  twoFloats operator*(Float aScale) const { return {a * aScale, b * aScale}; }

  twoFloats operator+(const Point& aPoint) const {
    return {a + aPoint.x, b + aPoint.y};
  }

  operator Point() const { return Point(a, b); }
};

void nsCSSBorderRenderer::DrawSingleWidthSolidBorder() {
  // Easy enough to deal with.
  Rect rect = mOuterRect;
  rect.Deflate(0.5);

  const twoFloats cornerAdjusts[4] = {
      {+0.5, 0}, {0, +0.5}, {-0.5, 0}, {0, -0.5}};
  NS_FOR_CSS_SIDES(side) {
    Point firstCorner = rect.CCWCorner(side) + cornerAdjusts[side];
    Point secondCorner = rect.CWCorner(side) + cornerAdjusts[side];

    ColorPattern color(ToDeviceColor(mBorderColors[side]));

    mDrawTarget->StrokeLine(firstCorner, secondCorner, color);
  }
}

// Intersect a ray from the inner corner to the outer corner
// with the border radius, yielding the intersection point.
static Point IntersectBorderRadius(const Point& aCenter, const Size& aRadius,
                                   const Point& aInnerCorner,
                                   const Point& aCornerDirection) {
  Point toCorner = aCornerDirection;
  // transform to-corner ray to unit-circle space
  toCorner.x /= aRadius.width;
  toCorner.y /= aRadius.height;
  // normalize to-corner ray
  Float cornerDist = toCorner.Length();
  if (cornerDist < 1.0e-6f) {
    return aInnerCorner;
  }
  toCorner = toCorner / cornerDist;
  // ray from inner corner to border radius center
  Point toCenter = aCenter - aInnerCorner;
  // transform to-center ray to unit-circle space
  toCenter.x /= aRadius.width;
  toCenter.y /= aRadius.height;
  // compute offset of intersection with border radius unit circle
  Float offset = toCenter.DotProduct(toCorner);
  // compute discriminant to check for intersections
  Float discrim = 1.0f - toCenter.DotProduct(toCenter) + offset * offset;
  // choose farthest intersection
  offset += sqrtf(std::max(discrim, 0.0f));
  // transform to-corner ray back out of unit-circle space
  toCorner.x *= aRadius.width;
  toCorner.y *= aRadius.height;
  return aInnerCorner + toCorner * offset;
}

// Calculate the split point and split angle for a border radius with
// differing sides.
static inline void SplitBorderRadius(const Point& aCenter, const Size& aRadius,
                                     const Point& aOuterCorner,
                                     const Point& aInnerCorner,
                                     const twoFloats& aCornerMults,
                                     Float aStartAngle, Point& aSplit,
                                     Float& aSplitAngle) {
  Point cornerDir = aOuterCorner - aInnerCorner;
  if (cornerDir.x == cornerDir.y && aRadius.IsSquare()) {
    // optimize 45-degree intersection with circle since we can assume
    // the circle center lies along the intersection edge
    aSplit = aCenter - aCornerMults * (aRadius * Float(1.0f / M_SQRT2));
    aSplitAngle = aStartAngle + 0.5f * M_PI / 2.0f;
  } else {
    aSplit = IntersectBorderRadius(aCenter, aRadius, aInnerCorner, cornerDir);
    aSplitAngle = atan2f((aSplit.y - aCenter.y) / aRadius.height,
                         (aSplit.x - aCenter.x) / aRadius.width);
  }
}

// Compute the size of the skirt needed, given the color alphas
// of each corner side and the slope between them.
static void ComputeCornerSkirtSize(Float aAlpha1, Float aAlpha2, Float aSlopeY,
                                   Float aSlopeX, Float& aSizeResult,
                                   Float& aSlopeResult) {
  // If either side is (almost) invisible or there is no diagonal edge,
  // then don't try to render a skirt.
  if (aAlpha1 < 0.01f || aAlpha2 < 0.01f) {
    return;
  }
  aSlopeX = fabs(aSlopeX);
  aSlopeY = fabs(aSlopeY);
  if (aSlopeX < 1.0e-6f || aSlopeY < 1.0e-6f) {
    return;
  }

  // If first and second color don't match, we need to split the corner in
  // half. The diagonal edges created may not have full pixel coverage given
  // anti-aliasing, so we need to compute a small subpixel skirt edge. This
  // assumes each half has half coverage to start with, and that coverage
  // increases as the skirt is pushed over, with the end result that we want
  // to roughly preserve the alpha value along this edge.
  // Given slope m, alphas a and A, use quadratic formula to solve for S in:
  //   a*(1 - 0.5*(1-S)*(1-mS))*(1 - 0.5*A) + 0.5*A = A
  // yielding:
  //   S = ((1+m) - sqrt((1+m)*(1+m) + 4*m*(1 - A/(a*(1-0.5*A))))) / (2*m)
  // and substitute k = (1+m)/(2*m):
  //   S = k - sqrt(k*k + (1 - A/(a*(1-0.5*A)))/m)
  Float slope = aSlopeY / aSlopeX;
  Float slopeScale = (1.0f + slope) / (2.0f * slope);
  Float discrim = slopeScale * slopeScale +
                  (1 - aAlpha2 / (aAlpha1 * (1.0f - 0.49f * aAlpha2))) / slope;
  if (discrim >= 0) {
    aSizeResult = slopeScale - sqrtf(discrim);
    aSlopeResult = slope;
  }
}

// Draws a border radius with possibly different sides.
// A skirt is drawn underneath the corner intersection to hide possible
// seams when anti-aliased drawing is used.
static void DrawBorderRadius(DrawTarget* aDrawTarget, Corner c,
                             const Point& aOuterCorner,
                             const Point& aInnerCorner,
                             const twoFloats& aCornerMultPrev,
                             const twoFloats& aCornerMultNext,
                             const Size& aCornerDims, const Size& aOuterRadius,
                             const Size& aInnerRadius, const Color& aFirstColor,
                             const Color& aSecondColor, Float aSkirtSize,
                             Float aSkirtSlope) {
  // Connect edge to outer arc start point
  Point outerCornerStart = aOuterCorner + aCornerMultPrev * aCornerDims;
  // Connect edge to outer arc end point
  Point outerCornerEnd = aOuterCorner + aCornerMultNext * aCornerDims;
  // Connect edge to inner arc start point
  Point innerCornerStart =
      outerCornerStart + aCornerMultNext * (aCornerDims - aInnerRadius);
  // Connect edge to inner arc end point
  Point innerCornerEnd =
      outerCornerEnd + aCornerMultPrev * (aCornerDims - aInnerRadius);

  // Outer arc start point
  Point outerArcStart = aOuterCorner + aCornerMultPrev * aOuterRadius;
  // Outer arc end point
  Point outerArcEnd = aOuterCorner + aCornerMultNext * aOuterRadius;
  // Inner arc start point
  Point innerArcStart = aInnerCorner + aCornerMultPrev * aInnerRadius;
  // Inner arc end point
  Point innerArcEnd = aInnerCorner + aCornerMultNext * aInnerRadius;

