Implement SVG's transform and effect paint property nodes

This patch starts generating transform and effect paint property nodes
for SVG. PaintPropertyTreeBuilder has been changed to walk both
LayoutBoxModelObjects and SVG nodes. The effect node generation is
straightforward, but SVG transform nodes need some svg-specific logic:
  1) SVG does not use paint offset because everything is effectively
     absolutely positioned. The SVG root element now always creates a
     paint offset transform so all children do not need to.
  2) SVG bakes the transform origin into all matrices. We may want to
     refactor this later to support compositor animations.
  3) At the SVG->HTML boundary, out-of-flow and fixed positioning
     data is kept up to date by checking for both xforms and isSVGRoot.

BUG=537409

Review URL: https://codereview.chromium.org/1461223002

Cr-Commit-Position: refs/heads/master@{#361183}

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

@@ -79,21 +79,26 @@ void PaintPropertyTreeBuilder::walk(FrameView& frameView, const PaintPropertyTre
         walk(*layoutView, localContext);
 }
 
-static void deriveBorderBoxFromContainerContext(const LayoutBoxModelObject& object, PaintPropertyTreeBuilderContext& context)
+static void deriveBorderBoxFromContainerContext(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
+    if (!object.isBoxModelObject())
+        return;
+
+    const LayoutBoxModelObject& boxModelObject = toLayoutBoxModelObject(object);
+
     // TODO(trchen): There is some insanity going on with tables. Double check results.
     switch (object.styleRef().position()) {
     case StaticPosition:
         break;
     case RelativePosition:
-        context.paintOffset += object.offsetForInFlowPosition();
+        context.paintOffset += boxModelObject.offsetForInFlowPosition();
         break;
     case AbsolutePosition:
         context.currentTransform = context.transformForOutOfFlowPositioned;
         context.paintOffset = context.paintOffsetForOutOfFlowPositioned;
         break;
     case StickyPosition:
-        context.paintOffset += object.offsetForInFlowPosition();
+        context.paintOffset += boxModelObject.offsetForInFlowPosition();
         break;
     case FixedPosition:
         context.currentTransform = context.transformForFixedPositioned;
@@ -102,14 +107,21 @@ static void deriveBorderBoxFromContainerContext(const LayoutBoxModelObject& obje
     default:
         ASSERT_NOT_REACHED();
     }
-    if (object.isBox())
-        context.paintOffset += toLayoutBox(object).locationOffset();
+    if (boxModelObject.isBox())
+        context.paintOffset += toLayoutBox(boxModelObject).locationOffset();
 }
 
-static PassRefPtr<TransformPaintPropertyNode> createPaintOffsetTranslationIfNeeded(const LayoutBoxModelObject& object, PaintPropertyTreeBuilderContext& context)
+static PassRefPtr<TransformPaintPropertyNode> createPaintOffsetTranslationIfNeeded(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
-    // TODO(trchen): Eliminate PaintLayer dependency.
-    bool shouldCreatePaintOffsetTranslationNode = object.layer() && object.layer()->paintsWithTransform(GlobalPaintNormalPhase);
+    bool shouldCreatePaintOffsetTranslationNode = false;
+    if (object.isSVGRoot()) {
+        // SVG doesn't use paint offset internally so emit a paint offset at the html->svg boundary.
+        shouldCreatePaintOffsetTranslationNode = true;
+    } else if (object.isBoxModelObject()) {
+        // TODO(trchen): Eliminate PaintLayer dependency.
+        PaintLayer* layer = toLayoutBoxModelObject(object).layer();
+        shouldCreatePaintOffsetTranslationNode = layer && layer->paintsWithTransform(GlobalPaintNormalPhase);
+    }
 
     if (context.paintOffset == LayoutPoint() || !shouldCreatePaintOffsetTranslationNode)
         return nullptr;
@@ -132,8 +144,20 @@ static FloatPoint3D transformOrigin(const LayoutBox& box)
         style.transformOriginZ());
 }
 
