Reuse existing paint property node is possible

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)
 {
-    RefPtr<TransformPaintPropertyNode> transformRoot = TransformPaintPropertyNode::create(TransformationMatrix(), FloatPoint3D(), nullptr);
-    context.current.transform = context.absolutePosition.transform = context.fixedPosition.transform = transformRoot.get();
-    rootFrame.setRootTransform(std::move(transformRoot));
+    if (!rootFrame.rootTransform() || rootFrame.rootTransform()->parent()) {
+        rootFrame.setRootTransform(TransformPaintPropertyNode::create(TransformationMatrix(), FloatPoint3D(), nullptr));
+        rootFrame.setRootClip(ClipPaintPropertyNode::create(rootFrame.rootTransform(), FloatRoundedRect(LayoutRect::infiniteIntRect()), nullptr));
+        rootFrame.setRootEffect(EffectPaintPropertyNode::create(1.0, nullptr));
+    } else {
+        DCHECK(rootFrame.rootClip() && !rootFrame.rootClip()->parent());
+        DCHECK(rootFrame.rootEffect() && !rootFrame.rootEffect()->parent());
+    }
 
-    RefPtr<ClipPaintPropertyNode> clipRoot = ClipPaintPropertyNode::create(transformRoot, FloatRoundedRect(LayoutRect::infiniteIntRect()), nullptr);
-    context.current.clip = context.absolutePosition.clip = context.fixedPosition.clip = clipRoot.get();
-    rootFrame.setRootClip(std::move(clipRoot));
-
-    RefPtr<EffectPaintPropertyNode> effectRoot = EffectPaintPropertyNode::create(1.0, nullptr);
-    context.currentEffect = effectRoot.get();
-    rootFrame.setRootEffect(std::move(effectRoot));
+    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.
 
     TransformationMatrix frameTranslate;
     frameTranslate.translate(frameView.x() + context.current.paintOffset.x(), frameView.y() + context.current.paintOffset.y());
-    RefPtr<TransformPaintPropertyNode> newTransformNodeForPreTranslation = TransformPaintPropertyNode::create(frameTranslate, FloatPoint3D(), context.current.transform);
+    if (!frameView.preTranslation() || frameView.preTranslation()->matrix() != frameTranslate)
+        frameView.setPreTranslation(TransformPaintPropertyNode::create(frameTranslate, FloatPoint3D(), context.current.transform));
 
     FloatRoundedRect contentClip(IntRect(IntPoint(), frameView.visibleContentSize()));
-    RefPtr<ClipPaintPropertyNode> newClipNodeForContentClip = ClipPaintPropertyNode::create(newTransformNodeForPreTranslation.get(), contentClip, context.current.clip);
+    if (!frameView.contentClip() || frameView.contentClip()->clipRect() != contentClip)
+        frameView.setContentClip(ClipPaintPropertyNode::create(frameView.preTranslation(), contentClip, context.current.clip));
 
     DoubleSize scrollOffset = frameView.scrollOffsetDouble();
     TransformationMatrix frameScroll;
     frameScroll.translate(-scrollOffset.width(), -scrollOffset.height());
-    RefPtr<TransformPaintPropertyNode> newTransformNodeForScrollTranslation = TransformPaintPropertyNode::create(frameScroll, FloatPoint3D(), newTransformNodeForPreTranslation);
+    if (!frameView.scrollTranslation() || frameView.scrollTranslation()->matrix() != frameScroll)
+        frameView.setScrollTranslation(TransformPaintPropertyNode::create(frameScroll, FloatPoint3D(), frameView.preTranslation()));
 
     // Initialize the context for current, absolute and fixed position cases.
     // They are the same, except that scroll translation does not apply to
     // fixed position descendants.
-    context.current.transform = newTransformNodeForScrollTranslation.get();
+    context.current.transform = frameView.scrollTranslation();
     context.current.paintOffset = LayoutPoint();
-    context.current.clip = newClipNodeForContentClip.get();
+    context.current.clip = frameView.contentClip();
     context.absolutePosition = context.current;
     context.containerForAbsolutePosition = nullptr;
     context.fixedPosition = context.current;
-    context.fixedPosition.transform = newTransformNodeForPreTranslation.get();
-
-    frameView.setPreTranslation(newTransformNodeForPreTranslation.release());
-    frameView.setScrollTranslation(newTransformNodeForScrollTranslation.release());
-    frameView.setContentClip(newClipNodeForContentClip.release());
+    context.fixedPosition.transform = frameView.preTranslation();
 }
 
