Fix PaintPropertyTreeBuilder for root layer scrolling.

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"
 #include "core/layout/LayoutPart.h"
 #include "core/layout/svg/LayoutSVGRoot.h"
 #include "core/paint/ObjectPaintProperties.h"
 #include "core/paint/PaintLayer.h"
 #include "core/paint/SVGRootPainter.h"
 #include "platform/transforms/TransformationMatrix.h"
 #include "wtf/PtrUtil.h"
 #include <memory>
 
 namespace blink {
 
 void PaintPropertyTreeBuilder::buildTreeRootNodes(FrameView& rootFrame, PaintPropertyTreeBuilderContext& context)
 {
+    Settings* settings = rootFrame.frame().settings();
+    if (settings && settings->rootLayerScrolls())
+        return;
+
     if (!rootFrame.rootTransform() || rootFrame.rootTransform()->parent()) {
         rootFrame.setRootTransform(TransformPaintPropertyNode::create(nullptr, TransformationMatrix(), FloatPoint3D()));
         rootFrame.setRootClip(ClipPaintPropertyNode::create(nullptr, rootFrame.rootTransform(), FloatRoundedRect(LayoutRect::infiniteIntRect())));
         rootFrame.setRootEffect(EffectPaintPropertyNode::create(nullptr, 1.0));
     } else {
         DCHECK(rootFrame.rootClip() && !rootFrame.rootClip()->parent());
         DCHECK(rootFrame.rootEffect() && !rootFrame.rootEffect()->parent());
     }
 
     context.current.transform = context.absolutePosition.transform = context.fixedPosition.transform = rootFrame.rootTransform();
     context.current.clip = context.absolutePosition.clip = context.fixedPosition.clip = rootFrame.rootClip();
     context.currentEffect = rootFrame.rootEffect();
 }
 
 void PaintPropertyTreeBuilder::buildTreeNodes(FrameView& frameView, PaintPropertyTreeBuilderContext& context)
 {
-    // TODO(pdr): Creating paint properties for FrameView here will not be
-    // needed once settings()->rootLayerScrolls() is enabled.
-    // TODO(pdr): Make this conditional on the rootLayerScrolls setting.
+    Settings* settings = frameView.frame().settings();
+    if (settings && settings->rootLayerScrolls()) {
+        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());
+        context.current.transform = layoutView->getMutableForPainting().ensureObjectPaintProperties().createOrUpdatePaintOffsetTranslation(
+            context.current.transform, frameTranslate, FloatPoint3D());
+        context.current.paintOffset = LayoutPoint();
+        context.current.clip = nullptr; // This will get set in updateOverflowClip().
+        context.current.renderingContextID = 0;
+        context.current.shouldFlattenInheritedTransform = true;
+        context.absolutePosition = context.current;
+        context.containerForAbsolutePosition = nullptr; // This will get set in updateOutOfFlowContext().
+        context.fixedPosition = context.current;
+        return;
+    }
 
     TransformationMatrix frameTranslate;
     frameTranslate.translate(frameView.x() + context.current.paintOffset.x(), frameView.y() + context.current.paintOffset.y());
     if (TransformPaintPropertyNode* existingPreTranslation = frameView.preTranslation())
         existingPreTranslation->update(context.current.transform, frameTranslate, FloatPoint3D());
     else
         frameView.setPreTranslation(TransformPaintPropertyNode::create(context.current.transform, frameTranslate, FloatPoint3D()));
 
     FloatRoundedRect contentClip(IntRect(IntPoint(), frameView.visibleContentSize()));
     if (ClipPaintPropertyNode* existingContentClip = frameView.contentClip())
@@ skipping 38 matching lines @@
             LayoutPoint fractionalPaintOffset = LayoutPoint(context.current.paintOffset - roundedPaintOffset);
 
             context.current.transform = object.getMutableForPainting().ensureObjectPaintProperties().createOrUpdatePaintOffsetTranslation(
                 context.current.transform, TransformationMatrix().translate(roundedPaintOffset.x(), roundedPaintOffset.y()), FloatPoint3D(),
                 context.current.shouldFlattenInheritedTransform, context.current.renderingContextID);
             context.current.paintOffset = fractionalPaintOffset;
             return;
         }
     }
 
