Add m-esr52 at 52.6.0

1 files changed, 763 insertions, 0 deletions

diff --git a/layout/generic/nsAbsoluteContainingBlock.cpp b/layout/generic/nsAbsoluteContainingBlock.cpp
new file mode 100644
index 000000000..7c48aae92
--- /dev/null
+++ b/layout/generic/nsAbsoluteContainingBlock.cpp
@@ -0,0 +1,763 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+/*
+ * code for managing absolutely positioned children of a rendering
+ * object that is a containing block for them
+ */
+
+#include "nsAbsoluteContainingBlock.h"
+
+#include "nsContainerFrame.h"
+#include "nsGkAtoms.h"
+#include "nsIPresShell.h"
+#include "mozilla/CSSAlignUtils.h"
+#include "mozilla/ReflowInput.h"
+#include "nsPresContext.h"
+#include "nsCSSFrameConstructor.h"
+#include "nsGridContainerFrame.h"
+
+#include "mozilla/Sprintf.h"
+
+#ifdef DEBUG
+#include "nsBlockFrame.h"
+
+static void PrettyUC(nscoord aSize, char* aBuf, int aBufSize)
+{
+  if (NS_UNCONSTRAINEDSIZE == aSize) {
+    strcpy(aBuf, "UC");
+  } else {
+    if((int32_t)0xdeadbeef == aSize) {
+      strcpy(aBuf, "deadbeef");
+    } else {
+      snprintf(aBuf, aBufSize, "%d", aSize);
+    }
+  }
+}
+#endif
+
+using namespace mozilla;
+
+typedef mozilla::CSSAlignUtils::AlignJustifyFlags AlignJustifyFlags;
+
+void
+nsAbsoluteContainingBlock::SetInitialChildList(nsIFrame*       aDelegatingFrame,
+                                               ChildListID     aListID,
+                                               nsFrameList&    aChildList)
+{
+  NS_PRECONDITION(mChildListID == aListID, "unexpected child list name");
+#ifdef DEBUG
+  nsFrame::VerifyDirtyBitSet(aChildList);
+#endif
+  mAbsoluteFrames.SetFrames(aChildList);
+}
+
+void
+nsAbsoluteContainingBlock::AppendFrames(nsIFrame*      aDelegatingFrame,
+                                        ChildListID    aListID,
+                                        nsFrameList&   aFrameList)
+{
+  NS_ASSERTION(mChildListID == aListID, "unexpected child list");
+
+  // Append the frames to our list of absolutely positioned frames
+#ifdef DEBUG
+  nsFrame::VerifyDirtyBitSet(aFrameList);
+#endif
+  mAbsoluteFrames.AppendFrames(nullptr, aFrameList);
+
+  // no damage to intrinsic widths, since absolutely positioned frames can't
+  // change them
+  aDelegatingFrame->PresContext()->PresShell()->
+    FrameNeedsReflow(aDelegatingFrame, nsIPresShell::eResize,
+                     NS_FRAME_HAS_DIRTY_CHILDREN);
+}
+
+void
+nsAbsoluteContainingBlock::InsertFrames(nsIFrame*      aDelegatingFrame,
+                                        ChildListID    aListID,
+                                        nsIFrame*      aPrevFrame,
+                                        nsFrameList&   aFrameList)
+{
+  NS_ASSERTION(mChildListID == aListID, "unexpected child list");
+  NS_ASSERTION(!aPrevFrame || aPrevFrame->GetParent() == aDelegatingFrame,
+               "inserting after sibling frame with different parent");
+
+#ifdef DEBUG
+  nsFrame::VerifyDirtyBitSet(aFrameList);
+#endif
+  mAbsoluteFrames.InsertFrames(nullptr, aPrevFrame, aFrameList);
+
+  // no damage to intrinsic widths, since absolutely positioned frames can't
+  // change them
+  aDelegatingFrame->PresContext()->PresShell()->
+    FrameNeedsReflow(aDelegatingFrame, nsIPresShell::eResize,
+                     NS_FRAME_HAS_DIRTY_CHILDREN);
+}
+
+void
+nsAbsoluteContainingBlock::RemoveFrame(nsIFrame*       aDelegatingFrame,
+                                       ChildListID     aListID,
+                                       nsIFrame*       aOldFrame)
+{
+  NS_ASSERTION(mChildListID == aListID, "unexpected child list");
+  nsIFrame* nif = aOldFrame->GetNextInFlow();
+  if (nif) {
+    nif->GetParent()->DeleteNextInFlowChild(nif, false);
+  }
+
+  mAbsoluteFrames.DestroyFrame(aOldFrame);
+}
+
+void
+nsAbsoluteContainingBlock::Reflow(nsContainerFrame*        aDelegatingFrame,
+                                  nsPresContext*           aPresContext,
+                                  const ReflowInput& aReflowInput,
