[New Multicolumn] mapAbsoluteToLocalPoint() needs to convert to flow thread coordinates.

Source/core/layout/LayoutBoxModelObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 770 matching lines @@
     LayoutUnit y = paddingTop() + borderTop() + (verticalSpace / 2);
     return currentStyle.isHorizontalWritingMode() ? LayoutRect(x, y, caretWidth, height) : LayoutRect(y, x, height, caretWidth);
 }
 
 void LayoutBoxModelObject::mapAbsoluteToLocalPoint(MapCoordinatesFlags mode, TransformState& transformState) const
 {
     LayoutObject* o = container();
     if (!o)
         return;
 
-    if (o->isLayoutFlowThread())
-        transformState.move(o->columnOffset(LayoutPoint(transformState.mappedPoint())));
-
     o->mapAbsoluteToLocalPoint(mode, transformState);
 
     LayoutSize containerOffset = offsetFromContainer(o, LayoutPoint());
 
-    if (!style()->hasOutOfFlowPosition() && o->hasColumns()) {
+    if (o->isLayoutFlowThread()) {
+        // Descending into a flow thread. Convert to the local coordinate space, i.e. flow thread coordinates.
+        const LayoutFlowThread* flowThread = toLayoutFlowThread(o);
+        LayoutPoint visualPoint = LayoutPoint(transformState.mappedPoint());
+        transformState.move(visualPoint - flowThread->visualPointToFlowThreadPoint(visualPoint));
+        // |containerOffset| is also in visual coordinates. Convert to flow thread coordinates.
+        // TODO(mstensho): Wouldn't it be better add a parameter to instruct offsetFromContainer()
+        // to return flowthread coordinates in the first place? We're effectively performing two
+        // conversions here, when in fact none is needed.
+        containerOffset = toLayoutSize(flowThread->visualPointToFlowThreadPoint(toLayoutPoint(containerOffset)));
+    } else if (!style()->hasOutOfFlowPosition() && o->hasColumns()) {
         LayoutBlock* block = toLayoutBlock(o);
         LayoutPoint point(roundedLayoutPoint(transformState.mappedPoint()));
         point -= containerOffset;
         block->adjustForColumnRect(containerOffset, point);
     }
 
     bool preserve3D = mode & UseTransforms && (o->style()->preserves3D() || style()->preserves3D());
     if (mode & UseTransforms && shouldUseTransformFromContainer(o)) {
         TransformationMatrix t;
         getTransformFromContainer(o, containerOffset, t);
@@ skipping 72 matching lines @@
     ASSERT(!beforeChild || toBoxModelObject == beforeChild->parent());
     for (LayoutObject* child = startChild; child && child != endChild; ) {
         // Save our next sibling as moveChildTo will clear it.
         LayoutObject* nextSibling = child->nextSibling();
         moveChildTo(toBoxModelObject, child, beforeChild, fullRemoveInsert);
         child = nextSibling;
     }
 }
 
 } // namespace blink