+    if (object.isLayoutView())
+        return;
+
     if (ObjectPaintProperties* properties = object.getMutableForPainting().objectPaintProperties())
         properties->clearPaintOffsetTranslation();
 }
 
 static FloatPoint3D transformOrigin(const LayoutBox& box)
 {
     const ComputedStyle& style = box.styleRef();
     FloatSize borderBoxSize(box.size());
     return FloatPoint3D(
         floatValueForLength(style.transformOriginX(), borderBoxSize.width()),
@@ skipping 51 matching lines @@
             return;
         }
     }
 
     if (ObjectPaintProperties* properties = object.getMutableForPainting().objectPaintProperties())
         properties->clearTransform();
 }
 
 void PaintPropertyTreeBuilder::updateEffect(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
+    if (object.isLayoutView() && !context.currentEffect) {
+        const LayoutView& layoutView = toLayoutView(object);
+        DCHECK(layoutView.frameView()->frame().settings()->rootLayerScrolls());
+        DCHECK(layoutView.frameView()->frame().isMainFrame());
+        context.currentEffect = layoutView.getMutableForPainting().ensureObjectPaintProperties().createOrUpdateEffect(nullptr, 1.0);
+        return;
+    }
+
     if (!object.styleRef().hasOpacity()) {
         if (ObjectPaintProperties* properties = object.getMutableForPainting().objectPaintProperties())
             properties->clearEffect();
         return;
     }
 
     context.currentEffect = object.getMutableForPainting().ensureObjectPaintProperties().createOrUpdateEffect(
         context.currentEffect, object.styleRef().opacity());
 }
 
@@ skipping 131 matching lines @@
     context.current.shouldFlattenInheritedTransform = false;
     context.current.renderingContextID = 0;
 }
 
 void PaintPropertyTreeBuilder::updateScrollTranslation(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
     if (object.isBoxModelObject() && object.hasOverflowClip()) {
         PaintLayer* layer = toLayoutBoxModelObject(object).layer();
         DCHECK(layer);
         DoubleSize scrollOffset = layer->getScrollableArea()->scrollOffset();
+        bool needsScrollTranslation = !scrollOffset.isZero() || layer->scrollsOverflow();
+        if (!needsScrollTranslation && object.isLayoutView()) {
+            Settings* settings = object.document().settings();
+            needsScrollTranslation = (settings && settings->rootLayerScrolls());
+        }

[trchen, 2016/08/17 21:30:55]

This is difficult to read. How about this:
bool forceScrollingForLayoutView = false;
if (object.isLayoutView()) {
    Settings* settings = object.document().settings();
    forceScrollingForLayoutView = settings && settings->rootLayerScrolls();
}
if (forceScrollingForLayoutView || !scrollOffset.isZero() ||
layer->scrollsOverflow()) {

[szager1, 2016/08/19 01:52:13]

Done.

 
-        if (!scrollOffset.isZero() || layer->scrollsOverflow()) {
+        if (needsScrollTranslation) {
             TransformationMatrix matrix = TransformationMatrix().translate(-scrollOffset.width(), -scrollOffset.height());
             context.current.transform = object.getMutableForPainting().ensureObjectPaintProperties().createOrUpdateScrollTranslation(
                 context.current.transform, matrix, FloatPoint3D(), context.current.shouldFlattenInheritedTransform, context.current.renderingContextID);
             context.current.shouldFlattenInheritedTransform = false;
             return;
         }
     }
 
     if (ObjectPaintProperties* properties = object.getMutableForPainting().objectPaintProperties())
         properties->clearScrollTranslation();
 }
 
 void PaintPropertyTreeBuilder::updateOutOfFlowContext(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
     if (object.canContainAbsolutePositionObjects()) {
         context.absolutePosition = context.current;
         context.containerForAbsolutePosition = &object;
     }
 
-    // TODO(pdr): Remove the !object.isLayoutView() condition when removing FrameView
-    // paint properties for rootLayerScrolls.
-    if (!object.isLayoutView() && object.canContainFixedPositionObjects()) {
+    if (object.isLayoutView()) {
+        Settings* settings = object.document().settings();
+        if (settings && settings->rootLayerScrolls()) {
+            context.fixedPosition = context.current;
+            const TransformPaintPropertyNode* transform = object.objectPaintProperties()->paintOffsetTranslation();
+            DCHECK(transform);
+            context.fixedPosition.transform = transform;
+        }
+    } else if (object.canContainFixedPositionObjects()) {
         context.fixedPosition = context.current;
     } else if (object.getMutableForPainting().objectPaintProperties() && object.objectPaintProperties()->cssClip()) {
         // CSS clip applies to all descendants, even if this object is not a containing block
         // ancestor of the descendant. It is okay for absolute-position descendants because
         // having CSS clip implies being absolute position container. However for fixed-position
         // descendants we need to insert the clip here if we are not a containing block ancestor
         // of them.
         auto* cssClip = object.getMutableForPainting().objectPaintProperties()->cssClip();
 
         // Before we actually create anything, check whether in-flow context and fixed-position
@@ skipping 74 matching lines @@
     updateLocalBorderBoxContext(object, context);
     updateScrollbarPaintOffset(object, context);
     updateOverflowClip(object, context);
     updatePerspective(object, context);
     updateSvgLocalToBorderBoxTransform(object, context);
     updateScrollTranslation(object, context);
     updateOutOfFlowContext(object, context);
 }
 
 } // namespace blink