+                                  nsReflowStatus&          aReflowStatus,
+                                  const nsRect&            aContainingBlock,
+                                  AbsPosReflowFlags        aFlags,
+                                  nsOverflowAreas*         aOverflowAreas)
+{
+  nsReflowStatus reflowStatus = NS_FRAME_COMPLETE;
+
+  const bool reflowAll = aReflowInput.ShouldReflowAllKids();
+  const bool isGrid = !!(aFlags & AbsPosReflowFlags::eIsGridContainerCB);
+  nsIFrame* kidFrame;
+  nsOverflowContinuationTracker tracker(aDelegatingFrame, true);
+  for (kidFrame = mAbsoluteFrames.FirstChild(); kidFrame; kidFrame = kidFrame->GetNextSibling()) {
+    bool kidNeedsReflow = reflowAll || NS_SUBTREE_DIRTY(kidFrame) ||
+      FrameDependsOnContainer(kidFrame,
+                              !!(aFlags & AbsPosReflowFlags::eCBWidthChanged),
+                              !!(aFlags & AbsPosReflowFlags::eCBHeightChanged));
+    if (kidNeedsReflow && !aPresContext->HasPendingInterrupt()) {
+      // Reflow the frame
+      nsReflowStatus  kidStatus = NS_FRAME_COMPLETE;
+      const nsRect& cb = isGrid ? nsGridContainerFrame::GridItemCB(kidFrame)
+                                : aContainingBlock;
+      ReflowAbsoluteFrame(aDelegatingFrame, aPresContext, aReflowInput, cb,
+                          aFlags, kidFrame, kidStatus, aOverflowAreas);
+      nsIFrame* nextFrame = kidFrame->GetNextInFlow();
+      if (!NS_FRAME_IS_FULLY_COMPLETE(kidStatus) &&
+          aDelegatingFrame->IsFrameOfType(nsIFrame::eCanContainOverflowContainers)) {
+        // Need a continuation
+        if (!nextFrame) {
+          nextFrame =
+            aPresContext->PresShell()->FrameConstructor()->
+              CreateContinuingFrame(aPresContext, kidFrame, aDelegatingFrame);
+        }
+        // Add it as an overflow container.
+        //XXXfr This is a hack to fix some of our printing dataloss.
+        // See bug 154892. Not sure how to do it "right" yet; probably want
+        // to keep continuations within an nsAbsoluteContainingBlock eventually.
+        tracker.Insert(nextFrame, kidStatus);
+        NS_MergeReflowStatusInto(&reflowStatus, kidStatus);
+      }
+      else {
+        // Delete any continuations
+        if (nextFrame) {
+          nsOverflowContinuationTracker::AutoFinish fini(&tracker, kidFrame);
+          nextFrame->GetParent()->DeleteNextInFlowChild(nextFrame, true);
+        }
+      }
+    }
+    else {
+      tracker.Skip(kidFrame, reflowStatus);
+      if (aOverflowAreas) {
+        aDelegatingFrame->ConsiderChildOverflow(*aOverflowAreas, kidFrame);
+      }
+    }
+
+    // Make a CheckForInterrupt call, here, not just HasPendingInterrupt.  That
+    // will make sure that we end up reflowing aDelegatingFrame in cases when
+    // one of our kids interrupted.  Otherwise we'd set the dirty or
+    // dirty-children bit on the kid in the condition below, and then when
+    // reflow completes and we go to mark dirty bits on all ancestors of that
+    // kid we'll immediately bail out, because the kid already has a dirty bit.
+    // In particular, we won't set any dirty bits on aDelegatingFrame, so when
+    // the following reflow happens we won't reflow the kid in question.  This
+    // might be slightly suboptimal in cases where |kidFrame| itself did not
+    // interrupt, since we'll trigger a reflow of it too when it's not strictly
+    // needed.  But the logic to not do that is enough more complicated, and
+    // the case enough of an edge case, that this is probably better.
+    if (kidNeedsReflow && aPresContext->CheckForInterrupt(aDelegatingFrame)) {
+      if (aDelegatingFrame->GetStateBits() & NS_FRAME_IS_DIRTY) {
+        kidFrame->AddStateBits(NS_FRAME_IS_DIRTY);
+      } else {
+        kidFrame->AddStateBits(NS_FRAME_HAS_DIRTY_CHILDREN);
+      }
+    }
+  }
+
+  // Abspos frames can't cause their parent to be incomplete,
+  // only overflow incomplete.
