[New Multicolumn] Make positionForPoint() work.

Source/core/layout/LayoutMultiColumnSet.cpp

 /*
  * Copyright (C) 2012 Apple Inc.  All rights reserved.
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  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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 #include "config.h"
 #include "core/layout/LayoutMultiColumnSet.h"
 
+#include "core/editing/PositionWithAffinity.h"
 #include "core/layout/LayoutMultiColumnFlowThread.h"
 #include "core/layout/MultiColumnFragmentainerGroup.h"
 #include "core/paint/MultiColumnSetPainter.h"
 
 namespace blink {
 
 LayoutMultiColumnSet::LayoutMultiColumnSet(LayoutFlowThread* flowThread)
     : LayoutRegion(0, flowThread)
     , m_fragmentainerGroups(*this)
 {
@@ skipping 13 matching lines @@
     // FIXME: implement this, once we have support for multiple rows.
     return m_fragmentainerGroups.first();
 }
 
 const MultiColumnFragmentainerGroup& LayoutMultiColumnSet::fragmentainerGroupAtFlowThreadOffset(LayoutUnit) const
 {
     // FIXME: implement this, once we have support for multiple rows.
     return m_fragmentainerGroups.first();
 }
 
+const MultiColumnFragmentainerGroup& LayoutMultiColumnSet::fragmentainerGroupAtVisualPoint(const LayoutPoint&) const
+{
+    // FIXME: implement this, once we have support for multiple rows.
+    return m_fragmentainerGroups.first();
+}
+
 LayoutUnit LayoutMultiColumnSet::pageLogicalHeight() const
 {
     // FIXME: pageLogicalHeight() needs to take a flow thread offset parameter, so that we can
     // locate the right row.
     return firstFragmentainerGroup().logicalHeight();
 }
 
 LayoutMultiColumnSet* LayoutMultiColumnSet::nextSiblingMultiColumnSet() const
 {
     for (LayoutObject* sibling = nextSibling(); sibling; sibling = sibling->nextSibling()) {
@@ skipping 106 matching lines @@
 
 void LayoutMultiColumnSet::computeLogicalHeight(LayoutUnit, LayoutUnit logicalTop, LogicalExtentComputedValues& computedValues) const
 {
     LayoutUnit logicalHeight;
     for (const auto& group : m_fragmentainerGroups)
         logicalHeight += group.logicalHeight();
     computedValues.m_extent = logicalHeight;
     computedValues.m_position = logicalTop;
 }
 
+PositionWithAffinity LayoutMultiColumnSet::positionForPoint(const LayoutPoint& point)
+{
+    // Convert the visual point to a flow thread point.
+    const MultiColumnFragmentainerGroup& row = fragmentainerGroupAtVisualPoint(point);
+    LayoutPoint flowThreadPoint = row.visualPointToFlowThreadPoint(point + row.offsetFromColumnSet());
+    // Then drill into the flow thread, where we'll find the actual content.
+    return flowThread()->positionForPoint(flowThreadPoint);
+}
+
 LayoutUnit LayoutMultiColumnSet::columnGap() const
 {
     LayoutBlockFlow* parentBlock = multiColumnBlockFlow();
     if (parentBlock->style()->hasNormalColumnGap())
         return parentBlock->style()->fontDescription().computedPixelSize(); // "1em" is recommended as the normal gap setting. Matches <p> margins.
     return parentBlock->style()->columnGap();
 }
 
 unsigned LayoutMultiColumnSet::actualColumnCount() const
 {
@@ skipping 65 matching lines @@
 
 LayoutRect LayoutMultiColumnSet::flowThreadPortionRect() const
 {
     LayoutRect portionRect(LayoutUnit(), logicalTopInFlowThread(), pageLogicalWidth(), logicalHeightInFlowThread());
     if (!isHorizontalWritingMode())
         return portionRect.transposedRect();
     return portionRect;
 }
 
 }