Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 4982 insertions, 0 deletions

diff --git a/layout/painting/nsCSSRendering.cpp b/layout/painting/nsCSSRendering.cpp
new file mode 100644
index 0000000000..0662b54b30
--- /dev/null
+++ b/layout/painting/nsCSSRendering.cpp
@@ -0,0 +1,4982 @@
+/* -*- 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/. */
+
+/* utility functions for drawing borders and backgrounds */
+
+#include "nsCSSRendering.h"
+
+#include <ctime>
+
+#include "gfx2DGlue.h"
+#include "gfxContext.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/ComputedStyle.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/StaticPrefs_layout.h"
+#include "mozilla/gfx/2D.h"
+#include "mozilla/gfx/Helpers.h"
+#include "mozilla/gfx/Logging.h"
+#include "mozilla/gfx/PathHelpers.h"
+#include "mozilla/HashFunctions.h"
+#include "mozilla/MathAlgorithms.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/SVGImageContext.h"
+#include "gfxFont.h"
+#include "ScaledFontBase.h"
+#include "skia/include/core/SkTextBlob.h"
+
+#include "BorderConsts.h"
+#include "nsCanvasFrame.h"
+#include "nsStyleConsts.h"
+#include "nsPresContext.h"
+#include "nsIFrame.h"
+#include "nsIFrameInlines.h"
+#include "nsPageSequenceFrame.h"
+#include "nsPoint.h"
+#include "nsRect.h"
+#include "nsFrameManager.h"
+#include "nsGkAtoms.h"
+#include "nsCSSAnonBoxes.h"
+#include "nsIContent.h"
+#include "mozilla/dom/DocumentInlines.h"
+#include "nsIScrollableFrame.h"
+#include "imgIContainer.h"
+#include "ImageOps.h"
+#include "nsCSSColorUtils.h"
+#include "nsITheme.h"
+#include "nsLayoutUtils.h"
+#include "nsBlockFrame.h"
+#include "nsStyleStructInlines.h"
+#include "nsCSSFrameConstructor.h"
+#include "nsCSSProps.h"
+#include "nsContentUtils.h"
+#include "gfxDrawable.h"
+#include "nsCSSRenderingBorders.h"
+#include "mozilla/css/ImageLoader.h"
+#include "ImageContainer.h"
+#include "mozilla/ProfilerLabels.h"
+#include "mozilla/StaticPrefs_layout.h"
+#include "mozilla/Telemetry.h"
+#include "gfxUtils.h"
+#include "gfxGradientCache.h"
+#include "nsInlineFrame.h"
+#include "nsRubyTextContainerFrame.h"
+#include <algorithm>
+#include "TextDrawTarget.h"
+
+using namespace mozilla;
+using namespace mozilla::css;
+using namespace mozilla::gfx;
+using namespace mozilla::image;
+using mozilla::CSSSizeOrRatio;
+using mozilla::dom::Document;
+
+static int gFrameTreeLockCount = 0;
+
+// To avoid storing this data on nsInlineFrame (bloat) and to avoid
+// recalculating this for each frame in a continuation (perf), hold
+// a cache of various coordinate information that we need in order
+// to paint inline backgrounds.
+struct InlineBackgroundData {
+  InlineBackgroundData()
+      : mFrame(nullptr),
+        mLineContainer(nullptr),
+        mContinuationPoint(0),
+        mUnbrokenMeasure(0),
+        mLineContinuationPoint(0),
+        mPIStartBorderData{},
+        mBidiEnabled(false),
+        mVertical(false) {}
+
+  ~InlineBackgroundData() = default;
+
+  void Reset() {
+    mBoundingBox.SetRect(0, 0, 0, 0);
+    mContinuationPoint = mLineContinuationPoint = mUnbrokenMeasure = 0;
+    mFrame = mLineContainer = nullptr;
+    mPIStartBorderData.Reset();
+  }
+
+  /**
+   * Return a continuous rect for (an inline) aFrame relative to the
+   * continuation that draws the left-most part of the background.
+   * This is used when painting backgrounds.
+   */
+  nsRect GetContinuousRect(nsIFrame* aFrame) {
+    MOZ_ASSERT(static_cast<nsInlineFrame*>(do_QueryFrame(aFrame)));
+
+    SetFrame(aFrame);
+
+    nscoord pos;  // an x coordinate if writing-mode is horizontal;
+                  // y coordinate if vertical
+    if (mBidiEnabled) {
+      pos = mLineContinuationPoint;
+
+      // Scan continuations on the same line as aFrame and accumulate the widths
+      // of frames that are to the left (if this is an LTR block) or right
+      // (if it's RTL) of the current one.
+      bool isRtlBlock = (mLineContainer->StyleVisibility()->mDirection ==
+                         StyleDirection::Rtl);
+      nscoord curOffset = mVertical ? aFrame->GetOffsetTo(mLineContainer).y
+                                    : aFrame->GetOffsetTo(mLineContainer).x;
+
+      // If the continuation is fluid we know inlineFrame is not on the same
+      // line. If it's not fluid, we need to test further to be sure.
+      nsIFrame* inlineFrame = aFrame->GetPrevContinuation();
+      while (inlineFrame && !inlineFrame->GetNextInFlow() &&
+             AreOnSameLine(aFrame, inlineFrame)) {
+        nscoord frameOffset = mVertical
+                                  ? inlineFrame->GetOffsetTo(mLineContainer).y
+                                  : inlineFrame->GetOffsetTo(mLineContainer).x;
+        if (isRtlBlock == (frameOffset >= curOffset)) {
+          pos += mVertical ? inlineFrame->GetSize().height
+                           : inlineFrame->GetSize().width;
+        }
+        inlineFrame = inlineFrame->GetPrevContinuation();
+      }
+
+      inlineFrame = aFrame->GetNextContinuation();
+      while (inlineFrame && !inlineFrame->GetPrevInFlow() &&
+             AreOnSameLine(aFrame, inlineFrame)) {
+        nscoord frameOffset = mVertical
+                                  ? inlineFrame->GetOffsetTo(mLineContainer).y
+                                  : inlineFrame->GetOffsetTo(mLineContainer).x;
+        if (isRtlBlock == (frameOffset >= curOffset)) {
+          pos += mVertical ? inlineFrame->GetSize().height
+                           : inlineFrame->GetSize().width;
+        }
+        inlineFrame = inlineFrame->GetNextContinuation();
+      }
+      if (isRtlBlock) {
+        // aFrame itself is also to the right of its left edge, so add its
+        // width.
+        pos += mVertical ? aFrame->GetSize().height : aFrame->GetSize().width;
+        // pos is now the distance from the left [top] edge of aFrame to the
+        // right [bottom] edge of the unbroken content. Change it to indicate
+        // the distance from the left [top] edge of the unbroken content to the
+        // left [top] edge of aFrame.
+        pos = mUnbrokenMeasure - pos;
+      }
+    } else {
+      pos = mContinuationPoint;
+    }
+
+    // Assume background-origin: border and return a rect with offsets
+    // relative to (0,0).  If we have a different background-origin,
+    // then our rect should be deflated appropriately by our caller.
+    return mVertical
+               ? nsRect(0, -pos, mFrame->GetSize().width, mUnbrokenMeasure)
+               : nsRect(-pos, 0, mUnbrokenMeasure, mFrame->GetSize().height);
+  }
+
+  /**
+   * Return a continuous rect for (an inline) aFrame relative to the
+   * continuation that should draw the left[top]-border.  This is used when
+   * painting borders and clipping backgrounds.  This may NOT be the same
+   * continuous rect as for drawing backgrounds; the continuation with the
+   * left[top]-border might be somewhere in the middle of that rect (e.g. BIDI),
+   * in those cases we need the reverse background order starting at the
+   * left[top]-border continuation.
+   */
+  nsRect GetBorderContinuousRect(nsIFrame* aFrame, nsRect aBorderArea) {
+    // Calling GetContinuousRect(aFrame) here may lead to Reset/Init which
+    // resets our mPIStartBorderData so we save it ...
+    PhysicalInlineStartBorderData saved(mPIStartBorderData);
+    nsRect joinedBorderArea = GetContinuousRect(aFrame);
+    if (!saved.mIsValid || saved.mFrame != mPIStartBorderData.mFrame) {
+      if (aFrame == mPIStartBorderData.mFrame) {
+        if (mVertical) {
+          mPIStartBorderData.SetCoord(joinedBorderArea.y);
+        } else {
+          mPIStartBorderData.SetCoord(joinedBorderArea.x);
+        }
+      } else if (mPIStartBorderData.mFrame) {
+        // Copy data to a temporary object so that computing the
+        // continous rect here doesn't clobber our normal state.
+        InlineBackgroundData temp = *this;
+        if (mVertical) {
+          mPIStartBorderData.SetCoord(
+              temp.GetContinuousRect(mPIStartBorderData.mFrame).y);
+        } else {
+          mPIStartBorderData.SetCoord(
+              temp.GetContinuousRect(mPIStartBorderData.mFrame).x);
+        }
+      }
+    } else {
+      // ... and restore it when possible.
+      mPIStartBorderData.SetCoord(saved.mCoord);
+    }
+    if (mVertical) {
+      if (joinedBorderArea.y > mPIStartBorderData.mCoord) {
+        joinedBorderArea.y =
+            -(mUnbrokenMeasure + joinedBorderArea.y - aBorderArea.height);
+      } else {
+        joinedBorderArea.y -= mPIStartBorderData.mCoord;
+      }
+    } else {
+      if (joinedBorderArea.x > mPIStartBorderData.mCoord) {
+        joinedBorderArea.x =
+            -(mUnbrokenMeasure + joinedBorderArea.x - aBorderArea.width);
+      } else {
+        joinedBorderArea.x -= mPIStartBorderData.mCoord;
+      }
+    }
+    return joinedBorderArea;
+  }
+
+  nsRect GetBoundingRect(nsIFrame* aFrame) {
+    SetFrame(aFrame);
+
+    // Move the offsets relative to (0,0) which puts the bounding box into
+    // our coordinate system rather than our parent's.  We do this by
+    // moving it the back distance from us to the bounding box.
+    // This also assumes background-origin: border, so our caller will
+    // need to deflate us if needed.
+    nsRect boundingBox(mBoundingBox);
+    nsPoint point = mFrame->GetPosition();
+    boundingBox.MoveBy(-point.x, -point.y);
+
+    return boundingBox;
+  }
+
+ protected:
+  // This is a coordinate on the inline axis, but is not a true logical inline-
+  // coord because it is always measured from left to right (if horizontal) or
+  // from top to bottom (if vertical), ignoring any bidi RTL directionality.
+  // We'll call this "physical inline start", or PIStart for short.
+  struct PhysicalInlineStartBorderData {
+    nsIFrame* mFrame;  // the continuation that may have a left-border
+    nscoord mCoord;    // cached GetContinuousRect(mFrame).x or .y
+    bool mIsValid;     // true if mCoord is valid
+    void Reset() {
+      mFrame = nullptr;
+      mIsValid = false;
+    }
+    void SetCoord(nscoord aCoord) {
+      mCoord = aCoord;
+      mIsValid = true;
+    }
+  };
+
+  nsIFrame* mFrame;
+  nsIFrame* mLineContainer;
+  nsRect mBoundingBox;
+  nscoord mContinuationPoint;
+  nscoord mUnbrokenMeasure;
+  nscoord mLineContinuationPoint;
+  PhysicalInlineStartBorderData mPIStartBorderData;
+  bool mBidiEnabled;
+  bool mVertical;
+
+  void SetFrame(nsIFrame* aFrame) {
+    MOZ_ASSERT(aFrame, "Need a frame");
+    NS_ASSERTION(gFrameTreeLockCount > 0,
+                 "Can't call this when frame tree is not locked");
+
+    if (aFrame == mFrame) {
+      return;
+    }
+
+    nsIFrame* prevContinuation = GetPrevContinuation(aFrame);
+
+    if (!prevContinuation || mFrame != prevContinuation) {
+      // Ok, we've got the wrong frame.  We have to start from scratch.
+      Reset();
+      Init(aFrame);
+      return;
+    }
+
+    // Get our last frame's size and add its width to our continuation
+    // point before we cache the new frame.
+    mContinuationPoint +=
+        mVertical ? mFrame->GetSize().height : mFrame->GetSize().width;
+
+    // If this a new line, update mLineContinuationPoint.
+    if (mBidiEnabled &&
+        (aFrame->GetPrevInFlow() || !AreOnSameLine(mFrame, aFrame))) {
+      mLineContinuationPoint = mContinuationPoint;
+    }
+
+    mFrame = aFrame;
+  }
+
+  nsIFrame* GetPrevContinuation(nsIFrame* aFrame) {
+    nsIFrame* prevCont = aFrame->GetPrevContinuation();
+    if (!prevCont && aFrame->HasAnyStateBits(NS_FRAME_PART_OF_IBSPLIT)) {
+      nsIFrame* block = aFrame->GetProperty(nsIFrame::IBSplitPrevSibling());
+      if (block) {
+        // The {ib} properties are only stored on first continuations
+        NS_ASSERTION(!block->GetPrevContinuation(),
+                     "Incorrect value for IBSplitPrevSibling");
+        prevCont = block->GetProperty(nsIFrame::IBSplitPrevSibling());
+        NS_ASSERTION(prevCont, "How did that happen?");
+      }
+    }
+    return prevCont;
+  }
+
+  nsIFrame* GetNextContinuation(nsIFrame* aFrame) {
+    nsIFrame* nextCont = aFrame->GetNextContinuation();
+    if (!nextCont && aFrame->HasAnyStateBits(NS_FRAME_PART_OF_IBSPLIT)) {
+      // The {ib} properties are only stored on first continuations
+      aFrame = aFrame->FirstContinuation();
+      nsIFrame* block = aFrame->GetProperty(nsIFrame::IBSplitSibling());
+      if (block) {
+        nextCont = block->GetProperty(nsIFrame::IBSplitSibling());
+        NS_ASSERTION(nextCont, "How did that happen?");
+      }
+    }
+    return nextCont;
+  }
+
+  void Init(nsIFrame* aFrame) {
+    mPIStartBorderData.Reset();
+    mBidiEnabled = aFrame->PresContext()->BidiEnabled();
+    if (mBidiEnabled) {
+      // Find the line container frame
+      mLineContainer = aFrame;
+      while (mLineContainer && mLineContainer->IsLineParticipant()) {
+        mLineContainer = mLineContainer->GetParent();
+      }
+
+      MOZ_ASSERT(mLineContainer, "Cannot find line containing frame.");
+      MOZ_ASSERT(mLineContainer != aFrame,
+                 "line container frame "
+                 "should be an ancestor of the target frame.");
+    }
+
+    mVertical = aFrame->GetWritingMode().IsVertical();
+
+    // Start with the previous flow frame as our continuation point
+    // is the total of the widths of the previous frames.
+    nsIFrame* inlineFrame = GetPrevContinuation(aFrame);
+    bool changedLines = false;
+    while (inlineFrame) {
+      if (!mPIStartBorderData.mFrame &&
+          !(mVertical ? inlineFrame->GetSkipSides().Top()
+                      : inlineFrame->GetSkipSides().Left())) {
+        mPIStartBorderData.mFrame = inlineFrame;
+      }
+      nsRect rect = inlineFrame->GetRect();
+      mContinuationPoint += mVertical ? rect.height : rect.width;
+      if (mBidiEnabled &&
+          (changedLines || !AreOnSameLine(aFrame, inlineFrame))) {
+        mLineContinuationPoint += mVertical ? rect.height : rect.width;
+        changedLines = true;
+      }
+      mUnbrokenMeasure += mVertical ? rect.height : rect.width;
+      mBoundingBox.UnionRect(mBoundingBox, rect);
+      inlineFrame = GetPrevContinuation(inlineFrame);
+    }
+
+    // Next add this frame and subsequent frames to the bounding box and
+    // unbroken width.
+    inlineFrame = aFrame;
+    while (inlineFrame) {
+      if (!mPIStartBorderData.mFrame &&
+          !(mVertical ? inlineFrame->GetSkipSides().Top()
+                      : inlineFrame->GetSkipSides().Left())) {
+        mPIStartBorderData.mFrame = inlineFrame;
+      }
+      nsRect rect = inlineFrame->GetRect();
+      mUnbrokenMeasure += mVertical ? rect.height : rect.width;
+      mBoundingBox.UnionRect(mBoundingBox, rect);
+      inlineFrame = GetNextContinuation(inlineFrame);
+    }
+
+    mFrame = aFrame;
+  }
+
+  bool AreOnSameLine(nsIFrame* aFrame1, nsIFrame* aFrame2) {
+    if (nsBlockFrame* blockFrame = do_QueryFrame(mLineContainer)) {
+      bool isValid1, isValid2;
+      nsBlockInFlowLineIterator it1(blockFrame, aFrame1, &isValid1);
+      nsBlockInFlowLineIterator it2(blockFrame, aFrame2, &isValid2);
+      return isValid1 && isValid2 &&
+             // Make sure aFrame1 and aFrame2 are in the same continuation of
+             // blockFrame.
+             it1.GetContainer() == it2.GetContainer() &&
+             // And on the same line in it
+             it1.GetLine().get() == it2.GetLine().get();
+    }
+    if (nsRubyTextContainerFrame* rtcFrame = do_QueryFrame(mLineContainer)) {
+      nsBlockFrame* block = nsLayoutUtils::FindNearestBlockAncestor(rtcFrame);
+      // Ruby text container can only hold one line of text, so if they
+      // are in the same continuation, they are in the same line. Since
+      // ruby text containers are bidi isolate, they are never split for
+      // bidi reordering, which means being in different continuation
+      // indicates being in different lines.
+      for (nsIFrame* frame = rtcFrame->FirstContinuation(); frame;
+           frame = frame->GetNextContinuation()) {
+        bool isDescendant1 =
+            nsLayoutUtils::IsProperAncestorFrame(frame, aFrame1, block);
+        bool isDescendant2 =
+            nsLayoutUtils::IsProperAncestorFrame(frame, aFrame2, block);
+        if (isDescendant1 && isDescendant2) {
+          return true;
+        }
+        if (isDescendant1 || isDescendant2) {
+          return false;
+        }
+      }
+      MOZ_ASSERT_UNREACHABLE("None of the frames is a descendant of this rtc?");
+    }
+    MOZ_ASSERT_UNREACHABLE("Do we have any other type of line container?");
+    return false;
+  }
+};
+
+static StaticAutoPtr<InlineBackgroundData> gInlineBGData;
+
+// Initialize any static variables used by nsCSSRendering.
+void nsCSSRendering::Init() {
+  NS_ASSERTION(!gInlineBGData, "Init called twice");
+  gInlineBGData = new InlineBackgroundData();
+}
+
+// Clean up any global variables used by nsCSSRendering.
+void nsCSSRendering::Shutdown() { gInlineBGData = nullptr; }
+
+/**
+ * Make a bevel color
+ */
+static nscolor MakeBevelColor(mozilla::Side whichSide, StyleBorderStyle style,
+                              nscolor aBorderColor) {
+  nscolor colors[2];
+  nscolor theColor;
+
+  // Given a background color and a border color
+  // calculate the color used for the shading
+  NS_GetSpecial3DColors(colors, aBorderColor);
+
+  if ((style == StyleBorderStyle::Outset) ||
+      (style == StyleBorderStyle::Ridge)) {
+    // Flip colors for these two border styles
+    switch (whichSide) {
+      case eSideBottom:
+        whichSide = eSideTop;
+        break;
+      case eSideRight:
+        whichSide = eSideLeft;
+        break;
+      case eSideTop:
+        whichSide = eSideBottom;
+        break;
+      case eSideLeft:
+        whichSide = eSideRight;
+        break;
+    }
+  }
+
+  switch (whichSide) {
+    case eSideBottom:
+      theColor = colors[1];
+      break;
+    case eSideRight:
+      theColor = colors[1];
+      break;
+    case eSideTop:
+      theColor = colors[0];
+      break;
+    case eSideLeft:
+    default:
+      theColor = colors[0];
+      break;
+  }
+  return theColor;
+}
+
+static bool GetRadii(nsIFrame* aForFrame, const nsStyleBorder& aBorder,
+                     const nsRect& aOrigBorderArea, const nsRect& aBorderArea,
+                     nscoord aRadii[8]) {
+  bool haveRoundedCorners;
+  nsSize sz = aBorderArea.Size();
+  nsSize frameSize = aForFrame->GetSize();
+  if (&aBorder == aForFrame->StyleBorder() &&
+      frameSize == aOrigBorderArea.Size()) {
+    haveRoundedCorners = aForFrame->GetBorderRadii(sz, sz, Sides(), aRadii);
+  } else {
+    haveRoundedCorners = nsIFrame::ComputeBorderRadii(
+        aBorder.mBorderRadius, frameSize, sz, Sides(), aRadii);
+  }
+
+  return haveRoundedCorners;
+}
+
+static bool GetRadii(nsIFrame* aForFrame, const nsStyleBorder& aBorder,
+                     const nsRect& aOrigBorderArea, const nsRect& aBorderArea,
+                     RectCornerRadii* aBgRadii) {
+  nscoord radii[8];
+  bool haveRoundedCorners =
+      GetRadii(aForFrame, aBorder, aOrigBorderArea, aBorderArea, radii);
+
+  if (haveRoundedCorners) {
+    auto d2a = aForFrame->PresContext()->AppUnitsPerDevPixel();
+    nsCSSRendering::ComputePixelRadii(radii, d2a, aBgRadii);
+  }
+  return haveRoundedCorners;
+}
+
+static nsRect JoinBoxesForBlockAxisSlice(nsIFrame* aFrame,
+                                         const nsRect& aBorderArea) {
+  // Inflate the block-axis size as if our continuations were laid out
+  // adjacent in that axis.  Note that we don't touch the inline size.
+  const auto wm = aFrame->GetWritingMode();
+  const nsSize dummyContainerSize;
+  LogicalRect borderArea(wm, aBorderArea, dummyContainerSize);
+  nscoord bSize = 0;
+  nsIFrame* f = aFrame->GetNextContinuation();
+  for (; f; f = f->GetNextContinuation()) {
+    bSize += f->BSize(wm);
+  }
+  borderArea.BSize(wm) += bSize;
+  bSize = 0;
+  f = aFrame->GetPrevContinuation();
+  for (; f; f = f->GetPrevContinuation()) {
+    bSize += f->BSize(wm);
+  }
+  borderArea.BStart(wm) -= bSize;
+  borderArea.BSize(wm) += bSize;
+  return borderArea.GetPhysicalRect(wm, dummyContainerSize);
+}
+
+/**
+ * Inflate aBorderArea which is relative to aFrame's origin to calculate
+ * a hypothetical non-split frame area for all the continuations.
+ * See "Joining Boxes for 'slice'" in
+ * http://dev.w3.org/csswg/css-break/#break-decoration
+ */
+enum InlineBoxOrder { eForBorder, eForBackground };
+static nsRect JoinBoxesForSlice(nsIFrame* aFrame, const nsRect& aBorderArea,
+                                InlineBoxOrder aOrder) {
+  if (static_cast<nsInlineFrame*>(do_QueryFrame(aFrame))) {
+    return (aOrder == eForBorder
+                ? gInlineBGData->GetBorderContinuousRect(aFrame, aBorderArea)
+                : gInlineBGData->GetContinuousRect(aFrame)) +
+           aBorderArea.TopLeft();
+  }
+  return JoinBoxesForBlockAxisSlice(aFrame, aBorderArea);
+}
+
+/* static */
+bool nsCSSRendering::IsBoxDecorationSlice(const nsStyleBorder& aStyleBorder) {
+  return aStyleBorder.mBoxDecorationBreak == StyleBoxDecorationBreak::Slice;
+}
+
+/* static */
+nsRect nsCSSRendering::BoxDecorationRectForBorder(
+    nsIFrame* aFrame, const nsRect& aBorderArea, Sides aSkipSides,
+    const nsStyleBorder* aStyleBorder) {
+  if (!aStyleBorder) {
+    aStyleBorder = aFrame->StyleBorder();
+  }
+  // If aSkipSides.IsEmpty() then there are no continuations, or it's
+  // a ::first-letter that wants all border sides on the first continuation.
+  return IsBoxDecorationSlice(*aStyleBorder) && !aSkipSides.IsEmpty()
+             ? ::JoinBoxesForSlice(aFrame, aBorderArea, eForBorder)
+             : aBorderArea;
+}
+
+/* static */
+nsRect nsCSSRendering::BoxDecorationRectForBackground(
+    nsIFrame* aFrame, const nsRect& aBorderArea, Sides aSkipSides,
+    const nsStyleBorder* aStyleBorder) {
+  if (!aStyleBorder) {
+    aStyleBorder = aFrame->StyleBorder();
+  }
+  // If aSkipSides.IsEmpty() then there are no continuations, or it's
+  // a ::first-letter that wants all border sides on the first continuation.
+  return IsBoxDecorationSlice(*aStyleBorder) && !aSkipSides.IsEmpty()
+             ? ::JoinBoxesForSlice(aFrame, aBorderArea, eForBackground)
+             : aBorderArea;
+}
+
+//----------------------------------------------------------------------
+// Thebes Border Rendering Code Start
+
+/*
+ * Compute the float-pixel radii that should be used for drawing
+ * this border/outline, given the various input bits.
+ */
+/* static */
+void nsCSSRendering::ComputePixelRadii(const nscoord* aAppUnitsRadii,
+                                       nscoord aAppUnitsPerPixel,
+                                       RectCornerRadii* oBorderRadii) {
+  Float radii[8];
+  for (const auto corner : mozilla::AllPhysicalHalfCorners()) {
+    radii[corner] = Float(aAppUnitsRadii[corner]) / aAppUnitsPerPixel;
+  }
+
+  (*oBorderRadii)[C_TL] = Size(radii[eCornerTopLeftX], radii[eCornerTopLeftY]);
+  (*oBorderRadii)[C_TR] =
+      Size(radii[eCornerTopRightX], radii[eCornerTopRightY]);
+  (*oBorderRadii)[C_BR] =
+      Size(radii[eCornerBottomRightX], radii[eCornerBottomRightY]);
+  (*oBorderRadii)[C_BL] =
+      Size(radii[eCornerBottomLeftX], radii[eCornerBottomLeftY]);
+}
+
+static Maybe<nsStyleBorder> GetBorderIfVisited(const ComputedStyle& aStyle) {
+  Maybe<nsStyleBorder> result;
+  // Don't check RelevantLinkVisited here, since we want to take the
+  // same amount of time whether or not it's true.