+  if (NS_FRAME_IS_NOT_COMPLETE(reflowStatus))
+    NS_FRAME_SET_OVERFLOW_INCOMPLETE(reflowStatus);
+
+  NS_MergeReflowStatusInto(&aReflowStatus, reflowStatus);
+}
+
+static inline bool IsFixedPaddingSize(const nsStyleCoord& aCoord)
+  { return aCoord.ConvertsToLength(); }
+static inline bool IsFixedMarginSize(const nsStyleCoord& aCoord)
+  { return aCoord.ConvertsToLength(); }
+static inline bool IsFixedOffset(const nsStyleCoord& aCoord)
+  { return aCoord.ConvertsToLength(); }
+
+bool
+nsAbsoluteContainingBlock::FrameDependsOnContainer(nsIFrame* f,
+                                                   bool aCBWidthChanged,
+                                                   bool aCBHeightChanged)
+{
+  const nsStylePosition* pos = f->StylePosition();
+  // See if f's position might have changed because it depends on a
+  // placeholder's position
+  // This can happen in the following cases:
+  // 1) Vertical positioning.  "top" must be auto and "bottom" must be auto
+  //    (otherwise the vertical position is completely determined by
+  //    whichever of them is not auto and the height).
+  // 2) Horizontal positioning.  "left" must be auto and "right" must be auto
+  //    (otherwise the horizontal position is completely determined by
+  //    whichever of them is not auto and the width).
+  // See ReflowInput::InitAbsoluteConstraints -- these are the
+  // only cases when we call CalculateHypotheticalBox().
+  if ((pos->mOffset.GetTopUnit() == eStyleUnit_Auto &&
+       pos->mOffset.GetBottomUnit() == eStyleUnit_Auto) ||
+      (pos->mOffset.GetLeftUnit() == eStyleUnit_Auto &&
+       pos->mOffset.GetRightUnit() == eStyleUnit_Auto)) {
+    return true;
+  }
+  if (!aCBWidthChanged && !aCBHeightChanged) {
+    // skip getting style data
+    return false;
+  }
+  const nsStylePadding* padding = f->StylePadding();
+  const nsStyleMargin* margin = f->StyleMargin();
+  WritingMode wm = f->GetWritingMode();
+  if (wm.IsVertical() ? aCBHeightChanged : aCBWidthChanged) {
+    // See if f's inline-size might have changed.
+    // If margin-inline-start/end, padding-inline-start/end,
+    // inline-size, min/max-inline-size are all lengths, 'none', or enumerated,
+    // then our frame isize does not depend on the parent isize.
+    // Note that borders never depend on the parent isize.
+    // XXX All of the enumerated values except -moz-available are ok too.
+    if (pos->ISizeDependsOnContainer(wm) ||
+        pos->MinISizeDependsOnContainer(wm) ||
+        pos->MaxISizeDependsOnContainer(wm) ||
+        !IsFixedPaddingSize(padding->mPadding.GetIStart(wm)) ||
+        !IsFixedPaddingSize(padding->mPadding.GetIEnd(wm))) {
+      return true;
+    }
+
+    // See if f's position might have changed. If we're RTL then the
+    // rules are slightly different. We'll assume percentage or auto
+    // margins will always induce a dependency on the size
+    if (!IsFixedMarginSize(margin->mMargin.GetIStart(wm)) ||
+        !IsFixedMarginSize(margin->mMargin.GetIEnd(wm))) {
+      return true;
+    }
+    if (!wm.IsBidiLTR()) {
+      // Note that even if 'istart' is a length, our position can
+      // still depend on the containing block isze, because if
+      // 'iend' is also a length we will discard 'istart' and be
+      // positioned relative to the containing block iend edge.
+      // 'istart' length and 'iend' auto is the only combination
+      // we can be sure of.
+      if (!IsFixedOffset(pos->mOffset.GetIStart(wm)) ||
+          pos->mOffset.GetIEndUnit(wm) != eStyleUnit_Auto) {
+        return true;
+      }
+    } else {
+      if (!IsFixedOffset(pos->mOffset.GetIStart(wm))) {
+        return true;
+      }
+    }
+  }
+  if (wm.IsVertical() ? aCBWidthChanged : aCBHeightChanged) {
+    // See if f's block-size might have changed.
+    // If margin-block-start/end, padding-block-start/end,
+    // min-block-size, and max-block-size are all lengths or 'none',
+    // and bsize is a length or bsize and bend are auto and bstart is not auto,
+    // then our frame bsize does not depend on the parent bsize.
+    // Note that borders never depend on the parent bsize.
+    if ((pos->BSizeDependsOnContainer(wm) &&
+         !(pos->BSize(wm).GetUnit() == eStyleUnit_Auto &&
+           pos->mOffset.GetBEndUnit(wm) == eStyleUnit_Auto &&
+           pos->mOffset.GetBStartUnit(wm) != eStyleUnit_Auto)) ||
+        pos->MinBSizeDependsOnContainer(wm) ||
+        pos->MaxBSizeDependsOnContainer(wm) ||
+        !IsFixedPaddingSize(padding->mPadding.GetBStart(wm)) ||
+        !IsFixedPaddingSize(padding->mPadding.GetBEnd(wm))) {
+      return true;
+    }
+      
+    // See if f's position might have changed.