-void PaintPropertyTreeBuilder::updatePaintOffsetTranslation(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
+template <
+    typename PropertyNode,
+    PropertyNode* (ObjectPaintProperties::*Getter)() const,
+    void (ObjectPaintProperties::*Setter)(PassRefPtr<PropertyNode>),
+    bool (*ComputeProperty)(const LayoutObject&, PaintPropertyTreeBuilderContext&, typename PropertyNode::Value&)>
+PropertyNode* PaintPropertyTreeBuilder::updateObjectPaintProperty(const LayoutObject& object, PaintPropertyTreeBuilderContext& context, PropertyNode*& contextProperty)

[pdr., 2016/07/21 21:34:06]

This template approach is very clever. WDYT of this slight variation on your
design? https://codereview.chromium.org/2171943002. It doesn't require Value
types, and can more naturally handle updateScrollbarPaintOffset and
setLocalTransformSpace.

[Xianzhu, 2016/07/22 01:14:05]

Many thanks for the sample CL. Mixed your code into this CL.

 {
-    if (object.isBoxModelObject()) {
-        // TODO(trchen): Eliminate PaintLayer dependency.
-        PaintLayer* layer = toLayoutBoxModelObject(object).layer();
-        if (!layer || !layer->paintsWithTransform(GlobalPaintNormalPhase))
-            return;
+    ObjectPaintProperties* previousProperties = object.objectPaintProperties();
+    typename PropertyNode::Value newPropertyValue;
+    if (!ComputeProperty(object, context, newPropertyValue)) {
+        if (previousProperties)
+            (previousProperties->*Setter)(nullptr);
+        return nullptr;
     }
 
+    PropertyNode* previousPropertyNode = previousProperties ? (previousProperties->*Getter)() : nullptr;
+    if (previousPropertyNode && previousPropertyNode->value() == newPropertyValue) {
+        previousPropertyNode->setParent(contextProperty);
+        contextProperty = previousPropertyNode;
+        return previousPropertyNode;
+    }
+
+    RefPtr<PropertyNode> newPropertyNode = PropertyNode::create(newPropertyValue, contextProperty);
+    contextProperty = newPropertyNode.get();
+    (object.getMutableForPainting().ensureObjectPaintProperties().*Setter)(newPropertyNode.release());
+    return contextProperty;
+}
+
+bool PaintPropertyTreeBuilder::computePaintOffsetTranslation(const LayoutObject& object, PaintPropertyTreeBuilderContext& context, TransformPaintPropertyNode::Value& value)
+{
+    if (!object.isBoxModelObject())
+        return false;
+
+    // TODO(trchen): Eliminate PaintLayer dependency.
+    PaintLayer* layer = toLayoutBoxModelObject(object).layer();
+    if (!layer || !layer->paintsWithTransform(GlobalPaintNormalPhase))
+        return false;
+
     if (context.current.paintOffset == LayoutPoint())
-        return;
+        return false;
 
     // 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 called "subpixel accumulation". For more information, see
     // PaintLayer::subpixelAccumulation() and PaintLayerPainter::paintFragmentByApplyingTransform.
     IntPoint roundedPaintOffset = roundedIntPoint(context.current.paintOffset);
     LayoutPoint fractionalPaintOffset = LayoutPoint(context.current.paintOffset - roundedPaintOffset);
 
-    RefPtr<TransformPaintPropertyNode> paintOffsetTranslation = TransformPaintPropertyNode::create(
-        TransformationMatrix().translate(roundedPaintOffset.x(), roundedPaintOffset.y()),
-        FloatPoint3D(), context.current.transform);
-    context.current.transform = paintOffsetTranslation.get();
+    value.matrix.translate(roundedPaintOffset.x(), roundedPaintOffset.y());
     context.current.paintOffset = fractionalPaintOffset;
-    object.getMutableForPainting().ensureObjectPaintProperties().setPaintOffsetTranslation(paintOffsetTranslation.release());
+    return true;
+}
+
+void PaintPropertyTreeBuilder::updatePaintOffsetTranslation(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
+{
+    updateObjectPaintProperty<
+        TransformPaintPropertyNode,
+        &ObjectPaintProperties::paintOffsetTranslation,
+        &ObjectPaintProperties::setPaintOffsetTranslation,
+        &computePaintOffsetTranslation>(object, context, context.current.transform);
 }
 
