layout/base/nsLayoutUtils.h
author Ryan VanderMeulen <ryanvm@gmail.com>
Thu, 24 May 2018 14:12:20 -0400
changeset 473436 0f95c023462e4de617ebdd77cbe90ec523efad10
parent 473431 f89eb218615420225501ca0c1e32c05aae3445f0
child 473455 3b746f7885d7a1567658cb38207dd2efc87a6785
permissions -rw-r--r--
Backed out 5 changesets (bug 1462497) for causing widespread test failures. Backed out changeset f89eb2186154 (bug 1462497) Backed out changeset e8836b424826 (bug 1462497) Backed out changeset 3dcce8353e13 (bug 1462497) Backed out changeset 21f67c8e36fb (bug 1462497) Backed out changeset b14f835411db (bug 1462497)

/* -*- 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/. */

#ifndef nsLayoutUtils_h__
#define nsLayoutUtils_h__

#include "LayoutConstants.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/ArrayUtils.h"
#include "mozilla/LookAndFeel.h"
#include "mozilla/Maybe.h"
#include "mozilla/TypedEnumBits.h"
#include "nsBoundingMetrics.h"
#include "nsChangeHint.h"
#include "nsFrameList.h"
#include "mozilla/layout/FrameChildList.h"
#include "nsThreadUtils.h"
#include "nsIPrincipal.h"
#include "FrameMetrics.h"
#include "nsIWidget.h"
#include "nsCSSPropertyID.h"
#include "nsStyleCoord.h"
#include "nsStyleConsts.h"
#include "nsGkAtoms.h"
#include "imgIContainer.h"
#include "mozilla/gfx/2D.h"
#include "Units.h"
#include "mozilla/ToString.h"
#include "mozilla/ReflowOutput.h"
#include "ImageContainer.h"
#include "gfx2DGlue.h"
#include "nsStyleConsts.h"
#include "SVGImageContext.h"
#include <limits>
#include <algorithm>
#include "gfxPoint.h"
#include "nsClassHashtable.h"

class gfxContext;
class nsPresContext;
class nsIContent;
class nsAtom;
class nsIScrollableFrame;
class nsRegion;
class nsDisplayListBuilder;
enum class nsDisplayListBuilderMode : uint8_t;
class nsDisplayItem;
class nsFontMetrics;
class nsFontFaceList;
class nsIImageLoadingContent;
class nsBlockFrame;
class nsContainerFrame;
class nsView;
class nsIFrame;
class nsStyleCoord;
class nsStyleCorners;
class nsPIDOMWindowOuter;
class imgIRequest;
class nsIDocument;
struct nsStyleFont;
struct nsStyleImageOrientation;
struct nsOverflowAreas;

namespace mozilla {
class ComputedStyle;
enum class CSSPseudoElementType : uint8_t;
class EventListenerManager;
enum class LayoutFrameType : uint8_t;
struct IntrinsicSize;
struct ContainerLayerParameters;
class WritingMode;
class DisplayItemClip;
class EffectSet;
struct ActiveScrolledRoot;
namespace dom {
class CanvasRenderingContext2D;
class DOMRectList;
class Element;
class Event;
class HTMLImageElement;
class HTMLCanvasElement;
class HTMLVideoElement;
class InspectorFontFace;
class OffscreenCanvas;
class Selection;
} // namespace dom
namespace gfx {
struct RectCornerRadii;
enum class ShapedTextFlags : uint16_t;
} // namespace gfx
namespace layers {
class Image;
class StackingContextHelper;
class Layer;
} // namespace layers
} // namespace mozilla

namespace mozilla {

struct DisplayPortPropertyData {
  DisplayPortPropertyData(const nsRect& aRect, uint32_t aPriority)
    : mRect(aRect)
    , mPriority(aPriority)
  {}
  nsRect mRect;
  uint32_t mPriority;
};

struct DisplayPortMarginsPropertyData {
  DisplayPortMarginsPropertyData(const ScreenMargin& aMargins,
                                 uint32_t aPriority)
    : mMargins(aMargins)
    , mPriority(aPriority)
  {}
  ScreenMargin mMargins;
  uint32_t mPriority;
};

} // namespace mozilla

// For GetDisplayPort
enum class RelativeTo {
  ScrollPort,
  ScrollFrame
};

// Flags to customize the behavior of nsLayoutUtils::DrawString.
enum class DrawStringFlags {
  eDefault         = 0x0,
  eForceHorizontal = 0x1 // Forces the text to be drawn horizontally.
};
MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(DrawStringFlags)

/**
 * nsLayoutUtils is a namespace class used for various helper
 * functions that are useful in multiple places in layout.  The goal
 * is not to define multiple copies of the same static helper.
 */
class nsLayoutUtils
{
  typedef mozilla::ComputedStyle ComputedStyle;
  typedef mozilla::dom::DOMRectList DOMRectList;
  typedef mozilla::layers::Layer Layer;
  typedef mozilla::layers::StackingContextHelper StackingContextHelper;
  typedef mozilla::ContainerLayerParameters ContainerLayerParameters;
  typedef mozilla::IntrinsicSize IntrinsicSize;
  typedef mozilla::gfx::SourceSurface SourceSurface;
  typedef mozilla::gfx::Color Color;
  typedef mozilla::gfx::DrawTarget DrawTarget;
  typedef mozilla::gfx::ExtendMode ExtendMode;
  typedef mozilla::gfx::SamplingFilter SamplingFilter;
  typedef mozilla::gfx::Float Float;
  typedef mozilla::gfx::Point Point;
  typedef mozilla::gfx::Rect Rect;
  typedef mozilla::gfx::RectDouble RectDouble;
  typedef mozilla::gfx::Size Size;
  typedef mozilla::gfx::Matrix4x4 Matrix4x4;
  typedef mozilla::gfx::Matrix4x4Flagged Matrix4x4Flagged;
  typedef mozilla::gfx::RectCornerRadii RectCornerRadii;
  typedef mozilla::gfx::StrokeOptions StrokeOptions;
  typedef mozilla::image::ImgDrawResult ImgDrawResult;

public:
  typedef mozilla::layers::FrameMetrics FrameMetrics;
  typedef mozilla::layers::ScrollMetadata ScrollMetadata;
  typedef FrameMetrics::ViewID ViewID;
  typedef mozilla::CSSPoint CSSPoint;
  typedef mozilla::CSSSize CSSSize;
  typedef mozilla::CSSIntSize CSSIntSize;
  typedef mozilla::CSSRect CSSRect;
  typedef mozilla::ScreenMargin ScreenMargin;
  typedef mozilla::LayoutDeviceIntSize LayoutDeviceIntSize;
  typedef mozilla::LayoutDeviceRect LayoutDeviceRect;
  typedef mozilla::StyleGeometryBox StyleGeometryBox;
  typedef mozilla::SVGImageContext SVGImageContext;
  typedef mozilla::LogicalSize LogicalSize;

  /**
   * Finds previously assigned ViewID for the given content element, if any.
   * Returns whether a ViewID was previously assigned.
   */
  static bool FindIDFor(const nsIContent* aContent, ViewID* aOutViewId);

  /**
   * Finds previously assigned or generates a unique ViewID for the given
   * content element.
   */
  static ViewID FindOrCreateIDFor(nsIContent* aContent);

  /**
   * Find content for given ID.
   */
  static nsIContent* FindContentFor(ViewID aId);

  /**
   * Find the scrollable frame for a given ID.
   */
  static nsIScrollableFrame* FindScrollableFrameFor(ViewID aId);

  /**
   * Find the ID for a given scrollable frame.
   */
  static ViewID FindIDForScrollableFrame(nsIScrollableFrame* aScrollable);

  /**
   * Get display port for the given element, relative to the specified entity,
   * defaulting to the scrollport.
   */
  static bool GetDisplayPort(nsIContent* aContent, nsRect *aResult,
    RelativeTo aRelativeTo = RelativeTo::ScrollPort);

  /**
   * Check whether the given element has a displayport.
   */
  static bool HasDisplayPort(nsIContent* aContent);

  /**
   * Check whether the given frame has a displayport. It returns false
   * for scrolled frames and true for the corresponding scroll frame.
   * Optionally pass the child, and it only returns true if the child is the
   * scrolled frame for the displayport.
   */
  static bool FrameHasDisplayPort(nsIFrame* aFrame, nsIFrame* aScrolledFrame = nullptr);

  /**
   * Check if the given element has a margins based displayport but is missing a
   * displayport base rect that it needs to properly compute a displayport rect.
   */
  static bool IsMissingDisplayPortBaseRect(nsIContent* aContent);

  /**
   * Go through the IPC Channel and update displayport margins for content
   * elements based on UpdateFrame messages. The messages are left in the
   * queue and will be fully processed when dequeued. The aim is to paint
   * the most up-to-date displayport without waiting for these message to
   * go through the message queue.
   */
  static void UpdateDisplayPortMarginsFromPendingMessages();

  /**
   * @return the display port for the given element which should be used for
   * visibility testing purposes.
   *
   * If low-precision buffers are enabled, this is the critical display port;
   * otherwise, it's the same display port returned by GetDisplayPort().
   */
  static bool GetDisplayPortForVisibilityTesting(
    nsIContent* aContent,
    nsRect* aResult,
    RelativeTo aRelativeTo = RelativeTo::ScrollPort);

  enum class RepaintMode : uint8_t {
    Repaint,
    DoNotRepaint
  };

  /**
   * Invalidate for displayport change.
   */
  static void InvalidateForDisplayPortChange(nsIContent* aContent,
                                             bool aHadDisplayPort,
                                             const nsRect& aOldDisplayPort,
                                             const nsRect& aNewDisplayPort,
                                             RepaintMode aRepaintMode = RepaintMode::Repaint);

  /**
   * Set the display port margins for a content element to be used with a
   * display port base (see SetDisplayPortBase()).
   * See also nsIDOMWindowUtils.setDisplayPortMargins.
   * @param aContent the content element for which to set the margins
   * @param aPresShell the pres shell for the document containing the element
   * @param aMargins the margins to set
   * @param aAlignmentX, alignmentY the amount of pixels to which to align the
   *                                displayport built by combining the base
   *                                rect with the margins, in either direction
   * @param aPriority a priority value to determine which margins take effect
   *                  when multiple callers specify margins
   * @param aRepaintMode whether to schedule a paint after setting the margins
   * @return true if the new margins were applied.
   */
  static bool SetDisplayPortMargins(nsIContent* aContent,
                                    nsIPresShell* aPresShell,
                                    const ScreenMargin& aMargins,
                                    uint32_t aPriority = 0,
                                    RepaintMode aRepaintMode = RepaintMode::Repaint);

  /**
   * Set the display port base rect for given element to be used with display
   * port margins.
   * SetDisplayPortBaseIfNotSet is like SetDisplayPortBase except it only sets
   * the display port base to aBase if no display port base is currently set.
   */
  static void SetDisplayPortBase(nsIContent* aContent, const nsRect& aBase);
  static void SetDisplayPortBaseIfNotSet(nsIContent* aContent, const nsRect& aBase);

  /**
   * Get the critical display port for the given element.
   */
  static bool GetCriticalDisplayPort(nsIContent* aContent, nsRect* aResult);

  /**
   * Check whether the given element has a critical display port.
   */
  static bool HasCriticalDisplayPort(nsIContent* aContent);

  /**
   * If low-precision painting is turned on, delegates to GetCriticalDisplayPort.
   * Otherwise, delegates to GetDisplayPort.
   */
  static bool GetHighResolutionDisplayPort(nsIContent* aContent, nsRect* aResult);

  /**
   * Remove the displayport for the given element.
   */
  static void RemoveDisplayPort(nsIContent* aContent);

  /**
   * Use heuristics to figure out the child list that
   * aChildFrame is currently in.
   */
  static mozilla::layout::FrameChildListID GetChildListNameFor(nsIFrame* aChildFrame);

  /**
   * Returns the ::before pseudo-element for aContent, if any.
   */
  static mozilla::dom::Element* GetBeforePseudo(const nsIContent* aContent);

  /**
   * Returns the frame corresponding to the ::before pseudo-element for
   * aContent, if any.
   */
  static nsIFrame* GetBeforeFrame(const nsIContent* aContent);

  /**
   * Returns the ::after pseudo-element for aContent, if any.
   */
  static mozilla::dom::Element* GetAfterPseudo(const nsIContent* aContent);

  /**
   * Returns the frame corresponding to the ::after pseudo-element for aContent,
   * if any.
   */
  static nsIFrame* GetAfterFrame(const nsIContent* aContent);

  /**
   * Given a frame, search up the frame tree until we find an
   * ancestor that (or the frame itself) is of type aFrameType, if any.
   *
   * @param aFrame the frame to start at
   * @param aFrameType the frame type to look for
   * @param aStopAt a frame to stop at after we checked it
   * @return a frame of the given type or nullptr if no
   *         such ancestor exists
   */
  static nsIFrame* GetClosestFrameOfType(nsIFrame* aFrame,
                                         mozilla::LayoutFrameType aFrameType,
                                         nsIFrame* aStopAt = nullptr);

  /**
   * Given a frame, search up the frame tree until we find an
   * ancestor that (or the frame itself) is a "Page" frame, if any.
   *
   * @param aFrame the frame to start at
   * @return a frame of type mozilla::LayoutFrameType::Page or nullptr if no
   *         such ancestor exists
   */
  static nsIFrame* GetPageFrame(nsIFrame* aFrame);

  /**
   * Given a frame which is the primary frame for an element,
   * return the frame that has the non-pseudoelement ComputedStyle for
   * the content.
   * This is aPrimaryFrame itself except for tableWrapper frames.
   *
   * Given a non-null input, this will return null if and only if its
   * argument is a table wrapper frame that is mid-destruction (and its
   * table frame has been destroyed).
   */
  static nsIFrame* GetStyleFrame(nsIFrame* aPrimaryFrame);

  /**
   * Given a content node,
   * return the frame that has the non-pseudoelement ComputedStyle for
   * the content.  May return null.
   * This is aContent->GetPrimaryFrame() except for tableWrapper frames.
   */
  static nsIFrame* GetStyleFrame(const nsIContent* aContent);

  /**
   * Gets the real primary frame associated with the content object.
   *
   * In the case of absolutely positioned elements and floated elements,
   * the real primary frame is the frame that is out of the flow and not the
   * placeholder frame.
   */
  static nsIFrame* GetRealPrimaryFrameFor(const nsIContent* aContent);

#ifdef DEBUG
  // TODO: remove, see bug 598468.
  static bool gPreventAssertInCompareTreePosition;
#endif // DEBUG

  /**
   * CompareTreePosition determines whether aContent1 comes before or
   * after aContent2 in a preorder traversal of the content tree.
   *
   * @param aCommonAncestor either null, or a common ancestor of
   *                        aContent1 and aContent2.  Actually this is
   *                        only a hint; if it's not an ancestor of
   *                        aContent1 or aContent2, this function will
   *                        still work, but it will be slower than
   *                        normal.
   * @return < 0 if aContent1 is before aContent2
   *         > 0 if aContent1 is after aContent2,
   *         0 otherwise (meaning they're the same, or they're in
   *           different documents)
   */
  static int32_t CompareTreePosition(nsIContent* aContent1,
                                     nsIContent* aContent2,
                                     const nsIContent* aCommonAncestor = nullptr)
  {
    return DoCompareTreePosition(aContent1, aContent2, -1, 1, aCommonAncestor);
  }

  /*
   * More generic version of |CompareTreePosition|.  |aIf1Ancestor|
   * gives the value to return when 1 is an ancestor of 2, and likewise
   * for |aIf2Ancestor|.  Passing (-1, 1) gives preorder traversal
   * order, and (1, -1) gives postorder traversal order.
   */
  static int32_t DoCompareTreePosition(nsIContent* aContent1,
                                       nsIContent* aContent2,
                                       int32_t aIf1Ancestor,
                                       int32_t aIf2Ancestor,
                                       const nsIContent* aCommonAncestor = nullptr);