  // Outer radius center
  Point outerCenter =
      aOuterCorner + (aCornerMultPrev + aCornerMultNext) * aOuterRadius;
  // Inner radius center
  Point innerCenter =
      aInnerCorner + (aCornerMultPrev + aCornerMultNext) * aInnerRadius;

  RefPtr<PathBuilder> builder;
  RefPtr<Path> path;

  if (aFirstColor.a > 0) {
    builder = aDrawTarget->CreatePathBuilder();
    builder->MoveTo(outerCornerStart);
  }

  if (aFirstColor != aSecondColor) {
    // Start and end angles of corner quadrant
    Float startAngle = (c * M_PI) / 2.0f - M_PI,
          endAngle = startAngle + M_PI / 2.0f, outerSplitAngle, innerSplitAngle;
    Point outerSplit, innerSplit;

    // Outer half-way point
    SplitBorderRadius(outerCenter, aOuterRadius, aOuterCorner, aInnerCorner,
                      aCornerMultPrev + aCornerMultNext, startAngle, outerSplit,
                      outerSplitAngle);
    // Inner half-way point
    if (aInnerRadius.IsEmpty()) {
      innerSplit = aInnerCorner;
      innerSplitAngle = endAngle;
    } else {
      SplitBorderRadius(innerCenter, aInnerRadius, aOuterCorner, aInnerCorner,
                        aCornerMultPrev + aCornerMultNext, startAngle,
                        innerSplit, innerSplitAngle);
    }

    // Draw first half with first color
    if (aFirstColor.a > 0) {
      AcuteArcToBezier(builder.get(), outerCenter, aOuterRadius, outerArcStart,
                       outerSplit, startAngle, outerSplitAngle);
      // Draw skirt as part of first half
      if (aSkirtSize > 0) {
        builder->LineTo(outerSplit + aCornerMultNext * aSkirtSize);
        builder->LineTo(innerSplit -
                        aCornerMultPrev * (aSkirtSize * aSkirtSlope));
      }
      AcuteArcToBezier(builder.get(), innerCenter, aInnerRadius, innerSplit,
                       innerArcStart, innerSplitAngle, startAngle);
      if ((innerCornerStart - innerArcStart).DotProduct(aCornerMultPrev) > 0) {
        builder->LineTo(innerCornerStart);
      }
      builder->Close();
      path = builder->Finish();
      aDrawTarget->Fill(path, ColorPattern(aFirstColor));
    }

    // Draw second half with second color
    if (aSecondColor.a > 0) {
      builder = aDrawTarget->CreatePathBuilder();
      builder->MoveTo(outerCornerEnd);
      if ((innerArcEnd - innerCornerEnd).DotProduct(aCornerMultNext) < 0) {
        builder->LineTo(innerCornerEnd);
      }
      AcuteArcToBezier(builder.get(), innerCenter, aInnerRadius, innerArcEnd,
                       innerSplit, endAngle, innerSplitAngle);
      AcuteArcToBezier(builder.get(), outerCenter, aOuterRadius, outerSplit,
                       outerArcEnd, outerSplitAngle, endAngle);
      builder->Close();
      path = builder->Finish();
      aDrawTarget->Fill(path, ColorPattern(aSecondColor));
    }
  } else if (aFirstColor.a > 0) {
    // Draw corner with single color
    AcuteArcToBezier(builder.get(), outerCenter, aOuterRadius, outerArcStart,
                     outerArcEnd);
    builder->LineTo(outerCornerEnd);
    if ((innerArcEnd - innerCornerEnd).DotProduct(aCornerMultNext) < 0) {
      builder->LineTo(innerCornerEnd);
    }
    AcuteArcToBezier(builder.get(), innerCenter, aInnerRadius, innerArcEnd,
                     innerArcStart, -kKappaFactor);
    if ((innerCornerStart - innerArcStart).DotProduct(aCornerMultPrev) > 0) {
      builder->LineTo(innerCornerStart);
    }
    builder->Close();
    path = builder->Finish();
    aDrawTarget->Fill(path, ColorPattern(aFirstColor));
  }
}

// Draw a corner with possibly different sides.
// A skirt is drawn underneath the corner intersection to hide possible
// seams when anti-aliased drawing is used.
static void DrawCorner(DrawTarget* aDrawTarget, const Point& aOuterCorner,
                       const Point& aInnerCorner,
                       const twoFloats& aCornerMultPrev,
                       const twoFloats& aCornerMultNext,
                       const Size& aCornerDims, const Color& aFirstColor,
                       const Color& aSecondColor, Float aSkirtSize,
                       Float aSkirtSlope) {
  // Corner box start point
  Point cornerStart = aOuterCorner + aCornerMultPrev * aCornerDims;
  // Corner box end point
  Point cornerEnd = aOuterCorner + aCornerMultNext * aCornerDims;

  RefPtr<PathBuilder> builder;
  RefPtr<Path> path;

  if (aFirstColor.a > 0) {
    builder = aDrawTarget->CreatePathBuilder();
    builder->MoveTo(cornerStart);
  }

  if (aFirstColor != aSecondColor) {
    // Draw first half with first color
    if (aFirstColor.a > 0) {
      builder->LineTo(aOuterCorner);
      // Draw skirt as part of first half
      if (aSkirtSize > 0) {
        builder->LineTo(aOuterCorner + aCornerMultNext * aSkirtSize);
        builder->LineTo(aInnerCorner -
                        aCornerMultPrev * (aSkirtSize * aSkirtSlope));
      }
      builder->LineTo(aInnerCorner);
      builder->Close();
      path = builder->Finish();
      aDrawTarget->Fill(path, ColorPattern(aFirstColor));
    }

    // Draw second half with second color
    if (aSecondColor.a > 0) {
      builder = aDrawTarget->CreatePathBuilder();
      builder->MoveTo(cornerEnd);
      builder->LineTo(aInnerCorner);
      builder->LineTo(aOuterCorner);
      builder->Close();
      path = builder->Finish();
      aDrawTarget->Fill(path, ColorPattern(aSecondColor));
    }
  } else if (aFirstColor.a > 0) {
    // Draw corner with single color
    builder->LineTo(aOuterCorner);
    builder->LineTo(cornerEnd);
    builder->LineTo(aInnerCorner);
    builder->Close();
    path = builder->Finish();
    aDrawTarget->Fill(path, ColorPattern(aFirstColor));
  }
}

void nsCSSBorderRenderer::DrawSolidBorder() {
  const twoFloats cornerMults[4] = {{-1, 0}, {0, -1}, {+1, 0}, {0, +1}};

  const twoFloats centerAdjusts[4] = {
      {0, +0.5}, {-0.5, 0}, {0, -0.5}, {+0.5, 0}};

  RectCornerRadii innerRadii;
  ComputeInnerRadii(mBorderRadii, mBorderWidths, &innerRadii);

  Rect strokeRect = mOuterRect;
  strokeRect.Deflate(Margin(mBorderWidths[0] / 2.0, mBorderWidths[1] / 2.0,
                            mBorderWidths[2] / 2.0, mBorderWidths[3] / 2.0));

  NS_FOR_CSS_SIDES(i) {
    // We now draw the current side and the CW corner following it.
    // The CCW corner of this side was already drawn in the previous iteration.
    // The side will be drawn as an explicit stroke, and the CW corner will be
    // filled separately.
    // If the next side does not have a matching color, then we split the
    // corner into two halves, one of each side's color and draw both.
    // Thus, the CCW corner of the next side will end up drawn here.