+    if (!IsFixedMarginSize(margin->mMargin.GetBStart(wm)) ||
+        !IsFixedMarginSize(margin->mMargin.GetBEnd(wm))) {
+      return true;
+    }
+    if (!IsFixedOffset(pos->mOffset.GetBStart(wm))) {
+      return true;
+    }
+  }
+  return false;
+}
+
+void
+nsAbsoluteContainingBlock::DestroyFrames(nsIFrame* aDelegatingFrame,
+                                         nsIFrame* aDestructRoot)
+{
+  mAbsoluteFrames.DestroyFramesFrom(aDestructRoot);
+}
+
+void
+nsAbsoluteContainingBlock::MarkSizeDependentFramesDirty()
+{
+  DoMarkFramesDirty(false);
+}
+
+void
+nsAbsoluteContainingBlock::MarkAllFramesDirty()
+{
+  DoMarkFramesDirty(true);
+}
+
+void
+nsAbsoluteContainingBlock::DoMarkFramesDirty(bool aMarkAllDirty)
+{
+  for (nsIFrame* kidFrame : mAbsoluteFrames) {
+    if (aMarkAllDirty) {
+      kidFrame->AddStateBits(NS_FRAME_IS_DIRTY);
+    } else if (FrameDependsOnContainer(kidFrame, true, true)) {
+      // Add the weakest flags that will make sure we reflow this frame later
+      kidFrame->AddStateBits(NS_FRAME_HAS_DIRTY_CHILDREN);
+    }
+  }
+}
+
+// Given an out-of-flow frame, this method returns the parent frame of
+// its placeholder frame, if that parent is a nsContainerFrame.
+static nsContainerFrame*
+GetPlaceholderContainer(nsPresContext* aPresContext,
+                        nsIFrame* aPositionedFrame)
+{
+  MOZ_ASSERT(aPositionedFrame, "need non-null frame");
+  MOZ_ASSERT(aPositionedFrame->HasAnyStateBits(NS_FRAME_OUT_OF_FLOW),
+             "expecting abspos frame");
+  MOZ_ASSERT(aPresContext && aPresContext == aPositionedFrame->PresContext(),
+             "need non-null pres context which matches our frame");
+
+  nsIFrame* placeholder =
+    aPresContext->PresShell()->GetPlaceholderFrameFor(aPositionedFrame);
+
+  if (!placeholder) {
+    return nullptr;
+  }
+  return do_QueryFrame(placeholder->GetParent());
+}
+
+/**
+ * This function returns the offset of an abs/fixed-pos child's static
+ * position, with respect to the "start" corner of its alignment container,
+ * according to CSS Box Alignment.  This function only operates in a single
+ * axis at a time -- callers can choose which axis via the |aAbsPosCBAxis|
+ * parameter.
+ *
+ * @param aKidReflowInput The ReflowInput for the to-be-aligned abspos child.
+ * @param aKidSizeInAbsPosCBWM The child frame's size (after it's been given
+ *                             the opportunity to reflow), in terms of
+ *                             aAbsPosCBWM.
+ * @param aAbsPosCBSize The abspos CB size, in terms of aAbsPosCBWM.
+ * @param aPlaceholderContainer The parent of the child frame's corresponding
+ *                              placeholder frame, cast to a nsContainerFrame.
+ *                              (This will help us choose which alignment enum
+ *                              we should use for the child.)
+ * @param aAbsPosCBWM The child frame's containing block's WritingMode.
+ * @param aAbsPosCBAxis The axis (of the containing block) that we should
+ *                      be doing this computation for.
+ */
+static nscoord
+OffsetToAlignedStaticPos(const ReflowInput& aKidReflowInput,
+                         const LogicalSize& aKidSizeInAbsPosCBWM,
+                         const LogicalSize& aAbsPosCBSize,
+                         nsContainerFrame* aPlaceholderContainer,
+                         WritingMode aAbsPosCBWM,
+                         LogicalAxis aAbsPosCBAxis)
+{
+  if (!aPlaceholderContainer) {
+    // (The placeholder container should be the thing that kicks this whole
+    // process off, by setting PLACEHOLDER_STATICPOS_NEEDS_CSSALIGN.  So it
+    // should exist... but bail gracefully if it doesn't.)
+    NS_ERROR("Missing placeholder-container when computing a "
+             "CSS Box Alignment static position");
+    return 0;
+  }
+
+  // (Most of this function is simply preparing args that we'll pass to
+  // AlignJustifySelf at the end.)
+
+  // NOTE: Our alignment container is aPlaceholderContainer's content-box
+  // (or an area within it, if aPlaceholderContainer is a grid). So, we'll
+  // perform most of our arithmetic/alignment in aPlaceholderContainer's
+  // WritingMode. For brevity, we use the abbreviation "pc" for "placeholder
+  // container" in variables below.
+  WritingMode pcWM = aPlaceholderContainer->GetWritingMode();
+
+  // Find what axis aAbsPosCBAxis corresponds to, in placeholder's parent's
+  // writing-mode.
