[New Multicolumn] Support for paged overflow.

Source/core/rendering/RenderMultiColumnSet.cpp

Index: Source/core/rendering/RenderMultiColumnSet.cpp
diff --git a/Source/core/rendering/RenderMultiColumnSet.cpp b/Source/core/rendering/RenderMultiColumnSet.cpp
index eee9aee2b43f70076d1e24d18b42c194744d8cd1..7311e3a30991dff23693f17ea58459514545cd1a 100644
--- a/Source/core/rendering/RenderMultiColumnSet.cpp
+++ b/Source/core/rendering/RenderMultiColumnSet.cpp
@@ -193,7 +193,7 @@ LayoutUnit RenderMultiColumnSet::calculateColumnHeight(BalancedHeightCalculation
 
 void RenderMultiColumnSet::addContentRun(LayoutUnit endOffsetFromFirstPage)
 {
-    if (!multiColumnFlowThread()->requiresBalancing())
+    if (!multiColumnFlowThread()->heightIsAuto())
         return;
     if (!m_contentRuns.isEmpty() && endOffsetFromFirstPage <= m_contentRuns.last().breakOffset())
         return;
@@ -205,7 +205,7 @@ void RenderMultiColumnSet::addContentRun(LayoutUnit endOffsetFromFirstPage)
 
 bool RenderMultiColumnSet::recalculateColumnHeight(BalancedHeightCalculation calculationMode)
 {
-    ASSERT(multiColumnFlowThread()->requiresBalancing());
+    ASSERT(multiColumnFlowThread()->heightIsAuto());
 
     LayoutUnit oldColumnHeight = m_columnHeight;
     if (calculationMode == GuessFromFlowThreadPortion) {
@@ -254,7 +254,7 @@ void RenderMultiColumnSet::resetColumnHeight()
 
     LayoutUnit oldColumnHeight = pageLogicalHeight();
 
-    if (multiColumnFlowThread()->requiresBalancing())
+    if (multiColumnFlowThread()->heightIsAuto())
         m_columnHeight = 0;
     else
         setAndConstrainColumnHeight(heightAdjustedForSetOffset(multiColumnFlowThread()->columnHeightAvailable()));
@@ -337,10 +337,15 @@ LayoutRect RenderMultiColumnSet::columnRectAt(unsigned index) const
     LayoutUnit colLogicalTop = borderBefore() + paddingBefore();
     LayoutUnit colLogicalLeft = borderAndPaddingLogicalLeft();
     LayoutUnit colGap = columnGap();
-    if (style()->isLeftToRightDirection())
-        colLogicalLeft += index * (colLogicalWidth + colGap);
-    else
-        colLogicalLeft += contentLogicalWidth() - colLogicalWidth - index * (colLogicalWidth + colGap);
+
+    if (multiColumnFlowThread()->progressionIsInline()) {
+        if (style()->isLeftToRightDirection())
+            colLogicalLeft += index * (colLogicalWidth + colGap);
+        else
+            colLogicalLeft += contentLogicalWidth() - colLogicalWidth - index * (colLogicalWidth + colGap);
+    } else {
+        colLogicalTop += index * (colLogicalHeight + colGap);
+    }
 
     if (isHorizontalWritingMode())
         return LayoutRect(colLogicalLeft, colLogicalTop, colLogicalWidth, colLogicalHeight);
@@ -437,6 +442,9 @@ void RenderMultiColumnSet::paintColumnRules(PaintInfo& paintInfo, const LayoutPo
     if (paintInfo.context->paintingDisabled())
         return;
 
+    if (flowThread()->isRenderPagedFlowThread())
+        return;
+
     RenderStyle* blockStyle = multiColumnBlockFlow()->style();
     const Color& ruleColor = resolveColor(blockStyle, CSSPropertyWebkitColumnRuleColor);
     bool ruleTransparent = blockStyle->columnRuleIsTransparent();
@@ -566,6 +574,12 @@ void RenderMultiColumnSet::collectLayerFragments(LayerFragments& fragments, cons
     LayoutUnit colGap = columnGap();
     unsigned colCount = actualColumnCount();
 
+    RenderMultiColumnFlowThread* flowThread = multiColumnFlowThread();
+    bool progressionIsInline = flowThread->progressionIsInline();
+    bool leftToRight = style()->isLeftToRightDirection();
+
+    LayoutUnit initialBlockOffset = logicalTop() - flowThread->logicalTop();
+
     for (unsigned i = startColumn; i <= endColumn; i++) {
         // Get the portion of the flow thread that corresponds to this column.
         LayoutRect flowThreadPortion = flowThreadPortionRectAt(i);
@@ -582,11 +596,15 @@ void RenderMultiColumnSet::collectLayerFragments(LayerFragments& fragments, cons
         // We also need to intersect the dirty rect. We have to apply a translation and shift based off
         // our column index.
         LayoutPoint translationOffset;
-        LayoutUnit inlineOffset = i * (colLogicalWidth + colGap);
-        if (!style()->isLeftToRightDirection())
+        LayoutUnit inlineOffset = progressionIsInline ? i * (colLogicalWidth + colGap) : LayoutUnit();
+        if (!leftToRight)
             inlineOffset = -inlineOffset;
         translationOffset.setX(inlineOffset);
-        LayoutUnit blockOffset = isHorizontalWritingMode() ? -flowThreadPortion.y() : -flowThreadPortion.x();
+        LayoutUnit blockOffset;
+        if (progressionIsInline)
+            blockOffset = initialBlockOffset + (isHorizontalWritingMode() ? -flowThreadPortion.y() : -flowThreadPortion.x());
+        else
+            blockOffset = i * colGap;

[rune, 2014/06/18 22:09:05]

I had to stare at this for a while. I think this warrants a comment, or perhaps
rename colGap to pageSpacing or something. If you're not mstensho, this I
believe is due to the fact that the column-gap property is misused to apply
spacing between pages for overflow:paged-x/y. Not only when fragments are
"stacked" in the inline direction, but also in the block direction. For block
direction stacking, the coordinates follow the flow-thread coordinates, but we
have to add the colGap spacing that is added after each of the 'i' pages.

[rune, 2014/06/19 09:22:19]

Never mind renaming. This is in RenderMultiColumnSet and even if the block
direction stacking is only used for paged overflow, it doesn't make sense to use
pageSpacing. Still would like a comment about column-gap applying as "vertical"
spacing between fragments stacked in the block direction.

         if (isFlippedBlocksWritingMode(style()->writingMode()))
             blockOffset = -blockOffset;
         translationOffset.setY(blockOffset);
@@ -612,7 +630,7 @@ void RenderMultiColumnSet::collectLayerFragments(LayerFragments& fragments, cons
 
         LayoutRect flippedFlowThreadOverflowPortion(flowThreadOverflowPortion);
         // Flip it into more a physical (RenderLayer-style) rectangle.
-        flowThread()->flipForWritingMode(flippedFlowThreadOverflowPortion);
+        flowThread->flipForWritingMode(flippedFlowThreadOverflowPortion);
         fragment.paginationClip = flippedFlowThreadOverflowPortion;
         fragments.append(fragment);
     }