    // the corner index -- either 1 2 3 0 (cw) or 0 3 2 1 (ccw)
    Corner c = Corner((i + 1) % 4);
    Corner prevCorner = Corner(i);

    // i+2 and i+3 respectively.  These are used to index into the corner
    // multiplier table, and were deduced by calculating out the long form
    // of each corner and finding a pattern in the signs and values.
    int i1 = (i + 1) % 4;
    int i2 = (i + 2) % 4;
    int i3 = (i + 3) % 4;

    Float sideWidth = 0.0f;
    Color firstColor, secondColor;
    if (IsVisible(mBorderStyles[i]) && mBorderWidths[i]) {
      // draw the side since it is visible
      sideWidth = mBorderWidths[i];
      firstColor = ToDeviceColor(mBorderColors[i]);
      // if the next side is visible, use its color for corner
      secondColor = IsVisible(mBorderStyles[i1]) && mBorderWidths[i1]
                        ? ToDeviceColor(mBorderColors[i1])
                        : firstColor;
    } else if (IsVisible(mBorderStyles[i1]) && mBorderWidths[i1]) {
      // assign next side's color to both corner sides
      firstColor = ToDeviceColor(mBorderColors[i1]);
      secondColor = firstColor;
    } else {
      // neither side is visible, so nothing to do
      continue;
    }

    Point outerCorner = mOuterRect.AtCorner(c);
    Point innerCorner = mInnerRect.AtCorner(c);

    // start and end points of border side stroke between corners
    Point sideStart = mOuterRect.AtCorner(prevCorner) +
                      cornerMults[i2] * mBorderCornerDimensions[prevCorner];
    Point sideEnd = outerCorner + cornerMults[i] * mBorderCornerDimensions[c];
    // check if the side is visible and not inverted
    if (sideWidth > 0 && firstColor.a > 0 &&
        -(sideEnd - sideStart).DotProduct(cornerMults[i]) > 0) {
      mDrawTarget->StrokeLine(sideStart + centerAdjusts[i] * sideWidth,
                              sideEnd + centerAdjusts[i] * sideWidth,
                              ColorPattern(firstColor),
                              StrokeOptions(sideWidth));
    }

    Float skirtSize = 0.0f, skirtSlope = 0.0f;
    // the sides don't match, so compute a skirt
    if (firstColor != secondColor &&
        mPresContext->Type() != nsPresContext::eContext_Print) {
      Point cornerDir = outerCorner - innerCorner;
      ComputeCornerSkirtSize(
          firstColor.a, secondColor.a, cornerDir.DotProduct(cornerMults[i]),
          cornerDir.DotProduct(cornerMults[i3]), skirtSize, skirtSlope);
    }

    if (!mBorderRadii[c].IsEmpty()) {
      // the corner has a border radius
      DrawBorderRadius(mDrawTarget, c, outerCorner, innerCorner, cornerMults[i],
                       cornerMults[i3], mBorderCornerDimensions[c],
                       mBorderRadii[c], innerRadii[c], firstColor, secondColor,
                       skirtSize, skirtSlope);
    } else if (!mBorderCornerDimensions[c].IsEmpty()) {
      // a corner with no border radius
      DrawCorner(mDrawTarget, outerCorner, innerCorner, cornerMults[i],
                 cornerMults[i3], mBorderCornerDimensions[c], firstColor,
                 secondColor, skirtSize, skirtSlope);
    }
  }
}

void nsCSSBorderRenderer::DrawBorders() {
  if (mAllBordersSameStyle && (mBorderStyles[0] == StyleBorderStyle::None ||
                               mBorderStyles[0] == StyleBorderStyle::Hidden ||
                               mBorderColors[0] == NS_RGBA(0, 0, 0, 0))) {
    // All borders are the same style, and the style is either none or hidden,
    // or the color is transparent.
    return;
  }

  if (mAllBordersSameWidth && mBorderWidths[0] == 0.0) {
    // Some of the mAllBordersSameWidth codepaths depend on the border
    // width being greater than zero.
    return;
  }

  AutoRestoreTransform autoRestoreTransform;
  Matrix mat = mDrawTarget->GetTransform();

  // Clamp the CTM to be pixel-aligned; we do this only
  // for translation-only matrices now, but we could do it
  // if the matrix has just a scale as well.  We should not
  // do it if there's a rotation.
  if (mat.HasNonTranslation()) {
    if (!mat.HasNonAxisAlignedTransform()) {
      // Scale + transform. Avoid stroke fast-paths so that we have a chance
      // of snapping to pixel boundaries.
      mAvoidStroke = true;
    }
  } else {
    mat._31 = floor(mat._31 + 0.5);
    mat._32 = floor(mat._32 + 0.5);
    autoRestoreTransform.Init(mDrawTarget);
    mDrawTarget->SetTransform(mat);

    // round mOuterRect and mInnerRect; they're already an integer
    // number of pixels apart and should stay that way after
    // rounding. We don't do this if there's a scale in the current transform
    // since this loses information that might be relevant when we're scaling.
    mOuterRect.Round();
    mInnerRect.Round();
  }

  // Initial values only used when the border colors/widths are all the same:
  ColorPattern color(ToDeviceColor(mBorderColors[eSideTop]));
  StrokeOptions strokeOptions(mBorderWidths[eSideTop]);  // stroke width

  // First there's a couple of 'special cases' that have specifically optimized
  // drawing paths, when none of these can be used we move on to the generalized
  // border drawing code.
  if (mAllBordersSameStyle && mAllBordersSameWidth &&
      mBorderStyles[0] == StyleBorderStyle::Solid && mNoBorderRadius &&
      !mAvoidStroke) {
    // Very simple case.
    Rect rect = mOuterRect;
    rect.Deflate(mBorderWidths[0] / 2.0);
    mDrawTarget->StrokeRect(rect, color, strokeOptions);
    return;
  }

  if (mAllBordersSameStyle && mBorderStyles[0] == StyleBorderStyle::Solid &&
      !mAvoidStroke && !mNoBorderRadius) {
    // Relatively simple case.
    RoundedRect borderInnerRect(mOuterRect, mBorderRadii);
    borderInnerRect.Deflate(mBorderWidths[eSideTop], mBorderWidths[eSideBottom],
                            mBorderWidths[eSideLeft],
                            mBorderWidths[eSideRight]);