  /**
   * CompareTreePosition determines whether aFrame1 comes before or
   * after aFrame2 in a preorder traversal of the frame tree, where out
   * of flow frames are treated as children of their placeholders. This is
   * basically the same ordering as DoCompareTreePosition(nsIContent*) except
   * that it handles anonymous content properly and there are subtleties with
   * continuations.
   *
   * @param aCommonAncestor either null, or a common ancestor of
   *                        aContent1 and aContent2.  Actually this is
   *                        only a hint; if it's not an ancestor of
   *                        aContent1 or aContent2, this function will
   *                        still work, but it will be slower than
   *                        normal.
   * @return < 0 if aContent1 is before aContent2
   *         > 0 if aContent1 is after aContent2,
   *         0 otherwise (meaning they're the same, or they're in
   *           different frame trees)
   */
  static int32_t CompareTreePosition(nsIFrame* aFrame1,
                                     nsIFrame* aFrame2,
                                     nsIFrame* aCommonAncestor = nullptr)
  {
    return DoCompareTreePosition(aFrame1, aFrame2, -1, 1, aCommonAncestor);
  }

  static int32_t CompareTreePosition(nsIFrame* aFrame1,
                                     nsIFrame* aFrame2,
                                     nsTArray<nsIFrame*>& aFrame2Ancestors,
                                     nsIFrame* aCommonAncestor = nullptr)
  {
    return DoCompareTreePosition(aFrame1, aFrame2, aFrame2Ancestors,
                                 -1, 1, aCommonAncestor);
  }

  /*
   * More generic version of |CompareTreePosition|.  |aIf1Ancestor|
   * gives the value to return when 1 is an ancestor of 2, and likewise
   * for |aIf2Ancestor|.  Passing (-1, 1) gives preorder traversal
   * order, and (1, -1) gives postorder traversal order.
   */
  static int32_t DoCompareTreePosition(nsIFrame* aFrame1,
                                       nsIFrame* aFrame2,
                                       int32_t aIf1Ancestor,
                                       int32_t aIf2Ancestor,
                                       nsIFrame* aCommonAncestor = nullptr);

  static nsIFrame* FillAncestors(nsIFrame* aFrame,
                                 nsIFrame* aStopAtAncestor,
                                 nsTArray<nsIFrame*>* aAncestors);

  static int32_t DoCompareTreePosition(nsIFrame* aFrame1,
                                       nsIFrame* aFrame2,
                                       nsTArray<nsIFrame*>& aFrame2Ancestors,
                                       int32_t aIf1Ancestor,
                                       int32_t aIf2Ancestor,
                                       nsIFrame* aCommonAncestor);

  /**
   * LastContinuationWithChild gets the last continuation in aFrame's chain
   * that has a child, or the first continuation if the frame has no children.
   */
  static nsContainerFrame* LastContinuationWithChild(nsContainerFrame* aFrame);

  /**
   * GetLastSibling simply finds the last sibling of aFrame, or returns nullptr if
   * aFrame is null.
   */
  static nsIFrame* GetLastSibling(nsIFrame* aFrame);

  /**
   * FindSiblingViewFor locates the child of aParentView that aFrame's
   * view should be inserted 'above' (i.e., before in sibling view
   * order).  This is the first child view of aParentView whose
   * corresponding content is before aFrame's content (view siblings
   * are in reverse content order).
   */
  static nsView* FindSiblingViewFor(nsView* aParentView, nsIFrame* aFrame);

  /**
   * Get the parent of aFrame. If aFrame is the root frame for a document,
   * and the document has a parent document in the same view hierarchy, then
   * we try to return the subdocumentframe in the parent document.
   * @param aExtraOffset [in/out] if non-null, then as we cross documents
   * an extra offset may be required and it will be added to aCrossDocOffset.
   * Be careful dealing with this extra offset as it is in app units of the
   * parent document, which may have a different app units per dev pixel ratio
   * than the child document.
   */
  static nsIFrame* GetCrossDocParentFrame(const nsIFrame* aFrame,
                                          nsPoint* aCrossDocOffset = nullptr);

  /**
   * IsProperAncestorFrame checks whether aAncestorFrame is an ancestor
   * of aFrame and not equal to aFrame.
   * @param aCommonAncestor nullptr, or a common ancestor of aFrame and
   * aAncestorFrame. If non-null, this can bound the search and speed up
   * the function
   */
  static bool IsProperAncestorFrame(nsIFrame* aAncestorFrame, nsIFrame* aFrame,
                                      nsIFrame* aCommonAncestor = nullptr);

  /**
   * Like IsProperAncestorFrame, but looks across document boundaries.
   *
   * Just like IsAncestorFrameCrossDoc, except that it returns false when
   * aFrame == aAncestorFrame.
   */
  static bool IsProperAncestorFrameCrossDoc(nsIFrame* aAncestorFrame, nsIFrame* aFrame,
                                              nsIFrame* aCommonAncestor = nullptr);

  /**
   * IsAncestorFrameCrossDoc checks whether aAncestorFrame is an ancestor
   * of aFrame or equal to aFrame, looking across document boundaries.
   * @param aCommonAncestor nullptr, or a common ancestor of aFrame and
   * aAncestorFrame. If non-null, this can bound the search and speed up
   * the function.
   *
   * Just like IsProperAncestorFrameCrossDoc, except that it returns true when
   * aFrame == aAncestorFrame.
   */
  static bool IsAncestorFrameCrossDoc(const nsIFrame* aAncestorFrame, const nsIFrame* aFrame,
                                        const nsIFrame* aCommonAncestor = nullptr);

  /**
   * Sets the fixed-pos metadata properties on aLayer.
   * aAnchorRect is the basic anchor rectangle. If aFixedPosFrame is not a viewport
   * frame, then we pick a corner of aAnchorRect to as the anchor point for the
   * fixed-pos layer (i.e. the point to remain stable during zooming), based
   * on which of the fixed-pos frame's CSS absolute positioning offset
   * properties (top, left, right, bottom) are auto. aAnchorRect is in the
   * coordinate space of aLayer's container layer (i.e. relative to the reference
   * frame of the display item which is building aLayer's container layer).
   */
  static void SetFixedPositionLayerData(Layer* aLayer, const nsIFrame* aViewportFrame,
                                        const nsRect& aAnchorRect,
                                        const nsIFrame* aFixedPosFrame,
                                        nsPresContext* aPresContext,
                                        const ContainerLayerParameters& aContainerParameters);

  /**
   * Get the scroll id for the root scrollframe of the presshell of the given
   * prescontext. Returns NULL_SCROLL_ID if it couldn't be found.
   */
  static FrameMetrics::ViewID ScrollIdForRootScrollFrame(nsPresContext* aPresContext);

  /**
   * Return true if aPresContext's viewport has a displayport.
   */
  static bool ViewportHasDisplayPort(nsPresContext* aPresContext);

  /**
   * Return true if aFrame is a fixed-pos frame and is a child of a viewport
   * which has a displayport. These frames get special treatment from the compositor.
   * aDisplayPort, if non-null, is set to the display port rectangle (relative to
   * the viewport).
   */
  static bool IsFixedPosFrameInDisplayPort(const nsIFrame* aFrame);

  /**
    * GetScrollableFrameFor returns the scrollable frame for a scrolled frame
    */
  static nsIScrollableFrame* GetScrollableFrameFor(const nsIFrame *aScrolledFrame);

  /**
   * GetNearestScrollableFrameForDirection locates the first ancestor of
   * aFrame (or aFrame itself) that is scrollable with overflow:scroll or
   * overflow:auto in the given direction and where either the scrollbar for
   * that direction is visible or the frame can be scrolled by some
   * positive amount in that direction.
   * The search extends across document boundaries.
   *
   * @param  aFrame the frame to start with
   * @param  aDirection Whether it's for horizontal or vertical scrolling.
   * @return the nearest scrollable frame or nullptr if not found
   */
  enum Direction { eHorizontal, eVertical };
  static nsIScrollableFrame* GetNearestScrollableFrameForDirection(nsIFrame* aFrame,
                                                                   Direction aDirection);

  enum {
    /**
     * If the SCROLLABLE_SAME_DOC flag is set, then we only walk the frame tree
     * up to the root frame in the current document.
     */
    SCROLLABLE_SAME_DOC = 0x01,
    /**
     * If the SCROLLABLE_INCLUDE_HIDDEN flag is set then we allow
     * overflow:hidden scrollframes to be returned as scrollable frames.
     */
    SCROLLABLE_INCLUDE_HIDDEN = 0x02,
    /**
     * If the SCROLLABLE_ONLY_ASYNC_SCROLLABLE flag is set, then we only
     * want to match scrollable frames for which WantAsyncScroll() returns
     * true.
     */
    SCROLLABLE_ONLY_ASYNC_SCROLLABLE = 0x04,
    /**
     * If the SCROLLABLE_ALWAYS_MATCH_ROOT flag is set, then we will always
     * return the root scrollable frame for the root document (in the current
     * process) if we encounter it, whether or not it is async scrollable or
     * overflow: hidden.
     */
    SCROLLABLE_ALWAYS_MATCH_ROOT = 0x08,
    /**
     * If the SCROLLABLE_FIXEDPOS_FINDS_ROOT flag is set, then for fixed-pos
     * frames that are in the root document (in the current process) return the
     * root scrollable frame for that document.
     */
    SCROLLABLE_FIXEDPOS_FINDS_ROOT = 0x10
  };
  /**
   * GetNearestScrollableFrame locates the first ancestor of aFrame
   * (or aFrame itself) that is scrollable with overflow:scroll or
   * overflow:auto in some direction.
   *
   * @param  aFrame the frame to start with
   * @param  aFlags if SCROLLABLE_SAME_DOC is set, do not search across
   * document boundaries. If SCROLLABLE_INCLUDE_HIDDEN is set, include
   * frames scrollable with overflow:hidden.
   * @return the nearest scrollable frame or nullptr if not found
   */
  static nsIScrollableFrame* GetNearestScrollableFrame(nsIFrame* aFrame,
                                                       uint32_t aFlags = 0);

  /**
   * GetScrolledRect returns the range of allowable scroll offsets
   * for aScrolledFrame, assuming the scrollable overflow area is
   * aScrolledFrameOverflowArea and the scrollport size is aScrollPortSize.
   * aDirection is either NS_STYLE_DIRECTION_LTR or NS_STYLE_DIRECTION_RTL.
   */
  static nsRect GetScrolledRect(nsIFrame* aScrolledFrame,
                                const nsRect& aScrolledFrameOverflowArea,
                                const nsSize& aScrollPortSize,
                                uint8_t aDirection);

  /**
   * HasPseudoStyle returns true if aContent (whose primary style
   * context is aComputedStyle) has the aPseudoElement pseudo-style
   * attached to it; returns false otherwise.
   *
   * @param aContent the content node we're looking at
   * @param aComputedStyle aContent's ComputedStyle
   * @param aPseudoElement the id of the pseudo style we care about
   * @param aPresContext the presentation context
   * @return whether aContent has aPseudoElement style attached to it
   */
  static bool HasPseudoStyle(nsIContent* aContent,
                             ComputedStyle* aComputedStyle,
                             mozilla::CSSPseudoElementType aPseudoElement,
                             nsPresContext* aPresContext);

  /**
   * If this frame is a placeholder for a float, then return the float,
   * otherwise return nullptr.  aPlaceholder must be a placeholder frame.
   */
  static nsIFrame* GetFloatFromPlaceholder(nsIFrame* aPlaceholder);

  // Combine aNewBreakType with aOrigBreakType, but limit the break types
  // to StyleClear::Left, Right, Both.
  static mozilla::StyleClear CombineBreakType(mozilla::StyleClear aOrigBreakType,
                                              mozilla::StyleClear aNewBreakType);

  /**
   * Get the coordinates of a given DOM mouse event, relative to a given
   * frame. Works only for DOM events generated by WidgetGUIEvents.
   * @param aDOMEvent the event
   * @param aFrame the frame to make coordinates relative to
   * @return the point, or (NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE) if
   * for some reason the coordinates for the mouse are not known (e.g.,
   * the event is not a GUI event).
   */
  static nsPoint GetDOMEventCoordinatesRelativeTo(mozilla::dom::Event* aDOMEvent,
                                                  nsIFrame* aFrame);

  /**
   * Get the coordinates of a given native mouse event, relative to a given
   * frame.
   * @param aEvent the event
   * @param aFrame the frame to make coordinates relative to
   * @return the point, or (NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE) if
   * for some reason the coordinates for the mouse are not known (e.g.,
   * the event is not a GUI event).
   */
  static nsPoint GetEventCoordinatesRelativeTo(
                   const mozilla::WidgetEvent* aEvent,
                   nsIFrame* aFrame);

  /**
   * Get the coordinates of a given point relative to an event and a
   * given frame.
   * @param aEvent the event
   * @param aPoint the point to get the coordinates relative to
   * @param aFrame the frame to make coordinates relative to
   * @return the point, or (NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE) if
   * for some reason the coordinates for the mouse are not known (e.g.,
   * the event is not a GUI event).
   */
  static nsPoint GetEventCoordinatesRelativeTo(
                   const mozilla::WidgetEvent* aEvent,
                   const mozilla::LayoutDeviceIntPoint& aPoint,
                   nsIFrame* aFrame);

  /**
   * Get the coordinates of a given point relative to a widget and a
   * given frame.
   * @param aWidget the event src widget
   * @param aPoint the point to get the coordinates relative to
   * @param aFrame the frame to make coordinates relative to
   * @return the point, or (NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE) if
   * for some reason the coordinates for the mouse are not known (e.g.,
   * the event is not a GUI event).
   */
  static nsPoint GetEventCoordinatesRelativeTo(nsIWidget* aWidget,
                                               const mozilla::LayoutDeviceIntPoint& aPoint,
                                               nsIFrame* aFrame);

  /**
   * Get the popup frame of a given native mouse event.
   * @param aPresContext only check popups within aPresContext or a descendant
   * @param aEvent  the event.
   * @return        Null, if there is no popup frame at the point, otherwise,
   *                returns top-most popup frame at the point.
   */
  static nsIFrame* GetPopupFrameForEventCoordinates(
                     nsPresContext* aPresContext,
                     const mozilla::WidgetEvent* aEvent);

  /**
   * Translate from widget coordinates to the view's coordinates
   * @param aPresContext the PresContext for the view
   * @param aWidget the widget
   * @param aPt the point relative to the widget
   * @param aView  view to which returned coordinates are relative
   * @return the point in the view's coordinates
   */
  static nsPoint TranslateWidgetToView(nsPresContext* aPresContext,
                                       nsIWidget* aWidget,
                                       const mozilla::LayoutDeviceIntPoint& aPt,
                                       nsView* aView);

  /**
   * Translate from view coordinates to the widget's coordinates.
   * @param aPresContext the PresContext for the view
   * @param aView the view
   * @param aPt the point relative to the view
   * @param aWidget the widget to which returned coordinates are relative
   * @return the point in the view's coordinates
   */
  static mozilla::LayoutDeviceIntPoint
    TranslateViewToWidget(nsPresContext* aPresContext,
                          nsView* aView, nsPoint aPt,
                          nsIWidget* aWidget);

  static mozilla::LayoutDeviceIntPoint
    WidgetToWidgetOffset(nsIWidget* aFromWidget, nsIWidget* aToWidget);

  enum FrameForPointFlags {
    /**
     * When set, paint suppression is ignored, so we'll return non-root page
     * elements even if paint suppression is stopping them from painting.
     */
    IGNORE_PAINT_SUPPRESSION = 0x01,
    /**
     * When set, clipping due to the root scroll frame (and any other viewport-
     * related clipping) is ignored.
     */
    IGNORE_ROOT_SCROLL_FRAME = 0x02,
    /**
     * When set, return only content in the same document as aFrame.
     */
    IGNORE_CROSS_DOC = 0x04,
    /**
     * When set, return only content that is actually visible.
     */
    ONLY_VISIBLE = 0x08
  };

  /**
   * Given aFrame, the root frame of a stacking context, find its descendant
   * frame under the point aPt that receives a mouse event at that location,
   * or nullptr if there is no such frame.
   * @param aPt the point, relative to the frame origin
   * @param aFlags some combination of FrameForPointFlags
   */
  static nsIFrame* GetFrameForPoint(nsIFrame* aFrame, nsPoint aPt,
                                    uint32_t aFlags = 0);

  /**
   * Given aFrame, the root frame of a stacking context, find all descendant
   * frames under the area of a rectangle that receives a mouse event,
   * or nullptr if there is no such frame.
   * @param aRect the rect, relative to the frame origin
   * @param aOutFrames an array to add all the frames found
   * @param aFlags some combination of FrameForPointFlags
   */
  static nsresult GetFramesForArea(nsIFrame* aFrame, const nsRect& aRect,
                                   nsTArray<nsIFrame*> &aOutFrames,
                                   uint32_t aFlags = 0);

