Bug 1395501 - Part1. Store inherited scale in stacking context. r=jrmuizel,kats

MozReview-Commit-ID: 6LsTJa05uFV

gfx/layers/wr/StackingContextHelper.cpp

@@ -14,6 +14,7 @@ namespace layers {
 
 StackingContextHelper::StackingContextHelper()
   : mBuilder(nullptr)
+  , mScale(1.0f, 1.0f)
 {
   // mOrigin remains at 0,0
 }
@@ -24,6 +25,7 @@ StackingContextHelper::StackingContextHelper(const StackingContextHelper& aParen
                                              const Maybe<gfx::Matrix4x4>& aTransform,
                                              const nsTArray<wr::WrFilterOp>& aFilters)
   : mBuilder(&aBuilder)
+  , mScale(1.0f, 1.0f)
 {
   wr::LayoutRect scBounds = aParentSC.ToRelativeLayoutRect(aLayer->BoundsForStackingContext());
   Layer* layer = aLayer->GetLayer();
@@ -48,6 +50,7 @@ StackingContextHelper::StackingContextHelper(const StackingContextHelper& aParen
                                              gfx::Matrix4x4* aTransformPtr,
                                              const nsTArray<wr::WrFilterOp>& aFilters)
   : mBuilder(&aBuilder)
+  , mScale(1.0f, 1.0f)
 {
   wr::LayoutRect scBounds = aParentSC.ToRelativeLayoutRect(aLayer->BoundsForStackingContext());
   if (aTransformPtr) {
@@ -71,7 +74,7 @@ StackingContextHelper::StackingContextHelper(const StackingContextHelper& aParen
                                              nsDisplayListBuilder* aDisplayListBuilder,
                                              nsDisplayItem* aItem,
                                              nsDisplayList* aDisplayList,
-                                             gfx::Matrix4x4Typed<LayerPixel, LayerPixel>* aBoundTransform,
+                                             const gfx::Matrix4x4* aBoundTransform,
                                              uint64_t aAnimationsId,
                                              float* aOpacityPtr,
                                              gfx::Matrix4x4* aTransformPtr,
@@ -80,12 +83,19 @@ StackingContextHelper::StackingContextHelper(const StackingContextHelper& aParen
                                              const gfx::CompositionOp& aMixBlendMode,
                                              bool aBackfaceVisible)
   : mBuilder(&aBuilder)
+  , mScale(1.0f, 1.0f)
 {
   bool is2d = !aTransformPtr || (aTransformPtr->Is2D() && !aPerspectivePtr);
   if (aTransformPtr) {
     mTransform = *aTransformPtr;
   }
 
+  // Compute scale for fallback rendering.
+  gfx::Matrix transform2d;
+  if (aBoundTransform && aBoundTransform->CanDraw2D(&transform2d)) {
+    mScale = transform2d.ScaleFactors(true) * aParentSC.mScale;
+  }
+
   mBuilder->PushStackingContext(wr::LayoutRect(),
                                 aAnimationsId,
                                 aOpacityPtr,

gfx/layers/wr/StackingContextHelper.h

@@ -52,7 +52,7 @@ public:
                         nsDisplayListBuilder* aDisplayListBuilder,
                         nsDisplayItem* aItem,
                         nsDisplayList* aDisplayList,
-                        gfx::Matrix4x4Typed<LayerPixel, LayerPixel>* aBoundTransform,
+                        const gfx::Matrix4x4* aBoundTransform,
                         uint64_t aAnimationsId,
                         float* aOpacityPtr,
                         gfx::Matrix4x4* aTransformPtr,
@@ -86,12 +86,16 @@ public:
   // Same but for points
   wr::LayoutPoint ToRelativeLayoutPoint(const LayerPoint& aPoint) const;
 
+  // Export the inherited scale
+  gfx::Size GetInheritedScale() const { return mScale; }
+
   bool IsBackfaceVisible() const { return mTransform.IsBackfaceVisible(); }
 
 private:
   wr::DisplayListBuilder* mBuilder;
   LayerPoint mOrigin;
   gfx::Matrix4x4 mTransform;
+  gfx::Size mScale;
 };
 
 } // namespace layers

layout/painting/nsDisplayList.cpp

@@ -8063,15 +8063,13 @@ nsDisplayTransform::CreateWebRenderCommands(mozilla::wr::DisplayListBuilder& aBu
     animationsId = 0;
   }
 
-  gfx::Matrix4x4Typed<LayerPixel, LayerPixel> boundTransform = ViewAs<gfx::Matrix4x4Typed<LayerPixel, LayerPixel>>(newTransformMatrix);
-
   nsTArray<mozilla::wr::WrFilterOp> filters;
   StackingContextHelper sc(aSc,
                            aBuilder,
                            aDisplayListBuilder,
                            this,
                            mStoredList.GetChildren(),
-                           &boundTransform,
+                           &newTransformMatrix,
                            animationsId,
                            nullptr,
                            transformForSC,