Refactor LayoutView paint offset updates out of FrameView update code

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/PaintPropertyTreeBuilder.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/layout/LayoutInline.h"
@@ skipping 84 matching lines @@
     existingScroll->update(std::move(parent), std::move(scrollOffset), clip,
                            bounds, userScrollableHorizontal,
                            userScrollableVertical);
   } else {
     frameView.setScroll(ScrollPaintPropertyNode::create(
         std::move(parent), std::move(scrollOffset), clip, bounds,
         userScrollableHorizontal, userScrollableVertical));
   }
 }
 
-void PaintPropertyTreeBuilder::updatePropertiesAndContext(
+void PaintPropertyTreeBuilder::updateFramePropertiesAndContext(
     FrameView& frameView,
     PaintPropertyTreeBuilderContext& context) {
   if (RuntimeEnabledFeatures::rootLayerScrollingEnabled()) {
-    LayoutView* layoutView = frameView.layoutView();
-    if (!layoutView)
-      return;
-
-    TransformationMatrix frameTranslate;
-    frameTranslate.translate(frameView.x() + layoutView->location().x() +
-                                 context.current.paintOffset.x(),
-                             frameView.y() + layoutView->location().y() +
-                                 context.current.paintOffset.y());
-    layoutView->getMutableForPainting()
-        .ensurePaintProperties()
-        .updatePaintOffsetTranslation(context.current.transform, frameTranslate,
-                                      FloatPoint3D());
-
-    const auto* properties = layoutView->paintProperties();
-    DCHECK(properties && properties->paintOffsetTranslation());
-    context.current.transform = properties->paintOffsetTranslation();
-    context.current.paintOffset = LayoutPoint();
+    // With root layer scrolling, the LayoutView (a LayoutObject) properties are
+    // updated like other objects (see updatePropertiesAndContextForSelf and
+    // updatePropertiesAndContextForChildren) instead of needing LayoutView-
+    // specific property updates here.
+    context.current.paintOffset.moveBy(frameView.location());
     context.current.renderingContextID = 0;
     context.current.shouldFlattenInheritedTransform = true;
     context.absolutePosition = context.current;
-    context.containerForAbsolutePosition =
-        nullptr;  // This will get set in updateOutOfFlowContext().
+    context.containerForAbsolutePosition = nullptr;
     context.fixedPosition = context.current;
     return;
   }
 
   TransformationMatrix frameTranslate;
   frameTranslate.translate(frameView.x() + context.current.paintOffset.x(),
                            frameView.y() + context.current.paintOffset.y());
   updateFrameViewPreTranslation(frameView, context.current.transform,
                                 frameTranslate, FloatPoint3D());
 
@@ skipping 51 matching lines @@
 
   std::unique_ptr<PropertyTreeState> contentsState(
       new PropertyTreeState(context.current.transform, context.current.clip,
                             context.currentEffect, context.current.scroll));
   frameView.setTotalPropertyTreeStateForContents(std::move(contentsState));
 }
 
 void PaintPropertyTreeBuilder::updatePaintOffsetTranslation(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
-  // LayoutView's paint offset is updated in the FrameView property update.
-  if (object.isLayoutView()) {
-    DCHECK(context.current.paintOffset == LayoutPoint());
-    return;
-  }
-
   bool usesPaintOffsetTranslation = false;
-  if (object.isBoxModelObject() &&
-      context.current.paintOffset != LayoutPoint()) {
+  if (RuntimeEnabledFeatures::rootLayerScrollingEnabled() &&
+      object.isLayoutView()) {
+    // Root layer scrolling always creates a translation node for LayoutView to
+    // ensure fixed and absolute contexts use the correct transform space.
+    usesPaintOffsetTranslation = true;
+  } else if (object.isBoxModelObject() &&
+             context.current.paintOffset != LayoutPoint()) {
     // TODO(trchen): Eliminate PaintLayer dependency.
     PaintLayer* layer = toLayoutBoxModelObject(object).layer();
     if (layer && layer->paintsWithTransform(GlobalPaintNormalPhase))
       usesPaintOffsetTranslation = true;
   }
 
   // We should use the same subpixel paint offset values for snapping
   // regardless of whether a transform is present. If there is a transform
   // we round the paint offset but keep around the residual fractional
   // component for the transformed content to paint with.  In spv1 this was
@@ skipping 15 matching lines @@
             context.current.renderingContextID);
   } else {
     if (auto* properties = object.getMutableForPainting().paintProperties())
       properties->clearPaintOffsetTranslation();
   }
 
   const auto* properties = object.paintProperties();
   if (properties && properties->paintOffsetTranslation()) {
     context.current.transform = properties->paintOffsetTranslation();
     context.current.paintOffset = fractionalPaintOffset;
+    if (RuntimeEnabledFeatures::rootLayerScrollingEnabled() &&
+        object.isLayoutView()) {
+      context.absolutePosition.transform = properties->paintOffsetTranslation();
+      context.fixedPosition.transform = properties->paintOffsetTranslation();
+      context.absolutePosition.paintOffset = LayoutPoint();
+      context.fixedPosition.paintOffset = LayoutPoint();
+    }
   }
 }
 
 static FloatPoint3D transformOrigin(const LayoutBox& box) {
   const ComputedStyle& style = box.styleRef();
   FloatSize borderBoxSize(box.size());
   return FloatPoint3D(
       floatValueForLength(style.transformOriginX(), borderBoxSize.width()),
       floatValueForLength(style.transformOriginY(), borderBoxSize.height()),
       style.transformOriginZ());
@@ skipping 611 matching lines @@
     return;
 
   updateOverflowClip(object, context);
   updatePerspective(object, context);
   updateSvgLocalToBorderBoxTransform(object, context);
   updateScrollAndScrollTranslation(object, context);
   updateOutOfFlowContext(object, context);
 }
 
 }  // namespace blink