  /**
   * Transform aRect relative to aFrame up to the coordinate system of
   * aAncestor. Computes the bounding-box of the true quadrilateral.
   * Pass non-null aPreservesAxisAlignedRectangles and it will be set to true if
   * we only need to use a 2d transform that PreservesAxisAlignedRectangles().
   *
   * |aMatrixCache| allows for optimizations in recomputing the same matrix over
   * and over. The argument can be one of the following values:
   * nullptr (the default) - No optimization; the transform matrix is computed on
   *   every call to this function.
   * non-null pointer to an empty Maybe<Matrix4x4> - Upon return, the Maybe is
   *   filled with the transform matrix that was computed. This can then be passed
   *   in to subsequent calls with the same source and destination frames to avoid
   *   recomputing the matrix.
   * non-null pointer to a non-empty Matrix4x4 - The provided matrix will be used
   *   as the transform matrix and applied to the rect.
   */
  static nsRect TransformFrameRectToAncestor(nsIFrame* aFrame,
                                             const nsRect& aRect,
                                             const nsIFrame* aAncestor,
                                             bool* aPreservesAxisAlignedRectangles = nullptr,
                                             mozilla::Maybe<Matrix4x4Flagged>* aMatrixCache = nullptr,
                                             bool aStopAtStackingContextAndDisplayPort = false,
                                             nsIFrame** aOutAncestor = nullptr);


  /**
   * Gets the transform for aFrame relative to aAncestor. Pass null for
   * aAncestor to go up to the root frame. aInCSSUnits set to true will
   * return CSS units, set to false (the default) will return App units.
   */
  static Matrix4x4Flagged GetTransformToAncestor(nsIFrame *aFrame,
                                          const nsIFrame *aAncestor,
                                          uint32_t aFlags = 0,
                                          nsIFrame** aOutAncestor = nullptr);

  /**
   * Gets the scale factors of the transform for aFrame relative to the root
   * frame if this transform is 2D, or the identity scale factors otherwise.
   */
  static gfxSize GetTransformToAncestorScale(nsIFrame* aFrame);

  /**
   * Gets the scale factors of the transform for aFrame relative to the root
   * frame if this transform is 2D, or the identity scale factors otherwise.
   * If some frame on the path from aFrame to the display root frame may have an
   * animated scale, returns the identity scale factors.
   */
  static gfxSize GetTransformToAncestorScaleExcludingAnimated(nsIFrame* aFrame);

  /**
   * Find the nearest common ancestor frame for aFrame1 and aFrame2. The
   * ancestor frame could be cross-doc.
   */
  static nsIFrame* FindNearestCommonAncestorFrame(nsIFrame* aFrame1,
                                                  nsIFrame* aFrame2);

  /**
   * Transforms a list of CSSPoints from aFromFrame to aToFrame, taking into
   * account all relevant transformations on the frames up to (but excluding)
   * their nearest common ancestor.
   * If we encounter a transform that we need to invert but which is
   * non-invertible, we return NONINVERTIBLE_TRANSFORM. If the frames have
   * no common ancestor, we return NO_COMMON_ANCESTOR.
   * If this returns TRANSFORM_SUCCEEDED, the points in aPoints are transformed
   * in-place, otherwise they are untouched.
   */
  enum TransformResult {
    TRANSFORM_SUCCEEDED,
    NO_COMMON_ANCESTOR,
    NONINVERTIBLE_TRANSFORM
  };
  static TransformResult TransformPoints(nsIFrame* aFromFrame, nsIFrame* aToFrame,
                                         uint32_t aPointCount, CSSPoint* aPoints);

  /**
   * Same as above function, but transform points in app units and
   * handle 1 point per call.
   */
  static TransformResult TransformPoint(nsIFrame* aFromFrame, nsIFrame* aToFrame,
                                        nsPoint& aPoint);

  /**
   * Transforms a rect from aFromFrame to aToFrame. In app units.
   * Returns the bounds of the actual rect if the transform requires rotation
   * or anything complex like that.
   */
  static TransformResult TransformRect(nsIFrame* aFromFrame, nsIFrame* aToFrame,
                                       nsRect& aRect);

  /**
   * Converts app units to pixels (with optional snapping) and appends as a
   * translation to aTransform.
   */
  static void PostTranslate(Matrix4x4& aTransform, const nsPoint& aOrigin, float aAppUnitsPerPixel, bool aRounded);

  /**
   * Get the border-box of aElement's primary frame, transformed it to be
   * relative to aFrame.
   */
  static nsRect GetRectRelativeToFrame(mozilla::dom::Element* aElement,
                                       nsIFrame* aFrame);

  /**
   * Returns true if aRect with border inflation of size aInflateSize contains
   * aPoint.
   */
  static bool ContainsPoint(const nsRect& aRect, const nsPoint& aPoint,
                            nscoord aInflateSize);

  /**
   * Clamp aRect relative to aFrame to the scroll frames boundary searching from
   * aFrame.
   */
  static nsRect ClampRectToScrollFrames(nsIFrame* aFrame,
                                        const nsRect& aRect);

  /**
   * Return true if a "layer transform" could be computed for aFrame,
   * and optionally return the computed transform.  The returned
   * transform is what would be set on the layer currently if a layers
   * transaction were opened at the time this helper is called.
   */
  static bool GetLayerTransformForFrame(nsIFrame* aFrame,
                                        Matrix4x4Flagged* aTransform);

  /**
   * Given a point in the global coordinate space, returns that point expressed
   * in the coordinate system of aFrame.  This effectively inverts all
   * transforms between this point and the root frame.
   *
   * @param aFrame The frame that acts as the coordinate space container.
   * @param aPoint The point, in the global space, to get in the frame-local space.
   * @return aPoint, expressed in aFrame's canonical coordinate space.
   */
  static nsPoint TransformRootPointToFrame(nsIFrame* aFrame,
                                           const nsPoint &aPoint)
  {
    return TransformAncestorPointToFrame(aFrame, aPoint, nullptr);
  }

  /**
   * Transform aPoint relative to aAncestor down to the coordinate system of
   * aFrame.
   */
  static nsPoint TransformAncestorPointToFrame(nsIFrame* aFrame,
                                               const nsPoint& aPoint,
                                               nsIFrame* aAncestor);

  /**
   * Helper function that, given a rectangle and a matrix, returns the smallest
   * rectangle containing the image of the source rectangle.
   *
   * @param aBounds The rectangle to transform.
   * @param aMatrix The matrix to transform it with.
   * @param aFactor The number of app units per graphics unit.
   * @return The smallest rect that contains the image of aBounds.
   */
  static nsRect MatrixTransformRect(const nsRect &aBounds,
                                    const Matrix4x4 &aMatrix, float aFactor);
  static nsRect MatrixTransformRect(const nsRect &aBounds,
                                    const Matrix4x4Flagged &aMatrix, float aFactor);

  /**
   * Helper function that, given a point and a matrix, returns the image
   * of that point under the matrix transform.
   *
   * @param aPoint The point to transform.
   * @param aMatrix The matrix to transform it with.
   * @param aFactor The number of app units per graphics unit.
   * @return The image of the point under the transform.
   */
  static nsPoint MatrixTransformPoint(const nsPoint &aPoint,
                                      const Matrix4x4 &aMatrix, float aFactor);

  /**
   * Given a graphics rectangle in graphics space, return a rectangle in
   * app space that contains the graphics rectangle, rounding out as necessary.
   *
   * @param aRect The graphics rect to round outward.
   * @param aFactor The number of app units per graphics unit.
   * @return The smallest rectangle in app space that contains aRect.
   */
  static nsRect RoundGfxRectToAppRect(const Rect &aRect, float aFactor);

  /**
   * Given a graphics rectangle in graphics space, return a rectangle in
   * app space that contains the graphics rectangle, rounding out as necessary.
   *
   * @param aRect The graphics rect to round outward.
   * @param aFactor The number of app units per graphics unit.
   * @return The smallest rectangle in app space that contains aRect.
   */
  static nsRect RoundGfxRectToAppRect(const gfxRect &aRect, float aFactor);

  /**
   * Returns a subrectangle of aContainedRect that is entirely inside the rounded
   * rect. Complex cases are handled conservatively by returning a smaller
   * rect than necessary.
   */
  static nsRegion RoundedRectIntersectRect(const nsRect& aRoundedRect,
                                           const nscoord aRadii[8],
                                           const nsRect& aContainedRect);
  static nsIntRegion RoundedRectIntersectIntRect(const nsIntRect& aRoundedRect,
                                                 const RectCornerRadii& aCornerRadii,
                                                 const nsIntRect& aContainedRect);

  /**
   * Return whether any part of aTestRect is inside of the rounded
   * rectangle formed by aBounds and aRadii (which are indexed by the
   * enum HalfCorner constants in gfx/2d/Types.h). This is precise.
   */
  static bool RoundedRectIntersectsRect(const nsRect& aRoundedRect,
                                        const nscoord aRadii[8],
                                        const nsRect& aTestRect);

  static bool MaybeCreateDisplayPortInFirstScrollFrameEncountered(
    nsIFrame* aFrame, nsDisplayListBuilder& aBuilder);


  enum class PaintFrameFlags : uint32_t {
    PAINT_IN_TRANSFORM = 0x01,
    PAINT_SYNC_DECODE_IMAGES = 0x02,
    PAINT_WIDGET_LAYERS = 0x04,
    PAINT_IGNORE_SUPPRESSION = 0x08,
    PAINT_DOCUMENT_RELATIVE = 0x10,
    PAINT_HIDE_CARET = 0x20,
    PAINT_TO_WINDOW = 0x40,
    PAINT_EXISTING_TRANSACTION = 0x80,
    PAINT_NO_COMPOSITE = 0x100,
    PAINT_COMPRESSED = 0x200
  };

  /**
   * Given aFrame, the root frame of a stacking context, paint it and its
   * descendants to aRenderingContext.
   * @param aRenderingContext a rendering context translated so that (0,0)
   * is the origin of aFrame; for best results, (0,0) should transform
   * to pixel-aligned coordinates. This can be null, in which case
   * aFrame must be a "display root" (root frame for a root document,
   * or the root of a popup) with an associated widget and we draw using
   * the layer manager for the frame's widget.
   * @param aDirtyRegion the region that must be painted, in the coordinates
   * of aFrame.
   * @param aBackstop paint the dirty area with this color before drawing
   * the actual content; pass NS_RGBA(0,0,0,0) to draw no background.
   * @param aBuilderMode Passed through to the display-list builder.
   * @param aFlags if PAINT_IN_TRANSFORM is set, then we assume
   * this is inside a transform or SVG foreignObject. If
   * PAINT_SYNC_DECODE_IMAGES is set, we force synchronous decode on all
   * images. If PAINT_WIDGET_LAYERS is set, aFrame must be a display root,
   * and we will use the frame's widget's layer manager to paint
   * even if aRenderingContext is non-null. This is useful if you want
   * to force rendering to use the widget's layer manager for testing
   * or speed. PAINT_WIDGET_LAYERS must be set if aRenderingContext is null.
   * If PAINT_DOCUMENT_RELATIVE is used, the visible region is interpreted
   * as being relative to the document (normally it's relative to the CSS
   * viewport) and the document is painted as if no scrolling has occured.
   * Only considered if nsIPresShell::IgnoringViewportScrolling is true.
   * PAINT_TO_WINDOW sets painting to window to true on the display list
   * builder even if we can't tell that we are painting to the window.
   * If PAINT_EXISTING_TRANSACTION is set, then BeginTransaction() has already
   * been called on aFrame's widget's layer manager and should not be
   * called again.
   * If PAINT_COMPRESSED is set, the FrameLayerBuilder should be set to
   * compressed mode to avoid short cut optimizations.
   *
   * So there are three possible behaviours:
   * 1) PAINT_WIDGET_LAYERS is set and aRenderingContext is null; we paint
   * by calling BeginTransaction on the widget's layer manager.
   * 2) PAINT_WIDGET_LAYERS is set and aRenderingContext is non-null; we
   * paint by calling BeginTransactionWithTarget on the widget's layer
   * manager.
   * 3) PAINT_WIDGET_LAYERS is not set and aRenderingContext is non-null;
   * we paint by construct a BasicLayerManager and calling
   * BeginTransactionWithTarget on it. This is desirable if we're doing
   * something like drawWindow in a mode where what gets rendered doesn't
   * necessarily correspond to what's visible in the window; we don't
   * want to mess up the widget's layer tree.
   */
  static nsresult PaintFrame(gfxContext* aRenderingContext, nsIFrame* aFrame,
                             const nsRegion& aDirtyRegion, nscolor aBackstop,
                             nsDisplayListBuilderMode aBuilderMode,
                             PaintFrameFlags aFlags = PaintFrameFlags(0));

  /**
   * Uses a binary search for find where the cursor falls in the line of text
   * It also keeps track of the part of the string that has already been
   * measured so it doesn't have to keep measuring the same text over and over.
   *
   * @param "aBaseWidth" contains the width in twips of the portion
   * of the text that has already been measured, and aBaseInx contains
   * the index of the text that has already been measured.
   *
   * @param aTextWidth returns (in twips) the length of the text that falls
   * before the cursor aIndex contains the index of the text where the cursor
   * falls.
   */
  static bool
  BinarySearchForPosition(DrawTarget* aDrawTarget,
                          nsFontMetrics& aFontMetrics,
                          const char16_t* aText,
                          int32_t    aBaseWidth,
                          int32_t    aBaseInx,
                          int32_t    aStartInx,
                          int32_t    aEndInx,
                          int32_t    aCursorPos,
                          int32_t&   aIndex,
                          int32_t&   aTextWidth);

  class BoxCallback {
  public:
    BoxCallback() : mIncludeCaptionBoxForTable(true) {}
    virtual void AddBox(nsIFrame* aFrame) = 0;
    bool mIncludeCaptionBoxForTable;
  };
  /**
   * Collect all CSS boxes associated with aFrame and its
   * continuations, "drilling down" through table wrapper frames and
   * some anonymous blocks since they're not real CSS boxes.
   * If aFrame is null, no boxes are returned.
   * SVG frames return a single box, themselves.
   */
  static void GetAllInFlowBoxes(nsIFrame* aFrame, BoxCallback* aCallback);

  /**
   * Like GetAllInFlowBoxes, but doesn't include continuations.
   */
  static void AddBoxesForFrame(nsIFrame* aFrame, BoxCallback* aCallback);

  /**
   * Find the first frame descendant of aFrame (including aFrame) which is
   * not an anonymous frame that getBoxQuads/getClientRects should ignore.
   */
  static nsIFrame* GetFirstNonAnonymousFrame(nsIFrame* aFrame);

  class RectCallback {
  public:
    virtual void AddRect(const nsRect& aRect) = 0;
  };

  struct RectAccumulator : public RectCallback {
    nsRect mResultRect;
    nsRect mFirstRect;
    bool mSeenFirstRect;

    RectAccumulator();

    virtual void AddRect(const nsRect& aRect) override;
  };

  struct RectListBuilder : public RectCallback {
    DOMRectList* mRectList;

    explicit RectListBuilder(DOMRectList* aList);
    virtual void AddRect(const nsRect& aRect) override;
  };

  static nsIFrame* GetContainingBlockForClientRect(nsIFrame* aFrame);

  enum {
    RECTS_ACCOUNT_FOR_TRANSFORMS = 0x01,
    // Two bits for specifying which box type to use.
    // With neither bit set (default), use the border box.
    RECTS_USE_CONTENT_BOX = 0x02,
    RECTS_USE_PADDING_BOX = 0x04,
    RECTS_USE_MARGIN_BOX = 0x06, // both bits set
    RECTS_WHICH_BOX_MASK = 0x06 // bitmask for these two bits
  };
  /**
   * Collect all CSS boxes (content, padding, border, or margin) associated
   * with aFrame and its continuations, "drilling down" through table wrapper
   * frames and some anonymous blocks since they're not real CSS boxes.
   * The boxes are positioned relative to aRelativeTo (taking scrolling
   * into account) and passed to the callback in frame-tree order.
   * If aFrame is null, no boxes are returned.
   * For SVG frames, returns one rectangle, the bounding box.
   * If aFlags includes RECTS_ACCOUNT_FOR_TRANSFORMS, then when converting
   * the boxes into aRelativeTo coordinates, transforms (including CSS
   * and SVG transforms) are taken into account.
   * If aFlags includes one of RECTS_USE_CONTENT_BOX, RECTS_USE_PADDING_BOX,
   * or RECTS_USE_MARGIN_BOX, the corresponding type of box is used.
   * Otherwise (by default), the border box is used.
   */
  static void GetAllInFlowRects(nsIFrame* aFrame, nsIFrame* aRelativeTo,
                                RectCallback* aCallback, uint32_t aFlags = 0);

  static void GetAllInFlowRectsAndTexts(nsIFrame* aFrame, nsIFrame* aRelativeTo,
                                        RectCallback* aCallback,
                                        mozilla::dom::Sequence<nsString>* aTextList,
                                        uint32_t aFlags = 0);