+  const ComputedStyle* styleIfVisited = aStyle.GetStyleIfVisited();
+  if (MOZ_LIKELY(!styleIfVisited)) {
+    return result;
+  }
+
+  result.emplace(*aStyle.StyleBorder());
+  auto& newBorder = result.ref();
+  for (const auto side : mozilla::AllPhysicalSides()) {
+    nscolor color = aStyle.GetVisitedDependentColor(
+        nsStyleBorder::BorderColorFieldFor(side));
+    newBorder.BorderColorFor(side) = StyleColor::FromColor(color);
+  }
+
+  return result;
+}
+
+ImgDrawResult nsCSSRendering::PaintBorder(
+    nsPresContext* aPresContext, gfxContext& aRenderingContext,
+    nsIFrame* aForFrame, const nsRect& aDirtyRect, const nsRect& aBorderArea,
+    ComputedStyle* aStyle, PaintBorderFlags aFlags, Sides aSkipSides) {
+  AUTO_PROFILER_LABEL("nsCSSRendering::PaintBorder", GRAPHICS);
+
+  Maybe<nsStyleBorder> visitedBorder = GetBorderIfVisited(*aStyle);
+  return PaintBorderWithStyleBorder(
+      aPresContext, aRenderingContext, aForFrame, aDirtyRect, aBorderArea,
+      visitedBorder.refOr(*aStyle->StyleBorder()), aStyle, aFlags, aSkipSides);
+}
+
+Maybe<nsCSSBorderRenderer> nsCSSRendering::CreateBorderRenderer(
+    nsPresContext* aPresContext, DrawTarget* aDrawTarget, nsIFrame* aForFrame,
+    const nsRect& aDirtyRect, const nsRect& aBorderArea, ComputedStyle* aStyle,
+    bool* aOutBorderIsEmpty, Sides aSkipSides) {
+  Maybe<nsStyleBorder> visitedBorder = GetBorderIfVisited(*aStyle);
+  return CreateBorderRendererWithStyleBorder(
+      aPresContext, aDrawTarget, aForFrame, aDirtyRect, aBorderArea,
+      visitedBorder.refOr(*aStyle->StyleBorder()), aStyle, aOutBorderIsEmpty,
+      aSkipSides);
+}
+
+ImgDrawResult nsCSSRendering::CreateWebRenderCommandsForBorder(
+    nsDisplayItem* aItem, nsIFrame* aForFrame, const nsRect& aBorderArea,
+    mozilla::wr::DisplayListBuilder& aBuilder,
+    mozilla::wr::IpcResourceUpdateQueue& aResources,
+    const mozilla::layers::StackingContextHelper& aSc,
+    mozilla::layers::RenderRootStateManager* aManager,
+    nsDisplayListBuilder* aDisplayListBuilder) {
+  const auto* style = aForFrame->Style();
+  Maybe<nsStyleBorder> visitedBorder = GetBorderIfVisited(*style);
+  return nsCSSRendering::CreateWebRenderCommandsForBorderWithStyleBorder(
+      aItem, aForFrame, aBorderArea, aBuilder, aResources, aSc, aManager,
+      aDisplayListBuilder, visitedBorder.refOr(*style->StyleBorder()));
+}
+
+void nsCSSRendering::CreateWebRenderCommandsForNullBorder(
+    nsDisplayItem* aItem, nsIFrame* aForFrame, const nsRect& aBorderArea,
+    mozilla::wr::DisplayListBuilder& aBuilder,
+    mozilla::wr::IpcResourceUpdateQueue& aResources,
+    const mozilla::layers::StackingContextHelper& aSc,
+    const nsStyleBorder& aStyleBorder) {
+  bool borderIsEmpty = false;
+  Maybe<nsCSSBorderRenderer> br =
+      nsCSSRendering::CreateNullBorderRendererWithStyleBorder(
+          aForFrame->PresContext(), nullptr, aForFrame, nsRect(), aBorderArea,
+          aStyleBorder, aForFrame->Style(), &borderIsEmpty,
+          aForFrame->GetSkipSides());
+  if (!borderIsEmpty && br) {
+    br->CreateWebRenderCommands(aItem, aBuilder, aResources, aSc);
+  }
+}
+
+ImgDrawResult nsCSSRendering::CreateWebRenderCommandsForBorderWithStyleBorder(
+    nsDisplayItem* aItem, nsIFrame* aForFrame, const nsRect& aBorderArea,
+    mozilla::wr::DisplayListBuilder& aBuilder,
+    mozilla::wr::IpcResourceUpdateQueue& aResources,
+    const mozilla::layers::StackingContextHelper& aSc,
+    mozilla::layers::RenderRootStateManager* aManager,
+    nsDisplayListBuilder* aDisplayListBuilder,
+    const nsStyleBorder& aStyleBorder) {
+  auto& borderImage = aStyleBorder.mBorderImageSource;
+  // First try to create commands for simple borders.
+  if (borderImage.IsNone()) {
+    CreateWebRenderCommandsForNullBorder(
+        aItem, aForFrame, aBorderArea, aBuilder, aResources, aSc, aStyleBorder);
+    return ImgDrawResult::SUCCESS;
+  }
+
+  // Next we try image and gradient borders. Gradients are not supported at
+  // this very moment.
+  if (!borderImage.IsImageRequestType()) {
+    return ImgDrawResult::NOT_SUPPORTED;
+  }
+
+  if (aStyleBorder.mBorderImageRepeatH == StyleBorderImageRepeat::Space ||
+      aStyleBorder.mBorderImageRepeatV == StyleBorderImageRepeat::Space) {
+    return ImgDrawResult::NOT_SUPPORTED;
+  }
+
+  uint32_t flags = 0;
+  if (aDisplayListBuilder->IsPaintingToWindow()) {
+    flags |= nsImageRenderer::FLAG_PAINTING_TO_WINDOW;
+  }
+  if (aDisplayListBuilder->ShouldSyncDecodeImages()) {
+    flags |= nsImageRenderer::FLAG_SYNC_DECODE_IMAGES;
+  }
+
+  bool dummy;
+  image::ImgDrawResult result;
+  Maybe<nsCSSBorderImageRenderer> bir =
+      nsCSSBorderImageRenderer::CreateBorderImageRenderer(
+          aForFrame->PresContext(), aForFrame, aBorderArea, aStyleBorder,
+          aItem->GetBounds(aDisplayListBuilder, &dummy),
+          aForFrame->GetSkipSides(), flags, &result);
+
+  if (!bir) {
+    // We aren't ready. Try to fallback to the null border image if present but
+    // return the draw result for the border image renderer.
+    CreateWebRenderCommandsForNullBorder(
+        aItem, aForFrame, aBorderArea, aBuilder, aResources, aSc, aStyleBorder);
+    return result;
+  }
+
+  return bir->CreateWebRenderCommands(aItem, aForFrame, aBuilder, aResources,
+                                      aSc, aManager, aDisplayListBuilder);
+}
+
+static nsCSSBorderRenderer ConstructBorderRenderer(
+    nsPresContext* aPresContext, ComputedStyle* aStyle, DrawTarget* aDrawTarget,
+    nsIFrame* aForFrame, const nsRect& aDirtyRect, const nsRect& aBorderArea,
+    const nsStyleBorder& aStyleBorder, Sides aSkipSides, bool* aNeedsClip) {
+  nsMargin border = aStyleBorder.GetComputedBorder();
+
+  // Compute the outermost boundary of the area that might be painted.
+  // Same coordinate space as aBorderArea & aBGClipRect.
+  nsRect joinedBorderArea = nsCSSRendering::BoxDecorationRectForBorder(
+      aForFrame, aBorderArea, aSkipSides, &aStyleBorder);
+  RectCornerRadii bgRadii;
+  ::GetRadii(aForFrame, aStyleBorder, aBorderArea, joinedBorderArea, &bgRadii);
+
+  PrintAsFormatString(" joinedBorderArea: %d %d %d %d\n", joinedBorderArea.x,
+                      joinedBorderArea.y, joinedBorderArea.width,
+                      joinedBorderArea.height);
+
+  // start drawing
+  if (nsCSSRendering::IsBoxDecorationSlice(aStyleBorder)) {
+    if (joinedBorderArea.IsEqualEdges(aBorderArea)) {
+      // No need for a clip, just skip the sides we don't want.
+      border.ApplySkipSides(aSkipSides);
+    } else {
+      // We're drawing borders around the joined continuation boxes so we need
+      // to clip that to the slice that we want for this frame.
+      *aNeedsClip = true;
+    }
+  } else {
+    MOZ_ASSERT(joinedBorderArea.IsEqualEdges(aBorderArea),
+               "Should use aBorderArea for box-decoration-break:clone");
+    MOZ_ASSERT(
+        aForFrame->GetSkipSides().IsEmpty() ||
+            aForFrame->IsTrueOverflowContainer() ||
+            aForFrame->IsColumnSetFrame(),  // a little broader than column-rule
+        "Should not skip sides for box-decoration-break:clone except "
+        "::first-letter/line continuations or other frame types that "
+        "don't have borders but those shouldn't reach this point. "
+        "Overflow containers do reach this point though, as does "
+        "column-rule drawing (which always involves a columnset).");
+    border.ApplySkipSides(aSkipSides);
+  }
+
+  // Convert to dev pixels.
+  nscoord oneDevPixel = aPresContext->DevPixelsToAppUnits(1);
+  Rect joinedBorderAreaPx = NSRectToRect(joinedBorderArea, oneDevPixel);
+  Float borderWidths[4] = {
+      Float(border.top) / oneDevPixel, Float(border.right) / oneDevPixel,
+      Float(border.bottom) / oneDevPixel, Float(border.left) / oneDevPixel};
+  Rect dirtyRect = NSRectToRect(aDirtyRect, oneDevPixel);
+
+  StyleBorderStyle borderStyles[4];
+  nscolor borderColors[4];
+
+  // pull out styles, colors
+  for (const auto i : mozilla::AllPhysicalSides()) {
+    borderStyles[i] = aStyleBorder.GetBorderStyle(i);
+    borderColors[i] = aStyleBorder.BorderColorFor(i).CalcColor(*aStyle);
+  }
+
+  PrintAsFormatString(
+      " borderStyles: %d %d %d %d\n", static_cast<int>(borderStyles[0]),
+      static_cast<int>(borderStyles[1]), static_cast<int>(borderStyles[2]),
+      static_cast<int>(borderStyles[3]));
+
+  return nsCSSBorderRenderer(
+      aPresContext, aDrawTarget, dirtyRect, joinedBorderAreaPx, borderStyles,
+      borderWidths, bgRadii, borderColors, !aForFrame->BackfaceIsHidden(),
+      *aNeedsClip ? Some(NSRectToRect(aBorderArea, oneDevPixel)) : Nothing());
+}
+
+ImgDrawResult nsCSSRendering::PaintBorderWithStyleBorder(
+    nsPresContext* aPresContext, gfxContext& aRenderingContext,
+    nsIFrame* aForFrame, const nsRect& aDirtyRect, const nsRect& aBorderArea,
+    const nsStyleBorder& aStyleBorder, ComputedStyle* aStyle,
+    PaintBorderFlags aFlags, Sides aSkipSides) {
+  DrawTarget& aDrawTarget = *aRenderingContext.GetDrawTarget();
+
+  PrintAsStringNewline("++ PaintBorder");
+
+  // Check to see if we have an appearance defined.  If so, we let the theme
+  // renderer draw the border.  DO not get the data from aForFrame, since the
+  // passed in ComputedStyle may be different!  Always use |aStyle|!
+  StyleAppearance appearance = aStyle->StyleDisplay()->EffectiveAppearance();
+  if (appearance != StyleAppearance::None) {
+    nsITheme* theme = aPresContext->Theme();
+    if (theme->ThemeSupportsWidget(aPresContext, aForFrame, appearance)) {
+      return ImgDrawResult::SUCCESS;  // Let the theme handle it.
+    }
+  }
+
+  if (!aStyleBorder.mBorderImageSource.IsNone()) {
+    ImgDrawResult result = ImgDrawResult::SUCCESS;
+
+    uint32_t irFlags = 0;
+    if (aFlags & PaintBorderFlags::SyncDecodeImages) {
+      irFlags |= nsImageRenderer::FLAG_SYNC_DECODE_IMAGES;
+    }
+
+    // Creating the border image renderer will request a decode, and we rely on
+    // that happening.
+    Maybe<nsCSSBorderImageRenderer> renderer =
+        nsCSSBorderImageRenderer::CreateBorderImageRenderer(
+            aPresContext, aForFrame, aBorderArea, aStyleBorder, aDirtyRect,
+            aSkipSides, irFlags, &result);
+    // renderer was created successfully, which means border image is ready to
+    // be used.
+    if (renderer) {
+      MOZ_ASSERT(result == ImgDrawResult::SUCCESS);
+      return renderer->DrawBorderImage(aPresContext, aRenderingContext,
+                                       aForFrame, aDirtyRect);
+    }
+  }
+
+  ImgDrawResult result = ImgDrawResult::SUCCESS;
+
+  // If we had a border-image, but it wasn't loaded, then we should return
+  // ImgDrawResult::NOT_READY; we'll want to try again if we do a paint with
+  // sync decoding enabled.
+  if (!aStyleBorder.mBorderImageSource.IsNone()) {
+    result = ImgDrawResult::NOT_READY;
+  }
+
+  nsMargin border = aStyleBorder.GetComputedBorder();
+  if (0 == border.left && 0 == border.right && 0 == border.top &&
+      0 == border.bottom) {
+    // Empty border area
+    return result;
+  }
+
+  bool needsClip = false;
+  nsCSSBorderRenderer br = ConstructBorderRenderer(
+      aPresContext, aStyle, &aDrawTarget, aForFrame, aDirtyRect, aBorderArea,
+      aStyleBorder, aSkipSides, &needsClip);
+  if (needsClip) {
+    aDrawTarget.PushClipRect(NSRectToSnappedRect(
+        aBorderArea, aForFrame->PresContext()->AppUnitsPerDevPixel(),
+        aDrawTarget));
+  }
+
+  br.DrawBorders();
+
+  if (needsClip) {
+    aDrawTarget.PopClip();
+  }
+
+  PrintAsStringNewline();
+
+  return result;
+}
+
+Maybe<nsCSSBorderRenderer> nsCSSRendering::CreateBorderRendererWithStyleBorder(
+    nsPresContext* aPresContext, DrawTarget* aDrawTarget, nsIFrame* aForFrame,
+    const nsRect& aDirtyRect, const nsRect& aBorderArea,
+    const nsStyleBorder& aStyleBorder, ComputedStyle* aStyle,
+    bool* aOutBorderIsEmpty, Sides aSkipSides) {
+  if (!aStyleBorder.mBorderImageSource.IsNone()) {
+    return Nothing();
+  }
+  return CreateNullBorderRendererWithStyleBorder(
+      aPresContext, aDrawTarget, aForFrame, aDirtyRect, aBorderArea,
+      aStyleBorder, aStyle, aOutBorderIsEmpty, aSkipSides);
+}
+
+Maybe<nsCSSBorderRenderer>
+nsCSSRendering::CreateNullBorderRendererWithStyleBorder(
+    nsPresContext* aPresContext, DrawTarget* aDrawTarget, nsIFrame* aForFrame,
+    const nsRect& aDirtyRect, const nsRect& aBorderArea,
+    const nsStyleBorder& aStyleBorder, ComputedStyle* aStyle,
+    bool* aOutBorderIsEmpty, Sides aSkipSides) {
+  StyleAppearance appearance = aStyle->StyleDisplay()->EffectiveAppearance();
+  if (appearance != StyleAppearance::None) {
+    nsITheme* theme = aPresContext->Theme();
+    if (theme->ThemeSupportsWidget(aPresContext, aForFrame, appearance)) {
+      // The border will be draw as part of the themed background item created
+      // for this same frame. If no themed background item was created then not
+      // drawing also matches that we do without webrender and what
+      // nsDisplayBorder does for themed borders.
+      if (aOutBorderIsEmpty) {
+        *aOutBorderIsEmpty = true;
+      }
+      return Nothing();
+    }
+  }
+
+  nsMargin border = aStyleBorder.GetComputedBorder();
+  if (0 == border.left && 0 == border.right && 0 == border.top &&
+      0 == border.bottom) {
+    // Empty border area
+    if (aOutBorderIsEmpty) {
+      *aOutBorderIsEmpty = true;
+    }
+    return Nothing();
+  }
+
+  bool needsClip = false;
+  nsCSSBorderRenderer br = ConstructBorderRenderer(
+      aPresContext, aStyle, aDrawTarget, aForFrame, aDirtyRect, aBorderArea,
+      aStyleBorder, aSkipSides, &needsClip);
+  return Some(br);
+}
+
+Maybe<nsCSSBorderRenderer>
+nsCSSRendering::CreateBorderRendererForNonThemedOutline(
+    nsPresContext* aPresContext, DrawTarget* aDrawTarget, nsIFrame* aForFrame,
+    const nsRect& aDirtyRect, const nsRect& aInnerRect, ComputedStyle* aStyle) {
+  // Get our ComputedStyle's color struct.
+  const nsStyleOutline* ourOutline = aStyle->StyleOutline();
+  if (!ourOutline->ShouldPaintOutline()) {
+    // Empty outline
+    return Nothing();
+  }
+
+  nsRect innerRect = aInnerRect;
+
+  const nsSize effectiveOffset = ourOutline->EffectiveOffsetFor(innerRect);
+  innerRect.Inflate(effectiveOffset);
+
+  // If the dirty rect is completely inside the border area (e.g., only the
+  // content is being painted), then we can skip out now
+  // XXX this isn't exactly true for rounded borders, where the inside curves
+  // may encroach into the content area.  A safer calculation would be to
+  // shorten insideRect by the radius one each side before performing this test.
+  if (innerRect.Contains(aDirtyRect)) {
+    return Nothing();
+  }
+
+  const nscoord width = ourOutline->GetOutlineWidth();
+
+  StyleBorderStyle outlineStyle;
+  // Themed outlines are handled by our callers, if supported.
+  if (ourOutline->mOutlineStyle.IsAuto()) {
+    if (width == 0) {
+      return Nothing();  // empty outline
+    }
+    // http://dev.w3.org/csswg/css-ui/#outline
+    // "User agents may treat 'auto' as 'solid'."
+    outlineStyle = StyleBorderStyle::Solid;
+  } else {
+    outlineStyle = ourOutline->mOutlineStyle.AsBorderStyle();
+  }
+
+  RectCornerRadii outlineRadii;
+  nsRect outerRect = innerRect;
+  outerRect.Inflate(width);
+
+  const nscoord oneDevPixel = aPresContext->AppUnitsPerDevPixel();
+  Rect oRect(NSRectToRect(outerRect, oneDevPixel));
+
+  const Float outlineWidths[4] = {
+      Float(width) / oneDevPixel, Float(width) / oneDevPixel,
+      Float(width) / oneDevPixel, Float(width) / oneDevPixel};
+
+  // convert the radii
+  nscoord twipsRadii[8];
+
+  // get the radius for our outline
+  if (aForFrame->GetBorderRadii(twipsRadii)) {
+    RectCornerRadii innerRadii;
+    ComputePixelRadii(twipsRadii, oneDevPixel, &innerRadii);
+
+    const auto devPxOffset = LayoutDeviceSize::FromAppUnits(
+        effectiveOffset, aPresContext->AppUnitsPerDevPixel());
+
+    const Float widths[4] = {outlineWidths[0] + devPxOffset.Height(),
+                             outlineWidths[1] + devPxOffset.Width(),
+                             outlineWidths[2] + devPxOffset.Height(),
+                             outlineWidths[3] + devPxOffset.Width()};
+    nsCSSBorderRenderer::ComputeOuterRadii(innerRadii, widths, &outlineRadii);
+  }
+
+  StyleBorderStyle outlineStyles[4] = {outlineStyle, outlineStyle, outlineStyle,
+                                       outlineStyle};
+
+  // This handles treating the initial color as 'currentColor'; if we
+  // ever want 'invert' back we'll need to do a bit of work here too.
+  nscolor outlineColor =
+      aStyle->GetVisitedDependentColor(&nsStyleOutline::mOutlineColor);
+  nscolor outlineColors[4] = {outlineColor, outlineColor, outlineColor,
+                              outlineColor};
+
+  Rect dirtyRect = NSRectToRect(aDirtyRect, oneDevPixel);
+
+  return Some(nsCSSBorderRenderer(
+      aPresContext, aDrawTarget, dirtyRect, oRect, outlineStyles, outlineWidths,
+      outlineRadii, outlineColors, !aForFrame->BackfaceIsHidden(), Nothing()));
+}
+
+void nsCSSRendering::PaintNonThemedOutline(nsPresContext* aPresContext,
+                                           gfxContext& aRenderingContext,
+                                           nsIFrame* aForFrame,
+                                           const nsRect& aDirtyRect,
+                                           const nsRect& aInnerRect,
+                                           ComputedStyle* aStyle) {
+  Maybe<nsCSSBorderRenderer> br = CreateBorderRendererForNonThemedOutline(
+      aPresContext, aRenderingContext.GetDrawTarget(), aForFrame, aDirtyRect,
+      aInnerRect, aStyle);
+  if (!br) {
+    return;
+  }
+
+  // start drawing
+  br->DrawBorders();
+
+  PrintAsStringNewline();
+}
+
+void nsCSSRendering::PaintFocus(nsPresContext* aPresContext,
+                                DrawTarget* aDrawTarget,
+                                const nsRect& aFocusRect, nscolor aColor) {
+  nscoord oneCSSPixel = nsPresContext::CSSPixelsToAppUnits(1);
+  nscoord oneDevPixel = aPresContext->DevPixelsToAppUnits(1);
+
+  Rect focusRect(NSRectToRect(aFocusRect, oneDevPixel));
+
+  RectCornerRadii focusRadii;
+  {
+    nscoord twipsRadii[8] = {0, 0, 0, 0, 0, 0, 0, 0};
+    ComputePixelRadii(twipsRadii, oneDevPixel, &focusRadii);
+  }
+  Float focusWidths[4] = {
+      Float(oneCSSPixel) / oneDevPixel, Float(oneCSSPixel) / oneDevPixel,
+      Float(oneCSSPixel) / oneDevPixel, Float(oneCSSPixel) / oneDevPixel};
+
+  StyleBorderStyle focusStyles[4] = {
+      StyleBorderStyle::Dotted, StyleBorderStyle::Dotted,
+      StyleBorderStyle::Dotted, StyleBorderStyle::Dotted};
+  nscolor focusColors[4] = {aColor, aColor, aColor, aColor};
+
+  // Because this renders a dotted border, the background color
+  // should not be used.  Therefore, we provide a value that will
+  // be blatantly wrong if it ever does get used.  (If this becomes
+  // something that CSS can style, this function will then have access
+  // to a ComputedStyle and can use the same logic that PaintBorder
+  // and PaintOutline do.)
+  //
+  // WebRender layers-free mode don't use PaintFocus function. Just assign
+  // the backface-visibility to true for this case.
+  nsCSSBorderRenderer br(aPresContext, aDrawTarget, focusRect, focusRect,
+                         focusStyles, focusWidths, focusRadii, focusColors,
+                         true, Nothing());
+  br.DrawBorders();
+
+  PrintAsStringNewline();
+}
+
+// Thebes Border Rendering Code End
+//----------------------------------------------------------------------
+
+//----------------------------------------------------------------------
+
+/**
+ * Helper for ComputeObjectAnchorPoint; parameters are the same as for
+ * that function, except they're for a single coordinate / a single size
+ * dimension. (so, x/width vs. y/height)
+ */
+static void ComputeObjectAnchorCoord(const LengthPercentage& aCoord,
+                                     const nscoord aOriginBounds,
+                                     const nscoord aImageSize,
+                                     nscoord* aTopLeftCoord,
+                                     nscoord* aAnchorPointCoord) {
+  nscoord extraSpace = aOriginBounds - aImageSize;
+
+  // The anchor-point doesn't care about our image's size; just the size
+  // of the region we're rendering into.
+  *aAnchorPointCoord = aCoord.Resolve(
+      aOriginBounds, static_cast<nscoord (*)(float)>(NSToCoordRoundWithClamp));
+  // Adjust aTopLeftCoord by the specified % of the extra space.
+  *aTopLeftCoord = aCoord.Resolve(
+      extraSpace, static_cast<nscoord (*)(float)>(NSToCoordRoundWithClamp));
+}
+
+void nsImageRenderer::ComputeObjectAnchorPoint(const Position& aPos,
+                                               const nsSize& aOriginBounds,
+                                               const nsSize& aImageSize,
+                                               nsPoint* aTopLeft,
+                                               nsPoint* aAnchorPoint) {
+  ComputeObjectAnchorCoord(aPos.horizontal, aOriginBounds.width,
+                           aImageSize.width, &aTopLeft->x, &aAnchorPoint->x);
+
+  ComputeObjectAnchorCoord(aPos.vertical, aOriginBounds.height,
+                           aImageSize.height, &aTopLeft->y, &aAnchorPoint->y);
+}
+
+// In print / print preview we have multiple canvas frames (one for each page,
+// and one for the document as a whole). For the topmost one, we really want the
+// page sequence page background, not the root or body's background.
+static nsIFrame* GetPageSequenceForCanvas(const nsIFrame* aCanvasFrame) {
+  MOZ_ASSERT(aCanvasFrame->IsCanvasFrame(), "not a canvas frame");
+  nsPresContext* pc = aCanvasFrame->PresContext();
+  if (!pc->IsRootPaginatedDocument()) {
+    return nullptr;
+  }
+  auto* ps = pc->PresShell()->GetPageSequenceFrame();
+  if (NS_WARN_IF(!ps)) {
+    return nullptr;
+  }
+  if (ps->GetParent() != aCanvasFrame) {
+    return nullptr;
+  }
+  return ps;
+}
+
+auto nsCSSRendering::FindEffectiveBackgroundColor(nsIFrame* aFrame,
+                                                  bool aStopAtThemed,
+                                                  bool aPreferBodyToCanvas)
+    -> EffectiveBackgroundColor {
+  MOZ_ASSERT(aFrame);
+  nsPresContext* pc = aFrame->PresContext();
+  auto BgColorIfNotTransparent = [&](nsIFrame* aFrame) -> Maybe<nscolor> {
+    nscolor c =
+        aFrame->GetVisitedDependentColor(&nsStyleBackground::mBackgroundColor);
+    if (NS_GET_A(c) == 255) {
+      return Some(c);
+    }
+    if (NS_GET_A(c)) {
+      // TODO(emilio): We should maybe just blend with ancestor bg colors and
+      // such, but this is probably good enough for now, matches pre-existing
+      // behavior.
+      const nscolor defaultBg = pc->DefaultBackgroundColor();
+      MOZ_ASSERT(NS_GET_A(defaultBg) == 255, "PreferenceSheet guarantees this");
+      return Some(NS_ComposeColors(defaultBg, c));
+    }
+    return Nothing();
+  };
+
+  for (nsIFrame* frame = aFrame; frame;
+       frame = nsLayoutUtils::GetParentOrPlaceholderForCrossDoc(frame)) {
+    if (auto bg = BgColorIfNotTransparent(frame)) {
+      return {*bg};
+    }
+
+    if (aStopAtThemed && frame->IsThemed()) {
+      return {NS_TRANSPARENT, true};
+    }
+
+    if (frame->IsCanvasFrame()) {
+      if (aPreferBodyToCanvas && !GetPageSequenceForCanvas(frame)) {
+        if (auto* body = pc->Document()->GetBodyElement()) {
+          if (nsIFrame* f = body->GetPrimaryFrame()) {
+            if (auto bg = BgColorIfNotTransparent(f)) {
+              return {*bg};
+            }
+          }
+        }
+      }
+      if (nsIFrame* bgFrame = FindBackgroundFrame(frame)) {
+        if (auto bg = BgColorIfNotTransparent(bgFrame)) {
+          return {*bg};
+        }
+      }
+    }
+  }
+
+  return {pc->DefaultBackgroundColor()};
+}
+
+nsIFrame* nsCSSRendering::FindBackgroundStyleFrame(nsIFrame* aForFrame) {
+  const nsStyleBackground* result = aForFrame->StyleBackground();
+
+  // Check if we need to do propagation from BODY rather than HTML.
+  if (!result->IsTransparent(aForFrame)) {
+    return aForFrame;
+  }
+
+  nsIContent* content = aForFrame->GetContent();
+  // The root element content can't be null. We wouldn't know what
+  // frame to create for aFrame.
+  // Use |OwnerDoc| so it works during destruction.
+  if (!content) {
+    return aForFrame;
+  }
+
+  Document* document = content->OwnerDoc();
+
+  dom::Element* bodyContent = document->GetBodyElement();
+  // We need to null check the body node (bug 118829) since
+  // there are cases, thanks to the fix for bug 5569, where we
+  // will reflow a document with no body.  In particular, if a
+  // SCRIPT element in the head blocks the parser and then has a
+  // SCRIPT that does "document.location.href = 'foo'", then
+  // nsParser::Terminate will call |DidBuildModel| methods
+  // through to the content sink, which will call |StartLayout|
+  // and thus |Initialize| on the pres shell.  See bug 119351
+  // for the ugly details.
+  if (!bodyContent || aForFrame->StyleDisplay()->IsContainAny()) {
+    return aForFrame;
+  }
+
+  nsIFrame* bodyFrame = bodyContent->GetPrimaryFrame();
+  if (!bodyFrame || bodyFrame->StyleDisplay()->IsContainAny()) {
+    return aForFrame;
+  }
+
+  return nsLayoutUtils::GetStyleFrame(bodyFrame);
+}
+
+/**
+ * |FindBackground| finds the correct style data to use to paint the
+ * background.  It is responsible for handling the following two
+ * statements in section 14.2 of CSS2:
+ *
+ *   The background of the box generated by the root element covers the
+ *   entire canvas.