    // Instead of stroking we just use two paths: an inner and an outer.
    // This allows us to draw borders that we couldn't when stroking. For
    // example, borders with a border width >= the border radius. (i.e. when
    // there are square corners on the inside)
    //
    // Further, this approach can be more efficient because the backend
    // doesn't need to compute an offset curve to stroke the path. We know that
    // the rounded parts are elipses we can offset exactly and can just compute
    // a new cubic approximation.
    RefPtr<PathBuilder> builder = mDrawTarget->CreatePathBuilder();
    AppendRoundedRectToPath(builder, mOuterRect, mBorderRadii, true);
    AppendRoundedRectToPath(builder, borderInnerRect.rect,
                            borderInnerRect.corners, false);
    RefPtr<Path> path = builder->Finish();
    mDrawTarget->Fill(path, color);
    return;
  }

  const bool allBordersSolid = AllBordersSolid();

  // This leaves the border corners non-interpolated for single width borders.
  // Doing this is slightly faster and shouldn't be a problem visually.
  if (allBordersSolid && mAllBordersSameWidth && mBorderWidths[0] == 1 &&
      mNoBorderRadius && !mAvoidStroke) {
    DrawSingleWidthSolidBorder();
    return;
  }

  if (allBordersSolid && !mAvoidStroke) {
    DrawSolidBorder();
    return;
  }

  PrintAsString(" mOuterRect: ");
  PrintAsString(mOuterRect);
  PrintAsStringNewline();
  PrintAsString(" mInnerRect: ");
  PrintAsString(mInnerRect);
  PrintAsStringNewline();
  PrintAsFormatString(" mBorderColors: 0x%08x 0x%08x 0x%08x 0x%08x\n",
                      mBorderColors[0], mBorderColors[1], mBorderColors[2],
                      mBorderColors[3]);

  // if conditioning the outside rect failed, then bail -- the outside
  // rect is supposed to enclose the entire border
  {
    gfxRect outerRect = ThebesRect(mOuterRect);
    gfxUtils::ConditionRect(outerRect);
    if (outerRect.IsEmpty()) return;
    mOuterRect = ToRect(outerRect);

    gfxRect innerRect = ThebesRect(mInnerRect);
    gfxUtils::ConditionRect(innerRect);
    mInnerRect = ToRect(innerRect);
  }

  int dashedSides = 0;
  bool forceSeparateCorners = false;

  NS_FOR_CSS_SIDES(i) {
    StyleBorderStyle style = mBorderStyles[i];
    if (style == StyleBorderStyle::Dashed ||
        style == StyleBorderStyle::Dotted) {
      // we need to draw things separately for dashed/dotting
      forceSeparateCorners = true;
      dashedSides |= (1 << i);
    }
  }

  PrintAsFormatString(" mAllBordersSameStyle: %d dashedSides: 0x%02x\n",
                      mAllBordersSameStyle, dashedSides);

  if (mAllBordersSameStyle && !forceSeparateCorners) {
    /* Draw everything in one go */
    DrawBorderSides(eSideBitsAll);
    PrintAsStringNewline("---------------- (1)");
  } else {
    AUTO_PROFILER_LABEL("nsCSSBorderRenderer::DrawBorders:multipass", GRAPHICS);

    /* We have more than one pass to go.  Draw the corners separately from the
     * sides. */

    // The corner is going to have negligible size if its two adjacent border
    // sides are only 1px wide and there is no border radius.  In that case we
    // skip the overhead of painting the corner by setting the width or height
    // of the corner to zero, which effectively extends one of the corner's
    // adjacent border sides.  We extend the longer adjacent side so that
    // opposite sides will be the same length, which is necessary for opposite
    // dashed/dotted sides to be symmetrical.
    //
    //   if width > height
    //     +--+--------------+--+    +--------------------+
    //     |  |              |  |    |                    |
    //     +--+--------------+--+    +--+--------------+--+
    //     |  |              |  |    |  |              |  |
    //     |  |              |  | => |  |              |  |
    //     |  |              |  |    |  |              |  |
    //     +--+--------------+--+    +--+--------------+--+
    //     |  |              |  |    |                    |
    //     +--+--------------+--+    +--------------------+
    //
    //   if width <= height
    //     +--+--------+--+    +--+--------+--+
    //     |  |        |  |    |  |        |  |
    //     +--+--------+--+    |  +--------+  |
    //     |  |        |  |    |  |        |  |
    //     |  |        |  |    |  |        |  |
    //     |  |        |  |    |  |        |  |
    //     |  |        |  | => |  |        |  |
    //     |  |        |  |    |  |        |  |
    //     |  |        |  |    |  |        |  |
    //     |  |        |  |    |  |        |  |
    //     +--+--------+--+    |  +--------+  |
    //     |  |        |  |    |  |        |  |
    //     +--+--------+--+    +--+--------+--+
    //
    // Note that if we have different border widths we could end up with
    // opposite sides of different length.  For example, if the left and
    // bottom borders are 2px wide instead of 1px, we will end up doing
    // something like:
    //
    //     +----+------------+--+    +----+---------------+
    //     |    |            |  |    |    |               |
    //     +----+------------+--+    +----+------------+--+
    //     |    |            |  |    |    |            |  |
    //     |    |            |  | => |    |            |  |
    //     |    |            |  |    |    |            |  |
    //     +----+------------+--+    +----+------------+--+
    //     |    |            |  |    |    |            |  |
    //     |    |            |  |    |    |            |  |
    //     +----+------------+--+    +----+------------+--+
    //
    // XXX Should we only do this optimization if |mAllBordersSameWidth| is
    // true?
    //
    // XXX In fact is this optimization even worth the complexity it adds to
    // the code?  1px wide dashed borders are not overly common, and drawing
    // corners for them is not that expensive.
    NS_FOR_CSS_FULL_CORNERS(corner) {
      const mozilla::Side sides[2] = {mozilla::Side(corner), PREV_SIDE(corner)};

      if (!IsZeroSize(mBorderRadii[corner])) continue;

      if (mBorderWidths[sides[0]] == 1.0 && mBorderWidths[sides[1]] == 1.0) {
        if (mOuterRect.Width() > mOuterRect.Height()) {
          mBorderCornerDimensions[corner].width = 0.0;
        } else {
          mBorderCornerDimensions[corner].height = 0.0;
        }
      }
    }

    // First, the corners
    NS_FOR_CSS_FULL_CORNERS(corner) {
      // if there's no corner, don't do all this work for it
      if (IsZeroSize(mBorderCornerDimensions[corner])) continue;

      const int sides[2] = {corner, PREV_SIDE(corner)};
      int sideBits = (1 << sides[0]) | (1 << sides[1]);

      bool simpleCornerStyle = AreBorderSideFinalStylesSame(sideBits);

