WIP: backface visibility plumbing (not for review)

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 e534ded2b24f23af1db7817f785e0cb248cc34ac..219c007694157f662490c3c689114e0b0f77218c 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
@@ -26,7 +26,9 @@ struct PaintPropertyTreeBuilderContext {
         , clipForOutOfFlowPositioned(nullptr)
         , transformForFixedPositioned(nullptr)
         , clipForFixedPositioned(nullptr)
-        , currentEffect(nullptr) { }
+        , currentEffect(nullptr)
+        , preserving3d(false)
+        , backfaceHidden(false) { }
 
     // The combination of a transform and paint offset describes a linear space.
     // When a layout object recur to its children, the main context is expected to refer
@@ -59,6 +61,9 @@ struct PaintPropertyTreeBuilderContext {
     // DOM descendant is also a stacking context descendant. Therefore, we don't need extra
     // bookkeeping for effect nodes and can generate the effect tree from a DOM-order traversal.
     EffectPaintPropertyNode* currentEffect;
+
+    bool preserving3d;
+    bool backfaceHidden;
 };
 
 void PaintPropertyTreeBuilder::buildPropertyTrees(FrameView& rootFrame)
@@ -322,13 +327,38 @@ PassOwnPtr<ObjectPaintProperties::LocalBorderBoxProperties> recordTreeContextIfN
     recordedContext->properties.transform = context.currentTransform;
     recordedContext->properties.clip = context.currentClip;
     recordedContext->properties.effect = context.currentEffect;
+    recordedContext->properties.backfaceHidden = context.backfaceHidden;
     return recordedContext.release();
 }
 
 void PaintPropertyTreeBuilder::walk(LayoutObject& object, const PaintPropertyTreeBuilderContext& context)
 {
+
+//fprintf(stderr, "walk trees, build propz.\n");
+//if (object.node())
+//    object.node()->showTreeForThisInFlatTree();
+//fprintf(stderr, "layout object %s\n\n", object.node() ? object.node()->nodeName().utf8().data() : "dunno");
+
     PaintPropertyTreeBuilderContext localContext(context);
 
+    fprintf(stderr, "walking into %s, context.preserving3d %d, context.backfaceHidden %d, object.preserves3d %d, object.backfacehidden %d\n",
+        object.debugName().utf8().data(),
+        localContext.preserving3d,
+        localContext.backfaceHidden,
+        object.styleRef().preserves3D(),
+        object.hasHiddenBackface());
+
+    localContext.preserving3d = object.styleRef().preserves3D();
+    if (localContext.preserving3d) {
+        if (object.hasTransformRelatedProperty())
+            localContext.backfaceHidden = object.hasHiddenBackface();
+    } else {
+        //if (object.hasTransformRelatedProperty())
+        localContext.backfaceHidden = false;
+        if (object.hasHiddenBackface())
+            localContext.backfaceHidden = true;
+    }
+
     deriveBorderBoxFromContainerContext(object, localContext);
     RefPtr<TransformPaintPropertyNode> newTransformNodeForPaintOffsetTranslation = createPaintOffsetTranslationIfNeeded(object, localContext);
     RefPtr<TransformPaintPropertyNode> newTransformNodeForTransform = createTransformIfNeeded(object, localContext);