+ *
+ *   For HTML documents, however, we recommend that authors specify the
+ *   background for the BODY element rather than the HTML element. User
+ *   agents should observe the following precedence rules to fill in the
+ *   background: if the value of the 'background' property for the HTML
+ *   element is different from 'transparent' then use it, else use the
+ *   value of the 'background' property for the BODY element. If the
+ *   resulting value is 'transparent', the rendering is undefined.
+ *
+ * Thus, in our implementation, it is responsible for ensuring that:
+ *  + we paint the correct background on the |nsCanvasFrame| or |nsPageFrame|,
+ *  + we don't paint the background on the root element, and
+ *  + we don't paint the background on the BODY element in *some* cases,
+ *    and for SGML-based HTML documents only.
+ *
+ * |FindBackground| checks whether a background should be painted. If yes, it
+ * returns the resulting ComputedStyle to use for the background information;
+ * Otherwise, it returns nullptr.
+ */
+ComputedStyle* nsCSSRendering::FindRootFrameBackground(nsIFrame* aForFrame) {
+  return FindBackgroundStyleFrame(aForFrame)->Style();
+}
+
+static nsIFrame* FindCanvasBackgroundFrame(const nsIFrame* aForFrame,
+                                           nsIFrame* aRootElementFrame) {
+  MOZ_ASSERT(aForFrame->IsCanvasFrame(), "not a canvas frame");
+  if (auto* ps = GetPageSequenceForCanvas(aForFrame)) {
+    return ps;
+  }
+  if (aRootElementFrame) {
+    return nsCSSRendering::FindBackgroundStyleFrame(aRootElementFrame);
+  }
+  // This should always give transparent, so we'll fill it in with the default
+  // color if needed.  This seems to happen a bit while a page is being loaded.
+  return const_cast<nsIFrame*>(aForFrame);
+}
+
+// Helper for FindBackgroundFrame. Returns true if aForFrame has a meaningful
+// background that it should draw (i.e. that it hasn't propagated to another
+// frame).  See documentation for FindBackground.
+inline bool FrameHasMeaningfulBackground(const nsIFrame* aForFrame,
+                                         nsIFrame* aRootElementFrame) {
+  MOZ_ASSERT(!aForFrame->IsCanvasFrame(),
+             "FindBackgroundFrame handles canvas frames before calling us, "
+             "so we don't need to consider them here");
+
+  if (aForFrame == aRootElementFrame) {
+    // We must have propagated our background to the viewport or canvas. Abort.
+    return false;
+  }
+
+  // Return true unless the frame is for a BODY element whose background
+  // was propagated to the viewport.
+
+  nsIContent* content = aForFrame->GetContent();
+  if (!content || content->NodeInfo()->NameAtom() != nsGkAtoms::body) {
+    return true;  // not frame for a "body" element
+  }
+  // It could be a non-HTML "body" element but that's OK, we'd fail the
+  // bodyContent check below
+
+  if (aForFrame->Style()->GetPseudoType() != PseudoStyleType::NotPseudo ||
+      aForFrame->StyleDisplay()->IsContainAny()) {
+    return true;  // A pseudo-element frame, or contained.
+  }
+
+  // We should only look at the <html> background if we're in an HTML document
+  Document* document = content->OwnerDoc();
+
+  dom::Element* bodyContent = document->GetBodyElement();
+  if (bodyContent != content) {
+    return true;  // this wasn't the background that was propagated
+  }
+
+  // This can be called even when there's no root element yet, during frame
+  // construction, via nsLayoutUtils::FrameHasTransparency and
+  // nsContainerFrame::SyncFrameViewProperties.
+  if (!aRootElementFrame || aRootElementFrame->StyleDisplay()->IsContainAny()) {
+    return true;
+  }
+
+  const nsStyleBackground* htmlBG = aRootElementFrame->StyleBackground();
+  return !htmlBG->IsTransparent(aRootElementFrame);
+}
+
+nsIFrame* nsCSSRendering::FindBackgroundFrame(const nsIFrame* aForFrame) {
+  nsIFrame* rootElementFrame =
+      aForFrame->PresShell()->FrameConstructor()->GetRootElementStyleFrame();
+  if (aForFrame->IsCanvasFrame()) {
+    return FindCanvasBackgroundFrame(aForFrame, rootElementFrame);
+  }
+
+  if (FrameHasMeaningfulBackground(aForFrame, rootElementFrame)) {
+    return const_cast<nsIFrame*>(aForFrame);
+  }
+
+  return nullptr;
+}
+
+ComputedStyle* nsCSSRendering::FindBackground(const nsIFrame* aForFrame) {
+  if (auto* backgroundFrame = FindBackgroundFrame(aForFrame)) {
+    return backgroundFrame->Style();
+  }
+  return nullptr;
+}
+
+void nsCSSRendering::BeginFrameTreesLocked() { ++gFrameTreeLockCount; }
+
+void nsCSSRendering::EndFrameTreesLocked() {
+  NS_ASSERTION(gFrameTreeLockCount > 0, "Unbalanced EndFrameTreeLocked");
+  --gFrameTreeLockCount;
+  if (gFrameTreeLockCount == 0) {
+    gInlineBGData->Reset();
+  }
+}
+
+bool nsCSSRendering::HasBoxShadowNativeTheme(nsIFrame* aFrame,
+                                             bool& aMaybeHasBorderRadius) {
+  const nsStyleDisplay* styleDisplay = aFrame->StyleDisplay();
+  nsITheme::Transparency transparency;
+  if (aFrame->IsThemed(styleDisplay, &transparency)) {
+    aMaybeHasBorderRadius = false;
+    // For opaque (rectangular) theme widgets we can take the generic
+    // border-box path with border-radius disabled.
+    return transparency != nsITheme::eOpaque;
+  }
+
+  aMaybeHasBorderRadius = true;
+  return false;
+}
+
+gfx::sRGBColor nsCSSRendering::GetShadowColor(const StyleSimpleShadow& aShadow,
+                                              nsIFrame* aFrame,
+                                              float aOpacity) {
+  // Get the shadow color; if not specified, use the foreground color
+  nscolor shadowColor = aShadow.color.CalcColor(aFrame);
+  sRGBColor color = sRGBColor::FromABGR(shadowColor);
+  color.a *= aOpacity;
+  return color;
+}
+
+nsRect nsCSSRendering::GetShadowRect(const nsRect& aFrameArea,
+                                     bool aNativeTheme, nsIFrame* aForFrame) {
+  nsRect frameRect = aNativeTheme ? aForFrame->InkOverflowRectRelativeToSelf() +
+                                        aFrameArea.TopLeft()
+                                  : aFrameArea;
+  Sides skipSides = aForFrame->GetSkipSides();
+  frameRect = BoxDecorationRectForBorder(aForFrame, frameRect, skipSides);
+
+  // Explicitly do not need to account for the spread radius here
+  // Webrender does it for us or PaintBoxShadow will for non-WR
+  return frameRect;
+}
+
+bool nsCSSRendering::GetBorderRadii(const nsRect& aFrameRect,
+                                    const nsRect& aBorderRect, nsIFrame* aFrame,
+                                    RectCornerRadii& aOutRadii) {
+  const nscoord oneDevPixel = aFrame->PresContext()->DevPixelsToAppUnits(1);
+  nscoord twipsRadii[8];
+  NS_ASSERTION(
+      aBorderRect.Size() == aFrame->VisualBorderRectRelativeToSelf().Size(),
+      "unexpected size");
+  nsSize sz = aFrameRect.Size();
+  bool hasBorderRadius = aFrame->GetBorderRadii(sz, sz, Sides(), twipsRadii);
+  if (hasBorderRadius) {
+    ComputePixelRadii(twipsRadii, oneDevPixel, &aOutRadii);
+  }
+
+  return hasBorderRadius;
+}
+
+void nsCSSRendering::PaintBoxShadowOuter(nsPresContext* aPresContext,
+                                         gfxContext& aRenderingContext,
+                                         nsIFrame* aForFrame,
+                                         const nsRect& aFrameArea,
+                                         const nsRect& aDirtyRect,
+                                         float aOpacity) {
+  DrawTarget& aDrawTarget = *aRenderingContext.GetDrawTarget();
+  auto shadows = aForFrame->StyleEffects()->mBoxShadow.AsSpan();
+  if (shadows.IsEmpty()) {
+    return;
+  }
+
+  bool hasBorderRadius;
+  // mutually exclusive with hasBorderRadius
+  bool nativeTheme = HasBoxShadowNativeTheme(aForFrame, hasBorderRadius);
+  const nsStyleDisplay* styleDisplay = aForFrame->StyleDisplay();
+
+  nsRect frameRect = GetShadowRect(aFrameArea, nativeTheme, aForFrame);
+
+  // Get any border radius, since box-shadow must also have rounded corners if
+  // the frame does.
+  RectCornerRadii borderRadii;
+  const nscoord oneDevPixel = aPresContext->DevPixelsToAppUnits(1);
+  if (hasBorderRadius) {
+    nscoord twipsRadii[8];
+    NS_ASSERTION(
+        aFrameArea.Size() == aForFrame->VisualBorderRectRelativeToSelf().Size(),
+        "unexpected size");
+    nsSize sz = frameRect.Size();
+    hasBorderRadius = aForFrame->GetBorderRadii(sz, sz, Sides(), twipsRadii);
+    if (hasBorderRadius) {
+      ComputePixelRadii(twipsRadii, oneDevPixel, &borderRadii);
+    }
+  }
+
+  // We don't show anything that intersects with the frame we're blurring on. So
+  // tell the blurrer not to do unnecessary work there.
+  gfxRect skipGfxRect = ThebesRect(NSRectToRect(frameRect, oneDevPixel));
+  skipGfxRect.Round();
+  bool useSkipGfxRect = true;
+  if (nativeTheme) {
+    // Optimize non-leaf native-themed frames by skipping computing pixels
+    // in the padding-box. We assume the padding-box is going to be painted
+    // opaquely for non-leaf frames.
+    // XXX this may not be a safe assumption; we should make this go away
+    // by optimizing box-shadow drawing more for the cases where we don't have a
+    // skip-rect.
+    useSkipGfxRect = !aForFrame->IsLeaf();
+    nsRect paddingRect =
+        aForFrame->GetPaddingRectRelativeToSelf() + aFrameArea.TopLeft();
+    skipGfxRect = nsLayoutUtils::RectToGfxRect(paddingRect, oneDevPixel);
+  } else if (hasBorderRadius) {
+    skipGfxRect.Deflate(gfxMargin(
+        std::max(borderRadii[C_TL].height, borderRadii[C_TR].height), 0,
+        std::max(borderRadii[C_BL].height, borderRadii[C_BR].height), 0));
+  }
+
+  for (const StyleBoxShadow& shadow : Reversed(shadows)) {
+    if (shadow.inset) {
+      continue;
+    }
+
+    nsRect shadowRect = frameRect;
+    nsPoint shadowOffset(shadow.base.horizontal.ToAppUnits(),
+                         shadow.base.vertical.ToAppUnits());
+    shadowRect.MoveBy(shadowOffset);
+    nscoord shadowSpread = shadow.spread.ToAppUnits();
+    if (!nativeTheme) {
+      shadowRect.Inflate(shadowSpread);
+    }
+
+    // shadowRect won't include the blur, so make an extra rect here that
+    // includes the blur for use in the even-odd rule below.
+    nsRect shadowRectPlusBlur = shadowRect;
+    nscoord blurRadius = shadow.base.blur.ToAppUnits();
+    shadowRectPlusBlur.Inflate(
+        nsContextBoxBlur::GetBlurRadiusMargin(blurRadius, oneDevPixel));
+
+    Rect shadowGfxRectPlusBlur = NSRectToRect(shadowRectPlusBlur, oneDevPixel);
+    shadowGfxRectPlusBlur.RoundOut();
+    MaybeSnapToDevicePixels(shadowGfxRectPlusBlur, aDrawTarget, true);
+
+    sRGBColor gfxShadowColor = GetShadowColor(shadow.base, aForFrame, aOpacity);
+
+    if (nativeTheme) {
+      nsContextBoxBlur blurringArea;
+
+      // When getting the widget shape from the native theme, we're going
+      // to draw the widget into the shadow surface to create a mask.
+      // We need to ensure that there actually *is* a shadow surface
+      // and that we're not going to draw directly into aRenderingContext.
+      gfxContext* shadowContext = blurringArea.Init(
+          shadowRect, shadowSpread, blurRadius, oneDevPixel, &aRenderingContext,
+          aDirtyRect, useSkipGfxRect ? &skipGfxRect : nullptr,
+          nsContextBoxBlur::FORCE_MASK);
+      if (!shadowContext) continue;
+
+      MOZ_ASSERT(shadowContext == blurringArea.GetContext());
+
+      aRenderingContext.Save();
+      aRenderingContext.SetColor(gfxShadowColor);
+
+      // Draw the shape of the frame so it can be blurred. Recall how
+      // nsContextBoxBlur doesn't make any temporary surfaces if blur is 0 and
+      // it just returns the original surface? If we have no blur, we're
+      // painting this fill on the actual content surface (aRenderingContext ==
+      // shadowContext) which is why we set up the color and clip before doing
+      // this.
+
+      // We don't clip the border-box from the shadow, nor any other box.
+      // We assume that the native theme is going to paint over the shadow.
+
+      // Draw the widget shape
+      gfxContextMatrixAutoSaveRestore save(shadowContext);
+      gfxPoint devPixelOffset = nsLayoutUtils::PointToGfxPoint(
+          shadowOffset, aPresContext->AppUnitsPerDevPixel());
+      shadowContext->SetMatrixDouble(
+          shadowContext->CurrentMatrixDouble().PreTranslate(devPixelOffset));
+
+      nsRect nativeRect = aDirtyRect;
+      nativeRect.MoveBy(-shadowOffset);
+      nativeRect.IntersectRect(frameRect, nativeRect);
+      aPresContext->Theme()->DrawWidgetBackground(
+          shadowContext, aForFrame, styleDisplay->EffectiveAppearance(),
+          aFrameArea, nativeRect, nsITheme::DrawOverflow::No);
+
+      blurringArea.DoPaint();
+      aRenderingContext.Restore();
+    } else {
+      aRenderingContext.Save();
+
+      {
+        Rect innerClipRect = NSRectToRect(frameRect, oneDevPixel);
+        if (!MaybeSnapToDevicePixels(innerClipRect, aDrawTarget, true)) {
+          innerClipRect.Round();
+        }
+
+        // Clip out the interior of the frame's border edge so that the shadow
+        // is only painted outside that area.
+        RefPtr<PathBuilder> builder =
+            aDrawTarget.CreatePathBuilder(FillRule::FILL_EVEN_ODD);
+        AppendRectToPath(builder, shadowGfxRectPlusBlur);
+        if (hasBorderRadius) {
+          AppendRoundedRectToPath(builder, innerClipRect, borderRadii);
+        } else {
+          AppendRectToPath(builder, innerClipRect);
+        }
+        RefPtr<Path> path = builder->Finish();
+        aRenderingContext.Clip(path);
+      }
+
+      // Clip the shadow so that we only get the part that applies to aForFrame.
+      nsRect fragmentClip = shadowRectPlusBlur;
+      Sides skipSides = aForFrame->GetSkipSides();
+      if (!skipSides.IsEmpty()) {
+        if (skipSides.Left()) {
+          nscoord xmost = fragmentClip.XMost();
+          fragmentClip.x = aFrameArea.x;
+          fragmentClip.width = xmost - fragmentClip.x;
+        }
+        if (skipSides.Right()) {
+          nscoord xmost = fragmentClip.XMost();
+          nscoord overflow = xmost - aFrameArea.XMost();
+          if (overflow > 0) {
+            fragmentClip.width -= overflow;
+          }
+        }
+        if (skipSides.Top()) {
+          nscoord ymost = fragmentClip.YMost();
+          fragmentClip.y = aFrameArea.y;
+          fragmentClip.height = ymost - fragmentClip.y;
+        }
+        if (skipSides.Bottom()) {
+          nscoord ymost = fragmentClip.YMost();
+          nscoord overflow = ymost - aFrameArea.YMost();
+          if (overflow > 0) {
+            fragmentClip.height -= overflow;
+          }
+        }
+      }
+      fragmentClip = fragmentClip.Intersect(aDirtyRect);
+      aRenderingContext.Clip(NSRectToSnappedRect(
+          fragmentClip, aForFrame->PresContext()->AppUnitsPerDevPixel(),
+          aDrawTarget));
+
+      RectCornerRadii clipRectRadii;
+      if (hasBorderRadius) {
+        Float spreadDistance = Float(shadowSpread / oneDevPixel);
+
+        Float borderSizes[4];
+
+        borderSizes[eSideLeft] = spreadDistance;
+        borderSizes[eSideTop] = spreadDistance;
+        borderSizes[eSideRight] = spreadDistance;
+        borderSizes[eSideBottom] = spreadDistance;
+
+        nsCSSBorderRenderer::ComputeOuterRadii(borderRadii, borderSizes,
+                                               &clipRectRadii);
+      }
+      nsContextBoxBlur::BlurRectangle(
+          &aRenderingContext, shadowRect, oneDevPixel,
+          hasBorderRadius ? &clipRectRadii : nullptr, blurRadius,
+          gfxShadowColor, aDirtyRect, skipGfxRect);
+      aRenderingContext.Restore();
+    }
+  }
+}
+
+nsRect nsCSSRendering::GetBoxShadowInnerPaddingRect(nsIFrame* aFrame,
+                                                    const nsRect& aFrameArea) {
+  Sides skipSides = aFrame->GetSkipSides();
+  nsRect frameRect = BoxDecorationRectForBorder(aFrame, aFrameArea, skipSides);
+
+  nsRect paddingRect = frameRect;
+  nsMargin border = aFrame->GetUsedBorder();
+  paddingRect.Deflate(border);
+  return paddingRect;
+}
+
+bool nsCSSRendering::ShouldPaintBoxShadowInner(nsIFrame* aFrame) {
+  const Span<const StyleBoxShadow> shadows =
+      aFrame->StyleEffects()->mBoxShadow.AsSpan();
+  if (shadows.IsEmpty()) {
+    return false;
+  }
+
+  if (aFrame->IsThemed() && aFrame->GetContent() &&
+      !nsContentUtils::IsChromeDoc(aFrame->GetContent()->GetComposedDoc())) {
+    // There's no way of getting hold of a shape corresponding to a
+    // "padding-box" for native-themed widgets, so just don't draw
+    // inner box-shadows for them. But we allow chrome to paint inner
+    // box shadows since chrome can be aware of the platform theme.
+    return false;
+  }
+
+  return true;
+}
+
+bool nsCSSRendering::GetShadowInnerRadii(nsIFrame* aFrame,
+                                         const nsRect& aFrameArea,
+                                         RectCornerRadii& aOutInnerRadii) {
+  // Get any border radius, since box-shadow must also have rounded corners
+  // if the frame does.
+  nscoord twipsRadii[8];
+  nsRect frameRect =
+      BoxDecorationRectForBorder(aFrame, aFrameArea, aFrame->GetSkipSides());
+  nsSize sz = frameRect.Size();
+  nsMargin border = aFrame->GetUsedBorder();
+  aFrame->GetBorderRadii(sz, sz, Sides(), twipsRadii);
+  const nscoord oneDevPixel = aFrame->PresContext()->DevPixelsToAppUnits(1);
+
+  RectCornerRadii borderRadii;
+
+  const bool hasBorderRadius =
+      GetBorderRadii(frameRect, aFrameArea, aFrame, borderRadii);
+
+  if (hasBorderRadius) {
+    ComputePixelRadii(twipsRadii, oneDevPixel, &borderRadii);
+
+    Float borderSizes[4] = {
+        Float(border.top) / oneDevPixel, Float(border.right) / oneDevPixel,
+        Float(border.bottom) / oneDevPixel, Float(border.left) / oneDevPixel};
+    nsCSSBorderRenderer::ComputeInnerRadii(borderRadii, borderSizes,
+                                           &aOutInnerRadii);
+  }
+
+  return hasBorderRadius;
+}
+
+void nsCSSRendering::PaintBoxShadowInner(nsPresContext* aPresContext,
+                                         gfxContext& aRenderingContext,
+                                         nsIFrame* aForFrame,
+                                         const nsRect& aFrameArea) {
+  if (!ShouldPaintBoxShadowInner(aForFrame)) {
+    return;
+  }
+
+  const Span<const StyleBoxShadow> shadows =
+      aForFrame->StyleEffects()->mBoxShadow.AsSpan();
+  NS_ASSERTION(
+      aForFrame->IsFieldSetFrame() || aFrameArea.Size() == aForFrame->GetSize(),
+      "unexpected size");
+
+  nsRect paddingRect = GetBoxShadowInnerPaddingRect(aForFrame, aFrameArea);
+
+  RectCornerRadii innerRadii;
+  bool hasBorderRadius = GetShadowInnerRadii(aForFrame, aFrameArea, innerRadii);
+
+  const nscoord oneDevPixel = aPresContext->DevPixelsToAppUnits(1);
+
+  for (const StyleBoxShadow& shadow : Reversed(shadows)) {
+    if (!shadow.inset) {
+      continue;
+    }
+
+    // shadowPaintRect: the area to paint on the temp surface
+    // shadowClipRect: the area on the temporary surface within shadowPaintRect
+    //                 that we will NOT paint in
+    nscoord blurRadius = shadow.base.blur.ToAppUnits();
+    nsMargin blurMargin =
+        nsContextBoxBlur::GetBlurRadiusMargin(blurRadius, oneDevPixel);
+    nsRect shadowPaintRect = paddingRect;
+    shadowPaintRect.Inflate(blurMargin);
+
+    // Round the spread radius to device pixels (by truncation).
+    // This mostly matches what we do for borders, except that we don't round
+    // up values between zero and one device pixels to one device pixel.
+    // This way of rounding is symmetric around zero, which makes sense for
+    // the spread radius.
+    int32_t spreadDistance = shadow.spread.ToAppUnits() / oneDevPixel;
+    nscoord spreadDistanceAppUnits =
+        aPresContext->DevPixelsToAppUnits(spreadDistance);
+
+    nsRect shadowClipRect = paddingRect;
+    shadowClipRect.MoveBy(shadow.base.horizontal.ToAppUnits(),
+                          shadow.base.vertical.ToAppUnits());
+    shadowClipRect.Deflate(spreadDistanceAppUnits, spreadDistanceAppUnits);
+
+    Rect shadowClipGfxRect = NSRectToRect(shadowClipRect, oneDevPixel);
+    shadowClipGfxRect.Round();
+
+    RectCornerRadii clipRectRadii;
+    if (hasBorderRadius) {
+      // Calculate the radii the inner clipping rect will have
+      Float borderSizes[4] = {0, 0, 0, 0};
+
+      // See PaintBoxShadowOuter and bug 514670
+      if (innerRadii[C_TL].width > 0 || innerRadii[C_BL].width > 0) {
+        borderSizes[eSideLeft] = spreadDistance;
+      }
+
+      if (innerRadii[C_TL].height > 0 || innerRadii[C_TR].height > 0) {
+        borderSizes[eSideTop] = spreadDistance;
+      }
+
+      if (innerRadii[C_TR].width > 0 || innerRadii[C_BR].width > 0) {
+        borderSizes[eSideRight] = spreadDistance;
+      }
+
+      if (innerRadii[C_BL].height > 0 || innerRadii[C_BR].height > 0) {
+        borderSizes[eSideBottom] = spreadDistance;
+      }
+
+      nsCSSBorderRenderer::ComputeInnerRadii(innerRadii, borderSizes,
+                                             &clipRectRadii);
+    }
+
+    // Set the "skip rect" to the area within the frame that we don't paint in,
+    // including after blurring.
+    nsRect skipRect = shadowClipRect;
+    skipRect.Deflate(blurMargin);
+    gfxRect skipGfxRect = nsLayoutUtils::RectToGfxRect(skipRect, oneDevPixel);
+    if (hasBorderRadius) {
+      skipGfxRect.Deflate(gfxMargin(
+          std::max(clipRectRadii[C_TL].height, clipRectRadii[C_TR].height), 0,
+          std::max(clipRectRadii[C_BL].height, clipRectRadii[C_BR].height), 0));
+    }
+
+    // When there's a blur radius, gfxAlphaBoxBlur leaves the skiprect area
+    // unchanged. And by construction the gfxSkipRect is not touched by the
+    // rendered shadow (even after blurring), so those pixels must be completely
+    // transparent in the shadow, so drawing them changes nothing.
+    DrawTarget* drawTarget = aRenderingContext.GetDrawTarget();
+
+    // Clip the context to the area of the frame's padding rect, so no part of
+    // the shadow is painted outside. Also cut out anything beyond where the
+    // inset shadow will be.
+    Rect shadowGfxRect = NSRectToRect(paddingRect, oneDevPixel);
+    shadowGfxRect.Round();
+
+    sRGBColor shadowColor = GetShadowColor(shadow.base, aForFrame, 1.0);
+    aRenderingContext.Save();
+
+    // This clips the outside border radius.
+    // clipRectRadii is the border radius inside the inset shadow.
+    if (hasBorderRadius) {
+      RefPtr<Path> roundedRect =
+          MakePathForRoundedRect(*drawTarget, shadowGfxRect, innerRadii);
+      aRenderingContext.Clip(roundedRect);
+    } else {
+      aRenderingContext.Clip(shadowGfxRect);
+    }
+
+    nsContextBoxBlur insetBoxBlur;
+    gfxRect destRect =
+        nsLayoutUtils::RectToGfxRect(shadowPaintRect, oneDevPixel);
+    Point shadowOffset(shadow.base.horizontal.ToAppUnits() / oneDevPixel,
+                       shadow.base.vertical.ToAppUnits() / oneDevPixel);
+
+    insetBoxBlur.InsetBoxBlur(
+        &aRenderingContext, ToRect(destRect), shadowClipGfxRect, shadowColor,
+        blurRadius, spreadDistanceAppUnits, oneDevPixel, hasBorderRadius,
+        clipRectRadii, ToRect(skipGfxRect), shadowOffset);
+    aRenderingContext.Restore();
+  }
+}
+
+/* static */
+nsCSSRendering::PaintBGParams nsCSSRendering::PaintBGParams::ForAllLayers(
+    nsPresContext& aPresCtx, const nsRect& aDirtyRect,
+    const nsRect& aBorderArea, nsIFrame* aFrame, uint32_t aPaintFlags,
+    float aOpacity) {
+  MOZ_ASSERT(aFrame);
+
+  PaintBGParams result(aPresCtx, aDirtyRect, aBorderArea, aFrame, aPaintFlags,
+                       -1, CompositionOp::OP_OVER, aOpacity);
+
+  return result;
+}
+
+/* static */
+nsCSSRendering::PaintBGParams nsCSSRendering::PaintBGParams::ForSingleLayer(
+    nsPresContext& aPresCtx, const nsRect& aDirtyRect,
+    const nsRect& aBorderArea, nsIFrame* aFrame, uint32_t aPaintFlags,
+    int32_t aLayer, CompositionOp aCompositionOp, float aOpacity) {
+  MOZ_ASSERT(aFrame && (aLayer != -1));
+
+  PaintBGParams result(aPresCtx, aDirtyRect, aBorderArea, aFrame, aPaintFlags,
+                       aLayer, aCompositionOp, aOpacity);
+
+  return result;
+}
+
+ImgDrawResult nsCSSRendering::PaintStyleImageLayer(const PaintBGParams& aParams,
+                                                   gfxContext& aRenderingCtx) {
+  AUTO_PROFILER_LABEL("nsCSSRendering::PaintStyleImageLayer", GRAPHICS);
+
+  MOZ_ASSERT(aParams.frame,
+             "Frame is expected to be provided to PaintStyleImageLayer");
+
+  const ComputedStyle* sc = FindBackground(aParams.frame);
+  if (!sc) {
+    // We don't want to bail out if moz-appearance is set on a root
+    // node. If it has a parent content node, bail because it's not
+    // a root, otherwise keep going in order to let the theme stuff
+    // draw the background. The canvas really should be drawing the
+    // bg, but there's no way to hook that up via css.
