[New Multicolumn] Let a spanner's containing block be the multicol container.

Source/core/rendering/RenderBlockFlow.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 24 matching lines @@
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/html/HTMLDialogElement.h"
 #include "core/paint/BlockFlowPainter.h"
 #include "core/paint/DrawingRecorder.h"
 #include "core/rendering/HitTestLocation.h"
 #include "core/rendering/RenderFlowThread.h"
 #include "core/rendering/RenderLayer.h"
 #include "core/rendering/RenderMultiColumnFlowThread.h"
+#include "core/rendering/RenderMultiColumnSpannerPlaceholder.h"
 #include "core/rendering/RenderPagedFlowThread.h"
 #include "core/rendering/RenderText.h"
 #include "core/rendering/RenderView.h"
 #include "core/rendering/TextAutosizer.h"
 #include "core/rendering/line/LineWidth.h"
 #include "platform/geometry/TransformState.h"
 #include "platform/text/BidiTextRun.h"
 
 namespace blink {
 
@@ skipping 995 matching lines @@
         if (child->isOutOfFlowPositioned()) {
             child->containingBlock()->insertPositionedObject(child);
             adjustPositionedBlock(*child, marginInfo);
             continue;
         }
         if (child->isFloating()) {
             insertFloatingObject(*child);
             adjustFloatingBlock(marginInfo);
             continue;
         }
+        if (child->isColumnSpanAll()) {
+            // This is not the containing block of the spanner. The spanner's placeholder will lay
+            // it out in due course.
+            continue;
+        }

[Julien - ping for review, 2014/12/11 19:09:37]

We have some code to avoid laying out some children that are "special". It's
currently used for renderers that needs some special treatment (e.g. <legend>).
Maybe we could somehow extend the layoutSpecialExcludedChild() (methinks we
could have several of these now).

Also mildly orthogonal is that it is starting to be *really* hard to know what
should and shouldn't be laid out during "normal" layout (not positioned, not
special, not column-spanner, ...) so we will want to add some child iterator.

[mstensho (USE GERRIT), 2014/12/11 21:01:14]

Then we would need to have layoutSpecialExcludedChild() return a list of
renderers, since there may be more than one spanner (even along with e.g. a
legend, if this is a fieldset). BTW: I'm planning to add some code for the
placeholders here, as you may have noticed already. So it won't be just a
"continue" eventually.
Yeah, in this sense the spanners are neither more nor less special than floats
and absposses. So I think they should be treated in similar ways in the code.
Which makes me think that for now, the spanner skipping belongs right here.

I think it's rather clean to have everything here, rather than wasting time on
building a list of excluded renderers, but in any case, I don't think changing
this should be part of this CL.

Or did you want me to change it right away?

[Julien - ping for review, 2014/12/11 23:45:44]

No, we shouldn't do it as part of this change. The pressure is just building to
think about a cleaner design around
renderers-in-the-tree-but-specially-laid-out.

 
         // Lay out the child.
         layoutBlockChild(*child, marginInfo, previousFloatLogicalBottom);
         lastNormalFlowChild = child;
     }
 
     // Now do the handling of the bottom of the block, adding in our bottom border/padding and
     // determining the correct collapsed bottom margin information.
     handleAfterSideOfBlock(lastNormalFlowChild, beforeEdge, afterEdge, marginInfo);
 }
@@ skipping 894 matching lines @@
         }
 
         parentBlockFlow->markAllDescendantsWithFloatsForLayout();
         parentBlockFlow->markSiblingsWithFloatsForLayout();
     }
 
     if (diff.needsFullLayout() || !oldStyle)
         createOrDestroyMultiColumnFlowThreadIfNeeded(oldStyle);
 }
 
+void RenderBlockFlow::updateBlockChildDirtyBitsBeforeLayout(bool relayoutChildren, RenderBox& child)
+{
+    if (child.isRenderMultiColumnSpannerPlaceholder() && toRenderMultiColumnSpannerPlaceholder(child).rendererInFlowThread()->needsLayout()) {
+        // The containing block of a spanner is the multicol container (|this| block), but the spanner
+        // is laid out via its spanner set (|child|), so we need to make sure that we enter it.
+        child.setChildNeedsLayout(MarkOnlyThis);
+    }
+    RenderBlock::updateBlockChildDirtyBitsBeforeLayout(relayoutChildren, child);
+}
+
 void RenderBlockFlow::updateStaticInlinePositionForChild(RenderBox& child, LayoutUnit logicalTop)
 {
     if (child.style()->isOriginalDisplayInlineType())
         setStaticInlinePositionForChild(child, startAlignedOffsetForLine(logicalTop, false));
     else
         setStaticInlinePositionForChild(child, startOffsetForContent());
 }
 
 void RenderBlockFlow::setStaticInlinePositionForChild(RenderBox& child, LayoutUnit inlinePosition)
 {
@@ skipping 1108 matching lines @@
     FrameView* frameView = document().view();
     LayoutUnit top = (style()->position() == FixedPosition) ? 0 : frameView->scrollOffset().height();
     int visibleHeight = frameView->visibleContentRect(IncludeScrollbars).height();
     if (height() < visibleHeight)
         top += (visibleHeight - height()) / 2;
     setY(top);
     dialog->setCentered(top);
 }
 
 } // namespace blink