+  LogicalAxis pcAxis = (pcWM.IsOrthogonalTo(aAbsPosCBWM)
+                        ? GetOrthogonalAxis(aAbsPosCBAxis)
+                        : aAbsPosCBAxis);
+
+  nsIAtom* parentType = aPlaceholderContainer->GetType();
+  LogicalSize alignAreaSize(pcWM);
+  if (parentType == nsGkAtoms::flexContainerFrame) {
+    // The alignment container is the flex container's content box:
+    alignAreaSize = aPlaceholderContainer->GetLogicalSize(pcWM);
+    LogicalMargin pcBorderPadding =
+      aPlaceholderContainer->GetLogicalUsedBorderAndPadding(pcWM);
+    alignAreaSize -= pcBorderPadding.Size(pcWM);
+  } else if (parentType == nsGkAtoms::gridContainerFrame) {
+    // This abspos elem's parent is a grid container. Per CSS Grid 10.1 & 10.2:
+    //  - If the grid container *also* generates the abspos containing block (a
+    // grid area) for this abspos child, we use that abspos containing block as
+    // the alignment container, too. (And its size is aAbsPosCBSize.)
+    //  - Otherwise, we use the grid's padding box as the alignment container.
+    // https://drafts.csswg.org/css-grid/#static-position
+    if (aPlaceholderContainer == aKidReflowInput.mCBReflowInput->mFrame) {
+      // The alignment container is the grid area that we're using as the
+      // absolute containing block.
+      alignAreaSize = aAbsPosCBSize.ConvertTo(pcWM, aAbsPosCBWM);
+    } else {
+      // The alignment container is a the grid container's padding box (which
+      // we can get by subtracting away its border from frame's size):
+      alignAreaSize = aPlaceholderContainer->GetLogicalSize(pcWM);
+      LogicalMargin pcBorder =
+        aPlaceholderContainer->GetLogicalUsedBorder(pcWM);
+      alignAreaSize -= pcBorder.Size(pcWM);
+    }
+  } else {
+    NS_ERROR("Unsupported container for abpsos CSS Box Alignment");
+    return 0; // (leave the child at the start of its alignment container)
+  }
+
+  nscoord alignAreaSizeInAxis = (pcAxis == eLogicalAxisInline)
+    ? alignAreaSize.ISize(pcWM)
+    : alignAreaSize.BSize(pcWM);
+
+  AlignJustifyFlags flags = AlignJustifyFlags::eIgnoreAutoMargins;
+  uint16_t alignConst =
+    aPlaceholderContainer->CSSAlignmentForAbsPosChild(aKidReflowInput, pcAxis);
+  // XXXdholbert: Handle <overflow-position> in bug 1311892 (by conditionally
+  // setting AlignJustifyFlags::eOverflowSafe in |flags|.)  For now, we behave
+  // as if "unsafe" was the specified value (which is basically equivalent to
+  // the default behavior, when no value is specified -- though the default
+  // behavior also has some [at-risk] extra nuance about scroll containers...)
+  // For now we ignore & strip off <overflow-position> bits, until bug 1311892.
+  alignConst &= ~NS_STYLE_ALIGN_FLAG_BITS;
+
+  // Find out if placeholder-container & the OOF child have the same start-sides
+  // in the placeholder-container's pcAxis.
+  WritingMode kidWM = aKidReflowInput.GetWritingMode();
+  if (pcWM.ParallelAxisStartsOnSameSide(pcAxis, kidWM)) {
+    flags |= AlignJustifyFlags::eSameSide;
+  }
+
+  // (baselineAdjust is unused. CSSAlignmentForAbsPosChild() should've
+  // converted 'baseline'/'last baseline' enums to their fallback values.)
+  const nscoord baselineAdjust = nscoord(0);
+
+  // AlignJustifySelf operates in the kid's writing mode, so we need to
+  // represent the child's size and the desired axis in that writing mode:
+  LogicalSize kidSizeInOwnWM = aKidSizeInAbsPosCBWM.ConvertTo(kidWM,
+                                                              aAbsPosCBWM);
+  LogicalAxis kidAxis = (kidWM.IsOrthogonalTo(aAbsPosCBWM)
+                         ? GetOrthogonalAxis(aAbsPosCBAxis)
+                         : aAbsPosCBAxis);
+
+  nscoord offset =
+    CSSAlignUtils::AlignJustifySelf(alignConst, kidAxis, flags,
+                                    baselineAdjust, alignAreaSizeInAxis,
+                                    aKidReflowInput, kidSizeInOwnWM);
+
+  // "offset" is in terms of the CSS Box Alignment container (i.e. it's in
+  // terms of pcWM). But our return value needs to in terms of the containing
+  // block's writing mode, which might have the opposite directionality in the
+  // given axis. In that case, we just need to negate "offset" when returning,
+  // to make it have the right effect as an offset for coordinates in the
+  // containing block's writing mode.