      // If we don't have anything complex going on in this corner,
      // then we can just fill the corner with a solid color, and avoid
      // the potentially expensive clip.
      if (simpleCornerStyle && IsZeroSize(mBorderRadii[corner]) &&
          IsSolidCornerStyle(mBorderStyles[sides[0]], corner)) {
        Color color = MakeBorderColor(
            mBorderColors[sides[0]],
            BorderColorStyleForSolidCorner(mBorderStyles[sides[0]], corner));
        mDrawTarget->FillRect(GetCornerRect(corner),
                              ColorPattern(ToDeviceColor(color)));
        continue;
      }

      // clip to the corner
      mDrawTarget->PushClipRect(GetCornerRect(corner));

      if (simpleCornerStyle) {
        // we don't need a group for this corner, the sides are the same,
        // but we weren't able to render just a solid block for the corner.
        DrawBorderSides(sideBits);
      } else {
        // Sides are different.  We could draw using OP_ADD to
        // get correct color blending behaviour at the seam.  We'd need
        // to do it in an offscreen surface to ensure that we're
        // always compositing on transparent black.  If the colors
        // don't have transparency and the current destination surface
        // has an alpha channel, we could just clear the region and
        // avoid the temporary, but that situation doesn't happen all
        // that often in practice (we double buffer to no-alpha
        // surfaces). We choose just to seam though, as the performance
        // advantages outway the modest easthetic improvement.

        for (int cornerSide = 0; cornerSide < 2; cornerSide++) {
          mozilla::Side side = mozilla::Side(sides[cornerSide]);
          StyleBorderStyle style = mBorderStyles[side];

          PrintAsFormatString("corner: %d cornerSide: %d side: %d style: %d\n",
                              corner, cornerSide, side,
                              static_cast<int>(style));

          RefPtr<Path> path = GetSideClipSubPath(side);
          mDrawTarget->PushClip(path);

          DrawBorderSides(1 << side);

          mDrawTarget->PopClip();
        }
      }

      mDrawTarget->PopClip();

      PrintAsStringNewline();
    }

    // in the case of a single-unit border, we already munged the
    // corners up above; so we can just draw the top left and bottom
    // right sides separately, if they're the same.
    //
    // We need to check for mNoBorderRadius, because when there is
    // one, FillSolidBorder always draws the full rounded rectangle
    // and expects there to be a clip in place.
    int alreadyDrawnSides = 0;
    if (mOneUnitBorder && mNoBorderRadius &&
        (dashedSides & (eSideBitsTop | eSideBitsLeft)) == 0) {
      bool tlBordersSameStyle =
          AreBorderSideFinalStylesSame(eSideBitsTop | eSideBitsLeft);
      bool brBordersSameStyle =
          AreBorderSideFinalStylesSame(eSideBitsBottom | eSideBitsRight);

      if (tlBordersSameStyle) {
        DrawBorderSides(eSideBitsTop | eSideBitsLeft);
        alreadyDrawnSides |= (eSideBitsTop | eSideBitsLeft);
      }

      if (brBordersSameStyle &&
          (dashedSides & (eSideBitsBottom | eSideBitsRight)) == 0) {
        DrawBorderSides(eSideBitsBottom | eSideBitsRight);
        alreadyDrawnSides |= (eSideBitsBottom | eSideBitsRight);
      }
    }

    // We're done with the corners, now draw the sides.
    NS_FOR_CSS_SIDES(side) {
      // if we drew it above, skip it
      if (alreadyDrawnSides & (1 << side)) continue;

      // If there's no border on this side, skip it
      if (mBorderWidths[side] == 0.0 ||
          mBorderStyles[side] == StyleBorderStyle::Hidden ||
          mBorderStyles[side] == StyleBorderStyle::None)
        continue;

      if (dashedSides & (1 << side)) {
        // Dashed sides will always draw just the part ignoring the
        // corners for the side, so no need to clip.
        DrawDashedOrDottedSide(side);

        PrintAsStringNewline("---------------- (d)");
        continue;
      }

      // Undashed sides will currently draw the entire side,
      // including parts that would normally be covered by a corner,
      // so we need to clip.
      //
      // XXX Optimization -- it would be good to make this work like
      // DrawDashedOrDottedSide, and have a DrawOneSide function that just
      // draws one side and not the corners, because then we can
      // avoid the potentially expensive clip.
      mDrawTarget->PushClipRect(GetSideClipWithoutCornersRect(side));

      DrawBorderSides(1 << side);

      mDrawTarget->PopClip();

      PrintAsStringNewline("---------------- (*)");
    }
  }
}

void nsCSSBorderRenderer::CreateWebRenderCommands(
    nsDisplayItem* aItem, wr::DisplayListBuilder& aBuilder,
    wr::IpcResourceUpdateQueue& aResources,
    const layers::StackingContextHelper& aSc) {
  LayoutDeviceRect outerRect = LayoutDeviceRect::FromUnknownRect(mOuterRect);
  wr::LayoutRect roundedRect = wr::ToRoundedLayoutRect(outerRect);
  wr::BorderSide side[4];
  NS_FOR_CSS_SIDES(i) {
    side[i] =
        wr::ToBorderSide(ToDeviceColor(mBorderColors[i]), mBorderStyles[i]);
  }

  wr::BorderRadius borderRadius =
      wr::ToBorderRadius(LayoutDeviceSize::FromUnknownSize(mBorderRadii[0]),
                         LayoutDeviceSize::FromUnknownSize(mBorderRadii[1]),
                         LayoutDeviceSize::FromUnknownSize(mBorderRadii[3]),
                         LayoutDeviceSize::FromUnknownSize(mBorderRadii[2]));

  if (mLocalClip) {
    LayoutDeviceRect clip =
        LayoutDeviceRect::FromUnknownRect(mLocalClip.value());
    wr::LayoutRect clipRect = wr::ToRoundedLayoutRect(clip);
    wr::WrClipId clipId = aBuilder.DefineClip(Nothing(), clipRect);
    aBuilder.PushClip(clipId);
  }

  Range<const wr::BorderSide> wrsides(side, 4);
  aBuilder.PushBorder(roundedRect, roundedRect, mBackfaceIsVisible,
                      wr::ToBorderWidths(mBorderWidths[0], mBorderWidths[1],
                                         mBorderWidths[2], mBorderWidths[3]),
                      wrsides, borderRadius);

  if (mLocalClip) {
    aBuilder.PopClip();
  }
}

/* static */ Maybe<nsCSSBorderImageRenderer>
nsCSSBorderImageRenderer::CreateBorderImageRenderer(
    nsPresContext* aPresContext, nsIFrame* aForFrame, const nsRect& aBorderArea,
    const nsStyleBorder& aStyleBorder, const nsRect& aDirtyRect,
    Sides aSkipSides, uint32_t aFlags, ImgDrawResult* aDrawResult) {
  MOZ_ASSERT(aDrawResult);

  if (aDirtyRect.IsEmpty()) {
    *aDrawResult = ImgDrawResult::SUCCESS;
    return Nothing();
  }

  nsImageRenderer imgRenderer(aForFrame, &aStyleBorder.mBorderImageSource,
                              aFlags);
  if (!imgRenderer.PrepareImage()) {
    *aDrawResult = imgRenderer.PrepareResult();
    return Nothing();
  }