 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());
 }
 
-void PaintPropertyTreeBuilder::updateTransform(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
+bool PaintPropertyTreeBuilder::computeTransform(const LayoutObject& object, PaintPropertyTreeBuilderContext& context, TransformPaintPropertyNode::Value& value)
 {
     if (object.isSVG() && !object.isSVGRoot()) {
         // SVG does not use paint offset internally.
         DCHECK(context.current.paintOffset == LayoutPoint());
 
         // FIXME(pdr): Check for the presence of a transform instead of the value. Checking for an
         // identity matrix will cause the property tree structure to change during animations if
         // the animation passes through the identity matrix.
         // FIXME(pdr): Refactor this so all non-root SVG objects use the same transform function.
         const AffineTransform& transform = object.isSVGForeignObject() ? object.localSVGTransform() : object.localToSVGParentTransform();
         if (transform.isIdentity())
-            return;
+            return false;
 
-        // The origin is included in the local transform, so use an empty origin.
-        RefPtr<TransformPaintPropertyNode> svgTransform = TransformPaintPropertyNode::create(
-            transform, FloatPoint3D(0, 0, 0), context.current.transform);
-        context.current.transform = svgTransform.get();
-        object.getMutableForPainting().ensureObjectPaintProperties().setTransform(svgTransform.release());
-        return;
+        value.matrix = transform;
+        // The origin is included in the local transform, so leave origin empty.
+        return true;
     }
 
     const ComputedStyle& style = object.styleRef();
     if (!object.isBox() || !style.hasTransform())
-        return;
+        return false;
 
-    TransformationMatrix matrix;
-    style.applyTransform(matrix, toLayoutBox(object).size(), ComputedStyle::ExcludeTransformOrigin,
+    style.applyTransform(value.matrix, toLayoutBox(object).size(), ComputedStyle::ExcludeTransformOrigin,
         ComputedStyle::IncludeMotionPath, ComputedStyle::IncludeIndependentTransformProperties);
-    RefPtr<TransformPaintPropertyNode> transformNode = TransformPaintPropertyNode::create(
-        matrix, transformOrigin(toLayoutBox(object)), context.current.transform);
-    context.current.transform = transformNode.get();
-    object.getMutableForPainting().ensureObjectPaintProperties().setTransform(transformNode.release());
+    value.origin = transformOrigin(toLayoutBox(object));
+    return true;
+}
+
+void PaintPropertyTreeBuilder::updateTransform(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
+{
+    updateObjectPaintProperty<
+        TransformPaintPropertyNode,
+        &ObjectPaintProperties::transform,
+        &ObjectPaintProperties::setTransform,
+        &computeTransform>(object, context, context.current.transform);
+}
+
+bool PaintPropertyTreeBuilder::computeEffect(const LayoutObject& object, PaintPropertyTreeBuilderContext& context, EffectPaintPropertyNode::Value& value)
+{
+    if (!object.styleRef().hasOpacity())
+        return false;
+
+    value = object.styleRef().opacity();
+    return true;
 }
 
 void PaintPropertyTreeBuilder::updateEffect(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
-    if (!object.styleRef().hasOpacity())
-        return;
-    RefPtr<EffectPaintPropertyNode> effectNode = EffectPaintPropertyNode::create(object.styleRef().opacity(), context.currentEffect);
-    context.currentEffect = effectNode.get();
-    object.getMutableForPainting().ensureObjectPaintProperties().setEffect(effectNode.release());
+    updateObjectPaintProperty<
+        EffectPaintPropertyNode,
+        &ObjectPaintProperties::effect,
+        &ObjectPaintProperties::setEffect,
+        &computeEffect>(object, context, context.currentEffect);
 }
 
-void PaintPropertyTreeBuilder::updateCssClip(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
+bool PaintPropertyTreeBuilder::computeCssClip(const LayoutObject& object, PaintPropertyTreeBuilderContext& context, ClipPaintPropertyNode::Value& value)
 {
     if (!object.hasClip())
-        return;
-    ASSERT(object.canContainAbsolutePositionObjects());
+        return false;
+    DCHECK(object.canContainAbsolutePositionObjects());
 