+  if (!pcWM.ParallelAxisStartsOnSameSide(pcAxis, aAbsPosCBWM)) {
+    return -offset;
+  }
+  return offset;
+}
+
+void
+nsAbsoluteContainingBlock::ResolveSizeDependentOffsets(
+  nsPresContext* aPresContext,
+  ReflowInput& aKidReflowInput,
+  const LogicalSize& aKidSize,
+  const LogicalMargin& aMargin,
+  LogicalMargin* aOffsets,
+  LogicalSize* aLogicalCBSize)
+{
+  WritingMode wm = aKidReflowInput.GetWritingMode();
+  WritingMode outerWM = aKidReflowInput.mParentReflowInput->GetWritingMode();
+
+  // Now that we know the child's size, we resolve any sentinel values in its
+  // IStart/BStart offset coordinates that depend on that size.
+  //  * NS_AUTOOFFSET indicates that the child's position in the given axis
+  // is determined by its end-wards offset property, combined with its size and
+  // available space. e.g.: "top: auto; height: auto; bottom: 50px"
+  //  * m{I,B}OffsetsResolvedAfterSize indicate that the child is using its
+  // static position in that axis, *and* its static position is determined by
+  // the axis-appropriate css-align property (which may require the child's
+  // size, e.g. to center it within the parent).
+  if ((NS_AUTOOFFSET == aOffsets->IStart(outerWM)) ||
+      (NS_AUTOOFFSET == aOffsets->BStart(outerWM)) ||
+      aKidReflowInput.mFlags.mIOffsetsNeedCSSAlign ||
+      aKidReflowInput.mFlags.mBOffsetsNeedCSSAlign) {
+    if (-1 == aLogicalCBSize->ISize(wm)) {
+      // Get the containing block width/height
+      const ReflowInput* parentRI = aKidReflowInput.mParentReflowInput;
+      *aLogicalCBSize =
+        aKidReflowInput.ComputeContainingBlockRectangle(aPresContext,
+                                                        parentRI);
+    }
+
+    const LogicalSize logicalCBSizeOuterWM = aLogicalCBSize->ConvertTo(outerWM,
+                                                                       wm);
+
+    // placeholderContainer is used in each of the m{I,B}OffsetsNeedCSSAlign
+    // clauses. We declare it at this scope so we can avoid having to look
+    // it up twice (and only look it up if it's needed).
+    nsContainerFrame* placeholderContainer = nullptr;
+
+    if (NS_AUTOOFFSET == aOffsets->IStart(outerWM)) {
+      NS_ASSERTION(NS_AUTOOFFSET != aOffsets->IEnd(outerWM),
+                   "Can't solve for both start and end");
+      aOffsets->IStart(outerWM) =
+        logicalCBSizeOuterWM.ISize(outerWM) -
+        aOffsets->IEnd(outerWM) - aMargin.IStartEnd(outerWM) -
+        aKidSize.ISize(outerWM);
+    } else if (aKidReflowInput.mFlags.mIOffsetsNeedCSSAlign) {
+      placeholderContainer = GetPlaceholderContainer(aPresContext,
+                                                     aKidReflowInput.mFrame);
+      nscoord offset = OffsetToAlignedStaticPos(aKidReflowInput, aKidSize,
+                                                logicalCBSizeOuterWM,
+                                                placeholderContainer,
+                                                outerWM, eLogicalAxisInline);
+      // Shift IStart from its current position (at start corner of the
+      // alignment container) by the returned offset.  And set IEnd to the
+      // distance between the kid's end edge to containing block's end edge.
+      aOffsets->IStart(outerWM) += offset;
+      aOffsets->IEnd(outerWM) =
+        logicalCBSizeOuterWM.ISize(outerWM) -
+        (aOffsets->IStart(outerWM) + aKidSize.ISize(outerWM));
+    }
+
+    if (NS_AUTOOFFSET == aOffsets->BStart(outerWM)) {
+      aOffsets->BStart(outerWM) =
+        logicalCBSizeOuterWM.BSize(outerWM) -
+        aOffsets->BEnd(outerWM) - aMargin.BStartEnd(outerWM) -
+        aKidSize.BSize(outerWM);
+    } else if (aKidReflowInput.mFlags.mBOffsetsNeedCSSAlign) {
+      if (!placeholderContainer) {
+        placeholderContainer = GetPlaceholderContainer(aPresContext,
+                                                       aKidReflowInput.mFrame);
+      }
+      nscoord offset = OffsetToAlignedStaticPos(aKidReflowInput, aKidSize,
+                                                logicalCBSizeOuterWM,
+                                                placeholderContainer,
+                                                outerWM, eLogicalAxisBlock);
+      // Shift BStart from its current position (at start corner of the
+      // alignment container) by the returned offset.  And set BEnd to the
+      // distance between the kid's end edge to containing block's end edge.