  /**
   * Computes the union of all rects returned by GetAllInFlowRects. If
   * the union is empty, returns the first rect.
   * If aFlags includes RECTS_ACCOUNT_FOR_TRANSFORMS, then when converting
   * the boxes into aRelativeTo coordinates, transforms (including CSS
   * and SVG transforms) are taken into account.
   * If aFlags includes one of RECTS_USE_CONTENT_BOX, RECTS_USE_PADDING_BOX,
   * or RECTS_USE_MARGIN_BOX, the corresponding type of box is used.
   * Otherwise (by default), the border box is used.
   */
  static nsRect GetAllInFlowRectsUnion(nsIFrame* aFrame, nsIFrame* aRelativeTo,
                                       uint32_t aFlags = 0);

  enum {
    EXCLUDE_BLUR_SHADOWS = 0x01
  };
  /**
   * Takes a text-shadow array from the style properties of a given nsIFrame and
   * computes the union of those shadows along with the given initial rect.
   * If there are no shadows, the initial rect is returned.
   */
  static nsRect GetTextShadowRectsUnion(const nsRect& aTextAndDecorationsRect,
                                        nsIFrame* aFrame,
                                        uint32_t aFlags = 0);

  /**
   * Computes the destination rect that a given replaced element should render
   * into, based on its CSS 'object-fit' and 'object-position' properties.
   *
   * @param aConstraintRect The constraint rect that we have at our disposal,
   *                        which would e.g. be exactly filled by the image
   *                        if we had "object-fit: fill".
   * @param aIntrinsicSize The replaced content's intrinsic size, as reported
   *                       by nsIFrame::GetIntrinsicSize().
   * @param aIntrinsicRatio The replaced content's intrinsic ratio, as reported
   *                        by nsIFrame::GetIntrinsicRatio().
   * @param aStylePos The nsStylePosition struct that contains the 'object-fit'
   *                  and 'object-position' values that we should rely on.
   *                  (This should usually be the nsStylePosition for the
   *                  replaced element in question, but not always. For
   *                  example, a <video>'s poster-image has a dedicated
   *                  anonymous element & child-frame, but we should still use
   *                  the <video>'s 'object-fit' and 'object-position' values.)
   * @param aAnchorPoint [out] A point that should be pixel-aligned by functions
   *                           like nsLayoutUtils::DrawImage. See documentation
   *                           in nsCSSRendering.h for ComputeObjectAnchorPoint.
   * @return The nsRect into which we should render the replaced content (using
   *         the same coordinate space as the passed-in aConstraintRect).
   */
  static nsRect ComputeObjectDestRect(const nsRect& aConstraintRect,
                                      const IntrinsicSize& aIntrinsicSize,
                                      const nsSize& aIntrinsicRatio,
                                      const nsStylePosition* aStylePos,
                                      nsPoint* aAnchorPoint = nullptr);

  /**
   * Get the font metrics corresponding to the frame's style data.
   * @param aFrame the frame
   * @param aSizeInflation number to multiply font size by
   */
  static already_AddRefed<nsFontMetrics> GetFontMetricsForFrame(
    const nsIFrame* aFrame, float aSizeInflation);

  static already_AddRefed<nsFontMetrics>
    GetInflatedFontMetricsForFrame(const nsIFrame* aFrame)
  {
    return GetFontMetricsForFrame(aFrame, FontSizeInflationFor(aFrame));
  }

  /**
   * Get the font metrics corresponding to the given style data.
   * @param aComputedStyle the style data
   * @param aSizeInflation number to multiply font size by
   */
  static already_AddRefed<nsFontMetrics> GetFontMetricsForComputedStyle(
      ComputedStyle* aComputedStyle,
      nsPresContext* aPresContext,
      float aSizeInflation = 1.0f,
      uint8_t aVariantWidth = NS_FONT_VARIANT_WIDTH_NORMAL);

  /**
   * Get the font metrics of emphasis marks corresponding to the given
   * style data. The result is same as GetFontMetricsForComputedStyle
   * except that the font size is scaled down to 50%.
   * @param aComputedStyle the style data
   * @param aInflation number to multiple font size by
   */
  static already_AddRefed<nsFontMetrics> GetFontMetricsOfEmphasisMarks(
      ComputedStyle* aComputedStyle,
      nsPresContext* aPresContext,
      float aInflation)
  {
    return GetFontMetricsForComputedStyle(aComputedStyle,
                                          aPresContext,
                                          aInflation * 0.5f);
  }

  /**
   * Find the immediate child of aParent whose frame subtree contains
   * aDescendantFrame. Returns null if aDescendantFrame is not a descendant
   * of aParent.
   */
  static nsIFrame* FindChildContainingDescendant(nsIFrame* aParent, nsIFrame* aDescendantFrame);

  /**
   * Find the nearest ancestor that's a block
   */
  static nsBlockFrame* FindNearestBlockAncestor(nsIFrame* aFrame);

  /**
   * Find the nearest ancestor that's not for generated content. Will return
   * aFrame if aFrame is not for generated content.
   */
  static nsIFrame* GetNonGeneratedAncestor(nsIFrame* aFrame);

  /**
   * Cast aFrame to an nsBlockFrame* or return null if it's not
   * an nsBlockFrame.
   */
  static nsBlockFrame* GetAsBlock(nsIFrame* aFrame);

  /*
   * Whether the frame is an nsBlockFrame which is not a wrapper block.
   */
  static bool IsNonWrapperBlock(nsIFrame* aFrame);

  /**
   * If aFrame is an out of flow frame, return its placeholder, otherwise
   * return its parent.
   */
  static nsIFrame* GetParentOrPlaceholderFor(nsIFrame* aFrame);

  /**
   * If aFrame is an out of flow frame, return its placeholder, otherwise
   * return its (possibly cross-doc) parent.
   */
  static nsIFrame* GetParentOrPlaceholderForCrossDoc(nsIFrame* aFrame);

  /**
   * Get a frame's next-in-flow, or, if it doesn't have one, its
   * block-in-inline-split sibling.
   */
  static nsIFrame*
  GetNextContinuationOrIBSplitSibling(nsIFrame *aFrame);

  /**
   * Get the first frame in the continuation-plus-ib-split-sibling chain
   * containing aFrame.
   */
  static nsIFrame*
  FirstContinuationOrIBSplitSibling(const nsIFrame *aFrame);

  /**
   * Get the last frame in the continuation-plus-ib-split-sibling chain
   * containing aFrame.
   */
  static nsIFrame*
  LastContinuationOrIBSplitSibling(const nsIFrame *aFrame);

  /**
   * Is FirstContinuationOrIBSplitSibling(aFrame) going to return
   * aFrame?
   */
  static bool
  IsFirstContinuationOrIBSplitSibling(nsIFrame *aFrame);

  /**
   * Check whether aFrame is a part of the scrollbar or scrollcorner of
   * the root content.
   * @param aFrame the checking frame.
   * @return true if the frame is a part of the scrollbar or scrollcorner of
   *         the root content.
   */
  static bool IsViewportScrollbarFrame(nsIFrame* aFrame);

  /**
   * Get the contribution of aFrame to its containing block's intrinsic
   * size for the given physical axis.  This considers the child's intrinsic
   * width, its 'width', 'min-width', and 'max-width' properties (or 'height'
   * variations if that's what matches aAxis) and its padding, border and margin
   * in the corresponding dimension.
   * @param aPercentageBasis an optional percentage basis (in aFrame's WM).
   *   If the basis is indefinite in a given axis, pass a size with
   *   NS_UNCONSTRAINEDSIZE in that component.
   *   If you pass Nothing() a percentage basis will be calculated from aFrame's
   *   ancestors' computed size in the relevant axis, if needed.
   * @param aMarginBoxMinSizeClamp make the result fit within this margin-box
   * size by reducing the *content size* (flooring at zero).  This is used for:
   * https://drafts.csswg.org/css-grid/#min-size-auto
   */
  enum class IntrinsicISizeType { MIN_ISIZE, PREF_ISIZE };
  static const auto MIN_ISIZE = IntrinsicISizeType::MIN_ISIZE;
  static const auto PREF_ISIZE = IntrinsicISizeType::PREF_ISIZE;
  enum {
    IGNORE_PADDING = 0x01,
    BAIL_IF_REFLOW_NEEDED = 0x02, // returns NS_INTRINSIC_WIDTH_UNKNOWN if so
    MIN_INTRINSIC_ISIZE = 0x04, // use min-width/height instead of width/height
  };
  static nscoord
  IntrinsicForAxis(mozilla::PhysicalAxis aAxis,
                   gfxContext*           aRenderingContext,
                   nsIFrame*             aFrame,
                   IntrinsicISizeType    aType,
                   const mozilla::Maybe<LogicalSize>& aPercentageBasis = mozilla::Nothing(),
                   uint32_t              aFlags = 0,
                   nscoord               aMarginBoxMinSizeClamp = NS_MAXSIZE);
  /**
   * Calls IntrinsicForAxis with aFrame's parent's inline physical axis.
   */
  static nscoord IntrinsicForContainer(gfxContext*         aRenderingContext,
                                       nsIFrame*           aFrame,
                                       IntrinsicISizeType  aType,
                                       uint32_t            aFlags = 0);

  /**
   * Get the definite size contribution of aFrame for the given physical axis.
   * This considers the child's 'min-width' property (or 'min-height' if the
   * given axis is vertical), and its padding, border, and margin in the
   * corresponding dimension.  If the 'min-' property is 'auto' (and 'overflow'
   * is 'visible') and the corresponding 'width'/'height' is definite it returns
   * the "specified size" for:
   * https://drafts.csswg.org/css-grid/#min-size-auto
   * Note that the "transferred size" is not handled here; use IntrinsicForAxis.
   * Note that any percentage in 'width'/'height' makes it count as indefinite.
   * If the 'min-' property is 'auto' and 'overflow' is not 'visible', then it
   * calculates the result as if the 'min-' computed value is zero.
   * Otherwise, return NS_UNCONSTRAINEDSIZE.
   *
   * @param aPercentageBasis the percentage basis (in aFrame's WM).
   *   Pass NS_UNCONSTRAINEDSIZE if the basis is indefinite in either/both axes.
   * @note this behavior is specific to Grid/Flexbox (currently) so aFrame
   * should be a grid/flex item.
   */
  static nscoord
  MinSizeContributionForAxis(mozilla::PhysicalAxis aAxis,
                            gfxContext*            aRC,
                            nsIFrame*              aFrame,
                            IntrinsicISizeType     aType,
                            const LogicalSize&     aPercentageBasis,
                            uint32_t               aFlags = 0);

  /*
   * Convert nsStyleCoord to nscoord when percentages depend on the
   * containing block size.
   * @param aPercentBasis The width or height of the containing block
   * (whichever the client wants to use for resolving percentages).
   */
  static nscoord ComputeCBDependentValue(nscoord aPercentBasis,
                                         const nsStyleCoord& aCoord);

  static nscoord ComputeBSizeDependentValue(
                   nscoord              aContainingBlockBSize,
                   const nsStyleCoord&  aCoord);

  static nscoord ComputeBSizeValue(nscoord aContainingBlockBSize,
                                    nscoord aContentEdgeToBoxSizingBoxEdge,
                                    const nsStyleCoord& aCoord)
  {
    MOZ_ASSERT(aContainingBlockBSize != nscoord_MAX || !aCoord.HasPercent(),
               "caller must deal with %% of unconstrained block-size");
    MOZ_ASSERT(aCoord.IsCoordPercentCalcUnit());

    nscoord result = aCoord.ComputeCoordPercentCalc(aContainingBlockBSize);
    // Clamp calc(), and the subtraction for box-sizing.
    return std::max(0, result - aContentEdgeToBoxSizingBoxEdge);
  }

  // XXX to be removed
  static bool IsAutoHeight(const nsStyleCoord &aCoord, nscoord aCBHeight)
  {
    return IsAutoBSize(aCoord, aCBHeight);
  }

  static bool IsAutoBSize(const nsStyleCoord &aCoord, nscoord aCBBSize)
  {
    nsStyleUnit unit = aCoord.GetUnit();
    return unit == eStyleUnit_Auto ||  // only for 'height'
           unit == eStyleUnit_None ||  // only for 'max-height'
           // The enumerated values were originally aimed at inline-size
           // (or width, as it was before logicalization). For now, let them
           // return true here, so that we don't call ComputeBSizeValue with
           // value types that it doesn't understand. (See bug 1113216.)
           //
           // FIXME (bug 567039, bug 527285)
           // This isn't correct for the 'fill' value or for the 'min-*' or
           // 'max-*' properties, which need to be handled differently by
           // the callers of IsAutoBSize().
           unit == eStyleUnit_Enumerated ||
           (aCBBSize == nscoord_MAX && aCoord.HasPercent());
  }

  static bool IsPaddingZero(const nsStyleCoord &aCoord)
  {
    return (aCoord.GetUnit() == eStyleUnit_Coord &&
            aCoord.GetCoordValue() == 0) ||
           (aCoord.GetUnit() == eStyleUnit_Percent &&
            aCoord.GetPercentValue() == 0.0f) ||
           (aCoord.IsCalcUnit() &&
            // clamp negative calc() to 0
            aCoord.ComputeCoordPercentCalc(nscoord_MAX) <= 0 &&
            aCoord.ComputeCoordPercentCalc(0) <= 0);
  }

  static bool IsMarginZero(const nsStyleCoord &aCoord)
  {
    return (aCoord.GetUnit() == eStyleUnit_Coord &&
            aCoord.GetCoordValue() == 0) ||
           (aCoord.GetUnit() == eStyleUnit_Percent &&
            aCoord.GetPercentValue() == 0.0f) ||
           (aCoord.IsCalcUnit() &&
            aCoord.ComputeCoordPercentCalc(nscoord_MAX) == 0 &&
            aCoord.ComputeCoordPercentCalc(0) == 0);
  }

  static void MarkDescendantsDirty(nsIFrame *aSubtreeRoot);

  static void MarkIntrinsicISizesDirtyIfDependentOnBSize(nsIFrame* aFrame);

  /*
   * Calculate the used values for 'width' and 'height' when width
   * and height are 'auto'. The tentWidth and tentHeight arguments should be
   * the result of applying the rules for computing intrinsic sizes and ratios.
   * as specified by CSS 2.1 sections 10.3.2 and 10.6.2
   */
  static nsSize ComputeAutoSizeWithIntrinsicDimensions(nscoord minWidth, nscoord minHeight,
                                                       nscoord maxWidth, nscoord maxHeight,
                                                       nscoord tentWidth, nscoord tentHeight);

  // Implement nsIFrame::GetPrefISize in terms of nsIFrame::AddInlinePrefISize
  static nscoord PrefISizeFromInline(nsIFrame* aFrame,
                                     gfxContext* aRenderingContext);

  // Implement nsIFrame::GetMinISize in terms of nsIFrame::AddInlineMinISize
  static nscoord MinISizeFromInline(nsIFrame* aFrame,
                                    gfxContext* aRenderingContext);

  // Get a suitable foreground color for painting aColor for aFrame.
  static nscolor DarkenColorIfNeeded(nsIFrame* aFrame, nscolor aColor);

  // Get a suitable foreground color for painting aField for aFrame.
  // Type of aFrame is made a template parameter because nsIFrame is not
  // a complete type in the header. Type-safety is not harmed given that
  // DarkenColorIfNeeded requires an nsIFrame pointer.
  template<typename Frame, typename T, typename S>
  static nscolor GetColor(Frame* aFrame, T S::* aField) {
    nscolor color = aFrame->GetVisitedDependentColor(aField);
    return DarkenColorIfNeeded(aFrame, color);
  }