     // Create clip node for descendants that are not fixed position.
     // We don't have to setup context.absolutePosition.clip here because this object must be
     // a container for absolute position descendants, and will copy from in-flow context later
     // at updateOutOfFlowContext() step.
     LayoutRect clipRect = toLayoutBox(object).clipRect(context.current.paintOffset);
-    RefPtr<ClipPaintPropertyNode> clipNode = ClipPaintPropertyNode::create(
-        context.current.transform,
-        FloatRoundedRect(FloatRect(clipRect)),
-        context.current.clip);
-    context.current.clip = clipNode.get();
-    object.getMutableForPainting().ensureObjectPaintProperties().setCssClip(clipNode.release());
+    value = FloatRoundedRect(FloatRect(clipRect));
+    return true;
+}
+
+void PaintPropertyTreeBuilder::updateCssClip(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
+{
+    if (ClipPaintPropertyNode* node = updateObjectPaintProperty<
+        ClipPaintPropertyNode,
+        &ObjectPaintProperties::cssClip,
+        &ObjectPaintProperties::setCssClip,
+        &computeCssClip>(object, context, context.current.clip))
+        node->setLocalTransformSpace(context.current.transform);
 }
 
 void PaintPropertyTreeBuilder::updateLocalBorderBoxContext(const LayoutObject& object, const PaintPropertyTreeBuilderContext& context)
 {
     // Avoid adding an ObjectPaintProperties for non-boxes to save memory, since we don't need them at the moment.
     if (!object.isBox() && !object.hasLayer())
         return;
 
     std::unique_ptr<ObjectPaintProperties::LocalBorderBoxProperties> borderBoxContext =
         wrapUnique(new ObjectPaintProperties::LocalBorderBoxProperties);
     borderBoxContext->paintOffset = context.current.paintOffset;
     borderBoxContext->propertyTreeState = PropertyTreeState(context.current.transform, context.current.clip, context.currentEffect);
     object.getMutableForPainting().ensureObjectPaintProperties().setLocalBorderBoxProperties(std::move(borderBoxContext));
 }
 
 // TODO(trchen): Remove this once we bake the paint offset into frameRect.
+bool PaintPropertyTreeBuilder::computeScrollbarPaintOffset(const LayoutObject& object, const PaintPropertyTreeBuilderContext& context, TransformPaintPropertyNode::Value& value)
+{
+    IntPoint roundedPaintOffset = roundedIntPoint(context.current.paintOffset);
+    if (roundedPaintOffset == IntPoint())
+        return false;
+
+    if (!object.isBoxModelObject())
+        return false;
+    PaintLayerScrollableArea* scrollableArea = toLayoutBoxModelObject(object).getScrollableArea();
+    if (!scrollableArea)
+        return false;
+    if (!scrollableArea->horizontalScrollbar() && !scrollableArea->verticalScrollbar())
+        return false;
+
+    value.matrix.translate(roundedPaintOffset.x(), roundedPaintOffset.y());
+    return true;
+}
+
+// TODO(trchen): Remove this once we bake the paint offset into frameRect.
 void PaintPropertyTreeBuilder::updateScrollbarPaintOffset(const LayoutObject& object, const PaintPropertyTreeBuilderContext& context)
 {
-    IntPoint roundedPaintOffset = roundedIntPoint(context.current.paintOffset);
-    if (roundedPaintOffset == IntPoint())
+    // This method is almost the same as updateObjectPaintProperty template, except that it doesn't

[pdr., 2016/07/21 21:34:06]

Can you think of a way to use the same update object paint property template
here? Could we pass in a dummy context property?

[Xianzhu, 2016/07/22 01:14:04]

Done.