-static PassRefPtr<TransformPaintPropertyNode> createTransformIfNeeded(const LayoutBoxModelObject& object, PaintPropertyTreeBuilderContext& context)
+static PassRefPtr<TransformPaintPropertyNode> createTransformIfNeeded(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
+    if (object.isSVG() && !object.isSVGRoot()) {
+        const AffineTransform& transform = object.localToParentTransform();
+        if (transform.isIdentity())
+            return nullptr;
+
+        // SVG's transform origin is baked into the localToParentTransform.
+        RefPtr<TransformPaintPropertyNode> newTransformNodeForTransform = TransformPaintPropertyNode::create(
+            transform, FloatPoint3D(0, 0, 0), context.currentTransform);
+        context.currentTransform = newTransformNodeForTransform.get();
+        return newTransformNodeForTransform.release();
+    }
+
     const ComputedStyle& style = object.styleRef();
     if (!object.isBox() || !style.hasTransform())
         return nullptr;
@@ -149,10 +173,10 @@ static PassRefPtr<TransformPaintPropertyNode> createTransformIfNeeded(const Layo
     return newTransformNodeForTransform.release();
 }
 
-static PassRefPtr<EffectPaintPropertyNode> createEffectIfNeeded(const LayoutBoxModelObject& object, PaintPropertyTreeBuilderContext& context)
+static PassRefPtr<EffectPaintPropertyNode> createEffectIfNeeded(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
     const ComputedStyle& style = object.styleRef();
-    if (!object.isBox() || !style.hasOpacity())
+    if (!style.hasOpacity())
         return nullptr;
     RefPtr<EffectPaintPropertyNode> newEffectNode = EffectPaintPropertyNode::create(style.opacity(), context.currentEffect);
     context.currentEffect = newEffectNode.get();
@@ -168,7 +192,7 @@ static FloatPoint perspectiveOrigin(const LayoutBox& box)
         floatValueForLength(style.perspectiveOriginY(), borderBoxSize.height()));
 }
 
-static PassRefPtr<TransformPaintPropertyNode> createPerspectiveIfNeeded(const LayoutBoxModelObject& object, PaintPropertyTreeBuilderContext& context)
+static PassRefPtr<TransformPaintPropertyNode> createPerspectiveIfNeeded(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
     const ComputedStyle& style = object.styleRef();
     if (!object.isBox() || !style.hasPerspective())
@@ -181,12 +205,12 @@ static PassRefPtr<TransformPaintPropertyNode> createPerspectiveIfNeeded(const La
     return newTransformNodeForPerspective.release();
 }
 
-static PassRefPtr<TransformPaintPropertyNode> createScrollTranslationIfNeeded(const LayoutBoxModelObject& object, PaintPropertyTreeBuilderContext& context)
+static PassRefPtr<TransformPaintPropertyNode> createScrollTranslationIfNeeded(const LayoutObject& object, PaintPropertyTreeBuilderContext& context)
 {
-    if (!object.hasOverflowClip())
+    if (!object.isBoxModelObject() || !object.hasOverflowClip())
         return nullptr;
 
-    PaintLayer* layer = object.layer();
+    PaintLayer* layer = toLayoutBoxModelObject(object).layer();
     ASSERT(layer);
     DoubleSize scrollOffset = layer->scrollableArea()->scrollOffset();
     if (scrollOffset.isZero() && !layer->scrollsOverflow())
@@ -199,24 +223,26 @@ static PassRefPtr<TransformPaintPropertyNode> createScrollTranslationIfNeeded(co
     return newTransformNodeForScrollTranslation.release();
 }
 