  // Ensure we get invalidated for loads and animations of the image.
  // We need to do this here because this might be the only code that
  // knows about the association of the style data with the frame.
  // XXX We shouldn't really... since if anybody is passing in a
  // different style, they'll potentially have the wrong size for the
  // border too.
  aForFrame->AssociateImage(aStyleBorder.mBorderImageSource, aPresContext, 0);

  nsCSSBorderImageRenderer renderer(aForFrame, aBorderArea, aStyleBorder,
                                    aSkipSides, imgRenderer);
  *aDrawResult = ImgDrawResult::SUCCESS;
  return Some(renderer);
}

ImgDrawResult nsCSSBorderImageRenderer::DrawBorderImage(
    nsPresContext* aPresContext, gfxContext& aRenderingContext,
    nsIFrame* aForFrame, const nsRect& aDirtyRect) {
  // NOTE: no Save() yet, we do that later by calling autoSR.EnsureSaved()
  // in case we need it.
  gfxContextAutoSaveRestore autoSR;

  if (!mClip.IsEmpty()) {
    autoSR.EnsureSaved(&aRenderingContext);
    aRenderingContext.Clip(NSRectToSnappedRect(
        mClip, aForFrame->PresContext()->AppUnitsPerDevPixel(),
        *aRenderingContext.GetDrawTarget()));
  }

  // intrinsicSize.CanComputeConcreteSize() return false means we can not
  // read intrinsic size from aStyleBorder.mBorderImageSource.
  // In this condition, we pass imageSize(a resolved size comes from
  // default sizing algorithm) to renderer as the viewport size.
  CSSSizeOrRatio intrinsicSize = mImageRenderer.ComputeIntrinsicSize();
  Maybe<nsSize> svgViewportSize =
      intrinsicSize.CanComputeConcreteSize() ? Nothing() : Some(mImageSize);
  bool hasIntrinsicRatio = intrinsicSize.HasRatio();
  mImageRenderer.PurgeCacheForViewportChange(svgViewportSize,
                                             hasIntrinsicRatio);

  // These helper tables recharacterize the 'slice' and 'width' margins
  // in a more convenient form: they are the x/y/width/height coords
  // required for various bands of the border, and they have been transformed
  // to be relative to the innerRect (for 'slice') or the page (for 'border').
  enum { LEFT, MIDDLE, RIGHT, TOP = LEFT, BOTTOM = RIGHT };
  const nscoord borderX[3] = {
      mArea.x + 0,
      mArea.x + mWidths.left,
      mArea.x + mArea.width - mWidths.right,
  };
  const nscoord borderY[3] = {
      mArea.y + 0,
      mArea.y + mWidths.top,
      mArea.y + mArea.height - mWidths.bottom,
  };
  const nscoord borderWidth[3] = {
      mWidths.left,
      mArea.width - mWidths.left - mWidths.right,
      mWidths.right,
  };
  const nscoord borderHeight[3] = {
      mWidths.top,
      mArea.height - mWidths.top - mWidths.bottom,
      mWidths.bottom,
  };
  const int32_t sliceX[3] = {
      0,
      mSlice.left,
      mImageSize.width - mSlice.right,
  };
  const int32_t sliceY[3] = {
      0,
      mSlice.top,
      mImageSize.height - mSlice.bottom,
  };
  const int32_t sliceWidth[3] = {
      mSlice.left,
      std::max(mImageSize.width - mSlice.left - mSlice.right, 0),
      mSlice.right,
  };
  const int32_t sliceHeight[3] = {
      mSlice.top,
      std::max(mImageSize.height - mSlice.top - mSlice.bottom, 0),
      mSlice.bottom,
  };

  ImgDrawResult result = ImgDrawResult::SUCCESS;

  for (int i = LEFT; i <= RIGHT; i++) {
    for (int j = TOP; j <= BOTTOM; j++) {
      StyleBorderImageRepeat fillStyleH, fillStyleV;
      nsSize unitSize;

      if (i == MIDDLE && j == MIDDLE) {
        // Discard the middle portion unless set to fill.
        if (NS_STYLE_BORDER_IMAGE_SLICE_NOFILL == mFill) {
          continue;
        }

        NS_ASSERTION(NS_STYLE_BORDER_IMAGE_SLICE_FILL == mFill,
                     "Unexpected border image fill");

        // css-background:
        //     The middle image's width is scaled by the same factor as the
        //     top image unless that factor is zero or infinity, in which
        //     case the scaling factor of the bottom is substituted, and
        //     failing that, the width is not scaled. The height of the
        //     middle image is scaled by the same factor as the left image
        //     unless that factor is zero or infinity, in which case the
        //     scaling factor of the right image is substituted, and failing
        //     that, the height is not scaled.
        gfxFloat hFactor, vFactor;

        if (0 < mWidths.left && 0 < mSlice.left)
          vFactor = gfxFloat(mWidths.left) / mSlice.left;
        else if (0 < mWidths.right && 0 < mSlice.right)
          vFactor = gfxFloat(mWidths.right) / mSlice.right;
        else
          vFactor = 1;

        if (0 < mWidths.top && 0 < mSlice.top)
          hFactor = gfxFloat(mWidths.top) / mSlice.top;
        else if (0 < mWidths.bottom && 0 < mSlice.bottom)
          hFactor = gfxFloat(mWidths.bottom) / mSlice.bottom;
        else
          hFactor = 1;

        unitSize.width = sliceWidth[i] * hFactor;
        unitSize.height = sliceHeight[j] * vFactor;
        fillStyleH = mRepeatModeHorizontal;
        fillStyleV = mRepeatModeVertical;

      } else if (i == MIDDLE) {  // top, bottom
        // Sides are always stretched to the thickness of their border,
        // and stretched proportionately on the other axis.
        gfxFloat factor;
        if (0 < borderHeight[j] && 0 < sliceHeight[j])
          factor = gfxFloat(borderHeight[j]) / sliceHeight[j];
        else
          factor = 1;

        unitSize.width = sliceWidth[i] * factor;
        unitSize.height = borderHeight[j];
        fillStyleH = mRepeatModeHorizontal;
        fillStyleV = StyleBorderImageRepeat::Stretch;

      } else if (j == MIDDLE) {  // left, right
        gfxFloat factor;
        if (0 < borderWidth[i] && 0 < sliceWidth[i])
          factor = gfxFloat(borderWidth[i]) / sliceWidth[i];
        else
          factor = 1;

        unitSize.width = borderWidth[i];
        unitSize.height = sliceHeight[j] * factor;
        fillStyleH = StyleBorderImageRepeat::Stretch;
        fillStyleV = mRepeatModeVertical;