+    // update any context property.
+    ObjectPaintProperties* previousProperties = object.objectPaintProperties();
+    TransformPaintPropertyNode::Value paintOffset;
+    if (!computeScrollbarPaintOffset(object, context, paintOffset)) {
+        if (previousProperties)
+            (previousProperties->setScrollbarPaintOffset(nullptr));
         return;
+    }
 
-    if (!object.isBoxModelObject())
+    TransformPaintPropertyNode* previousScrollbarPaintOffsetNode = previousProperties ? previousProperties->scrollbarPaintOffset() : nullptr;
+    if (previousScrollbarPaintOffsetNode && previousScrollbarPaintOffsetNode->value() == paintOffset) {
+        previousScrollbarPaintOffsetNode->setParent(context.current.transform);
         return;
-    PaintLayerScrollableArea* scrollableArea = toLayoutBoxModelObject(object).getScrollableArea();
-    if (!scrollableArea)
-        return;
-    if (!scrollableArea->horizontalScrollbar() && !scrollableArea->verticalScrollbar())
-        return;
+    }
 
-    auto paintOffset = TransformationMatrix().translate(roundedPaintOffset.x(), roundedPaintOffset.y());
     object.getMutableForPainting().ensureObjectPaintProperties().setScrollbarPaintOffset(
-        TransformPaintPropertyNode::create(paintOffset, FloatPoint3D(), context.current.transform));
+        TransformPaintPropertyNode::create(paintOffset, context.current.transform));
 }
 
-void PaintPropertyTreeBuilder::updateOverflowClip(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
+bool PaintPropertyTreeBuilder::computeOverflowClip(const LayoutObject& object, PaintPropertyTreeBuilderContext& context, ClipPaintPropertyNode::Value& value)
 {
-    if (!object.isBox())
-        return;
     const LayoutBox& box = toLayoutBox(object);
 
     // The <input> elements can't have contents thus CSS overflow property doesn't apply.
     // However for layout purposes we do generate child layout objects for them, e.g. button label.
     // We should clip the overflow from those children. This is called control clip and we
     // technically treat them like overflow clip.
     LayoutRect clipRect;
     if (box.hasControlClip())
         clipRect = box.controlClipRect(context.current.paintOffset);
     else if (box.hasOverflowClip())
         clipRect = box.overflowClipRect(context.current.paintOffset);
     else
+        return false;
+
+    value = FloatRoundedRect(FloatRect(clipRect));
+    return true;
+}
+
+void PaintPropertyTreeBuilder::updateOverflowClip(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
+{
+    if (!object.isBox())
         return;
+    const LayoutBox& box = toLayoutBox(object);
 
+    // This need to be in top-level block to hold the reference until we finish creating the normal clip node.
     RefPtr<ClipPaintPropertyNode> borderRadiusClip;
-    if (box.styleRef().hasBorderRadius()) {
+    if ((box.hasControlClip() || box.hasOverflowClip()) && box.styleRef().hasBorderRadius()) {
         auto innerBorder = box.styleRef().getRoundedInnerBorderFor(
             LayoutRect(context.current.paintOffset, box.size()));
-        borderRadiusClip = ClipPaintPropertyNode::create(
-            context.current.transform, innerBorder, context.current.clip);
+        borderRadiusClip = ClipPaintPropertyNode::create(context.current.transform, innerBorder, context.current.clip);
+        context.current.clip = borderRadiusClip.get();
     }
 
-    RefPtr<ClipPaintPropertyNode> overflowClip = ClipPaintPropertyNode::create(
-        context.current.transform,
-        FloatRoundedRect(FloatRect(clipRect)),
-        borderRadiusClip ? borderRadiusClip.release() : context.current.clip);
-    context.current.clip = overflowClip.get();
-    object.getMutableForPainting().ensureObjectPaintProperties().setOverflowClip(overflowClip.release());
+    if (ClipPaintPropertyNode* node = updateObjectPaintProperty<
+        ClipPaintPropertyNode,
+        &ObjectPaintProperties::overflowClip,
+        &ObjectPaintProperties::setOverflowClip,
+        &computeOverflowClip>(object, context, context.current.clip))
+        node->setLocalTransformSpace(context.current.transform);
 }
 
 static FloatPoint perspectiveOrigin(const LayoutBox& box)
 {
     const ComputedStyle& style = box.styleRef();
     FloatSize borderBoxSize(box.size());
     return FloatPoint(
         floatValueForLength(style.perspectiveOriginX(), borderBoxSize.width()),
         floatValueForLength(style.perspectiveOriginY(), borderBoxSize.height()));
 }
 
