Untangle multicol coordinate space conversion from offsetFromContainer().

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 2245 matching lines @@
             mode &= ~ApplyContainerFlip;
         } else if (o->isBox()) {
             if (o->style()->isFlippedBlocksWritingMode()) {
                 IntPoint centerPoint = roundedIntPoint(transformState.mappedPoint());
                 transformState.move(toLayoutBox(o)->flipForWritingMode(LayoutPoint(centerPoint)) - centerPoint);
             }
             mode &= ~ApplyContainerFlip;
         }
     }
 
-    LayoutSize containerOffset = offsetFromContainer(o, roundedLayoutPoint(transformState.mappedPoint()));
+    LayoutSize containerOffset = offsetFromContainer(o);
+    if (o->isLayoutFlowThread()) {
+        // So far the point has been in flow thread coordinates (i.e. as if everything in
+        // the fragmentation context lived in one tall single column). Convert it to a
+        // visual point now.
+        LayoutPoint pointInContainer = roundedLayoutPoint(transformState.mappedPoint()) + containerOffset;
+        containerOffset += o->columnOffset(pointInContainer);
+    }
 
     // Text objects just copy their parent's computed style, so we need to ignore them.
     bool preserve3D = mode & UseTransforms && ((o->style()->preserves3D() && !o->isText()) || (style()->preserves3D() && !isText()));
     if (mode & UseTransforms && shouldUseTransformFromContainer(o)) {
         TransformationMatrix t;
         getTransformFromContainer(o, containerOffset, t);
         transformState.applyTransform(t, preserve3D ? TransformState::AccumulateTransform : TransformState::FlattenTransform);
     } else {
         transformState.move(containerOffset.width(), containerOffset.height(), preserve3D ? TransformState::AccumulateTransform : TransformState::FlattenTransform);
     }
@@ skipping 31 matching lines @@
             mode &= ~ApplyContainerFlip;
         } else if (o->isBox()) {
             applyContainerFlip = o->style()->isFlippedBlocksWritingMode();
             mode &= ~ApplyContainerFlip;
         }
     }
 
     if (!containerSkipped)
         o->mapAncestorToLocal(ancestor, transformState, mode);
 
-    LayoutSize containerOffset = offsetFromContainer(o, LayoutPoint());
+    LayoutSize containerOffset = offsetFromContainer(o);
     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)));
+        transformState.move(visualPoint - toLayoutFlowThread(o)->visualPointToFlowThreadPoint(visualPoint));
     }
 
     bool preserve3D = mode & UseTransforms && (o->style()->preserves3D() || style()->preserves3D());
     if (mode & UseTransforms && shouldUseTransformFromContainer(o)) {
         TransformationMatrix t;
         getTransformFromContainer(o, containerOffset, t);
         transformState.applyTransform(t, preserve3D ? TransformState::AccumulateTransform : TransformState::FlattenTransform);
     } else {
         transformState.move(containerOffset.width(), containerOffset.height(), preserve3D ? TransformState::AccumulateTransform : TransformState::FlattenTransform);
     }
@@ skipping 92 matching lines @@
 
     // A layoutObject can have no invalidation backing if it is from a detached frame,
     // or when forced compositing is disabled.
     if (paintInvalidationContainer.layer()->compositingState() == NotComposited)
         return containerPoint;
 
     PaintLayer::mapPointToPaintBackingCoordinates(&paintInvalidationContainer, containerPoint);
     return containerPoint;
 }
 
-LayoutSize LayoutObject::offsetFromContainer(const LayoutObject* o, const LayoutPoint& point, bool* offsetDependsOnPoint) const
+LayoutSize LayoutObject::offsetFromContainer(const LayoutObject* o) const
 {
     ASSERT(o == container());
-
-    LayoutSize offset = o->columnOffset(point);
-
-    if (o->hasOverflowClip())
-        offset -= toLayoutBox(o)->scrolledContentOffset();
-
-    if (offsetDependsOnPoint)
-        *offsetDependsOnPoint = o->isLayoutFlowThread();
-
-    return offset;
+    return o->hasOverflowClip() ? LayoutSize(-toLayoutBox(o)->scrolledContentOffset()) : LayoutSize();
 }
 
 LayoutSize LayoutObject::offsetFromAncestorContainer(const LayoutObject* ancestorContainer) const
 {
     if (ancestorContainer == this)
         return LayoutSize();
 
     LayoutSize offset;
     LayoutPoint referencePoint;
     const LayoutObject* currContainer = this;
     do {
         const LayoutObject* nextContainer = currContainer->container();
         ASSERT(nextContainer); // This means we reached the top without finding container.
         if (!nextContainer)
             break;
         ASSERT(!currContainer->hasTransformRelatedProperty());
-        LayoutSize currentOffset = currContainer->offsetFromContainer(nextContainer, referencePoint);
+        LayoutSize currentOffset = currContainer->offsetFromContainer(nextContainer);
         offset += currentOffset;
         referencePoint.move(currentOffset);
         currContainer = nextContainer;
     } while (currContainer != ancestorContainer);
 
     return offset;
 }
 
 LayoutRect LayoutObject::localCaretRect(InlineBox*, int, LayoutUnit* extraWidthToEndOfLine)
 {
@@ skipping 1252 matching lines @@
         const blink::LayoutObject* root = object1;
         while (root->parent())
             root = root->parent();
         root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
     } else {
         fprintf(stderr, "Cannot showLayoutTree. Root is (nil)\n");
     }
 }
 
 #endif