  // Get a baseline y position in app units that is snapped to device pixels.
  static gfxFloat GetSnappedBaselineY(nsIFrame* aFrame, gfxContext* aContext,
                                      nscoord aY, nscoord aAscent);
  // Ditto for an x position (for vertical text). Note that for vertical-rl
  // writing mode, the ascent value should be negated by the caller.
  static gfxFloat GetSnappedBaselineX(nsIFrame* aFrame, gfxContext* aContext,
                                      nscoord aX, nscoord aAscent);

  static nscoord AppUnitWidthOfString(char16_t aC,
                                      nsFontMetrics& aFontMetrics,
                                      DrawTarget* aDrawTarget) {
    return AppUnitWidthOfString(&aC, 1, aFontMetrics, aDrawTarget);
  }
  static nscoord AppUnitWidthOfString(const nsString& aString,
                                      nsFontMetrics& aFontMetrics,
                                      DrawTarget* aDrawTarget) {
    return nsLayoutUtils::AppUnitWidthOfString(aString.get(), aString.Length(),
                                               aFontMetrics, aDrawTarget);
  }
  static nscoord AppUnitWidthOfString(const char16_t *aString,
                                      uint32_t aLength,
                                      nsFontMetrics& aFontMetrics,
                                      DrawTarget* aDrawTarget);
  static nscoord AppUnitWidthOfStringBidi(const nsString& aString,
                                          const nsIFrame* aFrame,
                                          nsFontMetrics& aFontMetrics,
                                          gfxContext& aContext) {
    return nsLayoutUtils::AppUnitWidthOfStringBidi(aString.get(),
                                                   aString.Length(), aFrame,
                                                   aFontMetrics, aContext);
  }
  static nscoord AppUnitWidthOfStringBidi(const char16_t* aString,
                                          uint32_t aLength,
                                          const nsIFrame* aFrame,
                                          nsFontMetrics& aFontMetrics,
                                          gfxContext& aContext);

  static bool StringWidthIsGreaterThan(const nsString& aString,
                                       nsFontMetrics& aFontMetrics,
                                       DrawTarget* aDrawTarget,
                                       nscoord aWidth);

  static nsBoundingMetrics AppUnitBoundsOfString(const char16_t* aString,
                                                 uint32_t aLength,
                                                 nsFontMetrics& aFontMetrics,
                                                 DrawTarget* aDrawTarget);

  static void DrawString(const nsIFrame*         aFrame,
                         nsFontMetrics&          aFontMetrics,
                         gfxContext*             aContext,
                         const char16_t*         aString,
                         int32_t                 aLength,
                         nsPoint                 aPoint,
                         ComputedStyle* aComputedStyle = nullptr,
                         DrawStringFlags         aFlags = DrawStringFlags::eDefault);

  static nsPoint GetBackgroundFirstTilePos(const nsPoint& aDest,
                                           const nsPoint& aFill,
                                           const nsSize& aRepeatSize);

  /**
   * Supports only LTR or RTL. Bidi (mixed direction) is not supported.
   */
  static void DrawUniDirString(const char16_t* aString,
                               uint32_t aLength,
                               const nsPoint& aPoint,
                               nsFontMetrics& aFontMetrics,
                               gfxContext& aContext);

  /**
   * Helper function for drawing text-shadow. The callback's job
   * is to draw whatever needs to be blurred onto the given context.
   */
  typedef void (* TextShadowCallback)(gfxContext* aCtx,
                                      nsPoint aShadowOffset,
                                      const nscolor& aShadowColor,
                                      void* aData);

  static void PaintTextShadow(const nsIFrame*     aFrame,
                              gfxContext*         aContext,
                              const nsRect&       aTextRect,
                              const nsRect&       aDirtyRect,
                              const nscolor&      aForegroundColor,
                              TextShadowCallback  aCallback,
                              void*               aCallbackData);

  /**
   * Gets the baseline to vertically center text from a font within a
   * line of specified height.
   * aIsInverted: true if the text is inverted relative to the block
   * direction, so that the block-dir "ascent" corresponds to font
   * descent. (Applies to sideways text in vertical-lr mode.)
   *
   * Returns the baseline position relative to the top of the line.
   */
  static nscoord GetCenteredFontBaseline(nsFontMetrics* aFontMetrics,
                                         nscoord        aLineHeight,
                                         bool           aIsInverted);

  /**
   * Derive a baseline of |aFrame| (measured from its top border edge)
   * from its first in-flow line box (not descending into anything with
   * 'overflow' not 'visible', potentially including aFrame itself).
   *
   * Returns true if a baseline was found (and fills in aResult).
   * Otherwise returns false.
   */
  static bool GetFirstLineBaseline(mozilla::WritingMode aWritingMode,
                                   const nsIFrame* aFrame, nscoord* aResult);

  /**
   * Just like GetFirstLineBaseline, except also returns the top and
   * bottom of the line with the baseline.
   *
   * Returns true if a line was found (and fills in aResult).
   * Otherwise returns false.
   */
  struct LinePosition {
    nscoord mBStart, mBaseline, mBEnd;

    LinePosition operator+(nscoord aOffset) const {
      LinePosition result;
      result.mBStart = mBStart + aOffset;
      result.mBaseline = mBaseline + aOffset;
      result.mBEnd = mBEnd + aOffset;
      return result;
    }
  };
  static bool GetFirstLinePosition(mozilla::WritingMode aWritingMode,
                                   const nsIFrame* aFrame,
                                   LinePosition* aResult);


  /**
   * Derive a baseline of |aFrame| (measured from its top border edge)
   * from its last in-flow line box (not descending into anything with
   * 'overflow' not 'visible', potentially including aFrame itself).
   *
   * Returns true if a baseline was found (and fills in aResult).
   * Otherwise returns false.
   */
  static bool GetLastLineBaseline(mozilla::WritingMode aWritingMode,
                                  const nsIFrame* aFrame, nscoord* aResult);

  /**
   * Returns a block-dir coordinate relative to this frame's origin that
   * represents the logical block-end of the frame or its visible content,
   * whichever is further from the origin.
   * Relative positioning is ignored and margins and glyph bounds are not
   * considered.
   * This value will be >= mRect.BSize() and <= overflowRect.BEnd() unless
   * relative positioning is applied.
   */
  static nscoord CalculateContentBEnd(mozilla::WritingMode aWritingMode,
                                      nsIFrame* aFrame);

  /**
   * Gets the closest frame (the frame passed in or one of its parents) that
   * qualifies as a "layer"; used in DOM0 methods that depends upon that
   * definition. This is the nearest frame that is either positioned or scrolled
   * (the child of a scroll frame).
   */
  static nsIFrame* GetClosestLayer(nsIFrame* aFrame);

  /**
   * Gets the graphics sampling filter for the frame
   */
  static SamplingFilter GetSamplingFilterForFrame(nsIFrame* aFrame);

  static inline void InitDashPattern(StrokeOptions& aStrokeOptions,
                                     uint8_t aBorderStyle) {
    if (aBorderStyle == NS_STYLE_BORDER_STYLE_DOTTED) {
      static Float dot[] = { 1.f, 1.f };
      aStrokeOptions.mDashLength = MOZ_ARRAY_LENGTH(dot);
      aStrokeOptions.mDashPattern = dot;
    } else if (aBorderStyle == NS_STYLE_BORDER_STYLE_DASHED) {
      static Float dash[] = { 5.f, 5.f };
      aStrokeOptions.mDashLength = MOZ_ARRAY_LENGTH(dash);
      aStrokeOptions.mDashPattern = dash;
    } else {
      aStrokeOptions.mDashLength = 0;
      aStrokeOptions.mDashPattern = nullptr;
    }
  }

  /**
   * Convert an nsRect to a gfxRect.
   */
  static gfxRect RectToGfxRect(const nsRect& aRect,
                               int32_t aAppUnitsPerDevPixel);

  static gfxPoint PointToGfxPoint(const nsPoint& aPoint,
                                  int32_t aAppUnitsPerPixel) {
    return gfxPoint(gfxFloat(aPoint.x) / aAppUnitsPerPixel,
                    gfxFloat(aPoint.y) / aAppUnitsPerPixel);
  }

  /* N.B. The only difference between variants of the Draw*Image
   * functions below is the type of the aImage argument.
   */

  /**
   * Draw a background image.  The image's dimensions are as specified in aDest;
   * the image itself is not consulted to determine a size.
   * See https://wiki.mozilla.org/Gecko:Image_Snapping_and_Rendering
   *   @param aContext          The context to draw to, already set up with an
   *                            appropriate scale and transform for drawing in
   *                            app units.
   *   @param aForFrame         The nsIFrame that we're drawing this image for.
   *   @param aImage            The image.
   *   @param aImageSize        The unscaled size of the image being drawn.
   *                            (This might be the image's size if no scaling
   *                            occurs, or it might be the image's size if
   *                            the image is a vector image being rendered at
   *                            that size.)
   *   @param aDest             The position and scaled area where one copy of
   *                            the image should be drawn. This area represents
   *                            the image itself in its correct position as defined
   *                            with the background-position css property.
   *   @param aFill             The area to be filled with copies of the image.
   *   @param aRepeatSize       The distance between the positions of two subsequent
   *                            repeats of the image. Sizes larger than aDest.Size()
   *                            create gaps between the images.
   *   @param aAnchor           A point in aFill which we will ensure is
   *                            pixel-aligned in the output.
   *   @param aDirty            Pixels outside this area may be skipped.
   *   @param aImageFlags       Image flags of the imgIContainer::FLAG_* variety.
   *   @param aExtendMode       How to extend the image over the dest rect.
   */
  static ImgDrawResult DrawBackgroundImage(gfxContext&         aContext,
                                        nsIFrame*           aForFrame,
                                        nsPresContext*      aPresContext,
                                        imgIContainer*      aImage,
                                        const CSSIntSize&   aImageSize,
                                        SamplingFilter      aSamplingFilter,
                                        const nsRect&       aDest,
                                        const nsRect&       aFill,
                                        const nsSize&       aRepeatSize,
                                        const nsPoint&      aAnchor,
                                        const nsRect&       aDirty,
                                        uint32_t            aImageFlags,
                                        ExtendMode          aExtendMode,
                                        float               aOpacity);

  /**
   * Draw an image.
   * See https://wiki.mozilla.org/Gecko:Image_Snapping_and_Rendering
   *   @param aRenderingContext Where to draw the image, set up with an
   *                            appropriate scale and transform for drawing in
   *                            app units.
   *   @param aComputedStyle    The ComputedStyle of the nsIFrame (or
   *                            pseudo-element) for which this image is being
   *                            drawn.
   *   @param aImage            The image.
   *   @param aDest             Where one copy of the image should mapped to.
   *   @param aFill             The area to be filled with copies of the
   *                            image.
   *   @param aAnchor           A point in aFill which we will ensure is
   *                            pixel-aligned in the output.
   *   @param aDirty            Pixels outside this area may be skipped.
   *   @param aImageFlags       Image flags of the imgIContainer::FLAG_* variety
   */
  static ImgDrawResult DrawImage(gfxContext&         aContext,
                                 ComputedStyle*      aComputedStyle,
                                 nsPresContext*      aPresContext,
                                 imgIContainer*      aImage,
                                 const SamplingFilter aSamplingFilter,
                                 const nsRect&       aDest,
                                 const nsRect&       aFill,
                                 const nsPoint&      aAnchor,
                                 const nsRect&       aDirty,
                                 uint32_t            aImageFlags,
                                 float               aOpacity = 1.0);

  /**
   * Draw a whole image without scaling or tiling.
   *
   *   @param aRenderingContext Where to draw the image, set up with an
   *                            appropriate scale and transform for drawing in
   *                            app units.
   *   @param aImage            The image.
   *   @param aDest             The top-left where the image should be drawn.
   *   @param aDirty            If non-null, then pixels outside this area may
   *                            be skipped.
   *   @param aSVGContext       Optionally provides an SVGImageContext.
   *                            Callers should pass an SVGImageContext with at
   *                            least the viewport size set if aImage may be of
   *                            type imgIContainer::TYPE_VECTOR, or pass
   *                            Nothing() if it is of type
   *                            imgIContainer::TYPE_RASTER (to save cycles
   *                            constructing an SVGImageContext, since this
   *                            argument will be ignored for raster images).
   *   @param aImageFlags       Image flags of the imgIContainer::FLAG_* variety
   *   @param aSourceArea       If non-null, this area is extracted from
   *                            the image and drawn at aDest. It's
   *                            in appunits. For best results it should
   *                            be aligned with image pixels.
   */
  static ImgDrawResult DrawSingleUnscaledImage(gfxContext&          aContext,
                                            nsPresContext*       aPresContext,
                                            imgIContainer*       aImage,
                                            const SamplingFilter aSamplingFilter,
                                            const nsPoint&       aDest,
                                            const nsRect*        aDirty,
                                            const mozilla::Maybe<SVGImageContext>& aSVGContext,
                                            uint32_t             aImageFlags,
                                            const nsRect*        aSourceArea = nullptr);

  /**
   * Draw a whole image without tiling.
   *
   *   @param aRenderingContext Where to draw the image, set up with an
   *                            appropriate scale and transform for drawing in
   *                            app units.
   *   @param aImage            The image.
   *   @param aDest             The area that the image should fill.
   *   @param aDirty            Pixels outside this area may be skipped.
   *   @param aSVGContext       Optionally provides an SVGImageContext.
   *                            Callers should pass an SVGImageContext with at
   *                            least the viewport size set if aImage may be of
   *                            type imgIContainer::TYPE_VECTOR, or pass
   *                            Nothing() if it is of type
   *                            imgIContainer::TYPE_RASTER (to save cycles
   *                            constructing an SVGImageContext, since this
   *                            argument will be ignored for raster images).
   *   @param aImageFlags       Image flags of the imgIContainer::FLAG_*
   *                            variety.
   *   @param aAnchor           If non-null, a point which we will ensure
   *                            is pixel-aligned in the output.
   *   @param aSourceArea       If non-null, this area is extracted from
   *                            the image and drawn in aDest. It's
   *                            in appunits. For best results it should
   *                            be aligned with image pixels.
   */
  static ImgDrawResult DrawSingleImage(gfxContext&         aContext,
                                    nsPresContext*      aPresContext,
                                    imgIContainer*      aImage,
                                    const SamplingFilter aSamplingFilter,
                                    const nsRect&       aDest,
                                    const nsRect&       aDirty,
                                    const mozilla::Maybe<SVGImageContext>& aSVGContext,
                                    uint32_t            aImageFlags,
                                    const nsPoint*      aAnchorPoint = nullptr,
                                    const nsRect*       aSourceArea = nullptr);

  /**
   * Given an imgIContainer, this method attempts to obtain an intrinsic
   * px-valued height & width for it.  If the imgIContainer has a non-pixel
   * value for either height or width, this method tries to generate a pixel
   * value for that dimension using the intrinsic ratio (if available).  The
   * intrinsic ratio will be assigned to aIntrinsicRatio; if there's no
   * intrinsic ratio then (0, 0) will be assigned.
   *
   * This method will always set aGotWidth and aGotHeight to indicate whether
   * we were able to successfully obtain (or compute) a value for each
   * dimension.
   *
   * NOTE: This method is similar to ComputeSizeWithIntrinsicDimensions.  The
   * difference is that this one is simpler and is suited to places where we
   * have less information about the frame tree.
   */
  static void ComputeSizeForDrawing(imgIContainer* aImage,
                                    CSSIntSize&    aImageSize,
                                    nsSize&        aIntrinsicRatio,
                                    bool&          aGotWidth,
                                    bool&          aGotHeight);

  /**
   * Given an imgIContainer, this method attempts to obtain an intrinsic
   * px-valued height & width for it. If the imgIContainer has a non-pixel
   * value for either height or width, this method tries to generate a pixel
   * value for that dimension using the intrinsic ratio (if available). If,
   * after trying all these methods, no value is available for one or both
   * dimensions, the corresponding dimension of aFallbackSize is used instead.
   */
  static CSSIntSize
  ComputeSizeForDrawingWithFallback(imgIContainer* aImage,
                                    const nsSize&  aFallbackSize);

  /**
   * Given the image container, frame, and dest rect, determine the best fitting
   * size to decode the image at, and calculate any necessary SVG parameters.
   */
  static mozilla::gfx::IntSize
  ComputeImageContainerDrawingParameters(imgIContainer*            aImage,
                                         nsIFrame*                 aForFrame,
                                         const LayoutDeviceRect&   aDestRect,
                                         const StackingContextHelper& aSc,
                                         uint32_t                  aFlags,
                                         mozilla::Maybe<SVGImageContext>& aSVGContext);

  /**
   * Given a source area of an image (in appunits) and a destination area
   * that we want to map that source area too, computes the area that
   * would be covered by the whole image. This is useful for passing to
   * the aDest parameter of DrawImage, when we want to draw a subimage
   * of an overall image.
   */
  static nsRect GetWholeImageDestination(const nsSize& aWholeImageSize,
                                         const nsRect& aImageSourceArea,
                                         const nsRect& aDestArea);

  /**
   * Given an image container and an orientation, returns an image container
   * that contains the same image, reoriented appropriately. May return the
   * original image container if no changes are needed.
   *
   * @param aContainer   The image container to apply the orientation to.
   * @param aOrientation The desired orientation.
   */
  static already_AddRefed<imgIContainer>
  OrientImage(imgIContainer* aContainer,
              const nsStyleImageOrientation& aOrientation);

