[SPv2] Respect transform-style in the Blink and cc property trees.

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

Index: third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
index 1d394cb7cd37438feba099574ccad966af718cfb..c643b6c4d462dcffc0244a145769c68e5f550fb8 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
@@ -19,9 +19,27 @@
 
 namespace blink {
 
+namespace {
+
+// Creates a transform node which uses the current rendering context ID and
+// flattening behavior from the tree builder context.
+PassRefPtr<TransformPaintPropertyNode> createTransformNode(
+    const PaintPropertyTreeBuilderContext& context,
+    const TransformationMatrix& matrix,
+    const FloatPoint3D& origin,
+    PassRefPtr<TransformPaintPropertyNode> parent)
+{
+    return TransformPaintPropertyNode::create(
+        matrix, origin, parent,
+        context.current.shouldFlattenInheritedTransform,
+        context.current.renderingContextID);
+}
+
+} // namespace
+
 void PaintPropertyTreeBuilder::buildTreeRootNodes(FrameView& rootFrame, PaintPropertyTreeBuilderContext& context)
 {
-    RefPtr<TransformPaintPropertyNode> transformRoot = TransformPaintPropertyNode::create(TransformationMatrix(), FloatPoint3D(), nullptr);
+    RefPtr<TransformPaintPropertyNode> transformRoot = TransformPaintPropertyNode::create(TransformationMatrix(), FloatPoint3D(), nullptr, true);
     context.current.transform = context.absolutePosition.transform = context.fixedPosition.transform = transformRoot.get();
     rootFrame.setRootTransform(std::move(transformRoot));
 
@@ -42,7 +60,7 @@ void PaintPropertyTreeBuilder::buildTreeNodes(FrameView& frameView, PaintPropert
 
     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);
+    RefPtr<TransformPaintPropertyNode> newTransformNodeForPreTranslation = createTransformNode(context, frameTranslate, FloatPoint3D(), context.current.transform);
 
     FloatRoundedRect contentClip(IntRect(IntPoint(), frameView.visibleContentSize()));
     RefPtr<ClipPaintPropertyNode> newClipNodeForContentClip = ClipPaintPropertyNode::create(newTransformNodeForPreTranslation.get(), contentClip, context.current.clip);
@@ -58,6 +76,8 @@ void PaintPropertyTreeBuilder::buildTreeNodes(FrameView& frameView, PaintPropert
     context.current.transform = newTransformNodeForScrollTranslation.get();
     context.current.paintOffset = LayoutPoint();
     context.current.clip = newClipNodeForContentClip.get();
+    context.current.renderingContextID = 0;
+    context.current.shouldFlattenInheritedTransform = true;
     context.absolutePosition = context.current;
     context.containerForAbsolutePosition = nullptr;
     context.fixedPosition = context.current;
@@ -88,11 +108,13 @@ void PaintPropertyTreeBuilder::updatePaintOffsetTranslation(const LayoutObject&
     IntPoint roundedPaintOffset = roundedIntPoint(context.current.paintOffset);
     LayoutPoint fractionalPaintOffset = LayoutPoint(context.current.paintOffset - roundedPaintOffset);
 
-    RefPtr<TransformPaintPropertyNode> paintOffsetTranslation = TransformPaintPropertyNode::create(
+    RefPtr<TransformPaintPropertyNode> paintOffsetTranslation = createTransformNode(
+        context,
         TransformationMatrix().translate(roundedPaintOffset.x(), roundedPaintOffset.y()),
         FloatPoint3D(), context.current.transform);
     context.current.transform = paintOffsetTranslation.get();
     context.current.paintOffset = fractionalPaintOffset;
+    context.current.shouldFlattenInheritedTransform = false;
     object.getMutableForPainting().ensureObjectPaintProperties().setPaintOffsetTranslation(paintOffsetTranslation.release());
 }
 
@@ -124,20 +146,42 @@ void PaintPropertyTreeBuilder::updateTransform(const LayoutObject& object, Paint
         RefPtr<TransformPaintPropertyNode> svgTransform = TransformPaintPropertyNode::create(
             transform, FloatPoint3D(0, 0, 0), context.current.transform);
         context.current.transform = svgTransform.get();
+        context.current.renderingContextID = 0;
+        context.current.shouldFlattenInheritedTransform = false;
         object.getMutableForPainting().ensureObjectPaintProperties().setTransform(svgTransform.release());
         return;
     }
 