+      aOffsets->BStart(outerWM) += offset;
+      aOffsets->BEnd(outerWM) =
+        logicalCBSizeOuterWM.BSize(outerWM) -
+        (aOffsets->BStart(outerWM) + aKidSize.BSize(outerWM));
+    }
+    aKidReflowInput.SetComputedLogicalOffsets(aOffsets->ConvertTo(wm, outerWM));
+  }
+}
+
+// XXX Optimize the case where it's a resize reflow and the absolutely
+// positioned child has the exact same size and position and skip the
+// reflow...
+
+// When bug 154892 is checked in, make sure that when 
+// mChildListID == kFixedList, the height is unconstrained.
+// since we don't allow replicated frames to split.
+
+void
+nsAbsoluteContainingBlock::ReflowAbsoluteFrame(nsIFrame*                aDelegatingFrame,
+                                               nsPresContext*           aPresContext,
+                                               const ReflowInput& aReflowInput,
+                                               const nsRect&            aContainingBlock,
+                                               AbsPosReflowFlags        aFlags,
+                                               nsIFrame*                aKidFrame,
+                                               nsReflowStatus&          aStatus,
+                                               nsOverflowAreas*         aOverflowAreas)
+{
+#ifdef DEBUG
+  if (nsBlockFrame::gNoisyReflow) {
+    nsFrame::IndentBy(stdout,nsBlockFrame::gNoiseIndent);
+    printf("abs pos ");
+    nsAutoString name;
+    aKidFrame->GetFrameName(name);
+    printf("%s ", NS_LossyConvertUTF16toASCII(name).get());
+
+    char width[16];
+    char height[16];
+    PrettyUC(aReflowInput.AvailableWidth(), width, 16);
+    PrettyUC(aReflowInput.AvailableHeight(), height, 16);
+    printf(" a=%s,%s ", width, height);
+    PrettyUC(aReflowInput.ComputedWidth(), width, 16);
+    PrettyUC(aReflowInput.ComputedHeight(), height, 16);
+    printf("c=%s,%s \n", width, height);
+  }
+  AutoNoisyIndenter indent(nsBlockFrame::gNoisy);
+#endif // DEBUG
+
+  WritingMode wm = aKidFrame->GetWritingMode();
+  LogicalSize logicalCBSize(wm, aContainingBlock.Size());
+  nscoord availISize = logicalCBSize.ISize(wm);
+  if (availISize == -1) {
+    NS_ASSERTION(aReflowInput.ComputedSize(wm).ISize(wm) !=
+                   NS_UNCONSTRAINEDSIZE,
+                 "Must have a useful inline-size _somewhere_");
+    availISize =
+      aReflowInput.ComputedSizeWithPadding(wm).ISize(wm);
+  }
+
+  uint32_t rsFlags = 0;
+  if (aFlags & AbsPosReflowFlags::eIsGridContainerCB) {
+    // When a grid container generates the abs.pos. CB for a *child* then
+    // the static position is determined via CSS Box Alignment within the
+    // abs.pos. CB (a grid area, i.e. a piece of the grid). In this scenario,
+    // due to the multiple coordinate spaces in play, we use a convenience flag
+    // to simply have the child's ReflowInput give it a static position at its
+    // abs.pos. CB origin, and then we'll align & offset it from there.
+    nsIFrame* placeholder =
+      aPresContext->PresShell()->GetPlaceholderFrameFor(aKidFrame);
+    if (placeholder && placeholder->GetParent() == aDelegatingFrame) {
+      rsFlags |= ReflowInput::STATIC_POS_IS_CB_ORIGIN;
+    }
+  }
+  ReflowInput kidReflowInput(aPresContext, aReflowInput, aKidFrame,
+                                   LogicalSize(wm, availISize,
+                                               NS_UNCONSTRAINEDSIZE),
+                                   &logicalCBSize, rsFlags);
+
+  // Get the border values
+  WritingMode outerWM = aReflowInput.GetWritingMode();
+  const LogicalMargin border(outerWM,
+                             aReflowInput.mStyleBorder->GetComputedBorder());
+  LogicalMargin margin =
+    kidReflowInput.ComputedLogicalMargin().ConvertTo(outerWM, wm);
+
+  // If we're doing CSS Box Alignment in either axis, that will apply the
+  // margin for us in that axis (since the thing that's aligned is the margin
+  // box).  So, we clear out the margin here to avoid applying it twice.