  /**
   * Determine if any corner radius is of nonzero size
   *   @param aCorners the |nsStyleCorners| object to check
   *   @return true unless all the coordinates are 0%, 0 or null.
   *
   * A corner radius with one dimension zero and one nonzero is
   * treated as a nonzero-radius corner, even though it will end up
   * being rendered like a zero-radius corner.  This is because such
   * corners are not expected to appear outside of test cases, and it's
   * simpler to implement the test this way.
   */
  static bool HasNonZeroCorner(const nsStyleCorners& aCorners);

  /**
   * Determine if there is any corner radius on corners adjacent to the
   * given side.
   */
  static bool HasNonZeroCornerOnSide(const nsStyleCorners& aCorners,
                                       mozilla::Side aSide);

  /**
   * Determine if a widget is likely to require transparency or translucency.
   *   @param aBackgroundFrame The frame that the background is set on. For
   *                           <window>s, this will be the canvas frame.
   *   @param aCSSRootFrame    The frame that holds CSS properties affecting
   *                           the widget's transparency. For menupopups,
   *                           aBackgroundFrame and aCSSRootFrame will be the
   *                           same.
   *   @return a value suitable for passing to SetWindowTranslucency.
   */
  static nsTransparencyMode GetFrameTransparency(nsIFrame* aBackgroundFrame,
                                                 nsIFrame* aCSSRootFrame);

  /**
   * A frame is a popup if it has its own floating window. Menus, panels
   * and combobox dropdowns are popups.
   */
  static bool IsPopup(nsIFrame* aFrame);

  /**
   * Find the nearest "display root". This is the nearest enclosing
   * popup frame or the root prescontext's root frame.
   */
  static nsIFrame* GetDisplayRootFrame(nsIFrame* aFrame);

  /**
   * Get the reference frame that would be used when constructing a
   * display item for this frame.  Rather than using their own frame
   * as a reference frame.)
   *
   * This duplicates some of the logic of GetDisplayRootFrame above and
   * of nsDisplayListBuilder::FindReferenceFrameFor.
   *
   * If you have an nsDisplayListBuilder, you should get the reference
   * frame from it instead of calling this.
   */
  static nsIFrame* GetReferenceFrame(nsIFrame* aFrame);

  /**
   * Get textrun construction flags determined by a given style; in particular
   * some combination of:
   * -- TEXT_DISABLE_OPTIONAL_LIGATURES if letter-spacing is in use
   * -- TEXT_OPTIMIZE_SPEED if the text-rendering CSS property and font size
   * and prefs indicate we should be optimizing for speed over quality
   */
  static mozilla::gfx::ShapedTextFlags
  GetTextRunFlagsForStyle(ComputedStyle* aComputedStyle,
                          nsPresContext* aPresContext,
                          const nsStyleFont* aStyleFont,
                          const nsStyleText* aStyleText,
                          nscoord aLetterSpacing);

  /**
   * Get orientation flags for textrun construction.
   */
  static mozilla::gfx::ShapedTextFlags
  GetTextRunOrientFlagsForStyle(ComputedStyle* aComputedStyle);

  /**
   * Takes two rectangles whose origins must be the same, and computes
   * the difference between their union and their intersection as two
   * rectangles. (This difference is a superset of the difference
   * between the two rectangles.)
   */
  static void GetRectDifferenceStrips(const nsRect& aR1, const nsRect& aR2,
                                      nsRect* aHStrip, nsRect* aVStrip);

  /**
   * Get a device context that can be used to get up-to-date device
   * dimensions for the given window. For some reason, this is more
   * complicated than it ought to be in multi-monitor situations.
   */
  static nsDeviceContext*
  GetDeviceContextForScreenInfo(nsPIDOMWindowOuter* aWindow);

  /**
   * Some frames with 'position: fixed' (nsStyleDisplay::mPosition ==
   * NS_STYLE_POSITION_FIXED) are not really fixed positioned, since
   * they're inside an element with -moz-transform.  This function says
   * whether such an element is a real fixed-pos element.
   */
  static bool IsReallyFixedPos(const nsIFrame* aFrame);

  /**
   * This function says whether `aFrame` would really be a fixed positioned
   * frame if the frame was created with NS_STYLE_POSITION_FIXED.
   *
   * It is effectively the same as IsReallyFixedPos, but without asserting the
   * position value. Use it only when you know what you're doing, like when
   * tearing down the frame tree (where styles may have changed due to
   * ::first-line reparenting and rule changes at the same time).
   */
  static bool MayBeReallyFixedPos(const nsIFrame* aFrame);

  /**
   * Obtain a SourceSurface from the given DOM element, if possible.
   * This obtains the most natural surface from the element; that
   * is, the one that can be obtained with the fewest conversions.
   *
   * The flags below can modify the behaviour of this function.  The
   * result is returned as a SurfaceFromElementResult struct, also
   * defined below.
   *
   * Currently, this will do:
   *  - HTML Canvas elements: will return the underlying canvas surface
   *  - HTML Video elements: will return the current video frame
   *  - Image elements: will return the image
   *
   * The above results are modified by the below flags (copying,
   * forcing image surface, etc.).
   */

  enum {
    /* When creating a new surface, create an image surface */
    SFE_WANT_IMAGE_SURFACE = 1 << 0,
    /* Whether to extract the first frame (as opposed to the
       current frame) in the case that the element is an image. */
    SFE_WANT_FIRST_FRAME_IF_IMAGE = 1 << 1,
    /* Whether we should skip colorspace/gamma conversion */
    SFE_NO_COLORSPACE_CONVERSION = 1 << 2,
    /* Specifies that the caller wants either OPAQUE or NON_PREMULT mAlphaType,
       if this is can be done efficiently. */
    SFE_PREFER_NO_PREMULTIPLY_ALPHA = 1 << 3,
    /* Whether we should skip getting a surface for vector images and
       return a DirectDrawInfo containing an imgIContainer instead. */
    SFE_NO_RASTERIZING_VECTORS = 1 << 4,
    /* If image type is vector, the return surface size will same as
       element size, not image's intrinsic size. */
    SFE_USE_ELEMENT_SIZE_IF_VECTOR = 1 << 5
  };

  struct DirectDrawInfo {
    /* imgIContainer to directly draw to a context */
    nsCOMPtr<imgIContainer> mImgContainer;
    /* which frame to draw */
    uint32_t mWhichFrame;
    /* imgIContainer flags to use when drawing */
    uint32_t mDrawingFlags;
  };

  struct SurfaceFromElementResult {
    friend class mozilla::dom::CanvasRenderingContext2D;
    friend class nsLayoutUtils;

    /* If SFEResult contains a valid surface, it either mLayersImage or mSourceSurface
     * will be non-null, and GetSourceSurface() will not be null.
     *
     * For valid surfaces, mSourceSurface may be null if mLayersImage is non-null, but
     * GetSourceSurface() will create mSourceSurface from mLayersImage when called.
     */

    /* Video elements (at least) often are already decoded as layers::Images. */
    RefPtr<mozilla::layers::Image> mLayersImage;

protected:
    /* GetSourceSurface() fills this and returns its non-null value if this SFEResult
     * was successful. */
    RefPtr<mozilla::gfx::SourceSurface> mSourceSurface;

public:
    /* Contains info for drawing when there is no mSourceSurface. */
    DirectDrawInfo mDrawInfo;

    /* The size of the surface */
    mozilla::gfx::IntSize mSize;
    /* The principal associated with the element whose surface was returned.
       If there is a surface, this will never be null. */
    nsCOMPtr<nsIPrincipal> mPrincipal;
    /* The image request, if the element is an nsIImageLoadingContent */
    nsCOMPtr<imgIRequest> mImageRequest;
    /* Whether the element was "write only", that is, the bits should not be exposed to content */
    bool mIsWriteOnly;
    /* Whether the element was still loading.  Some consumers need to handle
       this case specially. */
    bool mIsStillLoading;
    /* Whether the element has a valid size. */
    bool mHasSize;
    /* Whether the element used CORS when loading. */
    bool mCORSUsed;

    gfxAlphaType mAlphaType;

    // Methods:

    SurfaceFromElementResult();

    // Gets mSourceSurface, or makes a SourceSurface from mLayersImage.
    const RefPtr<mozilla::gfx::SourceSurface>& GetSourceSurface();
  };

  // This function can be called on any thread.
  static SurfaceFromElementResult
  SurfaceFromOffscreenCanvas(mozilla::dom::OffscreenCanvas *aOffscreenCanvas,
                             uint32_t aSurfaceFlags,
                             RefPtr<DrawTarget>& aTarget);
  static SurfaceFromElementResult
  SurfaceFromOffscreenCanvas(mozilla::dom::OffscreenCanvas *aOffscreenCanvas,
                             uint32_t aSurfaceFlags = 0) {
    RefPtr<DrawTarget> target = nullptr;
    return SurfaceFromOffscreenCanvas(aOffscreenCanvas, aSurfaceFlags, target);
  }

  static SurfaceFromElementResult SurfaceFromElement(mozilla::dom::Element *aElement,
                                                     uint32_t aSurfaceFlags,
                                                     RefPtr<DrawTarget>& aTarget);
  static SurfaceFromElementResult SurfaceFromElement(mozilla::dom::Element *aElement,
                                                     uint32_t aSurfaceFlags = 0) {
    RefPtr<DrawTarget> target = nullptr;
    return SurfaceFromElement(aElement, aSurfaceFlags, target);
  }

  // There are a bunch of callers of SurfaceFromElement.  Just mark it as
  // MOZ_CAN_RUN_SCRIPT_BOUNDARY for now.
  MOZ_CAN_RUN_SCRIPT_BOUNDARY
  static SurfaceFromElementResult SurfaceFromElement(nsIImageLoadingContent *aElement,
                                                     uint32_t aSurfaceFlags,
                                                     RefPtr<DrawTarget>& aTarget);
  // Need an HTMLImageElement overload, because otherwise the
  // nsIImageLoadingContent and mozilla::dom::Element overloads are ambiguous
  // for HTMLImageElement.
  static SurfaceFromElementResult SurfaceFromElement(mozilla::dom::HTMLImageElement *aElement,
                                                     uint32_t aSurfaceFlags,
                                                     RefPtr<DrawTarget>& aTarget);
  static SurfaceFromElementResult SurfaceFromElement(mozilla::dom::HTMLCanvasElement *aElement,
                                                     uint32_t aSurfaceFlags,
                                                     RefPtr<DrawTarget>& aTarget);
  static SurfaceFromElementResult SurfaceFromElement(mozilla::dom::HTMLVideoElement *aElement,
                                                     uint32_t aSurfaceFlags,
                                                     RefPtr<DrawTarget>& aTarget);

  /**
   * When the document is editable by contenteditable attribute of its root
   * content or body content.
   *
   * Be aware, this returns nullptr if it's in designMode.
   *
   * For example:
   *
   *  <html contenteditable="true"><body></body></html>
   *    returns the <html>.
   *
   *  <html><body contenteditable="true"></body></html>
   *  <body contenteditable="true"></body>
   *    With these cases, this returns the <body>.
   *    NOTE: The latter case isn't created normally, however, it can be
   *          created by script with XHTML.
   *
   *  <body><p contenteditable="true"></p></body>
   *    returns nullptr because <body> isn't editable.
   */
  static mozilla::dom::Element*
  GetEditableRootContentByContentEditable(nsIDocument* aDocument);

  static void AddExtraBackgroundItems(nsDisplayListBuilder& aBuilder,
                                      nsDisplayList& aList,
                                      nsIFrame* aFrame,
                                      const nsRect& aCanvasArea,
                                      const nsRegion& aVisibleRegion,
                                      nscolor aBackstop);

  /**
   * Returns true if the passed in prescontext needs the dark grey background
   * that goes behind the page of a print preview presentation.
   */
  static bool NeedsPrintPreviewBackground(nsPresContext* aPresContext);

  typedef nsClassHashtable<nsPtrHashKey<gfxFontEntry>,
                           mozilla::dom::InspectorFontFace> UsedFontFaceTable;

  /**
   * Adds all font faces used in the frame tree starting from aFrame
   * to the list aFontFaceList.
   * aMaxRanges: maximum number of text ranges to record for each face.
   */
  static nsresult GetFontFacesForFrames(nsIFrame* aFrame,
                                        UsedFontFaceTable& aResult,
                                        uint32_t aMaxRanges);

  /**
   * Adds all font faces used within the specified range of text in aFrame,
   * and optionally its continuations, to the list in aFontFaceList.
   * Pass 0 and INT32_MAX for aStartOffset and aEndOffset to specify the
   * entire text is to be considered.
   * aMaxRanges: maximum number of text ranges to record for each face.
   */
  static void GetFontFacesForText(nsIFrame* aFrame,
                                  int32_t aStartOffset,
                                  int32_t aEndOffset,
                                  bool aFollowContinuations,
                                  UsedFontFaceTable& aResult,
                                  uint32_t aMaxRanges);

  /**
   * Walks the frame tree starting at aFrame looking for textRuns.
   * If |clear| is true, just clears the TEXT_RUN_MEMORY_ACCOUNTED flag
   * on each textRun found (and |aMallocSizeOf| is not used).
   * If |clear| is false, adds the storage used for each textRun to the
   * total, and sets the TEXT_RUN_MEMORY_ACCOUNTED flag to avoid double-
   * accounting. (Runs with this flag already set will be skipped.)
   * Expected usage pattern is therefore to call twice:
   *    (void)SizeOfTextRunsForFrames(rootFrame, nullptr, true);
   *    total = SizeOfTextRunsForFrames(rootFrame, mallocSizeOf, false);
   */
  static size_t SizeOfTextRunsForFrames(nsIFrame* aFrame,
                                        mozilla::MallocSizeOf aMallocSizeOf,
                                        bool clear);

  /**
   * Returns true if the frame has any current CSS transitions.
   * A current transition is any transition that has not yet finished playing
   * including paused transitions.
   */
  static bool HasCurrentTransitions(const nsIFrame* aFrame);

  /**
   * Returns true if |aFrame| has an animation of |aProperty| regardless of
   * whether the property is overridden by !important rule.
   */
  static bool HasAnimationOfProperty(const nsIFrame* aFrame,
                                     nsCSSPropertyID aProperty);

  /**
   * Returns true if |aEffectSet| has an animation of |aProperty| regardless of
   * whether the property is overridden by !important rule.
   */
  static bool HasAnimationOfProperty(mozilla::EffectSet* aEffectSet,
                                     nsCSSPropertyID aProperty);

  /**
   * Returns true if |aFrame| has an animation of |aProperty| which is
   * not overridden by !important rules.
   */
  static bool HasEffectiveAnimation(const nsIFrame* aFrame,
                                    nsCSSPropertyID aProperty);

  /**
   * Checks if off-main-thread animations are enabled.
   */
  static bool AreAsyncAnimationsEnabled();

  /**
   * Checks if we should warn about animations that can't be async
   */
  static bool IsAnimationLoggingEnabled();

  /**
   * Checks if retained display lists are enabled.
   */
  static bool AreRetainedDisplayListsEnabled();

  /**
   * Find a suitable scale for a element (aFrame's content) over the course of any
   * animations and transitions of the CSS transform property on the
   * element that run on the compositor thread.
   * It will check the maximum and minimum scale during the animations and
   * transitions and return a suitable value for performance and quality.
   * Will return scale(1,1) if there are no such animations.
   * Always returns a positive value.
   * @param aVisibleSize is the size of the area we want to paint
   * @param aDisplaySize is the size of the display area of the pres context
   */
  static Size ComputeSuitableScaleForAnimation(const nsIFrame* aFrame,
                                               const nsSize& aVisibleSize,
                                               const nsSize& aDisplaySize);

  /**
   * Checks whether we want to use the GPU to scale images when
   * possible.
   */
  static bool GPUImageScalingEnabled();

  /**
   * Checks whether we want to layerize animated images whenever possible.
   */
  static bool AnimatedImageLayersEnabled();

  /**
   * Checks if we should enable parsing for CSS Filters.
   */
  static bool CSSFiltersEnabled();

  /**
   * Checks whether support for the CSS-wide "unset" value is enabled.
   */
  static bool UnsetValueEnabled();

  /**
   * Checks whether support for inter-character ruby is enabled.
   */
  static bool IsInterCharacterRubyEnabled();

  /**
   * Checks whether content-select is enabled.
   */
  static bool IsContentSelectEnabled();

  static bool InterruptibleReflowEnabled()
  {
    return sInterruptibleReflowEnabled;
  }