      } else {
        // Corners are always stretched to fit the corner.
        unitSize.width = borderWidth[i];
        unitSize.height = borderHeight[j];
        fillStyleH = StyleBorderImageRepeat::Stretch;
        fillStyleV = StyleBorderImageRepeat::Stretch;
      }

      nsRect destArea(borderX[i], borderY[j], borderWidth[i], borderHeight[j]);
      nsRect subArea(sliceX[i], sliceY[j], sliceWidth[i], sliceHeight[j]);
      if (subArea.IsEmpty()) continue;

      nsIntRect intSubArea = subArea.ToOutsidePixels(AppUnitsPerCSSPixel());
      result &= mImageRenderer.DrawBorderImageComponent(
          aPresContext, aRenderingContext, aDirtyRect, destArea,
          CSSIntRect(intSubArea.x, intSubArea.y, intSubArea.width,
                     intSubArea.height),
          fillStyleH, fillStyleV, unitSize, j * (RIGHT + 1) + i,
          svgViewportSize, hasIntrinsicRatio);
    }
  }

  return result;
}

ImgDrawResult nsCSSBorderImageRenderer::CreateWebRenderCommands(
    nsDisplayItem* aItem, nsIFrame* aForFrame,
    mozilla::wr::DisplayListBuilder& aBuilder,
    mozilla::wr::IpcResourceUpdateQueue& aResources,
    const mozilla::layers::StackingContextHelper& aSc,
    mozilla::layers::RenderRootStateManager* aManager,
    nsDisplayListBuilder* aDisplayListBuilder) {
  if (!mImageRenderer.IsReady()) {
    return ImgDrawResult::NOT_READY;
  }

  float widths[4];
  float slice[4];
  float outset[4];
  const int32_t appUnitsPerDevPixel =
      aForFrame->PresContext()->AppUnitsPerDevPixel();
  NS_FOR_CSS_SIDES(i) {
    slice[i] = (float)(mSlice.Side(i)) / appUnitsPerDevPixel;
    widths[i] = (float)(mWidths.Side(i)) / appUnitsPerDevPixel;
    outset[i] = (float)(mImageOutset.Side(i)) / appUnitsPerDevPixel;
  }

  LayoutDeviceRect destRect =
      LayoutDeviceRect::FromAppUnits(mArea, appUnitsPerDevPixel);
  wr::LayoutRect dest = wr::ToRoundedLayoutRect(destRect);

  wr::LayoutRect clip = dest;
  if (!mClip.IsEmpty()) {
    LayoutDeviceRect clipRect =
        LayoutDeviceRect::FromAppUnits(mClip, appUnitsPerDevPixel);
    clip = wr::ToRoundedLayoutRect(clipRect);
  }

  ImgDrawResult drawResult = ImgDrawResult::SUCCESS;
  switch (mImageRenderer.GetType()) {
    case eStyleImageType_Image: {
      uint32_t flags = imgIContainer::FLAG_ASYNC_NOTIFY;
      if (aDisplayListBuilder->IsPaintingToWindow()) {
        flags |= imgIContainer::FLAG_HIGH_QUALITY_SCALING;
      }
      if (aDisplayListBuilder->ShouldSyncDecodeImages()) {
        flags |= imgIContainer::FLAG_SYNC_DECODE;
      }

      RefPtr<imgIContainer> img = mImageRenderer.GetImage();
      Maybe<SVGImageContext> svgContext;
      gfx::IntSize decodeSize =
          nsLayoutUtils::ComputeImageContainerDrawingParameters(
              img, aForFrame, destRect, aSc, flags, svgContext);

      RefPtr<layers::ImageContainer> container;
      drawResult = img->GetImageContainerAtSize(aManager->LayerManager(),
                                                decodeSize, svgContext, flags,
                                                getter_AddRefs(container));
      if (!container) {
        break;
      }

      mozilla::wr::ImageRendering rendering = wr::ToImageRendering(
          nsLayoutUtils::GetSamplingFilterForFrame(aItem->Frame()));
      gfx::IntSize size;
      Maybe<wr::ImageKey> key = aManager->CommandBuilder().CreateImageKey(
          aItem, container, aBuilder, aResources, rendering, aSc, size,
          Nothing());
      if (key.isNothing()) {
        break;
      }

      aBuilder.PushBorderImage(
          dest, clip, !aItem->BackfaceIsHidden(),
          wr::ToBorderWidths(widths[0], widths[1], widths[2], widths[3]),
          key.value(), (float)(mImageSize.width) / appUnitsPerDevPixel,
          (float)(mImageSize.height) / appUnitsPerDevPixel,
          wr::ToSideOffsets2D_i32(slice[0], slice[1], slice[2], slice[3]),
          wr::ToSideOffsets2D_f32(outset[0], outset[1], outset[2], outset[3]),
          wr::ToRepeatMode(mRepeatModeHorizontal),
          wr::ToRepeatMode(mRepeatModeVertical));
      break;
    }
    case eStyleImageType_Gradient: {
      RefPtr<nsStyleGradient> gradientData = mImageRenderer.GetGradientData();
      nsCSSGradientRenderer renderer = nsCSSGradientRenderer::Create(
          aForFrame->PresContext(), aForFrame->Style(), gradientData,
          mImageSize);

      wr::ExtendMode extendMode;
      nsTArray<wr::GradientStop> stops;
      LayoutDevicePoint lineStart;
      LayoutDevicePoint lineEnd;
      LayoutDeviceSize gradientRadius;
      renderer.BuildWebRenderParameters(1.0, extendMode, stops, lineStart,
                                        lineEnd, gradientRadius);

      if (gradientData->mShape == NS_STYLE_GRADIENT_SHAPE_LINEAR) {
        LayoutDevicePoint startPoint =
            LayoutDevicePoint(dest.origin.x, dest.origin.y) + lineStart;
        LayoutDevicePoint endPoint =
            LayoutDevicePoint(dest.origin.x, dest.origin.y) + lineEnd;

        aBuilder.PushBorderGradient(
            dest, clip, !aItem->BackfaceIsHidden(),
            wr::ToBorderWidths(widths[0], widths[1], widths[2], widths[3]),
            (float)(mImageSize.width) / appUnitsPerDevPixel,
            (float)(mImageSize.height) / appUnitsPerDevPixel,
            wr::ToSideOffsets2D_i32(slice[0], slice[1], slice[2], slice[3]),
            wr::ToLayoutPoint(startPoint), wr::ToLayoutPoint(endPoint), stops,
            extendMode,
            wr::ToSideOffsets2D_f32(outset[0], outset[1], outset[2],
                                    outset[3]));
      } else {
        aBuilder.PushBorderRadialGradient(
            dest, clip, !aItem->BackfaceIsHidden(),
            wr::ToBorderWidths(widths[0], widths[1], widths[2], widths[3]),
            wr::ToLayoutPoint(lineStart), wr::ToLayoutSize(gradientRadius),
            stops, extendMode,
            wr::ToSideOffsets2D_f32(outset[0], outset[1], outset[2],
                                    outset[3]));
      }
      break;
    }
    default:
      MOZ_ASSERT_UNREACHABLE("Unsupport border image type");
      drawResult = ImgDrawResult::NOT_SUPPORTED;
  }