+  if (kidReflowInput.mFlags.mIOffsetsNeedCSSAlign) {
+    margin.IStart(outerWM) = margin.IEnd(outerWM) = 0;
+  }
+  if (kidReflowInput.mFlags.mBOffsetsNeedCSSAlign) {
+    margin.BStart(outerWM) = margin.BEnd(outerWM) = 0;
+  }
+
+  bool constrainBSize = (aReflowInput.AvailableBSize() != NS_UNCONSTRAINEDSIZE)
+    && (aFlags & AbsPosReflowFlags::eConstrainHeight)
+       // Don't split if told not to (e.g. for fixed frames)
+    && (aDelegatingFrame->GetType() != nsGkAtoms::inlineFrame)
+       //XXX we don't handle splitting frames for inline absolute containing blocks yet
+    && (aKidFrame->GetLogicalRect(aContainingBlock.Size()).BStart(wm) <=
+        aReflowInput.AvailableBSize());
+       // Don't split things below the fold. (Ideally we shouldn't *have*
+       // anything totally below the fold, but we can't position frames
+       // across next-in-flow breaks yet.
+  if (constrainBSize) {
+    kidReflowInput.AvailableBSize() =
+      aReflowInput.AvailableBSize() - border.ConvertTo(wm, outerWM).BStart(wm) -
+      kidReflowInput.ComputedLogicalMargin().BStart(wm);
+    if (NS_AUTOOFFSET != kidReflowInput.ComputedLogicalOffsets().BStart(wm)) {
+      kidReflowInput.AvailableBSize() -=
+        kidReflowInput.ComputedLogicalOffsets().BStart(wm);
+    }
+  }
+
+  // Do the reflow
+  ReflowOutput kidDesiredSize(kidReflowInput);
+  aKidFrame->Reflow(aPresContext, kidDesiredSize, kidReflowInput, aStatus);
+
+  const LogicalSize kidSize = kidDesiredSize.Size(wm).ConvertTo(outerWM, wm);
+
+  LogicalMargin offsets =
+    kidReflowInput.ComputedLogicalOffsets().ConvertTo(outerWM, wm);
+
+  // If we're solving for start in either inline or block direction,
+  // then compute it now that we know the dimensions.
+  ResolveSizeDependentOffsets(aPresContext, kidReflowInput, kidSize, margin,
+                              &offsets, &logicalCBSize);
+
+  // Position the child relative to our padding edge
+  LogicalRect rect(outerWM,
+                   border.IStart(outerWM) + offsets.IStart(outerWM) +
+                     margin.IStart(outerWM),
+                   border.BStart(outerWM) + offsets.BStart(outerWM) +
+                     margin.BStart(outerWM),
+                   kidSize.ISize(outerWM), kidSize.BSize(outerWM));
+  nsRect r =
+    rect.GetPhysicalRect(outerWM, logicalCBSize.GetPhysicalSize(wm) +
+                         border.Size(outerWM).GetPhysicalSize(outerWM));
+
+  // Offset the frame rect by the given origin of the absolute containing block.
+  // If the frame is auto-positioned on both sides of an axis, it will be
+  // positioned based on its containing block and we don't need to offset
+  // (unless the caller demands it (the STATIC_POS_IS_CB_ORIGIN case)).
+  if (aContainingBlock.TopLeft() != nsPoint(0, 0)) {
+    const nsStyleSides& offsets = kidReflowInput.mStylePosition->mOffset;
+    if (!(offsets.GetLeftUnit() == eStyleUnit_Auto &&
+          offsets.GetRightUnit() == eStyleUnit_Auto) ||
+        (rsFlags & ReflowInput::STATIC_POS_IS_CB_ORIGIN)) {
+      r.x += aContainingBlock.x;
+    }
+    if (!(offsets.GetTopUnit() == eStyleUnit_Auto &&
+          offsets.GetBottomUnit() == eStyleUnit_Auto) ||
+        (rsFlags & ReflowInput::STATIC_POS_IS_CB_ORIGIN)) {
+      r.y += aContainingBlock.y;
+    }
+  }
+
+  aKidFrame->SetRect(r);
+
+  nsView* view = aKidFrame->GetView();
+  if (view) {
+    // Size and position the view and set its opacity, visibility, content
+    // transparency, and clip
+    nsContainerFrame::SyncFrameViewAfterReflow(aPresContext, aKidFrame, view,
+                                               kidDesiredSize.VisualOverflow());
+  } else {
+    nsContainerFrame::PositionChildViews(aKidFrame);
+  }
+
+  aKidFrame->DidReflow(aPresContext, &kidReflowInput,
+                       nsDidReflowStatus::FINISHED);
+
+#ifdef DEBUG
+  if (nsBlockFrame::gNoisyReflow) {
+    nsFrame::IndentBy(stdout,nsBlockFrame::gNoiseIndent - 1);
+    printf("abs pos ");
+    nsAutoString name;
+    aKidFrame->GetFrameName(name);
+    printf("%s ", NS_LossyConvertUTF16toASCII(name).get());
+    printf("%p rect=%d,%d,%d,%d\n", static_cast<void*>(aKidFrame),
+           r.x, r.y, r.width, r.height);
+  }
+#endif
+
+  if (aOverflowAreas) {
+    aOverflowAreas->UnionWith(kidDesiredSize.mOverflowAreas + r.TopLeft());
+  }
+}