Consistently check if a block can handle pagination strut propagation.

third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 687 matching lines @@
     if (unsplittableAdjustmentDelta) {
         setPageBreak(newLogicalTop, childLogicalHeight - unsplittableAdjustmentDelta);
         paginationStrut = unsplittableAdjustmentDelta;
     } else if (childBlockFlow && childBlockFlow->paginationStrut()) {
         paginationStrut = childBlockFlow->paginationStrut();
     }
 
     if (paginationStrut) {
         // We are willing to propagate out to our parent block as long as we were at the top of the block prior
         // to collapsing our margins, and as long as we didn't clear or move as a result of other pagination.
-        if (atBeforeSideOfBlock && logicalTop == newLogicalTop && !isOutOfFlowPositioned() && !isTableCell()) {
+        if (atBeforeSideOfBlock && logicalTop == newLogicalTop && allowsPaginationStrut()) {
             // FIXME: Should really check if we're exceeding the page height before propagating the strut, but we don't
             // have all the information to do so (the strut only has the remaining amount to push). Gecko gets this wrong too
             // and pushes to the next page anyway, so not too concerned about it.
             paginationStrut += logicalTop;
             if (isFloating())
                 paginationStrut += marginBefore(); // Floats' margins do not collapse with page or column boundaries.
             setPaginationStrut(paginationStrut);
             if (childBlockFlow)
                 childBlockFlow->setPaginationStrut(0);
         } else {
@@ skipping 55 matching lines @@
         // line, and we don't want to move all that, since it has already been established that it
         // fits nicely where it is.
         LayoutUnit lineHeight = lineBox.lineBottomWithLeading() - lineBox.lineTopWithLeading();
         LayoutUnit totalLogicalHeight = lineHeight + std::max<LayoutUnit>(0, lineLogicalOffset);
         LayoutUnit pageLogicalHeightAtNewOffset = block.pageLogicalHeightForOffset(lineLogicalOffset + remainingLogicalHeight);
         // It's rather pointless to break before the block if the current line isn't going to
         // fit in the same column or page, so check that as well.
         if (totalLogicalHeight < pageLogicalHeightAtNewOffset)
             wantsStrutOnBlock = true;
     }
-    // The block needs to be contained by a LayoutBlockFlow (and not by e.g. a flexbox or a table
-    // (which would be the case for table cell or table caption)). The reason for this limitation is
-    // simply that LayoutBlockFlow child layout code is the only place where we pick up the struts
-    // and handle them. We handle floats and regular in-flow children, and that's all. We could
-    // handle this in other layout modes as well (and even for out-of-flow children), but currently
-    // we don't.
-    if (!wantsStrutOnBlock || block.isOutOfFlowPositioned())
-        return false;
-    LayoutBlock* containingBlock = block.containingBlock();
-    return containingBlock && containingBlock->isLayoutBlockFlow();
+    return wantsStrutOnBlock && block.allowsPaginationStrut();
 }
 
 void LayoutBlockFlow::adjustLinePositionForPagination(RootInlineBox& lineBox, LayoutUnit& delta)
 {
     // TODO(mstensho): Pay attention to line overflow. It should be painted in the same column as
     // the rest of the line, possibly overflowing the column. We currently only allow overflow above
     // the first column. We clip at all other column boundaries, and that's how it has to be for
     // now. The paint we have to do when a column has overflow has to be special. We need to exclude
     // content that paints in a previous column (and content that paints in the following column).
     //
@@ skipping 2098 matching lines @@
 {
     bool ltr = style()->isLeftToRightDirection();
     leftGap = (state == SelectionInside)
         || (state == SelectionEnd && ltr)
         || (state == SelectionStart && !ltr);
     rightGap = (state == SelectionInside)
         || (state == SelectionStart && ltr)
         || (state == SelectionEnd && !ltr);
 }
 
+bool LayoutBlockFlow::allowsPaginationStrut() const
+{
+    // The block needs to be contained by a LayoutBlockFlow (and not by e.g. a flexbox or a table
+    // (which would be the case for table cell or table caption)). The reason for this limitation is

[Julien - ping for review, 2015/10/05 17:33:05]

or a grid

[mstensho (USE GERRIT), 2015/10/05 19:51:32]

Done.

+    // simply that LayoutBlockFlow child layout code is the only place where we pick up the struts
+    // and handle them. We handle floats and regular in-flow children, and that's all. We could
+    // handle this in other layout modes as well (and even for out-of-flow children), but currently
+    // we don't.

[Julien - ping for review, 2015/10/05 17:33:05]

TODO(mstensho)?

[mstensho (USE GERRIT), 2015/10/05 19:51:32]

Done.

+    if (isOutOfFlowPositioned())
+        return false;
+    LayoutBlock* containingBlock = this->containingBlock();
+    return containingBlock && containingBlock->isLayoutBlockFlow();
+}
+
 void LayoutBlockFlow::setPaginationStrut(LayoutUnit strut)
 {
     if (!m_rareData) {
         if (!strut)
             return;
         m_rareData = adoptPtr(new LayoutBlockFlowRareData(this));
     }
     m_rareData->m_paginationStrut = strut;
 }
 
@@ skipping 162 matching lines @@
     FrameView* frameView = document().view();
     LayoutUnit top = (style()->position() == FixedPosition) ? 0 : frameView->scrollOffset().height();
     int visibleHeight = frameView->visibleContentRect(IncludeScrollbars).height();
     if (size().height() < visibleHeight)
         top += (visibleHeight - size().height()) / 2;
     setY(top);
     dialog->setCentered(top);
 }
 
 } // namespace blink