Fix LayoutObject::mapLocalToAncestor() for fixed under absolute

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/)
@@ skipping 2022 matching lines @@
   return transformState.lastPlanarQuad();
 }
 
 void LayoutObject::mapLocalToAncestor(const LayoutBoxModelObject* ancestor,
                                       TransformState& transformState,
                                       MapCoordinatesFlags mode) const {
   if (ancestor == this)
     return;
 
   bool ancestorSkipped;
   const LayoutObject* o = container(ancestor, &ancestorSkipped);

[chrishtr, 2016/10/21 22:40:32]

Could you take this opportunity to rename to containingBlock?

[Xianzhu, 2016/10/21 22:52:00]

I feel using containingBlock is confusing for now because we are still using
"containingBlock" and "container" for different purposes. Can we use "container"
for now before we replace all "container"s with "containingBlock"s?

   if (!o)
     return;
 
   if (mode & ApplyContainerFlip) {
     if (isBox()) {
       mode &= ~ApplyContainerFlip;
     } else if (o->isBox()) {
       if (o->style()->isFlippedBlocksWritingMode()) {
         IntPoint centerPoint = roundedIntPoint(transformState.mappedPoint());
         transformState.move(
@@ skipping 32 matching lines @@
   }
 
   if (ancestorSkipped) {
     // There can't be a transform between |ancestor| and |o|, because transforms
     // create containers, so it should be safe to just subtract the delta
     // between the ancestor and |o|.
     LayoutSize containerOffset = ancestor->offsetFromAncestorContainer(o);
     transformState.move(-containerOffset.width(), -containerOffset.height(),
                         preserve3D ? TransformState::AccumulateTransform
                                    : TransformState::FlattenTransform);
+    // If the ancestor is fixed, then the rect is already in its coordinates so
+    // doesn't need viewport-adjusting.
+    if (ancestor->style()->position() != FixedPosition && o->isLayoutView() &&
+        styleRef().position() == FixedPosition) {
+      LayoutRect rect;
+      toLayoutView(o)->adjustOffsetForFixedPosition(rect);
+      transformState.move(rect.x(), rect.y());
+    }
     return;
   }
 
   o->mapLocalToAncestor(ancestor, transformState, mode);
 }
 
 const LayoutObject* LayoutObject::pushMappingToContainer(
     const LayoutBoxModelObject* ancestorToStopAt,
     LayoutGeometryMap& geometryMap) const {
   ASSERT_NOT_REACHED();
@@ skipping 51 matching lines @@
   if (applyContainerFlip) {
     IntPoint centerPoint = roundedIntPoint(transformState.mappedPoint());
     transformState.move(
         centerPoint -
         toLayoutBox(o)->flipForWritingMode(LayoutPoint(centerPoint)));
   }
 
   if (ancestorSkipped) {
     containerOffset = ancestor->offsetFromAncestorContainer(o);
     transformState.move(-containerOffset.width(), -containerOffset.height());
+    // If the ancestor is fixed, then the rect is already in its coordinates so
+    // doesn't need viewport-adjusting.
+    if (ancestor->style()->position() != FixedPosition && o->isLayoutView() &&
+        styleRef().position() == FixedPosition) {
+      LayoutRect rect;
+      toLayoutView(o)->adjustOffsetForFixedPosition(rect);
+      transformState.move(rect.x(), rect.y());
+    }
   }
 }
 
 bool LayoutObject::shouldUseTransformFromContainer(
     const LayoutObject* containerObject) const {
   // hasTransform() indicates whether the object has transform, transform-style
   // or perspective. We just care about transform, so check the layer's
   // transform directly.
   return (hasLayer() && toLayoutBoxModelObject(this)->layer()->transform()) ||
          (containerObject && containerObject->style()->hasPerspective());
@@ skipping 1360 matching lines @@
     const blink::LayoutObject* root = object1;
     while (root->parent())
       root = root->parent();
     root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
   } else {
     WTFLogAlways("%s", "Cannot showLayoutTree. Root is (nil)");
   }
 }
 
 #endif