+    if (!aParams.frame->StyleDisplay()->HasAppearance()) {
+      return ImgDrawResult::SUCCESS;
+    }
+
+    nsIContent* content = aParams.frame->GetContent();
+    if (!content || content->GetParent()) {
+      return ImgDrawResult::SUCCESS;
+    }
+
+    sc = aParams.frame->Style();
+  }
+
+  return PaintStyleImageLayerWithSC(aParams, aRenderingCtx, sc,
+                                    *aParams.frame->StyleBorder());
+}
+
+bool nsCSSRendering::CanBuildWebRenderDisplayItemsForStyleImageLayer(
+    WebRenderLayerManager* aManager, nsPresContext& aPresCtx, nsIFrame* aFrame,
+    const nsStyleBackground* aBackgroundStyle, int32_t aLayer,
+    uint32_t aPaintFlags) {
+  if (!aBackgroundStyle) {
+    return false;
+  }
+
+  MOZ_ASSERT(aFrame && aLayer >= 0 &&
+             (uint32_t)aLayer < aBackgroundStyle->mImage.mLayers.Length());
+
+  // We cannot draw native themed backgrounds
+  StyleAppearance appearance = aFrame->StyleDisplay()->EffectiveAppearance();
+  if (appearance != StyleAppearance::None) {
+    nsITheme* theme = aPresCtx.Theme();
+    if (theme->ThemeSupportsWidget(&aPresCtx, aFrame, appearance)) {
+      return false;
+    }
+  }
+
+  // We only support painting gradients and image for a single style image
+  // layer, and we don't support crop-rects.
+  const auto& styleImage =
+      aBackgroundStyle->mImage.mLayers[aLayer].mImage.FinalImage();
+  if (styleImage.IsImageRequestType()) {
+    imgRequestProxy* requestProxy = styleImage.GetImageRequest();
+    if (!requestProxy) {
+      return false;
+    }
+
+    uint32_t imageFlags = imgIContainer::FLAG_NONE;
+    if (aPaintFlags & nsCSSRendering::PAINTBG_SYNC_DECODE_IMAGES) {
+      imageFlags |= imgIContainer::FLAG_SYNC_DECODE;
+    }
+
+    nsCOMPtr<imgIContainer> srcImage;
+    requestProxy->GetImage(getter_AddRefs(srcImage));
+    if (!srcImage ||
+        !srcImage->IsImageContainerAvailable(aManager, imageFlags)) {
+      return false;
+    }
+
+    return true;
+  }
+
+  if (styleImage.IsGradient()) {
+    return true;
+  }
+
+  return false;
+}
+
+ImgDrawResult nsCSSRendering::BuildWebRenderDisplayItemsForStyleImageLayer(
+    const PaintBGParams& aParams, mozilla::wr::DisplayListBuilder& aBuilder,
+    mozilla::wr::IpcResourceUpdateQueue& aResources,
+    const mozilla::layers::StackingContextHelper& aSc,
+    mozilla::layers::RenderRootStateManager* aManager, nsDisplayItem* aItem) {
+  MOZ_ASSERT(aParams.frame,
+             "Frame is expected to be provided to "
+             "BuildWebRenderDisplayItemsForStyleImageLayer");
+
+  ComputedStyle* sc = FindBackground(aParams.frame);
+  if (!sc) {
+    // We don't want to bail out if moz-appearance is set on a root
+    // node. If it has a parent content node, bail because it's not
+    // a root, otherwise keep going in order to let the theme stuff
+    // draw the background. The canvas really should be drawing the
+    // bg, but there's no way to hook that up via css.
+    if (!aParams.frame->StyleDisplay()->HasAppearance()) {
+      return ImgDrawResult::SUCCESS;
+    }
+
+    nsIContent* content = aParams.frame->GetContent();
+    if (!content || content->GetParent()) {
+      return ImgDrawResult::SUCCESS;
+    }
+
+    sc = aParams.frame->Style();
+  }
+  return BuildWebRenderDisplayItemsForStyleImageLayerWithSC(
+      aParams, aBuilder, aResources, aSc, aManager, aItem, sc,
+      *aParams.frame->StyleBorder());
+}
+
+static bool IsOpaqueBorderEdge(const nsStyleBorder& aBorder,
+                               mozilla::Side aSide) {
+  if (aBorder.GetComputedBorder().Side(aSide) == 0) return true;
+  switch (aBorder.GetBorderStyle(aSide)) {
+    case StyleBorderStyle::Solid:
+    case StyleBorderStyle::Groove:
+    case StyleBorderStyle::Ridge:
+    case StyleBorderStyle::Inset:
+    case StyleBorderStyle::Outset:
+      break;
+    default:
+      return false;
+  }
+
+  // If we're using a border image, assume it's not fully opaque,
+  // because we may not even have the image loaded at this point, and
+  // even if we did, checking whether the relevant tile is fully
+  // opaque would be too much work.
+  if (!aBorder.mBorderImageSource.IsNone()) {
+    return false;
+  }
+
+  StyleColor color = aBorder.BorderColorFor(aSide);
+  // We don't know the foreground color here, so if it's being used
+  // we must assume it might be transparent.
+  return !color.MaybeTransparent();
+}
+
+/**
+ * Returns true if all border edges are either missing or opaque.
+ */
+static bool IsOpaqueBorder(const nsStyleBorder& aBorder) {
+  for (const auto i : mozilla::AllPhysicalSides()) {
+    if (!IsOpaqueBorderEdge(aBorder, i)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+static inline void SetupDirtyRects(const nsRect& aBGClipArea,
+                                   const nsRect& aCallerDirtyRect,
+                                   nscoord aAppUnitsPerPixel,
+                                   /* OUT: */
+                                   nsRect* aDirtyRect, gfxRect* aDirtyRectGfx) {
+  aDirtyRect->IntersectRect(aBGClipArea, aCallerDirtyRect);
+
+  // Compute the Thebes equivalent of the dirtyRect.
+  *aDirtyRectGfx = nsLayoutUtils::RectToGfxRect(*aDirtyRect, aAppUnitsPerPixel);
+  NS_WARNING_ASSERTION(aDirtyRect->IsEmpty() || !aDirtyRectGfx->IsEmpty(),
+                       "converted dirty rect should not be empty");
+  MOZ_ASSERT(!aDirtyRect->IsEmpty() || aDirtyRectGfx->IsEmpty(),
+             "second should be empty if first is");
+}
+
+static bool IsSVGStyleGeometryBox(StyleGeometryBox aBox) {
+  return (aBox == StyleGeometryBox::FillBox ||
+          aBox == StyleGeometryBox::StrokeBox ||
+          aBox == StyleGeometryBox::ViewBox);
+}
+
+static bool IsHTMLStyleGeometryBox(StyleGeometryBox aBox) {
+  return (aBox == StyleGeometryBox::ContentBox ||
+          aBox == StyleGeometryBox::PaddingBox ||
+          aBox == StyleGeometryBox::BorderBox ||
+          aBox == StyleGeometryBox::MarginBox);
+}
+
+static StyleGeometryBox ComputeBoxValueForOrigin(nsIFrame* aForFrame,
+                                                 StyleGeometryBox aBox) {
+  // The mapping for mask-origin is from
+  // https://drafts.fxtf.org/css-masking/#the-mask-origin
+  if (!aForFrame->HasAnyStateBits(NS_FRAME_SVG_LAYOUT)) {
+    // For elements with associated CSS layout box, the values fill-box,
+    // stroke-box and view-box compute to the initial value of mask-origin.
+    if (IsSVGStyleGeometryBox(aBox)) {
+      return StyleGeometryBox::BorderBox;
+    }
+  } else {
+    // For SVG elements without associated CSS layout box, the values
+    // content-box, padding-box, border-box compute to fill-box.
+    if (IsHTMLStyleGeometryBox(aBox)) {
+      return StyleGeometryBox::FillBox;
+    }
+  }
+
+  return aBox;
+}
+
+static StyleGeometryBox ComputeBoxValueForClip(const nsIFrame* aForFrame,
+                                               StyleGeometryBox aBox) {
+  // The mapping for mask-clip is from
+  // https://drafts.fxtf.org/css-masking/#the-mask-clip
+  if (aForFrame->HasAnyStateBits(NS_FRAME_SVG_LAYOUT)) {
+    // For SVG elements without associated CSS layout box, the used values for
+    // content-box and padding-box compute to fill-box and for border-box and
+    // margin-box compute to stroke-box.
+    switch (aBox) {
+      case StyleGeometryBox::ContentBox:
+      case StyleGeometryBox::PaddingBox:
+        return StyleGeometryBox::FillBox;
+      case StyleGeometryBox::BorderBox:
+      case StyleGeometryBox::MarginBox:
+        return StyleGeometryBox::StrokeBox;
+      default:
+        return aBox;
+    }
+  }
+
+  // For elements with associated CSS layout box, the used values for fill-box
+  // compute to content-box and for stroke-box and view-box compute to
+  // border-box.
+  switch (aBox) {
+    case StyleGeometryBox::FillBox:
+      return StyleGeometryBox::ContentBox;
+    case StyleGeometryBox::StrokeBox:
+    case StyleGeometryBox::ViewBox:
+      return StyleGeometryBox::BorderBox;
+    default:
+      return aBox;
+  }
+}
+
+bool nsCSSRendering::ImageLayerClipState::IsValid() const {
+  // mDirtyRectInDevPx comes from mDirtyRectInAppUnits. mDirtyRectInAppUnits
+  // can not be empty if mDirtyRectInDevPx is not.
+  if (!mDirtyRectInDevPx.IsEmpty() && mDirtyRectInAppUnits.IsEmpty()) {
+    return false;
+  }
+
+  if (mHasRoundedCorners == mClippedRadii.IsEmpty()) {
+    return false;
+  }
+
+  return true;
+}
+
+/* static */
+void nsCSSRendering::GetImageLayerClip(
+    const nsStyleImageLayers::Layer& aLayer, nsIFrame* aForFrame,
+    const nsStyleBorder& aBorder, const nsRect& aBorderArea,
+    const nsRect& aCallerDirtyRect, bool aWillPaintBorder,
+    nscoord aAppUnitsPerPixel,
+    /* out */ ImageLayerClipState* aClipState) {
+  StyleGeometryBox layerClip = ComputeBoxValueForClip(aForFrame, aLayer.mClip);
+  if (IsSVGStyleGeometryBox(layerClip)) {
+    MOZ_ASSERT(aForFrame->HasAnyStateBits(NS_FRAME_SVG_LAYOUT));
+
+    // The coordinate space of clipArea is svg user space.
+    nsRect clipArea =
+        nsLayoutUtils::ComputeSVGReferenceRect(aForFrame, layerClip);
+
+    nsRect strokeBox = (layerClip == StyleGeometryBox::StrokeBox)
+                           ? clipArea
+                           : nsLayoutUtils::ComputeSVGReferenceRect(
+                                 aForFrame, StyleGeometryBox::StrokeBox);
+    nsRect clipAreaRelativeToStrokeBox = clipArea - strokeBox.TopLeft();
+
+    // aBorderArea is the stroke-box area in a coordinate space defined by
+    // the caller. This coordinate space can be svg user space of aForFrame,
+    // the space of aForFrame's reference-frame, or anything else.
+    //
+    // Which coordinate space chosen for aBorderArea is not matter. What
+    // matter is to ensure returning aClipState->mBGClipArea in the consistent
+    // coordiante space with aBorderArea. So we evaluate the position of clip
+    // area base on the position of aBorderArea here.
+    aClipState->mBGClipArea =
+        clipAreaRelativeToStrokeBox + aBorderArea.TopLeft();
+
+    SetupDirtyRects(aClipState->mBGClipArea, aCallerDirtyRect,
+                    aAppUnitsPerPixel, &aClipState->mDirtyRectInAppUnits,
+                    &aClipState->mDirtyRectInDevPx);
+    MOZ_ASSERT(aClipState->IsValid());
+    return;
+  }
+
+  if (layerClip == StyleGeometryBox::NoClip) {
+    aClipState->mBGClipArea = aCallerDirtyRect;
+
+    SetupDirtyRects(aClipState->mBGClipArea, aCallerDirtyRect,
+                    aAppUnitsPerPixel, &aClipState->mDirtyRectInAppUnits,
+                    &aClipState->mDirtyRectInDevPx);
+    MOZ_ASSERT(aClipState->IsValid());
+    return;
+  }
+
+  MOZ_ASSERT(!aForFrame->HasAnyStateBits(NS_FRAME_SVG_LAYOUT));
+
+  // Compute the outermost boundary of the area that might be painted.
+  // Same coordinate space as aBorderArea.
+  Sides skipSides = aForFrame->GetSkipSides();
+  nsRect clipBorderArea =
+      BoxDecorationRectForBorder(aForFrame, aBorderArea, skipSides, &aBorder);
+
+  bool haveRoundedCorners = false;
+  LayoutFrameType fType = aForFrame->Type();
+  if (fType != LayoutFrameType::TableColGroup &&
+      fType != LayoutFrameType::TableCol &&
+      fType != LayoutFrameType::TableRow &&
+      fType != LayoutFrameType::TableRowGroup) {
+    haveRoundedCorners = GetRadii(aForFrame, aBorder, aBorderArea,
+                                  clipBorderArea, aClipState->mRadii);
+  }
+  bool isSolidBorder = aWillPaintBorder && IsOpaqueBorder(aBorder);
+  if (isSolidBorder && layerClip == StyleGeometryBox::BorderBox) {
+    // If we have rounded corners, we need to inflate the background
+    // drawing area a bit to avoid seams between the border and
+    // background.
+    layerClip = haveRoundedCorners ? StyleGeometryBox::MozAlmostPadding
+                                   : StyleGeometryBox::PaddingBox;
+  }
+
+  aClipState->mBGClipArea = clipBorderArea;
+
+  if (aForFrame->IsScrollFrame() &&
+      StyleImageLayerAttachment::Local == aLayer.mAttachment) {
+    // As of this writing, this is still in discussion in the CSS Working Group
+    // http://lists.w3.org/Archives/Public/www-style/2013Jul/0250.html
+
+    // The rectangle for 'background-clip' scrolls with the content,
+    // but the background is also clipped at a non-scrolling 'padding-box'
+    // like the content. (See below.)
+    // Therefore, only 'content-box' makes a difference here.
+    if (layerClip == StyleGeometryBox::ContentBox) {
+      nsIScrollableFrame* scrollableFrame = do_QueryFrame(aForFrame);
+      // Clip at a rectangle attached to the scrolled content.
+      aClipState->mHasAdditionalBGClipArea = true;
+      aClipState->mAdditionalBGClipArea =
+          nsRect(aClipState->mBGClipArea.TopLeft() +
+                     scrollableFrame->GetScrolledFrame()->GetPosition()
+                     // For the dir=rtl case:
+                     + scrollableFrame->GetScrollRange().TopLeft(),
+                 scrollableFrame->GetScrolledRect().Size());
+      nsMargin padding = aForFrame->GetUsedPadding();
+      // padding-bottom is ignored on scrollable frames:
+      // https://bugzilla.mozilla.org/show_bug.cgi?id=748518
+      padding.bottom = 0;
+      padding.ApplySkipSides(skipSides);
+      aClipState->mAdditionalBGClipArea.Deflate(padding);
+    }
+
+    // Also clip at a non-scrolling, rounded-corner 'padding-box',
+    // same as the scrolled content because of the 'overflow' property.
+    layerClip = StyleGeometryBox::PaddingBox;
+  }
+
+  // See the comment of StyleGeometryBox::Margin.
+  // Hitting this assertion means we decide to turn on margin-box support for
+  // positioned mask from CSS parser and style system. In this case, you
+  // should *inflate* mBGClipArea by the margin returning from
+  // aForFrame->GetUsedMargin() in the code chunk bellow.
+  MOZ_ASSERT(layerClip != StyleGeometryBox::MarginBox,
+             "StyleGeometryBox::MarginBox rendering is not supported yet.\n");
+
+  if (layerClip != StyleGeometryBox::BorderBox &&
+      layerClip != StyleGeometryBox::Text) {
+    nsMargin border = aForFrame->GetUsedBorder();
+    if (layerClip == StyleGeometryBox::MozAlmostPadding) {
+      // Reduce |border| by 1px (device pixels) on all sides, if
+      // possible, so that we don't get antialiasing seams between the
+      // {background|mask} and border.
+      border.top = std::max(0, border.top - aAppUnitsPerPixel);
+      border.right = std::max(0, border.right - aAppUnitsPerPixel);
+      border.bottom = std::max(0, border.bottom - aAppUnitsPerPixel);
+      border.left = std::max(0, border.left - aAppUnitsPerPixel);
+    } else if (layerClip != StyleGeometryBox::PaddingBox) {
+      NS_ASSERTION(layerClip == StyleGeometryBox::ContentBox,
+                   "unexpected background-clip");
+      border += aForFrame->GetUsedPadding();
+    }
+    border.ApplySkipSides(skipSides);
+    aClipState->mBGClipArea.Deflate(border);
+
+    if (haveRoundedCorners) {
+      nsIFrame::AdjustBorderRadii(aClipState->mRadii, -border);
+    }
+  }
+
+  if (haveRoundedCorners) {
+    auto d2a = aForFrame->PresContext()->AppUnitsPerDevPixel();
+    nsCSSRendering::ComputePixelRadii(aClipState->mRadii, d2a,
+                                      &aClipState->mClippedRadii);
+    aClipState->mHasRoundedCorners = !aClipState->mClippedRadii.IsEmpty();
+  }
+
+  if (!haveRoundedCorners && aClipState->mHasAdditionalBGClipArea) {
+    // Do the intersection here to account for the fast path(?) below.
+    aClipState->mBGClipArea =
+        aClipState->mBGClipArea.Intersect(aClipState->mAdditionalBGClipArea);
+    aClipState->mHasAdditionalBGClipArea = false;
+  }
+
+  SetupDirtyRects(aClipState->mBGClipArea, aCallerDirtyRect, aAppUnitsPerPixel,
+                  &aClipState->mDirtyRectInAppUnits,
+                  &aClipState->mDirtyRectInDevPx);
+
+  MOZ_ASSERT(aClipState->IsValid());
+}
+
+static void SetupImageLayerClip(nsCSSRendering::ImageLayerClipState& aClipState,
+                                gfxContext* aCtx, nscoord aAppUnitsPerPixel,
+                                gfxContextAutoSaveRestore* aAutoSR) {
+  if (aClipState.mDirtyRectInDevPx.IsEmpty()) {
+    // Our caller won't draw anything under this condition, so no need
+    // to set more up.
+    return;
+  }
+
+  if (aClipState.mCustomClip) {
+    // We don't support custom clips and rounded corners, arguably a bug, but
+    // table painting seems to depend on it.
+    return;
+  }
+
+  // If we have rounded corners, clip all subsequent drawing to the
+  // rounded rectangle defined by bgArea and bgRadii (we don't know
+  // whether the rounded corners intrude on the dirtyRect or not).
+  // Do not do this if we have a caller-provided clip rect --
+  // as above with bgArea, arguably a bug, but table painting seems
+  // to depend on it.
+
+  if (aClipState.mHasAdditionalBGClipArea) {
+    gfxRect bgAreaGfx = nsLayoutUtils::RectToGfxRect(
+        aClipState.mAdditionalBGClipArea, aAppUnitsPerPixel);
+    bgAreaGfx.Round();
+    gfxUtils::ConditionRect(bgAreaGfx);
+
+    aAutoSR->EnsureSaved(aCtx);
+    aCtx->SnappedClip(bgAreaGfx);
+  }
+
+  if (aClipState.mHasRoundedCorners) {
+    Rect bgAreaGfx = NSRectToRect(aClipState.mBGClipArea, aAppUnitsPerPixel);
+    bgAreaGfx.Round();
+
+    if (bgAreaGfx.IsEmpty()) {
+      // I think it's become possible to hit this since
+      // https://hg.mozilla.org/mozilla-central/rev/50e934e4979b landed.
+      NS_WARNING("converted background area should not be empty");
+      // Make our caller not do anything.
+      aClipState.mDirtyRectInDevPx.SizeTo(gfxSize(0.0, 0.0));
+      return;
+    }
+
+    aAutoSR->EnsureSaved(aCtx);
+
+    RefPtr<Path> roundedRect = MakePathForRoundedRect(
+        *aCtx->GetDrawTarget(), bgAreaGfx, aClipState.mClippedRadii);
+    aCtx->Clip(roundedRect);
+  }
+}
+
+static void DrawBackgroundColor(nsCSSRendering::ImageLayerClipState& aClipState,
+                                gfxContext* aCtx, nscoord aAppUnitsPerPixel) {
+  if (aClipState.mDirtyRectInDevPx.IsEmpty()) {
+    // Our caller won't draw anything under this condition, so no need
+    // to set more up.
+    return;
+  }
+
+  DrawTarget* drawTarget = aCtx->GetDrawTarget();
+
+  // We don't support custom clips and rounded corners, arguably a bug, but
+  // table painting seems to depend on it.
+  if (!aClipState.mHasRoundedCorners || aClipState.mCustomClip) {
+    aCtx->NewPath();
+    aCtx->SnappedRectangle(aClipState.mDirtyRectInDevPx);
+    aCtx->Fill();
+    return;
+  }
+
+  Rect bgAreaGfx = NSRectToRect(aClipState.mBGClipArea, aAppUnitsPerPixel);
+  bgAreaGfx.Round();
+
+  if (bgAreaGfx.IsEmpty()) {
+    // I think it's become possible to hit this since
+    // https://hg.mozilla.org/mozilla-central/rev/50e934e4979b landed.
+    NS_WARNING("converted background area should not be empty");
+    // Make our caller not do anything.
+    aClipState.mDirtyRectInDevPx.SizeTo(gfxSize(0.0, 0.0));
+    return;
+  }
+
+  aCtx->Save();
+  gfxRect dirty = ThebesRect(bgAreaGfx).Intersect(aClipState.mDirtyRectInDevPx);
+
+  aCtx->SnappedClip(dirty);
+
+  if (aClipState.mHasAdditionalBGClipArea) {
+    gfxRect bgAdditionalAreaGfx = nsLayoutUtils::RectToGfxRect(
+        aClipState.mAdditionalBGClipArea, aAppUnitsPerPixel);
+    bgAdditionalAreaGfx.Round();
+    gfxUtils::ConditionRect(bgAdditionalAreaGfx);
+    aCtx->SnappedClip(bgAdditionalAreaGfx);
+  }
+
+  RefPtr<Path> roundedRect =
+      MakePathForRoundedRect(*drawTarget, bgAreaGfx, aClipState.mClippedRadii);
+  aCtx->SetPath(roundedRect);
+  aCtx->Fill();
+  aCtx->Restore();
+}
+
+enum class ScrollbarColorKind {
+  Thumb,
+  Track,
+};
+
+static Maybe<nscolor> CalcScrollbarColor(nsIFrame* aFrame,
+                                         ScrollbarColorKind aKind) {
+  ComputedStyle* scrollbarStyle = nsLayoutUtils::StyleForScrollbar(aFrame);
+  const auto& colors = scrollbarStyle->StyleUI()->mScrollbarColor;
+  if (colors.IsAuto()) {
+    return Nothing();
+  }
+  const auto& color = aKind == ScrollbarColorKind::Thumb
+                          ? colors.AsColors().thumb
+                          : colors.AsColors().track;
+  return Some(color.CalcColor(*scrollbarStyle));
+}
+
+static nscolor GetBackgroundColor(nsIFrame* aFrame,
+                                  const ComputedStyle* aStyle) {
+  switch (aStyle->StyleDisplay()->EffectiveAppearance()) {
+    case StyleAppearance::ScrollbarthumbVertical:
+    case StyleAppearance::ScrollbarthumbHorizontal: {
+      if (Maybe<nscolor> overrideColor =
+              CalcScrollbarColor(aFrame, ScrollbarColorKind::Thumb)) {
+        return *overrideColor;
+      }
+      break;
+    }
+    case StyleAppearance::ScrollbarVertical:
+    case StyleAppearance::ScrollbarHorizontal:
+    case StyleAppearance::Scrollcorner: {
+      if (Maybe<nscolor> overrideColor =
+              CalcScrollbarColor(aFrame, ScrollbarColorKind::Track)) {
+        return *overrideColor;
+      }
+      break;
+    }
+    default:
+      break;
+  }
+  return aStyle->GetVisitedDependentColor(&nsStyleBackground::mBackgroundColor);
+}
+
+nscolor nsCSSRendering::DetermineBackgroundColor(nsPresContext* aPresContext,
+                                                 const ComputedStyle* aStyle,
+                                                 nsIFrame* aFrame,
+                                                 bool& aDrawBackgroundImage,
+                                                 bool& aDrawBackgroundColor) {
+  auto shouldPaint = aFrame->ComputeShouldPaintBackground();
+  aDrawBackgroundImage = shouldPaint.mImage;
+  aDrawBackgroundColor = shouldPaint.mColor;
+
+  const nsStyleBackground* bg = aStyle->StyleBackground();
+  nscolor bgColor;
+  if (aDrawBackgroundColor) {
+    bgColor = GetBackgroundColor(aFrame, aStyle);
+    if (NS_GET_A(bgColor) == 0) {
+      aDrawBackgroundColor = false;
+    }
+  } else {
+    // If GetBackgroundColorDraw() is false, we are still expected to
+    // draw color in the background of any frame that's not completely
+    // transparent, but we are expected to use white instead of whatever
+    // color was specified.
+    bgColor = NS_RGB(255, 255, 255);
+    if (aDrawBackgroundImage || !bg->IsTransparent(aStyle)) {
+      aDrawBackgroundColor = true;
+    } else {
+      bgColor = NS_RGBA(0, 0, 0, 0);
+    }
+  }
+
+  // We can skip painting the background color if a background image is opaque.
+  nsStyleImageLayers::Repeat repeat = bg->BottomLayer().mRepeat;
+  bool xFullRepeat = repeat.mXRepeat == StyleImageLayerRepeat::Repeat ||
+                     repeat.mXRepeat == StyleImageLayerRepeat::Round;
+  bool yFullRepeat = repeat.mYRepeat == StyleImageLayerRepeat::Repeat ||
+                     repeat.mYRepeat == StyleImageLayerRepeat::Round;
+  if (aDrawBackgroundColor && xFullRepeat && yFullRepeat &&
+      bg->BottomLayer().mImage.IsOpaque() &&
+      bg->BottomLayer().mBlendMode == StyleBlend::Normal) {
+    aDrawBackgroundColor = false;
+  }
+
+  return bgColor;
+}
+
+static CompositionOp DetermineCompositionOp(
+    const nsCSSRendering::PaintBGParams& aParams,
+    const nsStyleImageLayers& aLayers, uint32_t aLayerIndex) {
+  if (aParams.layer >= 0) {
+    // When drawing a single layer, use the specified composition op.
+    return aParams.compositionOp;
+  }
+
+  const nsStyleImageLayers::Layer& layer = aLayers.mLayers[aLayerIndex];
+  // When drawing all layers, get the compositon op from each image layer.
+  if (aParams.paintFlags & nsCSSRendering::PAINTBG_MASK_IMAGE) {
+    // Always using OP_OVER mode while drawing the bottom mask layer.
+    if (aLayerIndex == (aLayers.mImageCount - 1)) {
+      return CompositionOp::OP_OVER;
+    }
+
+    return nsCSSRendering::GetGFXCompositeMode(layer.mComposite);
+  }
+
+  return nsCSSRendering::GetGFXBlendMode(layer.mBlendMode);
+}
+
+ImgDrawResult nsCSSRendering::PaintStyleImageLayerWithSC(
+    const PaintBGParams& aParams, gfxContext& aRenderingCtx,
+    const ComputedStyle* aBackgroundSC, const nsStyleBorder& aBorder) {
+  MOZ_ASSERT(aParams.frame,
+             "Frame is expected to be provided to PaintStyleImageLayerWithSC");
+
+  // If we're drawing all layers, aCompositonOp is ignored, so make sure that
+  // it was left at its default value.
+  MOZ_ASSERT(aParams.layer != -1 ||
+             aParams.compositionOp == CompositionOp::OP_OVER);
+
+  // Check to see if we have an appearance defined.  If so, we let the theme
+  // renderer draw the background and bail out.
+  // XXXzw this ignores aParams.bgClipRect.