  return drawResult;
}

nsCSSBorderImageRenderer::nsCSSBorderImageRenderer(
    const nsCSSBorderImageRenderer& aRhs)
    : mImageRenderer(aRhs.mImageRenderer),
      mImageSize(aRhs.mImageSize),
      mSlice(aRhs.mSlice),
      mWidths(aRhs.mWidths),
      mImageOutset(aRhs.mImageOutset),
      mArea(aRhs.mArea),
      mClip(aRhs.mClip),
      mRepeatModeHorizontal(aRhs.mRepeatModeHorizontal),
      mRepeatModeVertical(aRhs.mRepeatModeVertical),
      mFill(aRhs.mFill) {
  Unused << mImageRenderer.PrepareResult();
}

nsCSSBorderImageRenderer& nsCSSBorderImageRenderer::operator=(
    const nsCSSBorderImageRenderer& aRhs) {
  mImageRenderer = aRhs.mImageRenderer;
  mImageSize = aRhs.mImageSize;
  mSlice = aRhs.mSlice;
  mWidths = aRhs.mWidths;
  mImageOutset = aRhs.mImageOutset;
  mArea = aRhs.mArea;
  mClip = aRhs.mClip;
  mRepeatModeHorizontal = aRhs.mRepeatModeHorizontal;
  mRepeatModeVertical = aRhs.mRepeatModeVertical;
  mFill = aRhs.mFill;
  Unused << mImageRenderer.PrepareResult();

  return *this;
}

nsCSSBorderImageRenderer::nsCSSBorderImageRenderer(
    nsIFrame* aForFrame, const nsRect& aBorderArea,
    const nsStyleBorder& aStyleBorder, Sides aSkipSides,
    const nsImageRenderer& aImageRenderer)
    : mImageRenderer(aImageRenderer) {
  // Determine the border image area, which by default corresponds to the
  // border box but can be modified by 'border-image-outset'.
  // Note that 'border-radius' do not apply to 'border-image' borders per
  // <http://dev.w3.org/csswg/css-backgrounds/#corner-clipping>.
  nsMargin borderWidths(aStyleBorder.GetComputedBorder());
  mImageOutset = aStyleBorder.GetImageOutset();
  if (nsCSSRendering::IsBoxDecorationSlice(aStyleBorder) &&
      !aSkipSides.IsEmpty()) {
    mArea = nsCSSRendering::BoxDecorationRectForBorder(
        aForFrame, aBorderArea, aSkipSides, &aStyleBorder);
    if (mArea.IsEqualEdges(aBorderArea)) {
      // No need for a clip, just skip the sides we don't want.
      borderWidths.ApplySkipSides(aSkipSides);
      mImageOutset.ApplySkipSides(aSkipSides);
      mArea.Inflate(mImageOutset);
    } else {
      // We're drawing borders around the joined continuation boxes so we need
      // to clip that to the slice that we want for this frame.
      mArea.Inflate(mImageOutset);
      mImageOutset.ApplySkipSides(aSkipSides);
      mClip = aBorderArea;
      mClip.Inflate(mImageOutset);
    }
  } else {
    mArea = aBorderArea;
    mArea.Inflate(mImageOutset);
  }

  // Calculate the image size used to compute slice points.
  CSSSizeOrRatio intrinsicSize = mImageRenderer.ComputeIntrinsicSize();
  mImageSize = nsImageRenderer::ComputeConcreteSize(
      CSSSizeOrRatio(), intrinsicSize, mArea.Size());
  mImageRenderer.SetPreferredSize(intrinsicSize, mImageSize);

  // Compute the used values of 'border-image-slice' and 'border-image-width';
  // we do them together because the latter can depend on the former.
  nsMargin slice;
  nsMargin border;
  NS_FOR_CSS_SIDES(s) {
    nsStyleCoord coord = aStyleBorder.mBorderImageSlice.Get(s);
    int32_t imgDimension =
        SideIsVertical(s) ? mImageSize.width : mImageSize.height;
    nscoord borderDimension = SideIsVertical(s) ? mArea.width : mArea.height;
    double value;
    switch (coord.GetUnit()) {
      case eStyleUnit_Percent:
        value = coord.GetPercentValue() * imgDimension;
        break;
      case eStyleUnit_Factor:
        value = nsPresContext::CSSPixelsToAppUnits(
            NS_lround(coord.GetFactorValue()));
        break;
      default:
        MOZ_ASSERT_UNREACHABLE("unexpected CSS unit for image slice");
        value = 0;
        break;
    }
    if (value < 0) value = 0;
    if (value > imgDimension) value = imgDimension;
    mSlice.Side(s) = value;

    coord = aStyleBorder.mBorderImageWidth.Get(s);
    switch (coord.GetUnit()) {
      case eStyleUnit_Coord:  // absolute dimension
        value = coord.GetCoordValue();
        break;
      case eStyleUnit_Percent:
        value = coord.GetPercentValue() * borderDimension;
        break;
      case eStyleUnit_Factor:
        value = coord.GetFactorValue() * borderWidths.Side(s);
        break;
      case eStyleUnit_Auto:  // same as the slice value, in CSS pixels
        value = mSlice.Side(s);
        break;
      case eStyleUnit_Calc:
        value = std::max(0, coord.ComputeComputedCalc(borderDimension));
        break;
      default:
        MOZ_ASSERT_UNREACHABLE(
            "unexpected CSS unit for border image area "
            "division");
        value = 0;
        break;
    }
    // NSToCoordRoundWithClamp rounds towards infinity, but that's OK
    // because we expect value to be non-negative.
    MOZ_ASSERT(value >= 0);
    mWidths.Side(s) = NSToCoordRoundWithClamp(value);
    MOZ_ASSERT(mWidths.Side(s) >= 0);
  }

  // "If two opposite border-image-width offsets are large enough that they
  // overlap, their used values are proportionately reduced until they no
  // longer overlap."
  uint32_t combinedBorderWidth =
      uint32_t(mWidths.left) + uint32_t(mWidths.right);
  double scaleX = combinedBorderWidth > uint32_t(mArea.width)
                      ? mArea.width / double(combinedBorderWidth)
                      : 1.0;
  uint32_t combinedBorderHeight =
      uint32_t(mWidths.top) + uint32_t(mWidths.bottom);
  double scaleY = combinedBorderHeight > uint32_t(mArea.height)
                      ? mArea.height / double(combinedBorderHeight)
                      : 1.0;
  double scale = std::min(scaleX, scaleY);
  if (scale < 1.0) {
    mWidths.left *= scale;
    mWidths.right *= scale;
    mWidths.top *= scale;
    mWidths.bottom *= scale;
    NS_ASSERTION(mWidths.left + mWidths.right <= mArea.width &&
                     mWidths.top + mWidths.bottom <= mArea.height,
                 "rounding error in width reduction???");
  }

  mRepeatModeHorizontal = aStyleBorder.mBorderImageRepeatH;
  mRepeatModeVertical = aStyleBorder.mBorderImageRepeatV;
  mFill = aStyleBorder.mBorderImageFill;
}