+bool PaintPropertyTreeBuilder::computePerspective(const LayoutObject& object, PaintPropertyTreeBuilderContext& context, TransformPaintPropertyNode::Value& value)
+{
+    const ComputedStyle& style = object.styleRef();
+    if (!object.isBox() || !style.hasPerspective())
+        return false;
+
+    value.matrix.applyPerspective(style.perspective());
+    value.origin = perspectiveOrigin(toLayoutBox(object)) + toLayoutSize(context.current.paintOffset);
+    return true;
+}
+
 void PaintPropertyTreeBuilder::updatePerspective(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
-    const ComputedStyle& style = object.styleRef();
-    if (!object.isBox() || !style.hasPerspective())
-        return;
-
-    RefPtr<TransformPaintPropertyNode> perspective = TransformPaintPropertyNode::create(
-        TransformationMatrix().applyPerspective(style.perspective()),
-        perspectiveOrigin(toLayoutBox(object)) + toLayoutSize(context.current.paintOffset),
-        context.current.transform);
-    context.current.transform = perspective.get();
-    object.getMutableForPainting().ensureObjectPaintProperties().setPerspective(perspective.release());
+    updateObjectPaintProperty<
+        TransformPaintPropertyNode,
+        &ObjectPaintProperties::perspective,
+        &ObjectPaintProperties::setPerspective,
+        &computePerspective>(object, context, context.current.transform);
 }
 
-void PaintPropertyTreeBuilder::updateSvgLocalToBorderBoxTransform(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
+bool PaintPropertyTreeBuilder::computeSvgLocalToBorderBoxTransform(const LayoutObject& object, PaintPropertyTreeBuilderContext& context, TransformPaintPropertyNode::Value& value)
 {
     if (!object.isSVGRoot())
-        return;
+        return false;
 
     AffineTransform transformToBorderBox = SVGRootPainter(toLayoutSVGRoot(object)).transformToPixelSnappedBorderBox(context.current.paintOffset);
 
     // The paint offset is included in |transformToBorderBox| so SVG does not need to handle paint
     // offset internally.
     context.current.paintOffset = LayoutPoint();
 
     if (transformToBorderBox.isIdentity())
-        return;
+        return false;
 
-    RefPtr<TransformPaintPropertyNode> svgLocalToBorderBoxTransform = TransformPaintPropertyNode::create(
-        transformToBorderBox, FloatPoint3D(0, 0, 0), context.current.transform);
-    context.current.transform = svgLocalToBorderBoxTransform.get();
+    value.matrix = transformToBorderBox;
     context.current.paintOffset = LayoutPoint();
-    object.getMutableForPainting().ensureObjectPaintProperties().setSvgLocalToBorderBoxTransform(svgLocalToBorderBoxTransform.release());
+    return true;
 }
 
-void PaintPropertyTreeBuilder::updateScrollTranslation(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
+void PaintPropertyTreeBuilder::updateSvgLocalToBorderBoxTransform(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
+{
+    updateObjectPaintProperty<
+        TransformPaintPropertyNode,
+        &ObjectPaintProperties::svgLocalToBorderBoxTransform,
+        &ObjectPaintProperties::setSvgLocalToBorderBoxTransform,
+        &computeSvgLocalToBorderBoxTransform>(object, context, context.current.transform);
+}
+
+bool PaintPropertyTreeBuilder::computeScrollTranslation(const LayoutObject& object, PaintPropertyTreeBuilderContext& context, TransformPaintPropertyNode::Value& value)
 {
     if (!object.isBoxModelObject() || !object.hasOverflowClip())
-        return;
+        return false;
 
     PaintLayer* layer = toLayoutBoxModelObject(object).layer();
     ASSERT(layer);
     DoubleSize scrollOffset = layer->getScrollableArea()->scrollOffset();
     if (scrollOffset.isZero() && !layer->scrollsOverflow())
-        return;
+        return false;
 
-    RefPtr<TransformPaintPropertyNode> scrollTranslation = TransformPaintPropertyNode::create(
-        TransformationMatrix().translate(-scrollOffset.width(), -scrollOffset.height()),
-        FloatPoint3D(),
-        context.current.transform);
-    context.current.transform = scrollTranslation.get();
-    object.getMutableForPainting().ensureObjectPaintProperties().setScrollTranslation(scrollTranslation.release());
+    value.matrix.translate(-scrollOffset.width(), -scrollOffset.height());
+    return true;
 }
 