+  StyleAppearance appearance =
+      aParams.frame->StyleDisplay()->EffectiveAppearance();
+  if (appearance != StyleAppearance::None) {
+    nsITheme* theme = aParams.presCtx.Theme();
+    if (theme->ThemeSupportsWidget(&aParams.presCtx, aParams.frame,
+                                   appearance)) {
+      nsRect drawing(aParams.borderArea);
+      theme->GetWidgetOverflow(aParams.presCtx.DeviceContext(), aParams.frame,
+                               appearance, &drawing);
+      drawing.IntersectRect(drawing, aParams.dirtyRect);
+      theme->DrawWidgetBackground(&aRenderingCtx, aParams.frame, appearance,
+                                  aParams.borderArea, drawing);
+      return ImgDrawResult::SUCCESS;
+    }
+  }
+
+  // For canvas frames (in the CSS sense) we draw the background color using
+  // a solid color item that gets added in nsLayoutUtils::PaintFrame,
+  // or nsSubDocumentFrame::BuildDisplayList (bug 488242). (The solid
+  // color may be moved into nsDisplayCanvasBackground by
+  // PresShell::AddCanvasBackgroundColorItem(), and painted by
+  // nsDisplayCanvasBackground directly.) Either way we don't need to
+  // paint the background color here.
+  bool isCanvasFrame = aParams.frame->IsCanvasFrame();
+  const bool paintMask = aParams.paintFlags & PAINTBG_MASK_IMAGE;
+
+  // Determine whether we are drawing background images and/or
+  // background colors.
+  bool drawBackgroundImage = true;
+  bool drawBackgroundColor = !paintMask;
+  nscolor bgColor = NS_RGBA(0, 0, 0, 0);
+  if (!paintMask) {
+    bgColor =
+        DetermineBackgroundColor(&aParams.presCtx, aBackgroundSC, aParams.frame,
+                                 drawBackgroundImage, drawBackgroundColor);
+  }
+
+  // Masks shouldn't be suppressed for print.
+  MOZ_ASSERT_IF(paintMask, drawBackgroundImage);
+
+  const nsStyleImageLayers& layers =
+      paintMask ? aBackgroundSC->StyleSVGReset()->mMask
+                : aBackgroundSC->StyleBackground()->mImage;
+  // If we're drawing a specific layer, we don't want to draw the
+  // background color.
+  if (drawBackgroundColor && aParams.layer >= 0) {
+    drawBackgroundColor = false;
+  }
+
+  // At this point, drawBackgroundImage and drawBackgroundColor are
+  // true if and only if we are actually supposed to paint an image or
+  // color into aDirtyRect, respectively.
+  if (!drawBackgroundImage && !drawBackgroundColor) {
+    return ImgDrawResult::SUCCESS;
+  }
+
+  // The 'bgClipArea' (used only by the image tiling logic, far below)
+  // is the caller-provided aParams.bgClipRect if any, or else the area
+  // determined by the value of 'background-clip' in
+  // SetupCurrentBackgroundClip.  (Arguably it should be the
+  // intersection, but that breaks the table painter -- in particular,
+  // taking the intersection breaks reftests/bugs/403249-1[ab].)
+  nscoord appUnitsPerPixel = aParams.presCtx.AppUnitsPerDevPixel();
+  ImageLayerClipState clipState;
+  if (aParams.bgClipRect) {
+    clipState.mBGClipArea = *aParams.bgClipRect;
+    clipState.mCustomClip = true;
+    clipState.mHasRoundedCorners = false;
+    SetupDirtyRects(clipState.mBGClipArea, aParams.dirtyRect, appUnitsPerPixel,
+                    &clipState.mDirtyRectInAppUnits,
+                    &clipState.mDirtyRectInDevPx);
+  } else {
+    GetImageLayerClip(layers.BottomLayer(), aParams.frame, aBorder,
+                      aParams.borderArea, aParams.dirtyRect,
+                      (aParams.paintFlags & PAINTBG_WILL_PAINT_BORDER),
+                      appUnitsPerPixel, &clipState);
+  }
+
+  // If we might be using a background color, go ahead and set it now.
+  if (drawBackgroundColor && !isCanvasFrame) {
+    aRenderingCtx.SetColor(sRGBColor::FromABGR(bgColor));
+  }
+
+  // If there is no background image, draw a color.  (If there is
+  // neither a background image nor a color, we wouldn't have gotten
+  // this far.)
+  if (!drawBackgroundImage) {
+    if (!isCanvasFrame) {
+      DrawBackgroundColor(clipState, &aRenderingCtx, appUnitsPerPixel);
+    }
+    return ImgDrawResult::SUCCESS;
+  }
+
+  if (layers.mImageCount < 1) {
+    // Return if there are no background layers, all work from this point
+    // onwards happens iteratively on these.
+    return ImgDrawResult::SUCCESS;
+  }
+
+  MOZ_ASSERT((aParams.layer < 0) ||
+             (layers.mImageCount > uint32_t(aParams.layer)));
+
+  // The background color is rendered over the entire dirty area,
+  // even if the image isn't.
+  if (drawBackgroundColor && !isCanvasFrame) {
+    DrawBackgroundColor(clipState, &aRenderingCtx, appUnitsPerPixel);
+  }
+
+  // Compute the outermost boundary of the area that might be painted.
+  // Same coordinate space as aParams.borderArea & aParams.bgClipRect.
+  Sides skipSides = aParams.frame->GetSkipSides();
+  nsRect paintBorderArea = BoxDecorationRectForBackground(
+      aParams.frame, aParams.borderArea, skipSides, &aBorder);
+  nsRect clipBorderArea = BoxDecorationRectForBorder(
+      aParams.frame, aParams.borderArea, skipSides, &aBorder);
+
+  ImgDrawResult result = ImgDrawResult::SUCCESS;
+  StyleGeometryBox currentBackgroundClip = StyleGeometryBox::BorderBox;
+  const bool drawAllLayers = (aParams.layer < 0);
+  uint32_t count = drawAllLayers
+                       ? layers.mImageCount  // iterate all image layers.
+                       : layers.mImageCount -
+                             aParams.layer;  // iterate from the bottom layer to
+                                             // the 'aParams.layer-th' layer.
+  NS_FOR_VISIBLE_IMAGE_LAYERS_BACK_TO_FRONT_WITH_RANGE(
+      i, layers, layers.mImageCount - 1, count) {
+    // NOTE: no Save() yet, we do that later by calling autoSR.EnsureSaved(ctx)
+    // in the cases we need it.
+    gfxContextAutoSaveRestore autoSR;
+    const nsStyleImageLayers::Layer& layer = layers.mLayers[i];
+
+    ImageLayerClipState currentLayerClipState = clipState;
+    if (!aParams.bgClipRect) {
+      bool isBottomLayer = (i == layers.mImageCount - 1);
+      if (currentBackgroundClip != layer.mClip || isBottomLayer) {
+        currentBackgroundClip = layer.mClip;
+        if (!isBottomLayer) {
+          currentLayerClipState = {};
+          // For the bottom layer, we already called GetImageLayerClip above
+          // and it stored its results in clipState.
+          GetImageLayerClip(layer, aParams.frame, aBorder, aParams.borderArea,
+                            aParams.dirtyRect,
+                            (aParams.paintFlags & PAINTBG_WILL_PAINT_BORDER),
+                            appUnitsPerPixel, &currentLayerClipState);
+        }
+        SetupImageLayerClip(currentLayerClipState, &aRenderingCtx,
+                            appUnitsPerPixel, &autoSR);
+        if (!clipBorderArea.IsEqualEdges(aParams.borderArea)) {
+          // We're drawing the background for the joined continuation boxes
+          // so we need to clip that to the slice that we want for this
+          // frame.
+          gfxRect clip = nsLayoutUtils::RectToGfxRect(aParams.borderArea,
+                                                      appUnitsPerPixel);
+          autoSR.EnsureSaved(&aRenderingCtx);
+          aRenderingCtx.SnappedClip(clip);
+        }
+      }
+    }
+
+    // Skip the following layer preparing and painting code if the current
+    // layer is not selected for drawing.
+    if (aParams.layer >= 0 && i != (uint32_t)aParams.layer) {
+      continue;
+    }
+    nsBackgroundLayerState state = PrepareImageLayer(
+        &aParams.presCtx, aParams.frame, aParams.paintFlags, paintBorderArea,
+        currentLayerClipState.mBGClipArea, layer, nullptr);
+    result &= state.mImageRenderer.PrepareResult();
+
+    // Skip the layer painting code if we found the dirty region is empty.
+    if (currentLayerClipState.mDirtyRectInDevPx.IsEmpty()) {
+      continue;
+    }
+
+    if (!state.mFillArea.IsEmpty()) {
+      CompositionOp co = DetermineCompositionOp(aParams, layers, i);
+      if (co != CompositionOp::OP_OVER) {
+        NS_ASSERTION(aRenderingCtx.CurrentOp() == CompositionOp::OP_OVER,
+                     "It is assumed the initial op is OP_OVER, when it is "
+                     "restored later");
+        aRenderingCtx.SetOp(co);
+      }
+
+      result &= state.mImageRenderer.DrawLayer(
+          &aParams.presCtx, aRenderingCtx, state.mDestArea, state.mFillArea,
+          state.mAnchor + paintBorderArea.TopLeft(),
+          currentLayerClipState.mDirtyRectInAppUnits, state.mRepeatSize,
+          aParams.opacity);
+
+      if (co != CompositionOp::OP_OVER) {
+        aRenderingCtx.SetOp(CompositionOp::OP_OVER);
+      }
+    }
+  }
+
+  return result;
+}
+
+ImgDrawResult
+nsCSSRendering::BuildWebRenderDisplayItemsForStyleImageLayerWithSC(
+    const PaintBGParams& aParams, mozilla::wr::DisplayListBuilder& aBuilder,
+    mozilla::wr::IpcResourceUpdateQueue& aResources,
+    const mozilla::layers::StackingContextHelper& aSc,
+    mozilla::layers::RenderRootStateManager* aManager, nsDisplayItem* aItem,
+    ComputedStyle* aBackgroundSC, const nsStyleBorder& aBorder) {
+  MOZ_ASSERT(!(aParams.paintFlags & PAINTBG_MASK_IMAGE));
+
+  nscoord appUnitsPerPixel = aParams.presCtx.AppUnitsPerDevPixel();
+  ImageLayerClipState clipState;
+
+  clipState.mBGClipArea = *aParams.bgClipRect;
+  clipState.mCustomClip = true;
+  clipState.mHasRoundedCorners = false;
+  SetupDirtyRects(clipState.mBGClipArea, aParams.dirtyRect, appUnitsPerPixel,
+                  &clipState.mDirtyRectInAppUnits,
+                  &clipState.mDirtyRectInDevPx);
+
+  // Compute the outermost boundary of the area that might be painted.
+  // Same coordinate space as aParams.borderArea & aParams.bgClipRect.
+  Sides skipSides = aParams.frame->GetSkipSides();
+  nsRect paintBorderArea = BoxDecorationRectForBackground(
+      aParams.frame, aParams.borderArea, skipSides, &aBorder);
+
+  const nsStyleImageLayers& layers = aBackgroundSC->StyleBackground()->mImage;
+  const nsStyleImageLayers::Layer& layer = layers.mLayers[aParams.layer];
+
+  // Skip the following layer painting code if we found the dirty region is
+  // empty or the current layer is not selected for drawing.
+  if (clipState.mDirtyRectInDevPx.IsEmpty()) {
+    return ImgDrawResult::SUCCESS;
+  }
+
+  ImgDrawResult result = ImgDrawResult::SUCCESS;
+  nsBackgroundLayerState state =
+      PrepareImageLayer(&aParams.presCtx, aParams.frame, aParams.paintFlags,
+                        paintBorderArea, clipState.mBGClipArea, layer, nullptr);
+  result &= state.mImageRenderer.PrepareResult();
+
+  if (!state.mFillArea.IsEmpty()) {
+    result &= state.mImageRenderer.BuildWebRenderDisplayItemsForLayer(
+        &aParams.presCtx, aBuilder, aResources, aSc, aManager, aItem,
+        state.mDestArea, state.mFillArea,
+        state.mAnchor + paintBorderArea.TopLeft(),
+        clipState.mDirtyRectInAppUnits, state.mRepeatSize, aParams.opacity);
+  }
+
+  return result;
+}
+
+nsRect nsCSSRendering::ComputeImageLayerPositioningArea(
+    nsPresContext* aPresContext, nsIFrame* aForFrame, const nsRect& aBorderArea,
+    const nsStyleImageLayers::Layer& aLayer, nsIFrame** aAttachedToFrame,
+    bool* aOutIsTransformedFixed) {
+  // Compute {background|mask} origin area relative to aBorderArea now as we
+  // may need  it to compute the effective image size for a CSS gradient.
+  nsRect positionArea;
+
+  StyleGeometryBox layerOrigin =
+      ComputeBoxValueForOrigin(aForFrame, aLayer.mOrigin);
+
+  if (IsSVGStyleGeometryBox(layerOrigin)) {
+    MOZ_ASSERT(aForFrame->HasAnyStateBits(NS_FRAME_SVG_LAYOUT));
+    *aAttachedToFrame = aForFrame;
+
+    positionArea =
+        nsLayoutUtils::ComputeSVGReferenceRect(aForFrame, layerOrigin);
+
+    nsPoint toStrokeBoxOffset = nsPoint(0, 0);
+    if (layerOrigin != StyleGeometryBox::StrokeBox) {
+      nsRect strokeBox = nsLayoutUtils::ComputeSVGReferenceRect(
+          aForFrame, StyleGeometryBox::StrokeBox);
+      toStrokeBoxOffset = positionArea.TopLeft() - strokeBox.TopLeft();
+    }
+
+    // For SVG frames, the return value is relative to the stroke box
+    return nsRect(toStrokeBoxOffset, positionArea.Size());
+  }
+
+  MOZ_ASSERT(!aForFrame->HasAnyStateBits(NS_FRAME_SVG_LAYOUT));
+
+  LayoutFrameType frameType = aForFrame->Type();
+  nsIFrame* geometryFrame = aForFrame;
+  if (MOZ_UNLIKELY(frameType == LayoutFrameType::Scroll &&
+                   StyleImageLayerAttachment::Local == aLayer.mAttachment)) {
+    nsIScrollableFrame* scrollableFrame = do_QueryFrame(aForFrame);
+    positionArea = nsRect(scrollableFrame->GetScrolledFrame()->GetPosition()
+                              // For the dir=rtl case:
+                              + scrollableFrame->GetScrollRange().TopLeft(),
+                          scrollableFrame->GetScrolledRect().Size());
+    // The ScrolledRect’s size does not include the borders or scrollbars,
+    // reverse the handling of background-origin
+    // compared to the common case below.
+    if (layerOrigin == StyleGeometryBox::BorderBox) {
+      nsMargin border = geometryFrame->GetUsedBorder();
+      border.ApplySkipSides(geometryFrame->GetSkipSides());
+      positionArea.Inflate(border);
+      positionArea.Inflate(scrollableFrame->GetActualScrollbarSizes());
+    } else if (layerOrigin != StyleGeometryBox::PaddingBox) {
+      nsMargin padding = geometryFrame->GetUsedPadding();
+      padding.ApplySkipSides(geometryFrame->GetSkipSides());
+      positionArea.Deflate(padding);
+      NS_ASSERTION(layerOrigin == StyleGeometryBox::ContentBox,
+                   "unknown background-origin value");
+    }
+    *aAttachedToFrame = aForFrame;
+    return positionArea;
+  }
+
+  if (MOZ_UNLIKELY(frameType == LayoutFrameType::Canvas)) {
+    geometryFrame = aForFrame->PrincipalChildList().FirstChild();
+    // geometryFrame might be null if this canvas is a page created
+    // as an overflow container (e.g. the in-flow content has already
+    // finished and this page only displays the continuations of
+    // absolutely positioned content).
+    if (geometryFrame) {
+      positionArea =
+          nsPlaceholderFrame::GetRealFrameFor(geometryFrame)->GetRect();
+    }
+  } else {
+    positionArea = nsRect(nsPoint(0, 0), aBorderArea.Size());
+  }
+
+  // See the comment of StyleGeometryBox::MarginBox.
+  // Hitting this assertion means we decide to turn on margin-box support for
+  // positioned mask from CSS parser and style system. In this case, you
+  // should *inflate* positionArea by the margin returning from
+  // geometryFrame->GetUsedMargin() in the code chunk bellow.
+  MOZ_ASSERT(aLayer.mOrigin != StyleGeometryBox::MarginBox,
+             "StyleGeometryBox::MarginBox rendering is not supported yet.\n");
+
+  // {background|mask} images are tiled over the '{background|mask}-clip' area
+  // but the origin of the tiling is based on the '{background|mask}-origin'
+  // area.
+  if (layerOrigin != StyleGeometryBox::BorderBox && geometryFrame) {
+    nsMargin border = geometryFrame->GetUsedBorder();
+    if (layerOrigin != StyleGeometryBox::PaddingBox) {
+      border += geometryFrame->GetUsedPadding();
+      NS_ASSERTION(layerOrigin == StyleGeometryBox::ContentBox,
+                   "unknown background-origin value");
+    }
+    positionArea.Deflate(border);
+  }
+
+  nsIFrame* attachedToFrame = aForFrame;
+  if (StyleImageLayerAttachment::Fixed == aLayer.mAttachment) {
+    // If it's a fixed background attachment, then the image is placed
+    // relative to the viewport, which is the area of the root frame
+    // in a screen context or the page content frame in a print context.
+    attachedToFrame = aPresContext->PresShell()->GetRootFrame();
+    NS_ASSERTION(attachedToFrame, "no root frame");
+    nsIFrame* pageContentFrame = nullptr;
+    if (aPresContext->IsPaginated()) {
+      pageContentFrame = nsLayoutUtils::GetClosestFrameOfType(
+          aForFrame, LayoutFrameType::PageContent);
+      if (pageContentFrame) {
+        attachedToFrame = pageContentFrame;
+      }
+      // else this is an embedded shell and its root frame is what we want
+    }
+
+    // If the background is affected by a transform, treat is as if it
+    // wasn't fixed.
+    if (nsLayoutUtils::IsTransformed(aForFrame, attachedToFrame)) {
+      attachedToFrame = aForFrame;
+      *aOutIsTransformedFixed = true;
+    } else {
+      // Set the background positioning area to the viewport's area
+      // (relative to aForFrame)
+      positionArea = nsRect(-aForFrame->GetOffsetTo(attachedToFrame),
+                            attachedToFrame->GetSize());
+
+      if (!pageContentFrame) {
+        // Subtract the size of scrollbars.
+        nsIScrollableFrame* scrollableFrame =
+            aPresContext->PresShell()->GetRootScrollFrameAsScrollable();
+        if (scrollableFrame) {
+          nsMargin scrollbars = scrollableFrame->GetActualScrollbarSizes();
+          positionArea.Deflate(scrollbars);
+        }
+      }
+
+      // If we have the dynamic toolbar, we need to expand the image area to
+      // include the region under the dynamic toolbar, otherwise we will see a
+      // blank space under the toolbar.
+      if (aPresContext->IsRootContentDocumentCrossProcess() &&
+          aPresContext->HasDynamicToolbar()) {
+        positionArea.SizeTo(nsLayoutUtils::ExpandHeightForDynamicToolbar(
+            aPresContext, positionArea.Size()));
+      }
+    }
+  }
+  *aAttachedToFrame = attachedToFrame;
+
+  return positionArea;
+}
+
+/* static */
+nscoord nsCSSRendering::ComputeRoundedSize(nscoord aCurrentSize,
+                                           nscoord aPositioningSize) {
+  float repeatCount = NS_roundf(float(aPositioningSize) / float(aCurrentSize));
+  if (repeatCount < 1.0f) {
+    return aPositioningSize;
+  }
+  return nscoord(NS_lround(float(aPositioningSize) / repeatCount));
+}
+
+// Apply the CSS image sizing algorithm as it applies to background images.
+// See http://www.w3.org/TR/css3-background/#the-background-size .
+// aIntrinsicSize is the size that the background image 'would like to be'.
+// It can be found by calling nsImageRenderer::ComputeIntrinsicSize.
+static nsSize ComputeDrawnSizeForBackground(
+    const CSSSizeOrRatio& aIntrinsicSize, const nsSize& aBgPositioningArea,
+    const StyleBackgroundSize& aLayerSize, StyleImageLayerRepeat aXRepeat,
+    StyleImageLayerRepeat aYRepeat) {
+  nsSize imageSize;
+
+  // Size is dictated by cover or contain rules.
+  if (aLayerSize.IsContain() || aLayerSize.IsCover()) {
+    nsImageRenderer::FitType fitType = aLayerSize.IsCover()
+                                           ? nsImageRenderer::COVER
+                                           : nsImageRenderer::CONTAIN;
+    imageSize = nsImageRenderer::ComputeConstrainedSize(
+        aBgPositioningArea, aIntrinsicSize.mRatio, fitType);
+  } else {
+    MOZ_ASSERT(aLayerSize.IsExplicitSize());
+    const auto& width = aLayerSize.explicit_size.width;
+    const auto& height = aLayerSize.explicit_size.height;
+    // No cover/contain constraint, use default algorithm.
+    CSSSizeOrRatio specifiedSize;
+    if (width.IsLengthPercentage()) {
+      specifiedSize.SetWidth(
+          width.AsLengthPercentage().Resolve(aBgPositioningArea.width));
+    }
+    if (height.IsLengthPercentage()) {
+      specifiedSize.SetHeight(
+          height.AsLengthPercentage().Resolve(aBgPositioningArea.height));
+    }
+
+    imageSize = nsImageRenderer::ComputeConcreteSize(
+        specifiedSize, aIntrinsicSize, aBgPositioningArea);
+  }
+
+  // See https://www.w3.org/TR/css3-background/#background-size .
+  // "If 'background-repeat' is 'round' for one (or both) dimensions, there is a
+  // second
+  //  step. The UA must scale the image in that dimension (or both dimensions)
+  //  so that it fits a whole number of times in the background positioning
+  //  area."
+  // "If 'background-repeat' is 'round' for one dimension only and if
+  // 'background-size'
+  //  is 'auto' for the other dimension, then there is a third step: that other
+  //  dimension is scaled so that the original aspect ratio is restored."
+  bool isRepeatRoundInBothDimensions =
+      aXRepeat == StyleImageLayerRepeat::Round &&
+      aYRepeat == StyleImageLayerRepeat::Round;
+
+  // Calculate the rounded size only if the background-size computation
+  // returned a correct size for the image.
+  if (imageSize.width && aXRepeat == StyleImageLayerRepeat::Round) {
+    imageSize.width = nsCSSRendering::ComputeRoundedSize(
+        imageSize.width, aBgPositioningArea.width);
+    if (!isRepeatRoundInBothDimensions && aLayerSize.IsExplicitSize() &&
+        aLayerSize.explicit_size.height.IsAuto()) {
+      // Restore intrinsic ratio
+      if (aIntrinsicSize.mRatio) {
+        imageSize.height =
+            aIntrinsicSize.mRatio.Inverted().ApplyTo(imageSize.width);
+      }
+    }
+  }
+
+  // Calculate the rounded size only if the background-size computation
+  // returned a correct size for the image.
+  if (imageSize.height && aYRepeat == StyleImageLayerRepeat::Round) {
+    imageSize.height = nsCSSRendering::ComputeRoundedSize(
+        imageSize.height, aBgPositioningArea.height);
+    if (!isRepeatRoundInBothDimensions && aLayerSize.IsExplicitSize() &&
+        aLayerSize.explicit_size.width.IsAuto()) {
+      // Restore intrinsic ratio
+      if (aIntrinsicSize.mRatio) {
+        imageSize.width = aIntrinsicSize.mRatio.ApplyTo(imageSize.height);
+      }
+    }
+  }
+
+  return imageSize;
+}
+
+/* ComputeSpacedRepeatSize
+ * aImageDimension: the image width/height
+ * aAvailableSpace: the background positioning area width/height
+ * aRepeat: determine whether the image is repeated
+ * Returns the image size plus gap size of app units for use as spacing
+ */
+static nscoord ComputeSpacedRepeatSize(nscoord aImageDimension,
+                                       nscoord aAvailableSpace, bool& aRepeat) {
+  float ratio = static_cast<float>(aAvailableSpace) / aImageDimension;
+
+  if (ratio < 2.0f) {  // If you can't repeat at least twice, then don't repeat.
+    aRepeat = false;
+    return aImageDimension;
+  }
+
+  aRepeat = true;
+  return (aAvailableSpace - aImageDimension) / (NSToIntFloor(ratio) - 1);
+}
+
+/* static */
+nscoord nsCSSRendering::ComputeBorderSpacedRepeatSize(nscoord aImageDimension,
+                                                      nscoord aAvailableSpace,
+                                                      nscoord& aSpace) {
+  int32_t count = aImageDimension ? (aAvailableSpace / aImageDimension) : 0;
+  aSpace = (aAvailableSpace - aImageDimension * count) / (count + 1);
+  return aSpace + aImageDimension;
+}
+
+nsBackgroundLayerState nsCSSRendering::PrepareImageLayer(
+    nsPresContext* aPresContext, nsIFrame* aForFrame, uint32_t aFlags,
+    const nsRect& aBorderArea, const nsRect& aBGClipRect,
+    const nsStyleImageLayers::Layer& aLayer, bool* aOutIsTransformedFixed) {
+  /*
+   * The properties we need to keep in mind when drawing style image
+   * layers are:
+   *
+   *   background-image/ mask-image
+   *   background-repeat/ mask-repeat
+   *   background-attachment
+   *   background-position/ mask-position
+   *   background-clip/ mask-clip
+   *   background-origin/ mask-origin
+   *   background-size/ mask-size
+   *   background-blend-mode
+   *   box-decoration-break
+   *   mask-mode
+   *   mask-composite
+   *
+   * (background-color applies to the entire element and not to individual
+   * layers, so it is irrelevant to this method.)
+   *
+   * These properties have the following dependencies upon each other when
+   * determining rendering:
+   *
+   *   background-image/ mask-image
+   *     no dependencies
+   *   background-repeat/ mask-repeat
+   *     no dependencies
+   *   background-attachment
+   *     no dependencies
+   *   background-position/ mask-position
+   *     depends upon background-size/mask-size (for the image's scaled size)
+   *     and background-break (for the background positioning area)
+   *   background-clip/ mask-clip
+   *     no dependencies
+   *   background-origin/ mask-origin
+   *     depends upon background-attachment (only in the case where that value
+   *     is 'fixed')
+   *   background-size/ mask-size
+   *     depends upon box-decoration-break (for the background positioning area
+   *     for resolving percentages), background-image (for the image's intrinsic
+   *     size), background-repeat (if that value is 'round'), and
+   *     background-origin (for the background painting area, when
+   *     background-repeat is 'round')
+   *   background-blend-mode
+   *     no dependencies
+   *   mask-mode
+   *     no dependencies
+   *   mask-composite
+   *     no dependencies
+   *   box-decoration-break
+   *     no dependencies
+   *
+   * As a result of only-if dependencies we don't strictly do a topological
+   * sort of the above properties when processing, but it's pretty close to one:
+   *
+   *   background-clip/mask-clip (by caller)
+   *   background-image/ mask-image
+   *   box-decoration-break, background-origin/ mask origin
+   *   background-attachment (postfix for background-origin if 'fixed')
+   *   background-size/ mask-size
+   *   background-position/ mask-position
+   *   background-repeat/ mask-repeat
+   */
+
+  uint32_t irFlags = 0;
+  if (aFlags & nsCSSRendering::PAINTBG_SYNC_DECODE_IMAGES) {
+    irFlags |= nsImageRenderer::FLAG_SYNC_DECODE_IMAGES;
+  }
+  if (aFlags & nsCSSRendering::PAINTBG_TO_WINDOW) {
+    irFlags |= nsImageRenderer::FLAG_PAINTING_TO_WINDOW;
+  }
+  if (aFlags & nsCSSRendering::PAINTBG_HIGH_QUALITY_SCALING) {
+    irFlags |= nsImageRenderer::FLAG_HIGH_QUALITY_SCALING;
+  }
+  // Only do partial bg image drawing in content documents: non-content
+  // documents are viewed as UI of the browser and a partial draw of a bg image
+  // might look weird in that context.
+  if (StaticPrefs::layout_display_partial_background_images() &&
+      XRE_IsContentProcess() && !aPresContext->IsChrome()) {
+    irFlags |= nsImageRenderer::FLAG_DRAW_PARTIAL_FRAMES;
+  }
+
+  nsBackgroundLayerState state(aForFrame, &aLayer.mImage, irFlags);
+  if (!state.mImageRenderer.PrepareImage()) {
+    // There's no image or it's not ready to be painted.