  /**
   * Unions the overflow areas of the children of aFrame with aOverflowAreas.
   * aSkipChildLists specifies any child lists that should be skipped.
   * kSelectPopupList and kPopupList are always skipped.
   */
  static void UnionChildOverflow(nsIFrame* aFrame,
                                 nsOverflowAreas& aOverflowAreas,
                                 mozilla::layout::FrameChildListIDs aSkipChildLists =
                                     mozilla::layout::FrameChildListIDs());

  /**
   * Return the font size inflation *ratio* for a given frame.  This is
   * the factor by which font sizes should be inflated; it is never
   * smaller than 1.
   */
  static float FontSizeInflationFor(const nsIFrame *aFrame);

  /**
   * Perform the first half of the computation of FontSizeInflationFor
   * (see above).
   * This includes determining whether inflation should be performed
   * within this container and returning 0 if it should not be.
   *
   * The result is guaranteed not to vary between line participants
   * (inlines, text frames) within a line.
   *
   * The result should not be used directly since font sizes slightly
   * above the minimum should always be adjusted as done by
   * FontSizeInflationInner.
   */
  static nscoord InflationMinFontSizeFor(const nsIFrame *aFrame);

  /**
   * Perform the second half of the computation done by
   * FontSizeInflationFor (see above).
   *
   * aMinFontSize must be the result of one of the
   *   InflationMinFontSizeFor methods above.
   */
  static float FontSizeInflationInner(const nsIFrame *aFrame,
                                      nscoord aMinFontSize);

  static bool FontSizeInflationEnabled(nsPresContext *aPresContext);

  /**
   * See comment above "font.size.inflation.maxRatio" in
   * modules/libpref/src/init/all.js .
   */
  static uint32_t FontSizeInflationMaxRatio() {
    return sFontSizeInflationMaxRatio;
  }

  /**
   * See comment above "font.size.inflation.emPerLine" in
   * modules/libpref/src/init/all.js .
   */
  static uint32_t FontSizeInflationEmPerLine() {
    return sFontSizeInflationEmPerLine;
  }

  /**
   * See comment above "font.size.inflation.minTwips" in
   * modules/libpref/src/init/all.js .
   */
  static uint32_t FontSizeInflationMinTwips() {
    return sFontSizeInflationMinTwips;
  }

  /**
   * See comment above "font.size.inflation.lineThreshold" in
   * modules/libpref/src/init/all.js .
   */
  static uint32_t FontSizeInflationLineThreshold() {
    return sFontSizeInflationLineThreshold;
  }

  static bool FontSizeInflationForceEnabled() {
    return sFontSizeInflationForceEnabled;
  }

  static bool FontSizeInflationDisabledInMasterProcess() {
    return sFontSizeInflationDisabledInMasterProcess;
  }

  /**
   * See comment above "font.size.systemFontScale" in
   * modules/libpref/init/all.js.
   */
  static float SystemFontScale() {
    return sSystemFontScale / 100.0f;
  }

  static float MaxZoom() {
    return sZoomMaxPercent / 100.0f;
  }

  static float MinZoom() {
    return sZoomMinPercent / 100.0f;
  }

  static bool SVGTransformBoxEnabled() {
    return sSVGTransformBoxEnabled;
  }

  static bool TextCombineUprightDigitsEnabled() {
    return sTextCombineUprightDigitsEnabled;
  }

  static uint32_t IdlePeriodDeadlineLimit() {
    return sIdlePeriodDeadlineLimit;
  }

  static uint32_t QuiescentFramesBeforeIdlePeriod() {
    return sQuiescentFramesBeforeIdlePeriod;
  }

  /**
   * See comment above "font.size.inflation.mappingIntercept" in
   * modules/libpref/src/init/all.js .
   */
  static int32_t FontSizeInflationMappingIntercept() {
    return sFontSizeInflationMappingIntercept;
  }

  /**
   * Returns true if the nglayout.debug.invalidation pref is set to true.
   * Note that sInvalidationDebuggingIsEnabled is declared outside this function to
   * allow it to be accessed an manipulated from breakpoint conditions.
   */
  static bool InvalidationDebuggingIsEnabled() {
    return sInvalidationDebuggingIsEnabled || getenv("MOZ_DUMP_INVALIDATION") != 0;
  }

  static void Initialize();
  static void Shutdown();

  /**
   * Register an imgIRequest object with a refresh driver.
   *
   * @param aPresContext The nsPresContext whose refresh driver we want to
   *        register with.
   * @param aRequest A pointer to the imgIRequest object which the client wants
   *        to register with the refresh driver.
   * @param aRequestRegistered A pointer to a boolean value which indicates
   *        whether the given image request is registered. If
   *        *aRequestRegistered is true, then this request will not be
   *        registered again. If the request is registered by this function,
   *        then *aRequestRegistered will be set to true upon the completion of
   *        this function.
   *
   */
  static void RegisterImageRequest(nsPresContext* aPresContext,
                                   imgIRequest* aRequest,
                                   bool* aRequestRegistered);

  /**
   * Register an imgIRequest object with a refresh driver, but only if the
   * request is for an image that is animated.
   *
   * @param aPresContext The nsPresContext whose refresh driver we want to
   *        register with.
   * @param aRequest A pointer to the imgIRequest object which the client wants
   *        to register with the refresh driver.
   * @param aRequestRegistered A pointer to a boolean value which indicates
   *        whether the given image request is registered. If
   *        *aRequestRegistered is true, then this request will not be
   *        registered again. If the request is registered by this function,
   *        then *aRequestRegistered will be set to true upon the completion of
   *        this function.
   *
   */
  static void RegisterImageRequestIfAnimated(nsPresContext* aPresContext,
                                             imgIRequest* aRequest,
                                             bool* aRequestRegistered);

  /**
   * Deregister an imgIRequest object from a refresh driver.
   *
   * @param aPresContext The nsPresContext whose refresh driver we want to
   *        deregister from.
   * @param aRequest A pointer to the imgIRequest object with which the client
   *        previously registered and now wants to deregister from the refresh
   *        driver.
   * @param aRequestRegistered A pointer to a boolean value which indicates
   *        whether the given image request is registered. If
   *        *aRequestRegistered is false, then this request will not be
   *        deregistered. If the request is deregistered by this function,
   *        then *aRequestRegistered will be set to false upon the completion of
   *        this function.
   */
  static void DeregisterImageRequest(nsPresContext* aPresContext,
                                     imgIRequest* aRequest,
                                     bool* aRequestRegistered);

  /**
   * Shim to nsCSSFrameConstructor::PostRestyleEvent. Exists so that we
   * can avoid including nsCSSFrameConstructor.h and all its dependencies
   * in content files.
   */
  static void PostRestyleEvent(mozilla::dom::Element* aElement,
                               nsRestyleHint aRestyleHint,
                               nsChangeHint aMinChangeHint);

  /**
   * Updates a pair of x and y distances if a given point is closer to a given
   * rectangle than the original distance values.  If aPoint is closer to
   * aRect than aClosestXDistance and aClosestYDistance indicate, then those
   * two variables are updated with the distance between aPoint and aRect,
   * and true is returned.  If aPoint is not closer, then aClosestXDistance
   * and aClosestYDistance are left unchanged, and false is returned.
   *
   * Distances are measured in the two dimensions separately; a closer x
   * distance beats a closer y distance.
   */
  template<typename PointType, typename RectType, typename CoordType>
  static bool PointIsCloserToRect(PointType aPoint, const RectType& aRect,
                                  CoordType& aClosestXDistance,
                                  CoordType& aClosestYDistance);
  /**
   * Computes the box shadow rect for the frame, or returns an empty rect if
   * there are no shadows.
   *
   * @param aFrame Frame to compute shadows for.
   * @param aFrameSize Size of aFrame (in case it hasn't been set yet).
   */
  static nsRect GetBoxShadowRectForFrame(nsIFrame* aFrame, const nsSize& aFrameSize);

#ifdef DEBUG
  /**
   * Assert that there are no duplicate continuations of the same frame
   * within aFrameList.  Optimize the tests by assuming that all frames
   * in aFrameList have parent aContainer.
   */
  static void
  AssertNoDuplicateContinuations(nsIFrame* aContainer,
                                 const nsFrameList& aFrameList);

  /**
   * Assert that the frame tree rooted at |aSubtreeRoot| is empty, i.e.,
   * that it contains no first-in-flows.
   */
  static void
  AssertTreeOnlyEmptyNextInFlows(nsIFrame *aSubtreeRoot);
#endif

  /**
   * Helper method to get touch action behaviour from the frame
   */
  static uint32_t
  GetTouchActionFromFrame(nsIFrame* aFrame);

  /**
   * Helper method to transform |aBounds| from aFrame to aAncestorFrame,
   * and combine it with |aPreciseTargetDest| if it is axis-aligned, or
   * combine it with |aImpreciseTargetDest| if not. The transformed rect is
   * clipped to |aClip|; if |aClip| has rounded corners, that also causes
   * the imprecise target to be used.
   */
  static void
  TransformToAncestorAndCombineRegions(
    const nsRegion& aRegion,
    nsIFrame* aFrame,
    const nsIFrame* aAncestorFrame,
    nsRegion* aPreciseTargetDest,
    nsRegion* aImpreciseTargetDest,
    mozilla::Maybe<Matrix4x4Flagged>* aMatrixCache,
    const mozilla::DisplayItemClip* aClip);

  /**
   * Populate aOutSize with the size of the content viewer corresponding
   * to the given prescontext. Return true if the size was set, false
   * otherwise.
   */
  static bool
  GetContentViewerSize(nsPresContext* aPresContext,
                       LayoutDeviceIntSize& aOutSize);

 /**
  * Calculate the compostion size for a frame. See FrameMetrics.h for
  * defintion of composition size (or bounds).
  * Note that for the root content document's root scroll frame (RCD-RSF),
  * the returned size does not change as the document's resolution changes,
  * but for all other frames it does. This means that callers that pass in
  * a frame that may or may not be the RCD-RSF (which is most callers),
  * are likely to need special-case handling of the RCD-RSF.
  */
  static nsSize
  CalculateCompositionSizeForFrame(nsIFrame* aFrame, bool aSubtractScrollbars = true);

 /**
  * Calculate the composition size for the root scroll frame of the root
  * content document.
  * @param aFrame A frame in the root content document (or a descendant of it).
  * @param aIsRootContentDocRootScrollFrame Whether aFrame is already the root
  *          scroll frame of the root content document. In this case we just
  *          use aFrame's own composition size.
  * @param aMetrics A partially populated FrameMetrics for aFrame. Must have at
  *          least mCompositionBounds, mCumulativeResolution, and
  *          mDevPixelsPerCSSPixel set.
  */
  static CSSSize
  CalculateRootCompositionSize(nsIFrame* aFrame,
                               bool aIsRootContentDocRootScrollFrame,
                               const FrameMetrics& aMetrics);

 /**
  * Calculate the scrollable rect for a frame. See FrameMetrics.h for
  * defintion of scrollable rect. aScrollableFrame is the scroll frame to calculate
  * the scrollable rect for. If it's null then we calculate the scrollable rect
  * as the rect of the root frame.
  */
  static nsRect
  CalculateScrollableRectForFrame(nsIScrollableFrame* aScrollableFrame, nsIFrame* aRootFrame);

 /**
  * Calculate the expanded scrollable rect for a frame. See FrameMetrics.h for
  * defintion of expanded scrollable rect.
  */
  static nsRect
  CalculateExpandedScrollableRect(nsIFrame* aFrame);

  /**
   * Returns true if the widget owning the given frame uses asynchronous
   * scrolling.
   */
  static bool UsesAsyncScrolling(nsIFrame* aFrame);

  /**
   * Returns true if the widget owning the given frame has builtin APZ support
   * enabled.
   */
  static bool AsyncPanZoomEnabled(nsIFrame* aFrame);

  /**
   * Returns the current APZ Resolution Scale. When Java Pan/Zoom is
   * enabled in Fennec it will always return 1.0.
   */
  static float GetCurrentAPZResolutionScale(nsIPresShell* aShell);

  /**
   * Returns true if we need to disable async scrolling for this particular
   * element. Note that this does a partial disabling - the displayport still
   * exists but uses a very small margin, and the compositor doesn't apply the
   * async transform. However, the content may still be layerized.
   */
  static bool ShouldDisableApzForElement(nsIContent* aContent);

  /**
   * Log a key/value pair for APZ testing during a paint.
   * @param aManager   The data will be written to the APZTestData associated
   *                   with this layer manager.
   * @param aScrollId Identifies the scroll frame to which the data pertains.
   * @param aKey The key under which to log the data.
   * @param aValue The value of the data to be logged.
   */
  static void LogTestDataForPaint(mozilla::layers::LayerManager* aManager,
                                  ViewID aScrollId,
                                  const std::string& aKey,
                                  const std::string& aValue) {
    DoLogTestDataForPaint(aManager, aScrollId, aKey, aValue);
  }

  /**
   * A convenience overload of LogTestDataForPaint() that accepts any type
   * as the value, and passes it through mozilla::ToString() to obtain a string
   * value. The type passed must support streaming to an std::ostream.
   */
  template <typename Value>
  static void LogTestDataForPaint(mozilla::layers::LayerManager* aManager,
                                  ViewID aScrollId,
                                  const std::string& aKey,
                                  const Value& aValue) {
    DoLogTestDataForPaint(aManager, aScrollId, aKey,
                          mozilla::ToString(aValue));
  }

  /**
   * Calculate a basic FrameMetrics with enough fields set to perform some
   * layout calculations. The fields set are dev-to-css ratio, pres shell
   * resolution, cumulative resolution, zoom, composition size, root
   * composition size, scroll offset and scrollable rect.
   *
   * By contrast, ComputeFrameMetrics() computes all the fields, but requires
   * extra inputs and can only be called during frame layer building.
   */
  static FrameMetrics CalculateBasicFrameMetrics(nsIScrollableFrame* aScrollFrame);

  /**
   * Calculate a default set of displayport margins for the given scrollframe
   * and set them on the scrollframe's content element. The margins are set with
   * the default priority, which may clobber previously set margins. The repaint
   * mode provided is passed through to the call to SetDisplayPortMargins.
   * The |aScrollFrame| parameter must be non-null and queryable to an nsIFrame.
   * @return true iff the call to SetDisplayPortMargins returned true.
   */
  static bool CalculateAndSetDisplayPortMargins(nsIScrollableFrame* aScrollFrame,
                                                RepaintMode aRepaintMode);

  /**
   * If |aScrollFrame| WantsAsyncScroll() and we don't have a scrollable
   * displayport yet (as tracked by |aBuilder|), calculate and set a
   * displayport.
   *
   * If this is called during display list building pass DoNotRepaint in
   * aRepaintMode.
   *
   * Returns true if there is a displayport on an async scrollable scrollframe
   * after this call, either because one was just added or it already existed.
   */
  static bool MaybeCreateDisplayPort(nsDisplayListBuilder& aBuilder,
                                     nsIFrame* aScrollFrame,
                                     RepaintMode aRepaintMode);

  static nsIScrollableFrame* GetAsyncScrollableAncestorFrame(nsIFrame* aTarget);

  /**
   * Sets a zero margin display port on all proper ancestors of aFrame that
   * are async scrollable.
   */
  static void SetZeroMarginDisplayPortOnAsyncScrollableAncestors(nsIFrame* aFrame,
                                                                 RepaintMode aRepaintMode);
  /**
   * Finds the closest ancestor async scrollable frame from aFrame that has a
   * displayport and attempts to trigger the displayport expiry on that
   * ancestor.
   */
  static void ExpireDisplayPortOnAsyncScrollableAncestor(nsIFrame* aFrame);

  static bool IsOutlineStyleAutoEnabled();

  static void SetBSizeFromFontMetrics(const nsIFrame* aFrame,
                                      mozilla::ReflowOutput& aMetrics,
                                      const mozilla::LogicalMargin& aFramePadding,
                                      mozilla::WritingMode aLineWM,
                                      mozilla::WritingMode aFrameWM);

  static bool HasDocumentLevelListenersForApzAwareEvents(nsIPresShell* aShell);

  /**
   * Set the scroll port size for the purpose of clamping the scroll position
   * for the root scroll frame of this document
   * (see nsIDOMWindowUtils.setScrollPositionClampingScrollPortSize).
   */
  static void SetScrollPositionClampingScrollPortSize(nsIPresShell* aPresShell,
                                                      CSSSize aSize);

