Bug 1025669 - part 1, Implement layout of block margins for box-decoration-break:clone. r=roc

layout/generic/nsBlockFrame.cpp

@@ -2886,14 +2886,17 @@ nsBlockFrame::IsEmpty()
 
 bool
 nsBlockFrame::ShouldApplyBStartMargin(nsBlockReflowState& aState,
-                                   nsLineBox* aLine)
+                                      nsLineBox* aLine,
+                                      nsIFrame* aChildFrame)
 {
   if (aState.GetFlag(BRS_APPLYBSTARTMARGIN)) {
     // Apply short-circuit check to avoid searching the line list
     return true;
   }
 
-  if (!aState.IsAdjacentWithTop()) {
+  if (!aState.IsAdjacentWithTop() ||
+      aChildFrame->StyleBorder()->mBoxDecorationBreak ==
+        NS_STYLE_BOX_DECORATION_BREAK_CLONE) {
     // If we aren't at the top Y coordinate then something of non-zero
     // height must have been placed. Therefore the childs top-margin
     // applies.
@@ -2955,11 +2958,12 @@ nsBlockFrame::ReflowBlockFrame(nsBlockReflowState& aState,
 
   // See if we should apply the top margin. If the block frame being
   // reflowed is a continuation (non-null prev-in-flow) then we don't
-  // apply its top margin because it's not significant. Otherwise, dig
-  // deeper.
-  bool applyBStartMargin =
-    !frame->GetPrevInFlow() && ShouldApplyBStartMargin(aState, aLine);
-
+  // apply its top margin because it's not significant unless it has
+  // 'box-decoration-break:clone'.  Otherwise, dig deeper.
+  bool applyBStartMargin = (frame->StyleBorder()->mBoxDecorationBreak ==
+                              NS_STYLE_BOX_DECORATION_BREAK_CLONE ||
+                            !frame->GetPrevInFlow()) &&
+                           ShouldApplyBStartMargin(aState, aLine, frame);
   if (applyBStartMargin) {
     // The HasClearance setting is only valid if ShouldApplyBStartMargin
     // returned false (in which case the top-margin-root set our
@@ -3427,7 +3431,7 @@ nsBlockFrame::ReflowInlineFrames(nsBlockReflowState& aState,
 
   // Setup initial coordinate system for reflowing the inline frames
   // into. Apply a previous block frame's bottom margin first.
-  if (ShouldApplyBStartMargin(aState, aLine)) {
+  if (ShouldApplyBStartMargin(aState, aLine, aLine->mFirstChild)) {
     aState.mBCoord += aState.mPrevBEndMargin.get();
   }
   nsFlowAreaRect floatAvailableSpace = aState.GetFloatAvailableSpace();

layout/generic/nsBlockFrame.h

@@ -637,7 +637,8 @@ protected:
   // Methods for individual frame reflow
 
   bool ShouldApplyBStartMargin(nsBlockReflowState& aState,
-                               nsLineBox* aLine);
+                               nsLineBox* aLine,
+                               nsIFrame* aChildFrame);
 
   void ReflowBlockFrame(nsBlockReflowState& aState,
                         line_iterator aLine,

layout/generic/nsBlockReflowState.cpp

@@ -49,15 +49,18 @@ nsBlockReflowState::nsBlockReflowState(const nsHTMLReflowState& aReflowState,
   SetFlag(BRS_ISOVERFLOWCONTAINER,
           IS_TRUE_OVERFLOW_CONTAINER(aFrame));
 
-  mBorderPadding.ApplySkipSides(aFrame->GetLogicalSkipSides(&aReflowState));
+  int logicalSkipSides = aFrame->GetLogicalSkipSides(&aReflowState);
+  mBorderPadding.ApplySkipSides(logicalSkipSides);
 
   // Note that mContainerWidth is the physical width!
   mContainerWidth = aReflowState.ComputedWidth() + mBorderPadding.LeftRight(wm);
 
-  if (aBStartMarginRoot || 0 != mBorderPadding.BStart(wm)) {
+  if ((aBStartMarginRoot && !(logicalSkipSides & LOGICAL_SIDE_B_START)) ||
+      0 != mBorderPadding.BStart(wm)) {
     SetFlag(BRS_ISBSTARTMARGINROOT, true);
   }
-  if (aBEndMarginRoot || 0 != mBorderPadding.BEnd(wm)) {
+  if ((aBEndMarginRoot && !(logicalSkipSides & LOGICAL_SIDE_B_END)) ||
+      0 != mBorderPadding.BEnd(wm)) {
     SetFlag(BRS_ISBENDMARGINROOT, true);
   }
   if (GetFlag(BRS_ISBSTARTMARGINROOT)) {
@@ -166,6 +169,20 @@ nsBlockReflowState::ComputeReplacedBlockOffsetsForFloats(nsIFrame* aFrame,
   aRightResult = rightOffset;
 }
 
+static nscoord
+GetBEndMarginClone(nsIFrame* aFrame,
+                   nsRenderingContext* aRenderingContext,
+                   const LogicalRect& aContentArea,
+                   WritingMode aWritingMode)
+{
+  if (aFrame->StyleBorder()->mBoxDecorationBreak ==
+        NS_STYLE_BOX_DECORATION_BREAK_CLONE) {
+    nsCSSOffsetState os(aFrame, aRenderingContext, aContentArea.Width(aWritingMode));
+    return os.ComputedLogicalMargin().BEnd(aWritingMode);
+  }
+  return 0;
+}
+
 // Compute the amount of available space for reflowing a block frame
 // at the current Y coordinate. This method assumes that
 // GetAvailableSpace has already been called.
@@ -188,7 +205,8 @@ nsBlockReflowState::ComputeBlockAvailSpace(nsIFrame* aFrame,
   result.BStart(wm) = mBCoord;
   result.BSize(wm) = GetFlag(BRS_UNCONSTRAINEDBSIZE)
     ? NS_UNCONSTRAINEDSIZE
-    : mReflowState.AvailableBSize() - mBCoord;
+    : mReflowState.AvailableBSize() - mBCoord
+      - GetBEndMarginClone(aFrame, mReflowState.rendContext, mContentArea, wm);
   // mBCoord might be greater than mBEndEdge if the block's top margin pushes
   // it off the page/column. Negative available height can confuse other code
   // and is nonsense in principle.