+    if (aOutIsTransformedFixed &&
+        StyleImageLayerAttachment::Fixed == aLayer.mAttachment) {
+      nsIFrame* attachedToFrame = aPresContext->PresShell()->GetRootFrame();
+      NS_ASSERTION(attachedToFrame, "no root frame");
+      nsIFrame* pageContentFrame = nullptr;
+      if (aPresContext->IsPaginated()) {
+        pageContentFrame = nsLayoutUtils::GetClosestFrameOfType(
+            aForFrame, LayoutFrameType::PageContent);
+        if (pageContentFrame) {
+          attachedToFrame = pageContentFrame;
+        }
+        // else this is an embedded shell and its root frame is what we want
+      }
+
+      *aOutIsTransformedFixed =
+          nsLayoutUtils::IsTransformed(aForFrame, attachedToFrame);
+    }
+    return state;
+  }
+
+  // The frame to which the background is attached
+  nsIFrame* attachedToFrame = aForFrame;
+  // Is the background marked 'fixed', but affected by a transform?
+  bool transformedFixed = false;
+  // Compute background origin area relative to aBorderArea now as we may need
+  // it to compute the effective image size for a CSS gradient.
+  nsRect positionArea = ComputeImageLayerPositioningArea(
+      aPresContext, aForFrame, aBorderArea, aLayer, &attachedToFrame,
+      &transformedFixed);
+  if (aOutIsTransformedFixed) {
+    *aOutIsTransformedFixed = transformedFixed;
+  }
+
+  // For background-attachment:fixed backgrounds, we'll override the area
+  // where the background can be drawn to the viewport.
+  nsRect bgClipRect = aBGClipRect;
+
+  if (StyleImageLayerAttachment::Fixed == aLayer.mAttachment &&
+      !transformedFixed && (aFlags & nsCSSRendering::PAINTBG_TO_WINDOW)) {
+    bgClipRect = positionArea + aBorderArea.TopLeft();
+  }
+
+  StyleImageLayerRepeat repeatX = aLayer.mRepeat.mXRepeat;
+  StyleImageLayerRepeat repeatY = aLayer.mRepeat.mYRepeat;
+
+  // Scale the image as specified for background-size and background-repeat.
+  // Also as required for proper background positioning when background-position
+  // is defined with percentages.
+  CSSSizeOrRatio intrinsicSize = state.mImageRenderer.ComputeIntrinsicSize();
+  nsSize bgPositionSize = positionArea.Size();
+  nsSize imageSize = ComputeDrawnSizeForBackground(
+      intrinsicSize, bgPositionSize, aLayer.mSize, repeatX, repeatY);
+
+  if (imageSize.width <= 0 || imageSize.height <= 0) return state;
+
+  state.mImageRenderer.SetPreferredSize(intrinsicSize, imageSize);
+
+  // Compute the anchor point.
+  //
+  // relative to aBorderArea.TopLeft() (which is where the top-left
+  // of aForFrame's border-box will be rendered)
+  nsPoint imageTopLeft;
+
+  // Compute the position of the background now that the background's size is
+  // determined.
+  nsImageRenderer::ComputeObjectAnchorPoint(aLayer.mPosition, bgPositionSize,
+                                            imageSize, &imageTopLeft,
+                                            &state.mAnchor);
+  state.mRepeatSize = imageSize;
+  if (repeatX == StyleImageLayerRepeat::Space) {
+    bool isRepeat;
+    state.mRepeatSize.width = ComputeSpacedRepeatSize(
+        imageSize.width, bgPositionSize.width, isRepeat);
+    if (isRepeat) {
+      imageTopLeft.x = 0;
+      state.mAnchor.x = 0;
+    } else {
+      repeatX = StyleImageLayerRepeat::NoRepeat;
+    }
+  }
+
+  if (repeatY == StyleImageLayerRepeat::Space) {
+    bool isRepeat;
+    state.mRepeatSize.height = ComputeSpacedRepeatSize(
+        imageSize.height, bgPositionSize.height, isRepeat);
+    if (isRepeat) {
+      imageTopLeft.y = 0;
+      state.mAnchor.y = 0;
+    } else {
+      repeatY = StyleImageLayerRepeat::NoRepeat;
+    }
+  }
+
+  imageTopLeft += positionArea.TopLeft();
+  state.mAnchor += positionArea.TopLeft();
+  state.mDestArea = nsRect(imageTopLeft + aBorderArea.TopLeft(), imageSize);
+  state.mFillArea = state.mDestArea;
+
+  ExtendMode repeatMode = ExtendMode::CLAMP;
+  if (repeatX == StyleImageLayerRepeat::Repeat ||
+      repeatX == StyleImageLayerRepeat::Round ||
+      repeatX == StyleImageLayerRepeat::Space) {
+    state.mFillArea.x = bgClipRect.x;
+    state.mFillArea.width = bgClipRect.width;
+    repeatMode = ExtendMode::REPEAT_X;
+  }
+  if (repeatY == StyleImageLayerRepeat::Repeat ||
+      repeatY == StyleImageLayerRepeat::Round ||
+      repeatY == StyleImageLayerRepeat::Space) {
+    state.mFillArea.y = bgClipRect.y;
+    state.mFillArea.height = bgClipRect.height;
+
+    /***
+     * We're repeating on the X axis already,
+     * so if we have to repeat in the Y axis,
+     * we really need to repeat in both directions.
+     */
+    if (repeatMode == ExtendMode::REPEAT_X) {
+      repeatMode = ExtendMode::REPEAT;
+    } else {
+      repeatMode = ExtendMode::REPEAT_Y;
+    }
+  }
+  state.mImageRenderer.SetExtendMode(repeatMode);
+  state.mImageRenderer.SetMaskOp(aLayer.mMaskMode);
+
+  state.mFillArea.IntersectRect(state.mFillArea, bgClipRect);
+
+  return state;
+}
+
+nsRect nsCSSRendering::GetBackgroundLayerRect(
+    nsPresContext* aPresContext, nsIFrame* aForFrame, const nsRect& aBorderArea,
+    const nsRect& aClipRect, const nsStyleImageLayers::Layer& aLayer,
+    uint32_t aFlags) {
+  Sides skipSides = aForFrame->GetSkipSides();
+  nsRect borderArea =
+      BoxDecorationRectForBackground(aForFrame, aBorderArea, skipSides);
+  nsBackgroundLayerState state = PrepareImageLayer(
+      aPresContext, aForFrame, aFlags, borderArea, aClipRect, aLayer);
+  return state.mFillArea;
+}
+
+// Begin table border-collapsing section
+// These functions were written to not disrupt the normal ones and yet satisfy
+// some additional requirements At some point, all functions should be unified
+// to include the additional functionality that these provide
+
+static nscoord RoundIntToPixel(nscoord aValue, nscoord aOneDevPixel,
+                               bool aRoundDown = false) {
+  if (aOneDevPixel <= 0) {
+    // We must be rendering to a device that has a resolution greater than
+    // one device pixel!
+    // In that case, aValue is as accurate as it's going to get.
+    return aValue;
+  }
+
+  nscoord halfPixel = NSToCoordRound(aOneDevPixel / 2.0f);
+  nscoord extra = aValue % aOneDevPixel;
+  nscoord finalValue = (!aRoundDown && (extra >= halfPixel))
+                           ? aValue + (aOneDevPixel - extra)
+                           : aValue - extra;
+  return finalValue;
+}
+
+static nscoord RoundFloatToPixel(float aValue, nscoord aOneDevPixel,
+                                 bool aRoundDown = false) {
+  return RoundIntToPixel(NSToCoordRound(aValue), aOneDevPixel, aRoundDown);
+}
+
+static void SetPoly(const Rect& aRect, Point* poly) {
+  poly[0].x = aRect.x;
+  poly[0].y = aRect.y;
+  poly[1].x = aRect.x + aRect.width;
+  poly[1].y = aRect.y;
+  poly[2].x = aRect.x + aRect.width;
+  poly[2].y = aRect.y + aRect.height;
+  poly[3].x = aRect.x;
+  poly[3].y = aRect.y + aRect.height;
+}
+
+static void DrawDashedSegment(DrawTarget& aDrawTarget, nsRect aRect,
+                              nscoord aDashLength, nscolor aColor,
+                              int32_t aAppUnitsPerDevPixel, bool aHorizontal) {
+  ColorPattern color(ToDeviceColor(aColor));
+  DrawOptions drawOptions(1.f, CompositionOp::OP_OVER, AntialiasMode::NONE);
+  StrokeOptions strokeOptions;
+
+  Float dash[2];
+  dash[0] = Float(aDashLength) / aAppUnitsPerDevPixel;
+  dash[1] = dash[0];
+
+  strokeOptions.mDashPattern = dash;
+  strokeOptions.mDashLength = MOZ_ARRAY_LENGTH(dash);
+
+  if (aHorizontal) {
+    nsPoint left = (aRect.TopLeft() + aRect.BottomLeft()) / 2;
+    nsPoint right = (aRect.TopRight() + aRect.BottomRight()) / 2;
+    strokeOptions.mLineWidth = Float(aRect.height) / aAppUnitsPerDevPixel;
+    StrokeLineWithSnapping(left, right, aAppUnitsPerDevPixel, aDrawTarget,
+                           color, strokeOptions, drawOptions);
+  } else {
+    nsPoint top = (aRect.TopLeft() + aRect.TopRight()) / 2;
+    nsPoint bottom = (aRect.BottomLeft() + aRect.BottomRight()) / 2;
+    strokeOptions.mLineWidth = Float(aRect.width) / aAppUnitsPerDevPixel;
+    StrokeLineWithSnapping(top, bottom, aAppUnitsPerDevPixel, aDrawTarget,
+                           color, strokeOptions, drawOptions);
+  }
+}
+
+static void DrawSolidBorderSegment(
+    DrawTarget& aDrawTarget, nsRect aRect, nscolor aColor,
+    int32_t aAppUnitsPerDevPixel,
+    mozilla::Side aStartBevelSide = mozilla::eSideTop,
+    nscoord aStartBevelOffset = 0,
+    mozilla::Side aEndBevelSide = mozilla::eSideTop,
+    nscoord aEndBevelOffset = 0) {
+  ColorPattern color(ToDeviceColor(aColor));
+  DrawOptions drawOptions(1.f, CompositionOp::OP_OVER, AntialiasMode::NONE);
+
+  nscoord oneDevPixel = NSIntPixelsToAppUnits(1, aAppUnitsPerDevPixel);
+  // We don't need to bevel single pixel borders
+  if ((aRect.width == oneDevPixel) || (aRect.height == oneDevPixel) ||
+      ((0 == aStartBevelOffset) && (0 == aEndBevelOffset))) {
+    // simple rectangle
+    aDrawTarget.FillRect(
+        NSRectToSnappedRect(aRect, aAppUnitsPerDevPixel, aDrawTarget), color,
+        drawOptions);
+  } else {
+    // polygon with beveling
+    Point poly[4];
+    SetPoly(NSRectToSnappedRect(aRect, aAppUnitsPerDevPixel, aDrawTarget),
+            poly);
+
+    Float startBevelOffset =
+        NSAppUnitsToFloatPixels(aStartBevelOffset, aAppUnitsPerDevPixel);
+    switch (aStartBevelSide) {
+      case eSideTop:
+        poly[0].x += startBevelOffset;
+        break;
+      case eSideBottom:
+        poly[3].x += startBevelOffset;
+        break;
+      case eSideRight:
+        poly[1].y += startBevelOffset;
+        break;
+      case eSideLeft:
+        poly[0].y += startBevelOffset;
+    }
+
+    Float endBevelOffset =
+        NSAppUnitsToFloatPixels(aEndBevelOffset, aAppUnitsPerDevPixel);
+    switch (aEndBevelSide) {
+      case eSideTop:
+        poly[1].x -= endBevelOffset;
+        break;
+      case eSideBottom:
+        poly[2].x -= endBevelOffset;
+        break;
+      case eSideRight:
+        poly[2].y -= endBevelOffset;
+        break;
+      case eSideLeft:
+        poly[3].y -= endBevelOffset;
+    }
+
+    RefPtr<PathBuilder> builder = aDrawTarget.CreatePathBuilder();
+    builder->MoveTo(poly[0]);
+    builder->LineTo(poly[1]);
+    builder->LineTo(poly[2]);
+    builder->LineTo(poly[3]);
+    builder->Close();
+    RefPtr<Path> path = builder->Finish();
+    aDrawTarget.Fill(path, color, drawOptions);
+  }
+}
+
+static void GetDashInfo(nscoord aBorderLength, nscoord aDashLength,
+                        nscoord aOneDevPixel, int32_t& aNumDashSpaces,
+                        nscoord& aStartDashLength, nscoord& aEndDashLength) {
+  aNumDashSpaces = 0;
+  if (aStartDashLength + aDashLength + aEndDashLength >= aBorderLength) {
+    aStartDashLength = aBorderLength;
+    aEndDashLength = 0;
+  } else {
+    aNumDashSpaces =
+        (aBorderLength - aDashLength) / (2 * aDashLength);  // round down
+    nscoord extra = aBorderLength - aStartDashLength - aEndDashLength -
+                    (((2 * aNumDashSpaces) - 1) * aDashLength);
+    if (extra > 0) {
+      nscoord half = RoundIntToPixel(extra / 2, aOneDevPixel);
+      aStartDashLength += half;
+      aEndDashLength += (extra - half);
+    }
+  }
+}
+
+void nsCSSRendering::DrawTableBorderSegment(
+    DrawTarget& aDrawTarget, StyleBorderStyle aBorderStyle,
+    nscolor aBorderColor, const nsRect& aBorder, int32_t aAppUnitsPerDevPixel,
+    mozilla::Side aStartBevelSide, nscoord aStartBevelOffset,
+    mozilla::Side aEndBevelSide, nscoord aEndBevelOffset) {
+  bool horizontal =
+      ((eSideTop == aStartBevelSide) || (eSideBottom == aStartBevelSide));
+  nscoord oneDevPixel = NSIntPixelsToAppUnits(1, aAppUnitsPerDevPixel);
+
+  if ((oneDevPixel >= aBorder.width) || (oneDevPixel >= aBorder.height) ||
+      (StyleBorderStyle::Dashed == aBorderStyle) ||
+      (StyleBorderStyle::Dotted == aBorderStyle)) {
+    // no beveling for 1 pixel border, dash or dot
+    aStartBevelOffset = 0;
+    aEndBevelOffset = 0;
+  }
+
+  switch (aBorderStyle) {
+    case StyleBorderStyle::None:
+    case StyleBorderStyle::Hidden:
+      // NS_ASSERTION(false, "style of none or hidden");
+      break;
+    case StyleBorderStyle::Dotted:
+    case StyleBorderStyle::Dashed: {
+      nscoord dashLength =
+          (StyleBorderStyle::Dashed == aBorderStyle) ? DASH_LENGTH : DOT_LENGTH;
+      // make the dash length proportional to the border thickness
+      dashLength *= (horizontal) ? aBorder.height : aBorder.width;
+      // make the min dash length for the ends 1/2 the dash length
+      nscoord minDashLength =
+          (StyleBorderStyle::Dashed == aBorderStyle)
+              ? RoundFloatToPixel(((float)dashLength) / 2.0f,
+                                  aAppUnitsPerDevPixel)
+              : dashLength;
+      minDashLength = std::max(minDashLength, oneDevPixel);
+      nscoord numDashSpaces = 0;
+      nscoord startDashLength = minDashLength;
+      nscoord endDashLength = minDashLength;
+      if (horizontal) {
+        GetDashInfo(aBorder.width, dashLength, aAppUnitsPerDevPixel,
+                    numDashSpaces, startDashLength, endDashLength);
+        nsRect rect(aBorder.x, aBorder.y, startDashLength, aBorder.height);
+        DrawSolidBorderSegment(aDrawTarget, rect, aBorderColor,
+                               aAppUnitsPerDevPixel);
+
+        rect.x += startDashLength + dashLength;
+        rect.width =
+            aBorder.width - (startDashLength + endDashLength + dashLength);
+        DrawDashedSegment(aDrawTarget, rect, dashLength, aBorderColor,
+                          aAppUnitsPerDevPixel, horizontal);
+
+        rect.x += rect.width;
+        rect.width = endDashLength;
+        DrawSolidBorderSegment(aDrawTarget, rect, aBorderColor,
+                               aAppUnitsPerDevPixel);
+      } else {
+        GetDashInfo(aBorder.height, dashLength, aAppUnitsPerDevPixel,
+                    numDashSpaces, startDashLength, endDashLength);
+        nsRect rect(aBorder.x, aBorder.y, aBorder.width, startDashLength);
+        DrawSolidBorderSegment(aDrawTarget, rect, aBorderColor,
+                               aAppUnitsPerDevPixel);
+
+        rect.y += rect.height + dashLength;
+        rect.height =
+            aBorder.height - (startDashLength + endDashLength + dashLength);
+        DrawDashedSegment(aDrawTarget, rect, dashLength, aBorderColor,
+                          aAppUnitsPerDevPixel, horizontal);
+
+        rect.y += rect.height;
+        rect.height = endDashLength;
+        DrawSolidBorderSegment(aDrawTarget, rect, aBorderColor,
+                               aAppUnitsPerDevPixel);
+      }
+    } break;
+    default:
+      AutoTArray<SolidBeveledBorderSegment, 3> segments;
+      GetTableBorderSolidSegments(
+          segments, aBorderStyle, aBorderColor, aBorder, aAppUnitsPerDevPixel,
+          aStartBevelSide, aStartBevelOffset, aEndBevelSide, aEndBevelOffset);
+      for (const auto& segment : segments) {
+        DrawSolidBorderSegment(
+            aDrawTarget, segment.mRect, segment.mColor, aAppUnitsPerDevPixel,
+            segment.mStartBevel.mSide, segment.mStartBevel.mOffset,
+            segment.mEndBevel.mSide, segment.mEndBevel.mOffset);
+      }
+      break;
+  }
+}
+
+void nsCSSRendering::GetTableBorderSolidSegments(
+    nsTArray<SolidBeveledBorderSegment>& aSegments,
+    StyleBorderStyle aBorderStyle, nscolor aBorderColor, const nsRect& aBorder,
+    int32_t aAppUnitsPerDevPixel, mozilla::Side aStartBevelSide,
+    nscoord aStartBevelOffset, mozilla::Side aEndBevelSide,
+    nscoord aEndBevelOffset) {
+  const bool horizontal =
+      eSideTop == aStartBevelSide || eSideBottom == aStartBevelSide;
+  const nscoord oneDevPixel = NSIntPixelsToAppUnits(1, aAppUnitsPerDevPixel);
+
+  switch (aBorderStyle) {
+    case StyleBorderStyle::None:
+    case StyleBorderStyle::Hidden:
+      return;
+    case StyleBorderStyle::Dotted:
+    case StyleBorderStyle::Dashed:
+      MOZ_ASSERT_UNREACHABLE("Caller should have checked");
+      return;
+    case StyleBorderStyle::Groove:
+    case StyleBorderStyle::Ridge:
+      if ((horizontal && (oneDevPixel >= aBorder.height)) ||
+          (!horizontal && (oneDevPixel >= aBorder.width))) {
+        aSegments.AppendElement(
+            SolidBeveledBorderSegment{aBorder,
+                                      aBorderColor,
+                                      {aStartBevelSide, aStartBevelOffset},
+                                      {aEndBevelSide, aEndBevelOffset}});
+      } else {
+        nscoord startBevel =
+            (aStartBevelOffset > 0)
+                ? RoundFloatToPixel(0.5f * (float)aStartBevelOffset,
+                                    aAppUnitsPerDevPixel, true)
+                : 0;
+        nscoord endBevel =
+            (aEndBevelOffset > 0)
+                ? RoundFloatToPixel(0.5f * (float)aEndBevelOffset,
+                                    aAppUnitsPerDevPixel, true)
+                : 0;
+        mozilla::Side ridgeGrooveSide = (horizontal) ? eSideTop : eSideLeft;
+        // FIXME: In theory, this should use the visited-dependent
+        // background color, but I don't care.
+        nscolor bevelColor =
+            MakeBevelColor(ridgeGrooveSide, aBorderStyle, aBorderColor);
+        nsRect rect(aBorder);
+        nscoord half;
+        if (horizontal) {  // top, bottom
+          half = RoundFloatToPixel(0.5f * (float)aBorder.height,
+                                   aAppUnitsPerDevPixel);
+          rect.height = half;
+          if (eSideTop == aStartBevelSide) {
+            rect.x += startBevel;
+            rect.width -= startBevel;
+          }
+          if (eSideTop == aEndBevelSide) {
+            rect.width -= endBevel;
+          }
+          aSegments.AppendElement(
+              SolidBeveledBorderSegment{rect,
+                                        bevelColor,
+                                        {aStartBevelSide, startBevel},
+                                        {aEndBevelSide, endBevel}});
+        } else {  // left, right
+          half = RoundFloatToPixel(0.5f * (float)aBorder.width,
+                                   aAppUnitsPerDevPixel);
+          rect.width = half;
+          if (eSideLeft == aStartBevelSide) {
+            rect.y += startBevel;
+            rect.height -= startBevel;
+          }
+          if (eSideLeft == aEndBevelSide) {
+            rect.height -= endBevel;
+          }
+          aSegments.AppendElement(
+              SolidBeveledBorderSegment{rect,
+                                        bevelColor,
+                                        {aStartBevelSide, startBevel},
+                                        {aEndBevelSide, endBevel}});
+        }
+
+        rect = aBorder;
+        ridgeGrooveSide =
+            (eSideTop == ridgeGrooveSide) ? eSideBottom : eSideRight;
+        // FIXME: In theory, this should use the visited-dependent
+        // background color, but I don't care.
+        bevelColor =
+            MakeBevelColor(ridgeGrooveSide, aBorderStyle, aBorderColor);
+        if (horizontal) {
+          rect.y = rect.y + half;
+          rect.height = aBorder.height - half;
+          if (eSideBottom == aStartBevelSide) {
+            rect.x += startBevel;
+            rect.width -= startBevel;
+          }
+          if (eSideBottom == aEndBevelSide) {
+            rect.width -= endBevel;
+          }
+          aSegments.AppendElement(
+              SolidBeveledBorderSegment{rect,
+                                        bevelColor,
+                                        {aStartBevelSide, startBevel},
+                                        {aEndBevelSide, endBevel}});
+        } else {
+          rect.x = rect.x + half;
+          rect.width = aBorder.width - half;
+          if (eSideRight == aStartBevelSide) {
+            rect.y += aStartBevelOffset - startBevel;
+            rect.height -= startBevel;
+          }
+          if (eSideRight == aEndBevelSide) {
+            rect.height -= endBevel;
+          }
+          aSegments.AppendElement(
+              SolidBeveledBorderSegment{rect,
+                                        bevelColor,
+                                        {aStartBevelSide, startBevel},
+                                        {aEndBevelSide, endBevel}});
+        }
+      }
+      break;
+    case StyleBorderStyle::Double:
+      // We can only do "double" borders if the thickness of the border
+      // is more than 2px.  Otherwise, we fall through to painting a
+      // solid border.
+      if ((aBorder.width > 2 * oneDevPixel || horizontal) &&
+          (aBorder.height > 2 * oneDevPixel || !horizontal)) {
+        nscoord startBevel =
+            (aStartBevelOffset > 0)
+                ? RoundFloatToPixel(0.333333f * (float)aStartBevelOffset,
+                                    aAppUnitsPerDevPixel)
+                : 0;
+        nscoord endBevel =
+            (aEndBevelOffset > 0)
+                ? RoundFloatToPixel(0.333333f * (float)aEndBevelOffset,
+                                    aAppUnitsPerDevPixel)
+                : 0;
+        if (horizontal) {  // top, bottom
+          nscoord thirdHeight = RoundFloatToPixel(
+              0.333333f * (float)aBorder.height, aAppUnitsPerDevPixel);
+
+          // draw the top line or rect
+          nsRect topRect(aBorder.x, aBorder.y, aBorder.width, thirdHeight);
+          if (eSideTop == aStartBevelSide) {
+            topRect.x += aStartBevelOffset - startBevel;
+            topRect.width -= aStartBevelOffset - startBevel;
+          }
+          if (eSideTop == aEndBevelSide) {
+            topRect.width -= aEndBevelOffset - endBevel;
+          }
+
+          aSegments.AppendElement(
+              SolidBeveledBorderSegment{topRect,
+                                        aBorderColor,
+                                        {aStartBevelSide, startBevel},
+                                        {aEndBevelSide, endBevel}});
+
+          // draw the botom line or rect
+          nscoord heightOffset = aBorder.height - thirdHeight;
+          nsRect bottomRect(aBorder.x, aBorder.y + heightOffset, aBorder.width,
+                            aBorder.height - heightOffset);
+          if (eSideBottom == aStartBevelSide) {
+            bottomRect.x += aStartBevelOffset - startBevel;
+            bottomRect.width -= aStartBevelOffset - startBevel;
+          }
+          if (eSideBottom == aEndBevelSide) {
+            bottomRect.width -= aEndBevelOffset - endBevel;
+          }
+          aSegments.AppendElement(
+              SolidBeveledBorderSegment{bottomRect,
+                                        aBorderColor,
+                                        {aStartBevelSide, startBevel},
+                                        {aEndBevelSide, endBevel}});
+        } else {  // left, right
+          nscoord thirdWidth = RoundFloatToPixel(
+              0.333333f * (float)aBorder.width, aAppUnitsPerDevPixel);
+
+          nsRect leftRect(aBorder.x, aBorder.y, thirdWidth, aBorder.height);
+          if (eSideLeft == aStartBevelSide) {
+            leftRect.y += aStartBevelOffset - startBevel;
+            leftRect.height -= aStartBevelOffset - startBevel;
+          }
+          if (eSideLeft == aEndBevelSide) {
+            leftRect.height -= aEndBevelOffset - endBevel;
+          }
+
+          aSegments.AppendElement(
+              SolidBeveledBorderSegment{leftRect,
+                                        aBorderColor,
+                                        {aStartBevelSide, startBevel},
+                                        {aEndBevelSide, endBevel}});
+
+          nscoord widthOffset = aBorder.width - thirdWidth;
+          nsRect rightRect(aBorder.x + widthOffset, aBorder.y,
+                           aBorder.width - widthOffset, aBorder.height);
+          if (eSideRight == aStartBevelSide) {
+            rightRect.y += aStartBevelOffset - startBevel;
+            rightRect.height -= aStartBevelOffset - startBevel;
+          }
+          if (eSideRight == aEndBevelSide) {
+            rightRect.height -= aEndBevelOffset - endBevel;
+          }
+          aSegments.AppendElement(
+              SolidBeveledBorderSegment{rightRect,
+                                        aBorderColor,
+                                        {aStartBevelSide, startBevel},
+                                        {aEndBevelSide, endBevel}});
+        }
+        break;
+      }
+      // else fall through to solid
+      [[fallthrough]];
+    case StyleBorderStyle::Solid:
+      aSegments.AppendElement(
+          SolidBeveledBorderSegment{aBorder,
+                                    aBorderColor,
+                                    {aStartBevelSide, aStartBevelOffset},
+                                    {aEndBevelSide, aEndBevelOffset}});
+      break;
+    case StyleBorderStyle::Outset:
+    case StyleBorderStyle::Inset:
+      MOZ_ASSERT_UNREACHABLE(
+          "inset, outset should have been converted to groove, ridge");
+      break;
+  }
+}
+
+// End table border-collapsing section
+
+Rect nsCSSRendering::ExpandPaintingRectForDecorationLine(
+    nsIFrame* aFrame, const StyleTextDecorationStyle aStyle,
+    const Rect& aClippedRect, const Float aICoordInFrame,
+    const Float aCycleLength, bool aVertical) {
+  switch (aStyle) {
+    case StyleTextDecorationStyle::Dotted:
+    case StyleTextDecorationStyle::Dashed:
+    case StyleTextDecorationStyle::Wavy:
+      break;
+    default:
+      NS_ERROR("Invalid style was specified");
+      return aClippedRect;
+  }
+
+  nsBlockFrame* block = nullptr;
+  // Note that when we paint the decoration lines in relative positioned
+  // box, we should paint them like all of the boxes are positioned as static.