-static void updateOutOfFlowContext(const LayoutBoxModelObject& object, PaintPropertyTreeBuilderContext& context)
+static void updateOutOfFlowContext(const LayoutObject& object, bool createdNewTransform, PaintPropertyTreeBuilderContext& context)
 {
-    const ComputedStyle& style = object.styleRef();
-    bool hasTransform = object.isBox() && style.hasTransform();
-    if (style.position() != StaticPosition || hasTransform) {
+    // At the html->svg boundary (see: createPaintOffsetTranslationIfNeeded) the currentTransform is
+    // up-to-date for all children of the svg root element. Additionally, inside SVG, all positioning
+    // uses transforms. Therefore, we only need to check createdNewTransform and isSVGRoot() to
+    // ensure out-of-flow and fixed positioning is correct at the svg->html boundary.
+
+    if (object.styleRef().position() != StaticPosition || createdNewTransform || object.isSVGRoot()) {
         context.transformForOutOfFlowPositioned = context.currentTransform;
         context.paintOffsetForOutOfFlowPositioned = context.paintOffset;
     }
-    if (hasTransform) {
+
+    if (createdNewTransform || object.isSVGRoot()) {
         context.transformForFixedPositioned = context.currentTransform;
         context.paintOffsetForFixedPositioned = context.paintOffset;
     }
 }
 
-void PaintPropertyTreeBuilder::walk(LayoutBoxModelObject& object, const PaintPropertyTreeBuilderContext& context)
+void PaintPropertyTreeBuilder::walk(LayoutObject& object, const PaintPropertyTreeBuilderContext& context)
 {
-    ASSERT(object.isBox() != object.isLayoutInline()); // Either or.
-
     PaintPropertyTreeBuilderContext localContext(context);
 
     deriveBorderBoxFromContainerContext(object, localContext);
@@ -225,7 +251,7 @@ void PaintPropertyTreeBuilder::walk(LayoutBoxModelObject& object, const PaintPro
     RefPtr<EffectPaintPropertyNode> newEffectNode = createEffectIfNeeded(object, localContext);
     RefPtr<TransformPaintPropertyNode> newTransformNodeForPerspective = createPerspectiveIfNeeded(object, localContext);
     RefPtr<TransformPaintPropertyNode> newTransformNodeForScrollTranslation = createScrollTranslationIfNeeded(object, localContext);
-    updateOutOfFlowContext(object, localContext);
+    updateOutOfFlowContext(object, newTransformNodeForTransform, localContext);
 
     if (newTransformNodeForPaintOffsetTranslation || newTransformNodeForTransform || newEffectNode || newTransformNodeForPerspective || newTransformNodeForScrollTranslation) {
         OwnPtr<ObjectPaintProperties> updatedPaintProperties = ObjectPaintProperties::create(
@@ -241,15 +267,9 @@ void PaintPropertyTreeBuilder::walk(LayoutBoxModelObject& object, const PaintPro
 
     // TODO(trchen): Walk subframes for LayoutFrame.
 
-    // TODO(trchen): Implement SVG walk.
-    if (object.isSVGRoot()) {
-        return;
-    }
-
     for (LayoutObject* child = object.slowFirstChild(); child; child = child->nextSibling()) {
-        if (child->isText())
-            continue;
-        walk(toLayoutBoxModelObject(*child), localContext);
+        if (child->isBoxModelObject() || child->isSVG())
+            walk(*child, localContext);
     }
 }
 

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

@@ -8,7 +8,7 @@
 namespace blink {
 
 class FrameView;
-class LayoutBoxModelObject;
+class LayoutObject;
 struct PaintPropertyTreeBuilderContext;
 
 // This class walks the whole layout tree, beginning from the root FrameView, across
@@ -23,7 +23,7 @@ public:
 private:
 
     void walk(FrameView&, const PaintPropertyTreeBuilderContext&);
-    void walk(LayoutBoxModelObject&, const PaintPropertyTreeBuilderContext&);
+    void walk(LayoutObject&, const PaintPropertyTreeBuilderContext&);
 };
 
 } // namespace blink