  /**
   * Returns true if the given scroll origin is "higher priority" than APZ.
   * In general any content programmatic scrolls (e.g. scrollTo calls) are
   * higher priority, and take precedence over APZ scrolling. This function
   * returns true for those, and returns false for other origins like APZ
   * itself, or scroll position updates from the history restore code.
   */
  static bool CanScrollOriginClobberApz(nsAtom* aScrollOrigin);

  static ScrollMetadata ComputeScrollMetadata(nsIFrame* aForFrame,
                                              nsIFrame* aScrollFrame,
                                              nsIContent* aContent,
                                              const nsIFrame* aReferenceFrame,
                                              mozilla::layers::LayerManager* aLayerManager,
                                              ViewID aScrollParentId,
                                              const nsRect& aViewport,
                                              const mozilla::Maybe<nsRect>& aClipRect,
                                              bool aIsRoot,
                                              const ContainerLayerParameters& aContainerParameters);

  /**
   * Returns the metadata to put onto the root layer of a layer tree, if one is
   * needed. The last argument is a callback function to check if the caller
   * already has a metadata for a given scroll id.
   */
  static mozilla::Maybe<ScrollMetadata> GetRootMetadata(nsDisplayListBuilder* aBuilder,
                                                        mozilla::layers::LayerManager* aLayerManager,
                                                        const ContainerLayerParameters& aContainerParameters,
                                                        const std::function<bool(ViewID& aScrollId)>& aCallback);

  /**
   * If the given scroll frame needs an area excluded from its composition
   * bounds due to scrollbars, return that area, otherwise return an empty
   * margin.
   * There is no need to exclude scrollbars in the following cases:
   *   - If the scroll frame is not the RCD-RSF; in that case, the composition
   *     bounds is calculated based on the scroll port which already excludes
   *     the scrollbar area.
   *   - If the scrollbars are overlay, since then they are drawn on top of the
   *     scrollable content.
   */
  static nsMargin ScrollbarAreaToExcludeFromCompositionBoundsFor(nsIFrame* aScrollFrame);

  /**
   * Looks in the layer subtree rooted at aLayer for a metrics with scroll id
   * aScrollId. Returns true if such is found.
   */
  static bool ContainsMetricsWithId(const Layer* aLayer, const ViewID& aScrollId);

  static bool ShouldUseNoScriptSheet(nsIDocument* aDocument);
  static bool ShouldUseNoFramesSheet(nsIDocument* aDocument);

  /**
   * Get the text content inside the frame. This methods traverse the
   * frame tree and collect the content from text frames. Note that this
   * method is similiar to nsContentUtils::GetNodeTextContent, but it at
   * least differs from that method in the following things:
   * 1. it skips text content inside nodes like style, script, textarea
   *    which don't generate an in-tree text frame for the text;
   * 2. it skips elements with display property set to none;
   * 3. it skips out-of-flow elements;
   * 4. it includes content inside pseudo elements;
   * 5. it may include part of text content of a node if a text frame
   *    inside is split to different continuations.
   */
  static void GetFrameTextContent(nsIFrame* aFrame, nsAString& aResult);

  /**
   * Same as GetFrameTextContent but appends the result rather than sets it.
   */
  static void AppendFrameTextContent(nsIFrame* aFrame, nsAString& aResult);

  /**
   * Takes a selection, and returns selection's bounding rect which is relative
   * to its root frame.
   *
   * @param aSel      Selection to check
   */
  static nsRect GetSelectionBoundingRect(mozilla::dom::Selection* aSel);

  /**
   * Calculate the bounding rect of |aContent|, relative to the origin
   * of the scrolled content of |aRootScrollFrame|.
   * Where the element is contained inside a scrollable subframe, the
   * bounding rect is clipped to the bounds of the subframe.
   */
  static CSSRect GetBoundingContentRect(const nsIContent* aContent,
                                        const nsIScrollableFrame* aRootScrollFrame);

  /**
   * Returns the first ancestor who is a float containing block.
   */
  static nsBlockFrame* GetFloatContainingBlock(nsIFrame* aFrame);

  /**
   * Walks up the frame tree from |aForFrame| up to |aTopFrame|, or to the
   * root of the frame tree if |aTopFrame| is nullptr, and returns true if
   * a transformed frame is encountered.
   */
  static bool IsTransformed(nsIFrame* aForFrame, nsIFrame* aTopFrame = nullptr);

  /**
   * Walk up from aFrame to the cross-doc root, accumulating all the APZ callback
   * transforms on the content elements encountered along the way. Return the
   * accumulated value.
   * XXX: Note that this does not take into account CSS transforms, nor
   * differences in structure between the frame tree and the layer tree (which
   * is probably what we *want* to be computing).
   */
  static CSSPoint GetCumulativeApzCallbackTransform(nsIFrame* aFrame);

  /**
   * Compute a rect to pre-render in cases where we want to render more of
   * something than what is visible (usually to support async transformation).
   * @param aDirtyRect the area that's visible
   * @param aOverflow the total size of the thing we're rendering
   * @param aPrerenderSize how large of an area we're willing to render
   * @return A rectangle that includes |aDirtyRect|, is clamped to |aOverflow|,
   *         and is no larger than |aPrerenderSize| (unless |aPrerenderSize|
   *         is smaller than |aDirtyRect|, in which case the returned rect
   *         will still include |aDirtyRect| and thus be larger than
   *         |aPrerenderSize|).
   */
  static nsRect ComputePartialPrerenderArea(const nsRect& aDirtyRect,
                                            const nsRect& aOverflow,
                                            const nsSize& aPrerenderSize);

  /*
   * Checks whether a node is an invisible break.
   * If not, returns the first frame on the next line if such a next line exists.
   *
   * @return  true if the node is an invisible break.
   *          aNextLineFrame is returned null in this case.
   *          false if the node causes a visible break or if the node is no break.
   *
   * @param   aNextLineFrame  assigned to first frame on the next line if such a
   *                          next line exists, null otherwise.
   */
  static bool IsInvisibleBreak(nsINode* aNode, nsIFrame** aNextLineFrame = nullptr);

  static nsRect ComputeGeometryBox(nsIFrame* aFrame,
                                   StyleGeometryBox aGeometryBox);

  static nsPoint ComputeOffsetToUserSpace(nsDisplayListBuilder* aBuilder,
                                          nsIFrame* aFrame);

  // Return the default value to be used for -moz-control-character-visibility,
  // from preferences.
  static uint8_t ControlCharVisibilityDefault();

  enum class FlushUserFontSet {
    Yes,
    No,
  };

  static already_AddRefed<nsFontMetrics> GetMetricsFor(nsPresContext* aPresContext,
                                                       bool aIsVertical,
                                                       const nsStyleFont* aStyleFont,
                                                       nscoord aFontSize,
                                                       bool aUseUserFontSet,
                                                       FlushUserFontSet aFlushUserFontSet);

  /**
   * Appropriately add the correct font if we are using DocumentFonts or
   * overriding for XUL
   */
  static void FixupNoneGeneric(nsFont* aFont,
                               const nsPresContext* aPresContext,
                               uint8_t aGenericFontID,
                               const nsFont* aDefaultVariableFont);

  /**
   * For an nsStyleFont with mSize set, apply minimum font size constraints
   * from preferences, as well as -moz-min-font-size-ratio.
   */
  static void ApplyMinFontSize(nsStyleFont* aFont,
                               const nsPresContext* aPresContext,
                               nscoord aMinFontSize);

  static void ComputeSystemFont(nsFont* aSystemFont,
                                mozilla::LookAndFeel::FontID aFontID,
                                const nsPresContext* aPresContext,
                                const nsFont* aDefaultVariableFont);

  static void ComputeFontFeatures(const nsCSSValuePairList* aFeaturesList,
                                  nsTArray<gfxFontFeature>& aFeatureSettings);

  static void ComputeFontVariations(const nsCSSValuePairList* aVariationsList,
                                    nsTArray<gfxFontVariation>& aVariationSettings);

  static uint32_t ParseFontLanguageOverride(const nsAString& aLangTag);

  /**
   * Resolve a CSS <length-percentage> value to a definite size.
   */
  template<bool clampNegativeResultToZero>
  static nscoord ResolveToLength(const nsStyleCoord& aCoord,
                                 nscoord aPercentageBasis)
  {
    NS_WARNING_ASSERTION(aPercentageBasis >= nscoord(0), "nscoord overflow?");

    switch (aCoord.GetUnit()) {
      case eStyleUnit_Coord:
        MOZ_ASSERT(!clampNegativeResultToZero || aCoord.GetCoordValue() >= 0,
                   "This value should have been rejected by the style system");
        return aCoord.GetCoordValue();
      case eStyleUnit_Percent:
        if (aPercentageBasis == NS_UNCONSTRAINEDSIZE) {
          return nscoord(0);
        }
        MOZ_ASSERT(!clampNegativeResultToZero || aCoord.GetPercentValue() >= 0,
                   "This value should have been rejected by the style system");
        return NSToCoordFloorClamped(aPercentageBasis *
                                     aCoord.GetPercentValue());
      case eStyleUnit_Calc: {
        nsStyleCoord::Calc* calc = aCoord.GetCalcValue();
        nscoord result;
        if (aPercentageBasis == NS_UNCONSTRAINEDSIZE) {
          result = calc->mLength;
        } else {
          result = calc->mLength +
            NSToCoordFloorClamped(aPercentageBasis * calc->mPercent);
        }
        if (clampNegativeResultToZero && result < 0) {
          return nscoord(0);
        }
        return result;
      }
      default:
        MOZ_ASSERT_UNREACHABLE("Unexpected unit!");
        return nscoord(0);
    }
  }

  /**
   * Resolve a column-gap/row-gap to a definite size.
   * @note This method resolves 'normal' to zero.
   *   Callers who want different behavior should handle 'normal' on their own.
   */
  static nscoord ResolveGapToLength(const nsStyleCoord& aGap,
                                    nscoord aPercentageBasis)
  {
    if (aGap.GetUnit() == eStyleUnit_Normal) {
      return nscoord(0);
    }
    return ResolveToLength<true>(aGap, aPercentageBasis);
  }

private:
  static uint32_t sFontSizeInflationEmPerLine;
  static uint32_t sFontSizeInflationMinTwips;
  static uint32_t sFontSizeInflationLineThreshold;
  static int32_t  sFontSizeInflationMappingIntercept;
  static uint32_t sFontSizeInflationMaxRatio;
  static bool sFontSizeInflationForceEnabled;
  static bool sFontSizeInflationDisabledInMasterProcess;
  static uint32_t sSystemFontScale;
  static uint32_t sZoomMaxPercent;
  static uint32_t sZoomMinPercent;
  static bool sInvalidationDebuggingIsEnabled;
  static bool sInterruptibleReflowEnabled;
  static bool sSVGTransformBoxEnabled;
  static bool sTextCombineUprightDigitsEnabled;
  static uint32_t sIdlePeriodDeadlineLimit;
  static uint32_t sQuiescentFramesBeforeIdlePeriod;

  /**
   * Helper function for LogTestDataForPaint().
   */
  static void DoLogTestDataForPaint(mozilla::layers::LayerManager* aManager,
                                    ViewID aScrollId,
                                    const std::string& aKey,
                                    const std::string& aValue);

  static bool IsAPZTestLoggingEnabled();
};

MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(nsLayoutUtils::PaintFrameFlags)

template<typename PointType, typename RectType, typename CoordType>
/* static */ bool
nsLayoutUtils::PointIsCloserToRect(PointType aPoint, const RectType& aRect,
                                   CoordType& aClosestXDistance,
                                   CoordType& aClosestYDistance)
{
  CoordType fromLeft = aPoint.x - aRect.x;
  CoordType fromRight = aPoint.x - aRect.XMost();

  CoordType xDistance;
  if (fromLeft >= 0 && fromRight <= 0) {
    xDistance = 0;
  } else {
    xDistance = std::min(abs(fromLeft), abs(fromRight));
  }

  if (xDistance <= aClosestXDistance) {
    if (xDistance < aClosestXDistance) {
      aClosestYDistance = std::numeric_limits<CoordType>::max();
    }

    CoordType fromTop = aPoint.y - aRect.y;
    CoordType fromBottom = aPoint.y - aRect.YMost();

    CoordType yDistance;
    if (fromTop >= 0 && fromBottom <= 0) {
      yDistance = 0;
    } else {
      yDistance = std::min(abs(fromTop), abs(fromBottom));
    }

    if (yDistance < aClosestYDistance) {
      aClosestXDistance = xDistance;
      aClosestYDistance = yDistance;
      return true;
    }
  }

  return false;
}

namespace mozilla {

/**
 * Converts an nsPoint in app units to a Moz2D Point in pixels (whether those
 * are device pixels or CSS px depends on what the caller chooses to pass as
 * aAppUnitsPerPixel).
 */
inline gfx::Point NSPointToPoint(const nsPoint& aPoint,
                                 int32_t aAppUnitsPerPixel) {
  return gfx::Point(gfx::Float(aPoint.x) / aAppUnitsPerPixel,
                    gfx::Float(aPoint.y) / aAppUnitsPerPixel);
}

/**
 * Converts an nsRect in app units to a Moz2D Rect in pixels (whether those
 * are device pixels or CSS px depends on what the caller chooses to pass as
 * aAppUnitsPerPixel).
 */
gfx::Rect NSRectToRect(const nsRect& aRect, double aAppUnitsPerPixel);

/**
 * Converts an nsRect in app units to a Moz2D Rect in pixels (whether those
 * are device pixels or CSS px depends on what the caller chooses to pass as
 * aAppUnitsPerPixel).
 *
 * The passed DrawTarget is used to additionally snap the returned Rect to
 * device pixels, if appropriate (as decided and carried out by Moz2D's
 * MaybeSnapToDevicePixels helper, which this function calls to do any
 * snapping).
 */
gfx::Rect NSRectToSnappedRect(const nsRect& aRect, double aAppUnitsPerPixel,
                              const gfx::DrawTarget& aSnapDT);

/**
* Converts, where possible, an nsRect in app units to a Moz2D Rect in pixels
* (whether those are device pixels or CSS px depends on what the caller
*  chooses to pass as aAppUnitsPerPixel).
*
* If snapping results in a rectangle with zero width or height, the affected
* coordinates are left unsnapped
*/
gfx::Rect NSRectToNonEmptySnappedRect(const nsRect& aRect, double aAppUnitsPerPixel,
                                      const gfx::DrawTarget& aSnapDT);

void StrokeLineWithSnapping(const nsPoint& aP1, const nsPoint& aP2,
                            int32_t aAppUnitsPerDevPixel,
                            gfx::DrawTarget& aDrawTarget,
                            const gfx::Pattern& aPattern,
                            const gfx::StrokeOptions& aStrokeOptions = gfx::StrokeOptions(),
                            const gfx::DrawOptions& aDrawOptions = gfx::DrawOptions());

  namespace layout {

    /**
     * An RAII class which will, for the duration of its lifetime,
     * **if** the frame given is a container for font size inflation,
     * set the current inflation container on the pres context to null
     * (and then, in its destructor, restore the old value).
     */
    class AutoMaybeDisableFontInflation {
    public:
      explicit AutoMaybeDisableFontInflation(nsIFrame *aFrame);

      ~AutoMaybeDisableFontInflation();
    private:
      nsPresContext *mPresContext;
      bool mOldValue;
    };

    void MaybeSetupTransactionIdAllocator(layers::LayerManager* aManager,
                                          nsPresContext* aPresContext);

  } // namespace layout
} // namespace mozilla

class nsSetAttrRunnable : public mozilla::Runnable
{
public:
  nsSetAttrRunnable(mozilla::dom::Element* aElement, nsAtom* aAttrName,
                    const nsAString& aValue);
  nsSetAttrRunnable(mozilla::dom::Element* aElement, nsAtom* aAttrName,
                    int32_t aValue);

  NS_DECL_NSIRUNNABLE

  RefPtr<Element> mElement;
  RefPtr<nsAtom> mAttrName;
  nsAutoString mValue;
};

class nsUnsetAttrRunnable : public mozilla::Runnable
{
public:
  nsUnsetAttrRunnable(mozilla::dom::Element* aElement, nsAtom* aAttrName);

  NS_DECL_NSIRUNNABLE

  RefPtr<Element> mElement;
  RefPtr<nsAtom> mAttrName;
};

// This class allows you to easily set any pointer variable and ensure it's
// set to nullptr when leaving its scope.
template<typename T>
class MOZ_RAII SetAndNullOnExit
{
public:
  SetAndNullOnExit(T* &aVariable, T* aValue) {
    aVariable = aValue;
    mVariable = &aVariable;
  }
  ~SetAndNullOnExit() {
    *mVariable = nullptr;
  }
private:
  T** mVariable;
};

#endif // nsLayoutUtils_h__