+  nscoord framePosInBlockAppUnits = 0;
+  for (nsIFrame* f = aFrame; f; f = f->GetParent()) {
+    block = do_QueryFrame(f);
+    if (block) {
+      break;
+    }
+    framePosInBlockAppUnits +=
+        aVertical ? f->GetNormalPosition().y : f->GetNormalPosition().x;
+  }
+
+  NS_ENSURE_TRUE(block, aClippedRect);
+
+  nsPresContext* pc = aFrame->PresContext();
+  Float framePosInBlock =
+      Float(pc->AppUnitsToGfxUnits(framePosInBlockAppUnits));
+  int32_t rectPosInBlock = int32_t(NS_round(framePosInBlock + aICoordInFrame));
+  int32_t extraStartEdge =
+      rectPosInBlock - (rectPosInBlock / int32_t(aCycleLength) * aCycleLength);
+  Rect rect(aClippedRect);
+  if (aVertical) {
+    rect.y -= extraStartEdge;
+    rect.height += extraStartEdge;
+  } else {
+    rect.x -= extraStartEdge;
+    rect.width += extraStartEdge;
+  }
+  return rect;
+}
+
+// Converts a GfxFont to an SkFont
+// Either returns true if it was successful, or false if something went wrong
+static bool GetSkFontFromGfxFont(DrawTarget& aDrawTarget, gfxFont* aFont,
+                                 SkFont& aSkFont) {
+  RefPtr<ScaledFont> scaledFont = aFont->GetScaledFont(&aDrawTarget);
+  if (!scaledFont) {
+    return false;
+  }
+
+  ScaledFontBase* fontBase = static_cast<ScaledFontBase*>(scaledFont.get());
+
+  SkTypeface* typeface = fontBase->GetSkTypeface();
+  if (!typeface) {
+    return false;
+  }
+
+  aSkFont = SkFont(sk_ref_sp(typeface), SkFloatToScalar(fontBase->GetSize()));
+  return true;
+}
+
+// Computes data used to position the decoration line within a
+// SkTextBlob, data is returned through aBounds
+static void GetPositioning(
+    const nsCSSRendering::PaintDecorationLineParams& aParams, const Rect& aRect,
+    Float aOneCSSPixel, Float aCenterBaselineOffset, SkScalar aBounds[]) {
+  /**
+   * How Positioning in Skia Works
+   *  Take the letter "n" for example
+   *  We set textPos as 0, 0
+   *  This is represented in Skia like so (not to scale)
+   *        ^
+   *  -10px |  _ __
+   *        | | '_ \
+   *   -5px | | | | |
+   * y-axis | |_| |_|
+   *  (0,0) ----------------------->
+   *        |     5px        10px
+   *    5px |
+   *        |
+   *   10px |
+   *        v
+   *  0 on the x axis is a line that touches the bottom of the n
+   *  (0,0) is the bottom left-hand corner of the n character
+   *  Moving "up" from the n is going in a negative y direction
+   *  Moving "down" from the n is going in a positive y direction
+   *
+   *  The intercepts that are returned in this arrangement will be
+   *  offset by the original point it starts at. (This happens in
+   *  the SkipInk function below).
+   *
+   *  In Skia, text MUST be laid out such that the next character
+   *  in the RunBuffer is further along the x-axis than the previous
+   *  character, otherwise there is undefined/strange behavior.
+   */
+
+  Float rectThickness = aParams.vertical ? aRect.Width() : aRect.Height();
+
+  // the upper and lower lines/edges of the under or over line
+  SkScalar upperLine, lowerLine;
+  if (aParams.decoration == mozilla::StyleTextDecorationLine::OVERLINE) {
+    lowerLine =
+        -aParams.offset + aParams.defaultLineThickness - aCenterBaselineOffset;
+    upperLine = lowerLine - rectThickness;
+  } else {
+    // underlines in vertical text are offset from the center of
+    // the text, and not the baseline
+    // Skia sets the text at it's baseline so we have to offset it
+    // for text in vertical-* writing modes
+    upperLine = -aParams.offset - aCenterBaselineOffset;
+    lowerLine = upperLine + rectThickness;
+  }
+
+  // set up the bounds, add in a little padding to the thickness of the line
+  // (unless the line is <= 1 CSS pixel thick)
+  Float lineThicknessPadding = aParams.lineSize.height > aOneCSSPixel
+                                   ? 0.25f * aParams.lineSize.height
+                                   : 0;
+  // don't allow padding greater than 0.75 CSS pixel
+  lineThicknessPadding = std::min(lineThicknessPadding, 0.75f * aOneCSSPixel);
+  aBounds[0] = upperLine - lineThicknessPadding;
+  aBounds[1] = lowerLine + lineThicknessPadding;
+}
+
+// positions an individual glyph according to the given offset
+static SkPoint GlyphPosition(const gfxTextRun::DetailedGlyph& aGlyph,
+                             const SkPoint& aTextPos,
+                             int32_t aAppUnitsPerDevPixel) {
+  SkPoint point = {aGlyph.mOffset.x, aGlyph.mOffset.y};
+
+  // convert to device pixels
+  point.fX /= (float)aAppUnitsPerDevPixel;
+  point.fY /= (float)aAppUnitsPerDevPixel;
+
+  // add offsets
+  point.fX += aTextPos.fX;
+  point.fY += aTextPos.fY;
+  return point;
+}
+
+// returns a count of all the glyphs that will be rendered
+// excludes ligature continuations, includes the number of individual
+// glyph records. This includes the number of DetailedGlyphs that a single
+// CompressedGlyph record points to. This function is necessary because Skia
+// needs the total length of glyphs to add to it's run buffer before it creates
+// the RunBuffer object, and this cannot be resized later.
+static uint32_t CountAllGlyphs(
+    const gfxTextRun* aTextRun,
+    const gfxTextRun::CompressedGlyph* aCompressedGlyph, uint32_t aStringStart,
+    uint32_t aStringEnd) {
+  uint32_t totalGlyphCount = 0;
+
+  for (const gfxTextRun::CompressedGlyph* cg = aCompressedGlyph + aStringStart;
+       cg < aCompressedGlyph + aStringEnd; ++cg) {
+    totalGlyphCount += cg->IsSimpleGlyph() ? 1 : cg->GetGlyphCount();
+  }
+
+  return totalGlyphCount;
+}
+
+static void AddDetailedGlyph(const SkTextBlobBuilder::RunBuffer& aRunBuffer,
+                             const gfxTextRun::DetailedGlyph& aGlyph,
+                             int aIndex, float aAppUnitsPerDevPixel,
+                             SkPoint& aTextPos) {
+  // add glyph ID to the run buffer at i
+  aRunBuffer.glyphs[aIndex] = aGlyph.mGlyphID;
+
+  // position the glyph correctly using the detailed offsets
+  SkPoint position = GlyphPosition(aGlyph, aTextPos, aAppUnitsPerDevPixel);
+  aRunBuffer.pos[2 * aIndex] = position.fX;
+  aRunBuffer.pos[(2 * aIndex) + 1] = position.fY;
+
+  // increase aTextPos.fx by the advance
+  aTextPos.fX += ((float)aGlyph.mAdvance / aAppUnitsPerDevPixel);
+}
+
+static void AddSimpleGlyph(const SkTextBlobBuilder::RunBuffer& aRunBuffer,
+                           const gfxTextRun::CompressedGlyph& aGlyph,
+                           int aIndex, float aAppUnitsPerDevPixel,
+                           SkPoint& aTextPos) {
+  aRunBuffer.glyphs[aIndex] = aGlyph.GetSimpleGlyph();
+
+  // simple glyphs are offset from 0, so we'll just use textPos
+  aRunBuffer.pos[2 * aIndex] = aTextPos.fX;
+  aRunBuffer.pos[(2 * aIndex) + 1] = aTextPos.fY;
+
+  // increase aTextPos.fX by the advance
+  aTextPos.fX += ((float)aGlyph.GetSimpleAdvance() / aAppUnitsPerDevPixel);
+}
+
+// Sets up a Skia TextBlob of the specified font, text position, and made up of
+// the glyphs between aStringStart and aStringEnd. Handles RTL and LTR text
+// and positions each glyph within the text blob
+static sk_sp<const SkTextBlob> CreateTextBlob(
+    const gfxTextRun* aTextRun,
+    const gfxTextRun::CompressedGlyph* aCompressedGlyph, const SkFont& aFont,
+    const gfxTextRun::PropertyProvider::Spacing* aSpacing,
+    uint32_t aStringStart, uint32_t aStringEnd, float aAppUnitsPerDevPixel,
+    SkPoint& aTextPos, int32_t& aSpacingOffset) {
+  // allocate space for the run buffer, then fill it with the glyphs
+  uint32_t len =
+      CountAllGlyphs(aTextRun, aCompressedGlyph, aStringStart, aStringEnd);
+  if (len <= 0) {
+    return nullptr;
+  }
+
+  SkTextBlobBuilder builder;
+  const SkTextBlobBuilder::RunBuffer& run = builder.allocRunPos(aFont, len);
+
+  // RTL text should be read in by glyph starting at aStringEnd - 1 down until
+  // aStringStart.
+  bool isRTL = aTextRun->IsRightToLeft();
+  uint32_t currIndex = isRTL ? aStringEnd - 1 : aStringStart;  // textRun index
+  // currIndex will be advanced by |step| until it reaches |limit|, which is the
+  // final index to be handled (NOT one beyond the final index)
+  int step = isRTL ? -1 : 1;
+  uint32_t limit = isRTL ? aStringStart : aStringEnd - 1;
+
+  uint32_t i = 0;  // index into the SkTextBlob we're building
+  while (true) {
+    // Loop exit test is below, just before we update currIndex.
+    aTextPos.fX +=
+        isRTL ? aSpacing[aSpacingOffset].mAfter / aAppUnitsPerDevPixel
+              : aSpacing[aSpacingOffset].mBefore / aAppUnitsPerDevPixel;
+
+    if (aCompressedGlyph[currIndex].IsSimpleGlyph()) {
+      MOZ_ASSERT(i < len, "glyph count error!");
+      AddSimpleGlyph(run, aCompressedGlyph[currIndex], i, aAppUnitsPerDevPixel,
+                     aTextPos);
+      i++;
+    } else {
+      // if it's detailed, potentially add multiple into run.glyphs
+      uint32_t count = aCompressedGlyph[currIndex].GetGlyphCount();
+      if (count > 0) {
+        gfxTextRun::DetailedGlyph* detailGlyph =
+            aTextRun->GetDetailedGlyphs(currIndex);
+        for (uint32_t d = isRTL ? count - 1 : 0; count; count--, d += step) {
+          MOZ_ASSERT(i < len, "glyph count error!");
+          AddDetailedGlyph(run, detailGlyph[d], i, aAppUnitsPerDevPixel,
+                           aTextPos);
+          i++;
+        }
+      }
+    }
+    aTextPos.fX += isRTL
+                       ? aSpacing[aSpacingOffset].mBefore / aAppUnitsPerDevPixel
+                       : aSpacing[aSpacingOffset].mAfter / aAppUnitsPerDevPixel;
+    aSpacingOffset += step;
+
+    if (currIndex == limit) {
+      break;
+    }
+    currIndex += step;
+  }
+
+  MOZ_ASSERT(i == len, "glyph count error!");
+
+  return builder.make();
+}
+
+// Given a TextBlob, the bounding lines, and the set of current intercepts this
+// function adds the intercepts for the current TextBlob into the given set of
+// previoulsy calculated intercepts. This set is either of length 0, or a
+// multiple of 2 (since every intersection with a piece of text results in two
+// intercepts: entering/exiting)
+static void GetTextIntercepts(const sk_sp<const SkTextBlob>& aBlob,
+                              const SkScalar aBounds[],
+                              nsTArray<SkScalar>& aIntercepts) {
+  // It's possible that we'll encounter a Windows exception deep inside
+  // Skia's DirectWrite code while trying to get the intercepts. To avoid
+  // crashing in this case, catch any such exception here and discard the
+  // newly-added (and incompletely filled in) elements.
+  int count = 0;
+  MOZ_SEH_TRY {
+    // https://skia.org/user/api/SkTextBlob_Reference#Text_Blob_Text_Intercepts
+    count = aBlob->getIntercepts(aBounds, nullptr);
+    if (count < 2) {
+      return;
+    }
+    aBlob->getIntercepts(aBounds, aIntercepts.AppendElements(count));
+  }
+  MOZ_SEH_EXCEPT(EXCEPTION_EXECUTE_HANDLER) {
+    gfxCriticalNote << "Exception occurred getting text intercepts";
+    aIntercepts.TruncateLength(aIntercepts.Length() - count);
+  }
+}
+
+// This function, given a set of intercepts that represent each intersection
+// between an under/overline and text, makes a series of calls to
+// PaintDecorationLineInternal that paints a series of clip rects which
+// implement the text-decoration-skip-ink property
+// Logic for where to place each clipped rect, and the length of each rect is
+// included here
+static void SkipInk(nsIFrame* aFrame, DrawTarget& aDrawTarget,
+                    const nsCSSRendering::PaintDecorationLineParams& aParams,
+                    const nsTArray<SkScalar>& aIntercepts, Float aPadding,
+                    Rect& aRect) {
+  nsCSSRendering::PaintDecorationLineParams clipParams = aParams;
+  int length = aIntercepts.Length();
+
+  SkScalar startIntercept = 0;
+  SkScalar endIntercept = 0;
+
+  // keep track of the direction we are drawing the clipped rects in
+  // for sideways text, our intercepts from the first glyph are actually
+  // decreasing (towards the top edge of the page), so we use a negative
+  // direction
+  Float dir = 1.0f;
+  Float lineStart = aParams.vertical ? aParams.pt.y : aParams.pt.x;
+  Float lineEnd = lineStart + aParams.lineSize.width;
+  if (aParams.sidewaysLeft) {
+    dir = -1.0f;
+    std::swap(lineStart, lineEnd);
+  }
+
+  for (int i = 0; i <= length; i += 2) {
+    // handle start/end edge cases and set up general case
+    startIntercept = (i > 0) ? (dir * aIntercepts[i - 1]) + lineStart
+                             : lineStart - (dir * aPadding);
+    endIntercept = (i < length) ? (dir * aIntercepts[i]) + lineStart
+                                : lineEnd + (dir * aPadding);
+
+    // remove padding at both ends for width
+    // the start of the line is calculated so the padding removes just
+    // enough so that the line starts at its normal position
+    clipParams.lineSize.width =
+        (dir * (endIntercept - startIntercept)) - (2.0 * aPadding);
+
+    // Don't draw decoration lines that have a smaller width than 1, or half
+    // the line-end padding dimension.
+    if (clipParams.lineSize.width < std::max(aPadding * 0.5, 1.0)) {
+      continue;
+    }
+
+    // Start the line right after the intercept's location plus room for
+    // padding; snap the rect edges to device pixels for consistent rendering
+    // of dots across separate fragments of a dotted line.
+    if (aParams.vertical) {
+      clipParams.pt.y = aParams.sidewaysLeft ? endIntercept + aPadding
+                                             : startIntercept + aPadding;
+      aRect.y = std::floor(clipParams.pt.y + 0.5);
+      aRect.SetBottomEdge(
+          std::floor(clipParams.pt.y + clipParams.lineSize.width + 0.5));
+    } else {
+      clipParams.pt.x = startIntercept + aPadding;
+      aRect.x = std::floor(clipParams.pt.x + 0.5);
+      aRect.SetRightEdge(
+          std::floor(clipParams.pt.x + clipParams.lineSize.width + 0.5));
+    }
+
+    nsCSSRendering::PaintDecorationLineInternal(aFrame, aDrawTarget, clipParams,
+                                                aRect);
+  }
+}
+
+void nsCSSRendering::PaintDecorationLine(
+    nsIFrame* aFrame, DrawTarget& aDrawTarget,
+    const PaintDecorationLineParams& aParams) {
+  NS_ASSERTION(aParams.style != StyleTextDecorationStyle::None,
+               "aStyle is none");
+
+  Rect rect = ToRect(GetTextDecorationRectInternal(aParams.pt, aParams));
+  if (rect.IsEmpty() || !rect.Intersects(aParams.dirtyRect)) {
+    return;
+  }
+
+  if (aParams.decoration != StyleTextDecorationLine::UNDERLINE &&
+      aParams.decoration != StyleTextDecorationLine::OVERLINE &&
+      aParams.decoration != StyleTextDecorationLine::LINE_THROUGH) {
+    MOZ_ASSERT_UNREACHABLE("Invalid text decoration value");
+    return;
+  }
+
+  // Check if decoration line will skip past ascenders/descenders
+  // text-decoration-skip-ink only applies to overlines/underlines
+  mozilla::StyleTextDecorationSkipInk skipInk =
+      aFrame->StyleText()->mTextDecorationSkipInk;
+  bool skipInkEnabled =
+      skipInk != mozilla::StyleTextDecorationSkipInk::None &&
+      aParams.decoration != StyleTextDecorationLine::LINE_THROUGH;
+
+  if (!skipInkEnabled || aParams.glyphRange.Length() == 0) {
+    PaintDecorationLineInternal(aFrame, aDrawTarget, aParams, rect);
+    return;
+  }
+
+  // check if the frame is a text frame or not
+  nsTextFrame* textFrame = nullptr;
+  if (aFrame->IsTextFrame()) {
+    textFrame = static_cast<nsTextFrame*>(aFrame);
+  } else {
+    PaintDecorationLineInternal(aFrame, aDrawTarget, aParams, rect);
+    return;
+  }
+
+  // get text run and current text offset (for line wrapping)
+  gfxTextRun* textRun =
+      textFrame->GetTextRun(nsTextFrame::TextRunType::eInflated);
+
+  // used for conversions from app units to device pixels
+  int32_t appUnitsPerDevPixel = aFrame->PresContext()->AppUnitsPerDevPixel();
+
+  // pointer to the array of glyphs for this TextRun
+  gfxTextRun::CompressedGlyph* characterGlyphs = textRun->GetCharacterGlyphs();
+
+  // get positioning info
+  SkPoint textPos = {0, aParams.baselineOffset};
+  SkScalar bounds[] = {0, 0};
+  Float oneCSSPixel = aFrame->PresContext()->CSSPixelsToDevPixels(1.0f);
+  if (!textRun->UseCenterBaseline()) {
+    GetPositioning(aParams, rect, oneCSSPixel, 0, bounds);
+  }
+
+  // array for the text intercepts
+  AutoTArray<SkScalar, 256> intercepts;
+
+  // array for spacing data
+  AutoTArray<gfxTextRun::PropertyProvider::Spacing, 64> spacing;
+  spacing.SetLength(aParams.glyphRange.Length());
+  if (aParams.provider != nullptr) {
+    aParams.provider->GetSpacing(aParams.glyphRange, spacing.Elements());
+  }
+
+  // loop through each glyph run
+  // in most cases there will only be one
+  bool isRTL = textRun->IsRightToLeft();
+  int32_t spacingOffset = isRTL ? aParams.glyphRange.Length() - 1 : 0;
+  gfxTextRun::GlyphRunIterator iter(textRun, aParams.glyphRange, isRTL);
+
+  // For any glyph run where we don't actually do skipping, we'll need to
+  // advance the current position by its width.
+  // (For runs we do process, CreateTextBlob will update the position.)
+  auto currentGlyphRunAdvance = [&]() {
+    return textRun->GetAdvanceWidth(
+               gfxTextRun::Range(iter.StringStart(), iter.StringEnd()),
+               aParams.provider) /
+           appUnitsPerDevPixel;
+  };
+
+  for (; !iter.AtEnd(); iter.NextRun()) {
+    if (iter.GlyphRun()->mOrientation ==
+            mozilla::gfx::ShapedTextFlags::TEXT_ORIENT_VERTICAL_UPRIGHT ||
+        (iter.GlyphRun()->mIsCJK &&
+         skipInk == mozilla::StyleTextDecorationSkipInk::Auto)) {
+      // We don't support upright text in vertical modes currently
+      // (see https://bugzilla.mozilla.org/show_bug.cgi?id=1572294),
+      // but we do need to update textPos so that following runs will be
+      // correctly positioned.
+      // We also don't apply skip-ink to CJK text runs because many fonts
+      // have an underline that looks really bad if this is done
+      // (see https://bugzilla.mozilla.org/show_bug.cgi?id=1573249),
+      // when skip-ink is set to 'auto'.
+      textPos.fX += currentGlyphRunAdvance();
+      continue;
+    }
+
+    gfxFont* font = iter.GlyphRun()->mFont;
+    // Don't try to apply skip-ink to 'sbix' fonts like Apple Color Emoji,
+    // because old macOS (10.9) may crash trying to retrieve glyph paths
+    // that don't exist.
+    if (font->GetFontEntry()->HasFontTable(TRUETYPE_TAG('s', 'b', 'i', 'x'))) {
+      textPos.fX += currentGlyphRunAdvance();
+      continue;
+    }
+
+    // get a Skia version of the glyph run's font
+    SkFont skiafont;
+    if (!GetSkFontFromGfxFont(aDrawTarget, font, skiafont)) {
+      PaintDecorationLineInternal(aFrame, aDrawTarget, aParams, rect);
+      return;
+    }
+
+    // Create a text blob with correctly positioned glyphs. This also updates
+    // textPos.fX with the advance of the glyphs.
+    sk_sp<const SkTextBlob> textBlob =
+        CreateTextBlob(textRun, characterGlyphs, skiafont, spacing.Elements(),
+                       iter.StringStart(), iter.StringEnd(),
+                       (float)appUnitsPerDevPixel, textPos, spacingOffset);
+
+    if (!textBlob) {
+      textPos.fX += currentGlyphRunAdvance();
+      continue;
+    }
+
+    if (textRun->UseCenterBaseline()) {
+      // writing modes that use a center baseline need to be adjusted on a
+      // font-by-font basis since Skia lines up the text on a alphabetic
+      // baseline, but for some vertical-* writing modes the offset is from the
+      // center.
+      gfxFont::Metrics metrics = font->GetMetrics(nsFontMetrics::eHorizontal);
+      Float centerToBaseline = (metrics.emAscent - metrics.emDescent) / 2.0f;
+      GetPositioning(aParams, rect, oneCSSPixel, centerToBaseline, bounds);
+    }
+
+    // compute the text intercepts that need to be skipped
+    GetTextIntercepts(textBlob, bounds, intercepts);
+  }
+  bool needsSkipInk = intercepts.Length() > 0;
+
+  if (needsSkipInk) {
+    // Padding between glyph intercepts and the decoration line: we use the
+    // decoration line thickness, clamped to a minimum of 1px and a maximum
+    // of 0.2em.
+    Float padding =
+        std::min(std::max(aParams.lineSize.height, oneCSSPixel),
+                 Float(textRun->GetFontGroup()->GetStyle()->size / 5.0));
+    SkipInk(aFrame, aDrawTarget, aParams, intercepts, padding, rect);
+  } else {
+    PaintDecorationLineInternal(aFrame, aDrawTarget, aParams, rect);
+  }
+}
+
+void nsCSSRendering::PaintDecorationLineInternal(
+    nsIFrame* aFrame, DrawTarget& aDrawTarget,
+    const PaintDecorationLineParams& aParams, Rect aRect) {
+  Float lineThickness = std::max(NS_round(aParams.lineSize.height), 1.0);
+
+  DeviceColor color = ToDeviceColor(aParams.color);
+  ColorPattern colorPat(color);
+  StrokeOptions strokeOptions(lineThickness);
+  DrawOptions drawOptions;
+
+  Float dash[2];
+
+  AutoPopClips autoPopClips(&aDrawTarget);
+
+  mozilla::layout::TextDrawTarget* textDrawer = nullptr;
+  if (aDrawTarget.GetBackendType() == BackendType::WEBRENDER_TEXT) {
+    textDrawer = static_cast<mozilla::layout::TextDrawTarget*>(&aDrawTarget);
+  }
+
+  switch (aParams.style) {
+    case StyleTextDecorationStyle::Solid:
+    case StyleTextDecorationStyle::Double:
+      break;
+    case StyleTextDecorationStyle::Dashed: {
+      autoPopClips.PushClipRect(aRect);
+      Float dashWidth = lineThickness * DOT_LENGTH * DASH_LENGTH;
+      dash[0] = dashWidth;
+      dash[1] = dashWidth;
+      strokeOptions.mDashPattern = dash;
+      strokeOptions.mDashLength = MOZ_ARRAY_LENGTH(dash);
+      strokeOptions.mLineCap = CapStyle::BUTT;
+      aRect = ExpandPaintingRectForDecorationLine(
+          aFrame, aParams.style, aRect, aParams.icoordInFrame, dashWidth * 2,
+          aParams.vertical);
+      // We should continue to draw the last dash even if it is not in the rect.
+      aRect.width += dashWidth;
+      break;
+    }
+    case StyleTextDecorationStyle::Dotted: {
+      autoPopClips.PushClipRect(aRect);
+      Float dashWidth = lineThickness * DOT_LENGTH;
+      if (lineThickness > 2.0) {
+        dash[0] = 0.f;
+        dash[1] = dashWidth * 2.f;
+        strokeOptions.mLineCap = CapStyle::ROUND;
+      } else {
+        dash[0] = dashWidth;
+        dash[1] = dashWidth;
+      }
+      strokeOptions.mDashPattern = dash;
+      strokeOptions.mDashLength = MOZ_ARRAY_LENGTH(dash);
+      aRect = ExpandPaintingRectForDecorationLine(
+          aFrame, aParams.style, aRect, aParams.icoordInFrame, dashWidth * 2,
+          aParams.vertical);
+      // We should continue to draw the last dot even if it is not in the rect.
+      aRect.width += dashWidth;
+      break;
+    }
+    case StyleTextDecorationStyle::Wavy:
+      autoPopClips.PushClipRect(aRect);
+      if (lineThickness > 2.0) {
+        drawOptions.mAntialiasMode = AntialiasMode::SUBPIXEL;
+      } else {
+        // Don't use anti-aliasing here.  Because looks like lighter color wavy
+        // line at this case.  And probably, users don't think the
+        // non-anti-aliased wavy line is not pretty.
+        drawOptions.mAntialiasMode = AntialiasMode::NONE;
+      }
+      break;
+    default:
+      NS_ERROR("Invalid style value!");
+      return;
+  }
+
+  // The block-direction position should be set to the middle of the line.
+  if (aParams.vertical) {
+    aRect.x += lineThickness / 2;
+  } else {
+    aRect.y += lineThickness / 2;
+  }
+
+  switch (aParams.style) {
+    case StyleTextDecorationStyle::Solid:
+    case StyleTextDecorationStyle::Dotted:
+    case StyleTextDecorationStyle::Dashed: {
+      Point p1 = aRect.TopLeft();
+      Point p2 = aParams.vertical ? aRect.BottomLeft() : aRect.TopRight();
+      if (textDrawer) {
+        textDrawer->AppendDecoration(p1, p2, lineThickness, aParams.vertical,
+                                     color, aParams.style);
+      } else {
+        aDrawTarget.StrokeLine(p1, p2, colorPat, strokeOptions, drawOptions);
+      }
+      return;
+    }
+    case StyleTextDecorationStyle::Double: {
+      /**
+       *  We are drawing double line as:
+       *
+       * +-------------------------------------------+
+       * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| ^
+       * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| | lineThickness
+       * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| v
+       * |                                           |
+       * |                                           |
+       * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| ^
+       * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| | lineThickness
+       * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| v
+       * +-------------------------------------------+
+       */
+      Point p1a = aRect.TopLeft();
+      Point p2a = aParams.vertical ? aRect.BottomLeft() : aRect.TopRight();
+
+      if (aParams.vertical) {
+        aRect.width -= lineThickness;
+      } else {
+        aRect.height -= lineThickness;
+      }
+
+      Point p1b = aParams.vertical ? aRect.TopRight() : aRect.BottomLeft();
+      Point p2b = aRect.BottomRight();
+
+      if (textDrawer) {
+        textDrawer->AppendDecoration(p1a, p2a, lineThickness, aParams.vertical,
+                                     color, StyleTextDecorationStyle::Solid);
+        textDrawer->AppendDecoration(p1b, p2b, lineThickness, aParams.vertical,
+                                     color, StyleTextDecorationStyle::Solid);
+      } else {
+        aDrawTarget.StrokeLine(p1a, p2a, colorPat, strokeOptions, drawOptions);
+        aDrawTarget.StrokeLine(p1b, p2b, colorPat, strokeOptions, drawOptions);
+      }
+      return;
+    }
+    case StyleTextDecorationStyle::Wavy: {
+      /**
+       *  We are drawing wavy line as:
+       *
+       *  P: Path, X: Painted pixel
+       *
+       *     +---------------------------------------+
+       *   XX|X            XXXXXX            XXXXXX  |
+       *   PP|PX          XPPPPPPX          XPPPPPPX |    ^
+       *   XX|XPX        XPXXXXXXPX        XPXXXXXXPX|    |
+       *     | XPX      XPX      XPX      XPX      XP|X   |adv
+       *     |  XPXXXXXXPX        XPXXXXXXPX        X|PX  |
+       *     |   XPPPPPPX          XPPPPPPX          |XPX v
+       *     |    XXXXXX            XXXXXX           | XX
+       *     +---------------------------------------+
+       *      <---><--->                                ^
+       *      adv  flatLengthAtVertex                   rightMost
+       *
+       *  1. Always starts from top-left of the drawing area, however, we need
+       *     to draw  the line from outside of the rect.  Because the start
+       *     point of the line is not good style if we draw from inside it.