+    if (!object.isBox())
+        return;
     const ComputedStyle& style = object.styleRef();
-    if (!object.isBox() || !style.hasTransform())
+    if (!style.hasTransform() && !style.preserves3D())
         return;
 
     TransformationMatrix matrix;
     style.applyTransform(matrix, toLayoutBox(object).size(), ComputedStyle::ExcludeTransformOrigin,
         ComputedStyle::IncludeMotionPath, ComputedStyle::IncludeIndependentTransformProperties);
+
+    unsigned renderingContextID = context.current.renderingContextID;
+    unsigned renderingContextIDForChildren = 0;
+    bool flattensInheritedTransform = context.current.shouldFlattenInheritedTransform;
+    bool childrenFlattenInheritedTransform = true;
+
+    if (style.preserves3D()) {
+        // If a node with transform-style: preserve-3d does not exist in an
+        // existing rendering context, it establishes a new one.
+        if (!renderingContextID)
+            renderingContextID = PtrHash<const LayoutObject>::hash(&object);
+        renderingContextIDForChildren = renderingContextID;
+        childrenFlattenInheritedTransform = false;

[trchen, 2016/07/19 22:19:42]

Note: transform-style should be respected if and only if a PaintLayer is
created, but let's ignore the little details for now.

[jbroman, 2016/07/20 15:30:56]

Are you asking for a TODO, a bug, or would you like this as-is?

+    }
+
     RefPtr<TransformPaintPropertyNode> transformNode = TransformPaintPropertyNode::create(
-        matrix, transformOrigin(toLayoutBox(object)), context.current.transform);
+        matrix, transformOrigin(toLayoutBox(object)), context.current.transform,
+        flattensInheritedTransform, renderingContextID);
     context.current.transform = transformNode.get();
+    context.current.renderingContextID = renderingContextIDForChildren;
+    context.current.shouldFlattenInheritedTransform = childrenFlattenInheritedTransform;
     object.getMutableForPainting().ensureObjectPaintProperties().setTransform(transformNode.release());
 }
 
@@ -251,11 +295,17 @@ void PaintPropertyTreeBuilder::updatePerspective(const LayoutObject& object, Pai
     if (!object.isBox() || !style.hasPerspective())
         return;
 
-    RefPtr<TransformPaintPropertyNode> perspective = TransformPaintPropertyNode::create(
+    // The perspective node must not flatten (else nothing will get
+    // perspective), but it should still extend the rendering context as most
+    // transform nodes do.
+    RefPtr<TransformPaintPropertyNode> perspective = createTransformNode(
+        context,
         TransformationMatrix().applyPerspective(style.perspective()),
         perspectiveOrigin(toLayoutBox(object)) + toLayoutSize(context.current.paintOffset),
         context.current.transform);
     context.current.transform = perspective.get();
+    context.current.shouldFlattenInheritedTransform = false;
+
     object.getMutableForPainting().ensureObjectPaintProperties().setPerspective(perspective.release());
 }
 
@@ -277,6 +327,8 @@ void PaintPropertyTreeBuilder::updateSvgLocalToBorderBoxTransform(const LayoutOb
         transformToBorderBox, FloatPoint3D(0, 0, 0), context.current.transform);
     context.current.transform = svgLocalToBorderBoxTransform.get();
     context.current.paintOffset = LayoutPoint();
+    context.current.renderingContextID = 0;
+    context.current.shouldFlattenInheritedTransform = false;
     object.getMutableForPainting().ensureObjectPaintProperties().setSvgLocalToBorderBoxTransform(svgLocalToBorderBoxTransform.release());
 }
 
@@ -291,11 +343,13 @@ void PaintPropertyTreeBuilder::updateScrollTranslation(const LayoutObject& objec
     if (scrollOffset.isZero() && !layer->scrollsOverflow())
         return;
 
-    RefPtr<TransformPaintPropertyNode> scrollTranslation = TransformPaintPropertyNode::create(
+    RefPtr<TransformPaintPropertyNode> scrollTranslation = createTransformNode(
+        context,
         TransformationMatrix().translate(-scrollOffset.width(), -scrollOffset.height()),
         FloatPoint3D(),
         context.current.transform);
     context.current.transform = scrollTranslation.get();
+    context.current.shouldFlattenInheritedTransform = false;
     object.getMutableForPainting().ensureObjectPaintProperties().setScrollTranslation(scrollTranslation.release());
 }
 
@@ -399,8 +453,6 @@ void PaintPropertyTreeBuilder::buildTreeNodes(const LayoutObject& object, PaintP
     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);