-void PaintPropertyTreeBuilder::updateOutOfFlowContext(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
+void PaintPropertyTreeBuilder::updateScrollTranslation(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
+{
+    updateObjectPaintProperty<
+        TransformPaintPropertyNode,
+        &ObjectPaintProperties::scrollTranslation,
+        &ObjectPaintProperties::setScrollTranslation,
+        &computeScrollTranslation>(object, context, context.current.transform);
+}
+
+// Returns true if we need to create a cssClip node for fixed position.
+bool PaintPropertyTreeBuilder::computeOutOfFlowContext(const LayoutObject& object, PaintPropertyTreeBuilderContext& context, ClipPaintPropertyNode::Value& value)
 {
     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()) {
         context.fixedPosition = context.current;
-    } else if (object.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.objectPaintProperties()->cssClip();
+        return false;
+    }
 
-        // Before we actually create anything, check whether in-flow context and fixed-position
-        // context has exactly the same clip. Reuse if possible.
-        if (context.fixedPosition.clip == cssClip->parent()) {
-            context.fixedPosition.clip = cssClip;
-            return;
-        }
+    if (!object.objectPaintProperties() || !object.objectPaintProperties()->cssClip())
+        return false;
 
-        RefPtr<ClipPaintPropertyNode> clipFixedPosition = ClipPaintPropertyNode::create(
-            const_cast<TransformPaintPropertyNode*>(cssClip->localTransformSpace()),
-            cssClip->clipRect(),
-            context.fixedPosition.clip);
-        context.fixedPosition.clip = clipFixedPosition.get();
-        object.getMutableForPainting().ensureObjectPaintProperties().setCssClipFixedPosition(clipFixedPosition.release());
+    // 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.objectPaintProperties()->cssClip();
+
+    // Before we actually create anything, check whether in-flow context and fixed-position
+    // context has exactly the same clip. Reuse if possible.
+    if (context.fixedPosition.clip == cssClip->parent()) {
+        context.fixedPosition.clip = cssClip;
+        return false;
     }
+
+    value = cssClip->clipRect();
+    return true;
+}
+
+void PaintPropertyTreeBuilder::updateOutOfFlowContext(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
+{
+    if (ClipPaintPropertyNode* node = updateObjectPaintProperty<
+        ClipPaintPropertyNode,
+        &ObjectPaintProperties::cssClipFixedPosition,
+        &ObjectPaintProperties::setCssClipFixedPosition,
+        &computeOutOfFlowContext>(object, context, context.fixedPosition.clip))
+        node->setLocalTransformSpace(const_cast<TransformPaintPropertyNode*>(object.objectPaintProperties()->cssClip()->localTransformSpace()));
 }
 
 static void deriveBorderBoxFromContainerContext(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
     if (!object.isBoxModelObject())
         return;
 
     const LayoutBoxModelObject& boxModelObject = toLayoutBoxModelObject(object);
 
     switch (object.styleRef().position()) {
@@ skipping 33 matching lines @@
         if (boxModelObject.isTableCell()) {
             LayoutObject* parentRow = boxModelObject.parent();
             ASSERT(parentRow && parentRow->isTableRow());
             context.current.paintOffset.moveBy(-toLayoutBox(parentRow)->topLeftLocation());
         }
     }
 }
 
 void PaintPropertyTreeBuilder::buildTreeNodes(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
-    object.getMutableForPainting().clearObjectPaintProperties();
-
     if (!object.isBoxModelObject() && !object.isSVG())
         return;
 
     deriveBorderBoxFromContainerContext(object, context);
 
     updatePaintOffsetTranslation(object, context);
     updateTransform(object, context);
     updateEffect(object, context);
     updateCssClip(object, context);
     updateLocalBorderBoxContext(object, context);
     updateScrollbarPaintOffset(object, context);
     updateOverflowClip(object, context);
     // TODO(trchen): Insert flattening transform here, as specified by
     // http://www.w3.org/TR/css3-transforms/#transform-style-property
     updatePerspective(object, context);
     updateSvgLocalToBorderBoxTransform(object, context);
     updateScrollTranslation(object, context);
     updateOutOfFlowContext(object, context);
 }
 
 } // namespace blink