+       *  2. First, draw horizontal line from outside the rect to top-left of
+       *     the rect;
+       *  3. Goes down to bottom of the area at 45 degrees.
+       *  4. Slides to right horizontaly, see |flatLengthAtVertex|.
+       *  5. Goes up to top of the area at 45 degrees.
+       *  6. Slides to right horizontaly.
+       *  7. Repeat from 2 until reached to right-most edge of the area.
+       *
+       * In the vertical case, swap horizontal and vertical coordinates and
+       * directions in the above description.
+       */
+
+      Float& rectICoord = aParams.vertical ? aRect.y : aRect.x;
+      Float& rectISize = aParams.vertical ? aRect.height : aRect.width;
+      const Float rectBSize = aParams.vertical ? aRect.width : aRect.height;
+
+      const Float adv = rectBSize - lineThickness;
+      const Float flatLengthAtVertex =
+          std::max((lineThickness - 1.0) * 2.0, 1.0);
+
+      // Align the start of wavy lines to the nearest ancestor block.
+      const Float cycleLength = 2 * (adv + flatLengthAtVertex);
+      aRect = ExpandPaintingRectForDecorationLine(
+          aFrame, aParams.style, aRect, aParams.icoordInFrame, cycleLength,
+          aParams.vertical);
+
+      if (textDrawer) {
+        // Undo attempted centering
+        Float& rectBCoord = aParams.vertical ? aRect.x : aRect.y;
+        rectBCoord -= lineThickness / 2;
+
+        textDrawer->AppendWavyDecoration(aRect, lineThickness, aParams.vertical,
+                                         color);
+        return;
+      }
+
+      // figure out if we can trim whole cycles from the left and right edges
+      // of the line, to try and avoid creating an unnecessarily long and
+      // complex path (but don't do this for webrender, )
+      const Float dirtyRectICoord =
+          aParams.vertical ? aParams.dirtyRect.y : aParams.dirtyRect.x;
+      int32_t skipCycles = floor((dirtyRectICoord - rectICoord) / cycleLength);
+      if (skipCycles > 0) {
+        rectICoord += skipCycles * cycleLength;
+        rectISize -= skipCycles * cycleLength;
+      }
+
+      rectICoord += lineThickness / 2.0;
+
+      Point pt(aRect.TopLeft());
+      Float& ptICoord = aParams.vertical ? pt.y.value : pt.x.value;
+      Float& ptBCoord = aParams.vertical ? pt.x.value : pt.y.value;
+      if (aParams.vertical) {
+        ptBCoord += adv;
+      }
+      Float iCoordLimit = ptICoord + rectISize + lineThickness;
+
+      const Float dirtyRectIMost = aParams.vertical ? aParams.dirtyRect.YMost()
+                                                    : aParams.dirtyRect.XMost();
+      skipCycles = floor((iCoordLimit - dirtyRectIMost) / cycleLength);
+      if (skipCycles > 0) {
+        iCoordLimit -= skipCycles * cycleLength;
+      }
+
+      RefPtr<PathBuilder> builder = aDrawTarget.CreatePathBuilder();
+      RefPtr<Path> path;
+
+      ptICoord -= lineThickness;
+      builder->MoveTo(pt);  // 1
+
+      ptICoord = rectICoord;
+      builder->LineTo(pt);  // 2
+
+      // In vertical mode, to go "down" relative to the text we need to
+      // decrease the block coordinate, whereas in horizontal we increase
+      // it. So the sense of this flag is effectively inverted.
+      bool goDown = !aParams.vertical;
+      uint32_t iter = 0;
+      while (ptICoord < iCoordLimit) {
+        if (++iter > 1000) {
+          // stroke the current path and start again, to avoid pathological
+          // behavior in cairo with huge numbers of path segments
+          path = builder->Finish();
+          aDrawTarget.Stroke(path, colorPat, strokeOptions, drawOptions);
+          builder = aDrawTarget.CreatePathBuilder();
+          builder->MoveTo(pt);
+          iter = 0;
+        }
+        ptICoord += adv;
+        ptBCoord += goDown ? adv : -adv;
+
+        builder->LineTo(pt);  // 3 and 5
+
+        ptICoord += flatLengthAtVertex;
+        builder->LineTo(pt);  // 4 and 6
+
+        goDown = !goDown;
+      }
+      path = builder->Finish();
+      aDrawTarget.Stroke(path, colorPat, strokeOptions, drawOptions);
+      return;
+    }
+    default:
+      NS_ERROR("Invalid style value!");
+  }
+}
+
+Rect nsCSSRendering::DecorationLineToPath(
+    const PaintDecorationLineParams& aParams) {
+  NS_ASSERTION(aParams.style != StyleTextDecorationStyle::None,
+               "aStyle is none");
+
+  Rect path;  // To benefit from RVO, we return this from all return points
+
+  Rect rect = ToRect(GetTextDecorationRectInternal(aParams.pt, aParams));
+  if (rect.IsEmpty() || !rect.Intersects(aParams.dirtyRect)) {
+    return path;
+  }
+
+  if (aParams.decoration != StyleTextDecorationLine::UNDERLINE &&
+      aParams.decoration != StyleTextDecorationLine::OVERLINE &&
+      aParams.decoration != StyleTextDecorationLine::LINE_THROUGH) {
+    MOZ_ASSERT_UNREACHABLE("Invalid text decoration value");
+    return path;
+  }
+
+  if (aParams.style != StyleTextDecorationStyle::Solid) {
+    // For the moment, we support only solid text decorations.
+    return path;
+  }
+
+  Float lineThickness = std::max(NS_round(aParams.lineSize.height), 1.0);
+
+  // The block-direction position should be set to the middle of the line.
+  if (aParams.vertical) {
+    rect.x += lineThickness / 2;
+    path = Rect(rect.TopLeft() - Point(lineThickness / 2, 0.0),
+                Size(lineThickness, rect.Height()));
+  } else {
+    rect.y += lineThickness / 2;
+    path = Rect(rect.TopLeft() - Point(0.0, lineThickness / 2),
+                Size(rect.Width(), lineThickness));
+  }
+
+  return path;
+}
+
+nsRect nsCSSRendering::GetTextDecorationRect(
+    nsPresContext* aPresContext, const DecorationRectParams& aParams) {
+  NS_ASSERTION(aPresContext, "aPresContext is null");
+  NS_ASSERTION(aParams.style != StyleTextDecorationStyle::None,
+               "aStyle is none");
+
+  gfxRect rect = GetTextDecorationRectInternal(Point(0, 0), aParams);
+  // The rect values are already rounded to nearest device pixels.
+  nsRect r;
+  r.x = aPresContext->GfxUnitsToAppUnits(rect.X());
+  r.y = aPresContext->GfxUnitsToAppUnits(rect.Y());
+  r.width = aPresContext->GfxUnitsToAppUnits(rect.Width());
+  r.height = aPresContext->GfxUnitsToAppUnits(rect.Height());
+  return r;
+}
+
+gfxRect nsCSSRendering::GetTextDecorationRectInternal(
+    const Point& aPt, const DecorationRectParams& aParams) {
+  NS_ASSERTION(aParams.style <= StyleTextDecorationStyle::Wavy,
+               "Invalid aStyle value");
+
+  if (aParams.style == StyleTextDecorationStyle::None) {
+    return gfxRect(0, 0, 0, 0);
+  }
+
+  bool canLiftUnderline = aParams.descentLimit >= 0.0;
+
+  gfxFloat iCoord = aParams.vertical ? aPt.y : aPt.x;
+  gfxFloat bCoord = aParams.vertical ? aPt.x : aPt.y;
+
+  // 'left' and 'right' are relative to the line, so for vertical writing modes
+  // they will actually become top and bottom of the rendered line.
+  // Similarly, aLineSize.width and .height are actually length and thickness
+  // of the line, which runs horizontally or vertically according to aVertical.
+  const gfxFloat left = floor(iCoord + 0.5),
+                 right = floor(iCoord + aParams.lineSize.width + 0.5);
+
+  // We compute |r| as if for a horizontal text run, and then swap vertical
+  // and horizontal coordinates at the end if vertical was requested.
+  gfxRect r(left, 0, right - left, 0);
+
+  gfxFloat lineThickness = NS_round(aParams.lineSize.height);
+  lineThickness = std::max(lineThickness, 1.0);
+  gfxFloat defaultLineThickness = NS_round(aParams.defaultLineThickness);
+  defaultLineThickness = std::max(defaultLineThickness, 1.0);
+
+  gfxFloat ascent = NS_round(aParams.ascent);
+  gfxFloat descentLimit = floor(aParams.descentLimit);
+
+  gfxFloat suggestedMaxRectHeight =
+      std::max(std::min(ascent, descentLimit), 1.0);
+  r.height = lineThickness;
+  if (aParams.style == StyleTextDecorationStyle::Double) {
+    /**
+     *  We will draw double line as:
+     *
+     * +-------------------------------------------+
+     * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| ^
+     * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| | lineThickness
+     * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| v
+     * |                                           | ^
+     * |                                           | | gap
+     * |                                           | v
+     * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| ^
+     * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| | lineThickness
+     * |XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX| v
+     * +-------------------------------------------+
+     */
+    gfxFloat gap = NS_round(lineThickness / 2.0);
+    gap = std::max(gap, 1.0);
+    r.height = lineThickness * 2.0 + gap;
+    if (canLiftUnderline) {
+      if (r.Height() > suggestedMaxRectHeight) {
+        // Don't shrink the line height, because the thickness has some meaning.
+        // We can just shrink the gap at this time.
+        r.height = std::max(suggestedMaxRectHeight, lineThickness * 2.0 + 1.0);
+      }
+    }
+  } else if (aParams.style == StyleTextDecorationStyle::Wavy) {
+    /**
+     *  We will draw wavy line as:
+     *
+     * +-------------------------------------------+
+     * |XXXXX            XXXXXX            XXXXXX  | ^
+     * |XXXXXX          XXXXXXXX          XXXXXXXX | | lineThickness
+     * |XXXXXXX        XXXXXXXXXX        XXXXXXXXXX| v
+     * |     XXX      XXX      XXX      XXX      XX|
+     * |      XXXXXXXXXX        XXXXXXXXXX        X|
+     * |       XXXXXXXX          XXXXXXXX          |
+     * |        XXXXXX            XXXXXX           |
+     * +-------------------------------------------+
+     */
+    r.height = lineThickness > 2.0 ? lineThickness * 4.0 : lineThickness * 3.0;
+    if (canLiftUnderline) {
+      if (r.Height() > suggestedMaxRectHeight) {
+        // Don't shrink the line height even if there is not enough space,
+        // because the thickness has some meaning.  E.g., the 1px wavy line and
+        // 2px wavy line can be used for different meaning in IME selections
+        // at same time.
+        r.height = std::max(suggestedMaxRectHeight, lineThickness * 2.0);
+      }
+    }
+  }
+
+  gfxFloat baseline = floor(bCoord + aParams.ascent + 0.5);
+
+  // Calculate adjusted offset based on writing-mode/orientation and thickness
+  // of decoration line. The input value aParams.offset is the nominal position
+  // (offset from baseline) where we would draw a single, infinitely-thin line;
+  // but for a wavy or double line, we'll need to move the bounding rect of the
+  // decoration outwards from the baseline so that an underline remains below
+  // the glyphs, and an overline above them, despite the increased block-dir
+  // extent of the decoration.
+  //
+  // So adjustments by r.Height() are used to make the wider line styles (wavy
+  // and double) "grow" in the appropriate direction compared to the basic
+  // single line.
+  //
+  // Note that at this point, the decoration rect is being calculated in line-
+  // relative coordinates, where 'x' is line-rightwards, and 'y' is line-
+  // upwards. We'll swap them to be physical coords at the end.
+  gfxFloat offset = 0.0;
+
+  if (aParams.decoration == StyleTextDecorationLine::UNDERLINE) {
+    offset = aParams.offset;
+    if (canLiftUnderline) {
+      if (descentLimit < -offset + r.Height()) {
+        // If we can ignore the offset and the decoration line is overflowing,
+        // we should align the bottom edge of the decoration line rect if it's
+        // possible.  Otherwise, we should lift up the top edge of the rect as
+        // far as possible.
+        gfxFloat offsetBottomAligned = -descentLimit + r.Height();
+        gfxFloat offsetTopAligned = 0.0;
+        offset = std::min(offsetBottomAligned, offsetTopAligned);
+      }
+    }
+  } else if (aParams.decoration == StyleTextDecorationLine::OVERLINE) {
+    // For overline, we adjust the offset by defaultlineThickness (the default
+    // thickness of a single decoration line) because empirically it looks
+    // better to draw the overline just inside rather than outside the font's
+    // ascent, which is what nsTextFrame passes as aParams.offset (as fonts
+    // don't provide an explicit overline-offset).
+    offset = aParams.offset - defaultLineThickness + r.Height();
+  } else if (aParams.decoration == StyleTextDecorationLine::LINE_THROUGH) {
+    // To maintain a consistent mid-point for line-through decorations,
+    // we adjust the offset by half of the decoration rect's height.
+    gfxFloat extra = floor(r.Height() / 2.0 + 0.5);
+    extra = std::max(extra, lineThickness);
+    // computes offset for when user specifies a decoration width since
+    // aParams.offset is derived from the font metric's line height
+    gfxFloat decorationThicknessOffset =
+        (lineThickness - defaultLineThickness) / 2.0;
+    offset = aParams.offset - lineThickness + extra + decorationThicknessOffset;
+  } else {
+    MOZ_ASSERT_UNREACHABLE("Invalid text decoration value");
+  }
+
+  // Convert line-relative coordinate system (x = line-right, y = line-up)
+  // to physical coords, and move the decoration rect to the calculated
+  // offset from baseline.
+  if (aParams.vertical) {
+    std::swap(r.x, r.y);
+    std::swap(r.width, r.height);
+    // line-upwards in vertical mode = physical-right, so we /add/ offset
+    // to baseline. Except in sideways-lr mode, where line-upwards will be
+    // physical leftwards.
+    if (aParams.sidewaysLeft) {
+      r.x = baseline - floor(offset + 0.5);
+    } else {
+      r.x = baseline + floor(offset - r.Width() + 0.5);
+    }
+  } else {
+    // line-upwards in horizontal mode = physical-up, but our physical coord
+    // system works downwards, so we /subtract/ offset from baseline.
+    r.y = baseline - floor(offset + 0.5);
+  }
+
+  return r;
+}
+
+#define MAX_BLUR_RADIUS 300
+#define MAX_SPREAD_RADIUS 50
+
+static inline gfxPoint ComputeBlurStdDev(nscoord aBlurRadius,
+                                         int32_t aAppUnitsPerDevPixel,
+                                         gfxFloat aScaleX, gfxFloat aScaleY) {
+  // http://dev.w3.org/csswg/css3-background/#box-shadow says that the
+  // standard deviation of the blur should be half the given blur value.
+  gfxFloat blurStdDev = gfxFloat(aBlurRadius) / gfxFloat(aAppUnitsPerDevPixel);
+
+  return gfxPoint(
+      std::min((blurStdDev * aScaleX), gfxFloat(MAX_BLUR_RADIUS)) / 2.0,
+      std::min((blurStdDev * aScaleY), gfxFloat(MAX_BLUR_RADIUS)) / 2.0);
+}
+
+static inline IntSize ComputeBlurRadius(nscoord aBlurRadius,
+                                        int32_t aAppUnitsPerDevPixel,
+                                        gfxFloat aScaleX = 1.0,
+                                        gfxFloat aScaleY = 1.0) {
+  gfxPoint scaledBlurStdDev =
+      ComputeBlurStdDev(aBlurRadius, aAppUnitsPerDevPixel, aScaleX, aScaleY);
+  return gfxAlphaBoxBlur::CalculateBlurRadius(scaledBlurStdDev);
+}
+
+// -----
+// nsContextBoxBlur
+// -----
+gfxContext* nsContextBoxBlur::Init(const nsRect& aRect, nscoord aSpreadRadius,
+                                   nscoord aBlurRadius,
+                                   int32_t aAppUnitsPerDevPixel,
+                                   gfxContext* aDestinationCtx,
+                                   const nsRect& aDirtyRect,
+                                   const gfxRect* aSkipRect, uint32_t aFlags) {
+  if (aRect.IsEmpty()) {
+    mContext = nullptr;
+    return nullptr;
+  }
+
+  IntSize blurRadius;
+  IntSize spreadRadius;
+  GetBlurAndSpreadRadius(aDestinationCtx->GetDrawTarget(), aAppUnitsPerDevPixel,
+                         aBlurRadius, aSpreadRadius, blurRadius, spreadRadius);
+
+  mDestinationCtx = aDestinationCtx;
+
+  // If not blurring, draw directly onto the destination device
+  if (blurRadius.width <= 0 && blurRadius.height <= 0 &&
+      spreadRadius.width <= 0 && spreadRadius.height <= 0 &&
+      !(aFlags & FORCE_MASK)) {
+    mContext = aDestinationCtx;
+    return mContext;
+  }
+
+  // Convert from app units to device pixels
+  gfxRect rect = nsLayoutUtils::RectToGfxRect(aRect, aAppUnitsPerDevPixel);
+
+  gfxRect dirtyRect =
+      nsLayoutUtils::RectToGfxRect(aDirtyRect, aAppUnitsPerDevPixel);
+  dirtyRect.RoundOut();
+
+  gfxMatrix transform = aDestinationCtx->CurrentMatrixDouble();
+  rect = transform.TransformBounds(rect);
+
+  mPreTransformed = !transform.IsIdentity();
+
+  // Create the temporary surface for blurring
+  dirtyRect = transform.TransformBounds(dirtyRect);
+  bool useHardwareAccel = !(aFlags & DISABLE_HARDWARE_ACCELERATION_BLUR);
+  if (aSkipRect) {
+    gfxRect skipRect = transform.TransformBounds(*aSkipRect);
+    mOwnedContext =
+        mAlphaBoxBlur.Init(aDestinationCtx, rect, spreadRadius, blurRadius,
+                           &dirtyRect, &skipRect, useHardwareAccel);
+  } else {
+    mOwnedContext =
+        mAlphaBoxBlur.Init(aDestinationCtx, rect, spreadRadius, blurRadius,
+                           &dirtyRect, nullptr, useHardwareAccel);
+  }
+  mContext = mOwnedContext.get();
+
+  if (mContext) {
+    // we don't need to blur if skipRect is equal to rect
+    // and mContext will be nullptr
+    mContext->Multiply(transform);
+  }
+  return mContext;
+}
+
+void nsContextBoxBlur::DoPaint() {
+  if (mContext == mDestinationCtx) {
+    return;
+  }
+
+  gfxContextMatrixAutoSaveRestore saveMatrix(mDestinationCtx);
+
+  if (mPreTransformed) {
+    mDestinationCtx->SetMatrix(Matrix());
+  }
+
+  mAlphaBoxBlur.Paint(mDestinationCtx);
+}
+
+gfxContext* nsContextBoxBlur::GetContext() { return mContext; }
+
+/* static */
+nsMargin nsContextBoxBlur::GetBlurRadiusMargin(nscoord aBlurRadius,
+                                               int32_t aAppUnitsPerDevPixel) {
+  IntSize blurRadius = ComputeBlurRadius(aBlurRadius, aAppUnitsPerDevPixel);
+
+  nsMargin result;
+  result.top = result.bottom = blurRadius.height * aAppUnitsPerDevPixel;
+  result.left = result.right = blurRadius.width * aAppUnitsPerDevPixel;
+  return result;
+}
+
+/* static */
+void nsContextBoxBlur::BlurRectangle(
+    gfxContext* aDestinationCtx, const nsRect& aRect,
+    int32_t aAppUnitsPerDevPixel, RectCornerRadii* aCornerRadii,
+    nscoord aBlurRadius, const sRGBColor& aShadowColor,
+    const nsRect& aDirtyRect, const gfxRect& aSkipRect) {
+  DrawTarget& aDestDrawTarget = *aDestinationCtx->GetDrawTarget();
+
+  if (aRect.IsEmpty()) {
+    return;
+  }
+
+  Rect shadowGfxRect = NSRectToRect(aRect, aAppUnitsPerDevPixel);
+
+  if (aBlurRadius <= 0) {
+    ColorPattern color(ToDeviceColor(aShadowColor));
+    if (aCornerRadii) {
+      RefPtr<Path> roundedRect =
+          MakePathForRoundedRect(aDestDrawTarget, shadowGfxRect, *aCornerRadii);
+      aDestDrawTarget.Fill(roundedRect, color);
+    } else {
+      aDestDrawTarget.FillRect(shadowGfxRect, color);
+    }
+    return;
+  }
+
+  gfxFloat scaleX = 1;
+  gfxFloat scaleY = 1;
+
+  // Do blurs in device space when possible.
+  // Chrome/Skia always does the blurs in device space
+  // and will sometimes get incorrect results (e.g. rotated blurs)
+  gfxMatrix transform = aDestinationCtx->CurrentMatrixDouble();
+  // XXX: we could probably handle negative scales but for now it's easier just
+  // to fallback
+  if (!transform.HasNonAxisAlignedTransform() && transform._11 > 0.0 &&
+      transform._22 > 0.0) {
+    scaleX = transform._11;
+    scaleY = transform._22;
+    aDestinationCtx->SetMatrix(Matrix());
+  } else {
+    transform = gfxMatrix();
+  }
+
+  gfxPoint blurStdDev =
+      ComputeBlurStdDev(aBlurRadius, aAppUnitsPerDevPixel, scaleX, scaleY);
+
+  gfxRect dirtyRect =
+      nsLayoutUtils::RectToGfxRect(aDirtyRect, aAppUnitsPerDevPixel);
+  dirtyRect.RoundOut();
+
+  gfxRect shadowThebesRect =
+      transform.TransformBounds(ThebesRect(shadowGfxRect));
+  dirtyRect = transform.TransformBounds(dirtyRect);
+  gfxRect skipRect = transform.TransformBounds(aSkipRect);
+
+  if (aCornerRadii) {
+    aCornerRadii->Scale(scaleX, scaleY);
+  }
+
+  gfxAlphaBoxBlur::BlurRectangle(aDestinationCtx, shadowThebesRect,
+                                 aCornerRadii, blurStdDev, aShadowColor,
+                                 dirtyRect, skipRect);
+}
+
+/* static */
+void nsContextBoxBlur::GetBlurAndSpreadRadius(
+    DrawTarget* aDestDrawTarget, int32_t aAppUnitsPerDevPixel,
+    nscoord aBlurRadius, nscoord aSpreadRadius, IntSize& aOutBlurRadius,
+    IntSize& aOutSpreadRadius, bool aConstrainSpreadRadius) {
+  // Do blurs in device space when possible.
+  // Chrome/Skia always does the blurs in device space
+  // and will sometimes get incorrect results (e.g. rotated blurs)
+  Matrix transform = aDestDrawTarget->GetTransform();
+  // XXX: we could probably handle negative scales but for now it's easier just
+  // to fallback
+  gfxFloat scaleX, scaleY;
+  if (transform.HasNonAxisAlignedTransform() || transform._11 <= 0.0 ||
+      transform._22 <= 0.0) {
+    scaleX = 1;
+    scaleY = 1;
+  } else {
+    scaleX = transform._11;
+    scaleY = transform._22;
+  }
+
+  // compute a large or smaller blur radius
+  aOutBlurRadius =
+      ComputeBlurRadius(aBlurRadius, aAppUnitsPerDevPixel, scaleX, scaleY);
+  aOutSpreadRadius =
+      IntSize(int32_t(aSpreadRadius * scaleX / aAppUnitsPerDevPixel),
+              int32_t(aSpreadRadius * scaleY / aAppUnitsPerDevPixel));
+
+  if (aConstrainSpreadRadius) {
+    aOutSpreadRadius.width =
+        std::min(aOutSpreadRadius.width, int32_t(MAX_SPREAD_RADIUS));
+    aOutSpreadRadius.height =
+        std::min(aOutSpreadRadius.height, int32_t(MAX_SPREAD_RADIUS));
+  }
+}
+
+/* static */
+bool nsContextBoxBlur::InsetBoxBlur(
+    gfxContext* aDestinationCtx, Rect aDestinationRect, Rect aShadowClipRect,
+    sRGBColor& aShadowColor, nscoord aBlurRadiusAppUnits,
+    nscoord aSpreadDistanceAppUnits, int32_t aAppUnitsPerDevPixel,
+    bool aHasBorderRadius, RectCornerRadii& aInnerClipRectRadii, Rect aSkipRect,
+    Point aShadowOffset) {
+  if (aDestinationRect.IsEmpty()) {
+    mContext = nullptr;
+    return false;
+  }
+
+  gfxContextAutoSaveRestore autoRestore(aDestinationCtx);
+
+  IntSize blurRadius;
+  IntSize spreadRadius;
+  // Convert the blur and spread radius to device pixels
+  bool constrainSpreadRadius = false;
+  GetBlurAndSpreadRadius(aDestinationCtx->GetDrawTarget(), aAppUnitsPerDevPixel,
+                         aBlurRadiusAppUnits, aSpreadDistanceAppUnits,
+                         blurRadius, spreadRadius, constrainSpreadRadius);
+
+  // The blur and spread radius are scaled already, so scale all
+  // input data to the blur. This way, we don't have to scale the min
+  // inset blur to the invert of the dest context, then rescale it back
+  // when we draw to the destination surface.
+  auto scale = aDestinationCtx->CurrentMatrix().ScaleFactors();
+  Matrix transform = aDestinationCtx->CurrentMatrix();
+
+  // XXX: we could probably handle negative scales but for now it's easier just
+  // to fallback
+  if (!transform.HasNonAxisAlignedTransform() && transform._11 > 0.0 &&
+      transform._22 > 0.0) {
+    // If we don't have a rotation, we're pre-transforming all the rects.
+    aDestinationCtx->SetMatrix(Matrix());
+  } else {
+    // Don't touch anything, we have a rotation.
+    transform = Matrix();
+  }
+
+  Rect transformedDestRect = transform.TransformBounds(aDestinationRect);
+  Rect transformedShadowClipRect = transform.TransformBounds(aShadowClipRect);
+  Rect transformedSkipRect = transform.TransformBounds(aSkipRect);
+
+  transformedDestRect.Round();
+  transformedShadowClipRect.Round();
+  transformedSkipRect.RoundIn();
+
+  for (size_t i = 0; i < 4; i++) {
+    aInnerClipRectRadii[i].width =
+        std::floor(scale.xScale * aInnerClipRectRadii[i].width);
+    aInnerClipRectRadii[i].height =
+        std::floor(scale.yScale * aInnerClipRectRadii[i].height);
+  }
+
+  mAlphaBoxBlur.BlurInsetBox(aDestinationCtx, transformedDestRect,
+                             transformedShadowClipRect, blurRadius,
+                             aShadowColor,
+                             aHasBorderRadius ? &aInnerClipRectRadii : nullptr,
+                             transformedSkipRect, aShadowOffset);
+  return true;
+}