Bug 1355012 - Add mask layer support for WebRenderDisplayItemLayer. r=kats

gfx/layers/wr/WebRenderCanvasLayer.cpp

@@ -66,7 +66,7 @@ WebRenderCanvasLayer::RenderLayer(wr::DisplayListBuilder& aBuilder)
   gfx::Rect rect = RelativeToVisible(gfx::Rect(0, 0, mBounds.width, mBounds.height));
 
   gfx::Rect clipRect = GetWrClipRect(rect);
-  Maybe<WrImageMask> mask = BuildWrMaskLayer();
+  Maybe<WrImageMask> mask = BuildWrMaskLayer(true);
   WrClipRegion clip = aBuilder.BuildClipRegion(wr::ToWrRect(clipRect), mask.ptrOr(nullptr));
 
   wr::ImageRendering filter = wr::ToImageRendering(mSamplingFilter);

gfx/layers/wr/WebRenderColorLayer.cpp

@@ -24,7 +24,7 @@ WebRenderColorLayer::RenderLayer(wr::DisplayListBuilder& aBuilder)
   gfx::Rect rect = GetWrBoundsRect();
 
   gfx::Rect clipRect = GetWrClipRect(rect);
-  Maybe<WrImageMask> mask = BuildWrMaskLayer();
+  Maybe<WrImageMask> mask = BuildWrMaskLayer(true);
   WrClipRegion clip = aBuilder.BuildClipRegion(wr::ToWrRect(clipRect), mask.ptrOr(nullptr));
 
   wr::MixBlendMode mixBlendMode = wr::ToWrMixBlendMode(GetMixBlendMode());

gfx/layers/wr/WebRenderContainerLayer.cpp

@@ -23,7 +23,7 @@ WebRenderContainerLayer::RenderLayer(wr::DisplayListBuilder& aBuilder)
   gfx::Rect relBounds = GetWrRelBounds();
   gfx::Rect overflow(0, 0, relBounds.width, relBounds.height);
 
-  Maybe<WrImageMask> mask = BuildWrMaskLayer();
+  Maybe<WrImageMask> mask = BuildWrMaskLayer(true);
 
   wr::MixBlendMode mixBlendMode = wr::ToWrMixBlendMode(GetMixBlendMode());
 

gfx/layers/wr/WebRenderDisplayItemLayer.cpp

@@ -22,6 +22,16 @@ WebRenderDisplayItemLayer::RenderLayer(wr::DisplayListBuilder& aBuilder)
     return;
   }
 
+  Maybe<WrImageMask> mask = BuildWrMaskLayer(false);
+  WrImageMask* imageMask = mask.ptrOr(nullptr);
+  if (imageMask) {
+    gfx::Rect rect = TransformedVisibleBoundsRelativeToParent();
+    gfx::Rect overflow(0.0, 0.0, rect.width, rect.height);
+    aBuilder.PushScrollLayer(wr::ToWrRect(rect),
+                             wr::ToWrRect(overflow),
+                             imageMask);
+  }
+
   if (mItem) {
     wr::DisplayListBuilder builder(WrBridge()->GetPipeline());
     // We might have recycled this layer. Throw away the old commands.
@@ -34,6 +44,10 @@ WebRenderDisplayItemLayer::RenderLayer(wr::DisplayListBuilder& aBuilder)
 
   aBuilder.PushBuiltDisplayList(Move(mBuiltDisplayList));
   WrBridge()->AddWebRenderParentCommands(mParentCommands);
+
+  if (imageMask) {
+    aBuilder.PopScrollLayer();
+  }
 }
 
 uint64_t

gfx/layers/wr/WebRenderImageLayer.cpp

@@ -139,7 +139,7 @@ WebRenderImageLayer::RenderLayer(wr::DisplayListBuilder& aBuilder)
   rect = RelativeToVisible(rect);
 
   gfx::Rect clipRect = GetWrClipRect(rect);
-  Maybe<WrImageMask> mask = BuildWrMaskLayer();
+  Maybe<WrImageMask> mask = BuildWrMaskLayer(true);
   WrClipRegion clip = aBuilder.BuildClipRegion(wr::ToWrRect(clipRect), mask.ptrOr(nullptr));
 
   wr::ImageRendering filter = wr::ToImageRendering(mSamplingFilter);

gfx/layers/wr/WebRenderLayerManager.cpp

@@ -103,14 +103,17 @@ WebRenderLayer::TransformedVisibleBoundsRelativeToParent()
 }
 
 Maybe<WrImageMask>
-WebRenderLayer::BuildWrMaskLayer()
+WebRenderLayer::BuildWrMaskLayer(bool aUnapplyLayerTransform)
 {
   if (GetLayer()->GetMaskLayer()) {
     WebRenderLayer* maskLayer = ToWebRenderLayer(GetLayer()->GetMaskLayer());
-    // The size of mask layer is transformed, and we also push the layer transform to wr stacking context.
+    // The size of mask layer is transformed, and we may set the layer transform to wr stacking context.
     // So we should apply inverse transform for mask layer.
-    gfx::Matrix4x4 transform = GetWrBoundTransform();
-    return maskLayer->RenderMaskLayer(transform.Inverse());
+    gfx::Matrix4x4 transform;
+    if (aUnapplyLayerTransform) {
+      transform = GetWrBoundTransform().Inverse();
+    }
+    return maskLayer->RenderMaskLayer(transform);
   }
 
   return Nothing();

gfx/layers/wr/WebRenderLayerManager.h

@@ -59,7 +59,7 @@ protected:
   gfx::Rect GetWrClipRect(gfx::Rect& aRect);
   gfx::Matrix4x4 GetWrBoundTransform();
   void DumpLayerInfo(const char* aLayerType, gfx::Rect& aRect);
-  Maybe<WrImageMask> BuildWrMaskLayer();
+  Maybe<WrImageMask> BuildWrMaskLayer(bool aUnapplyLayerTransform);
 };
 
 class WebRenderLayerManager final : public LayerManager

gfx/layers/wr/WebRenderPaintedLayer.cpp

@@ -189,7 +189,7 @@ WebRenderPaintedLayer::RenderLayer(wr::DisplayListBuilder& aBuilder)
   gfx::Rect rect(0, 0, size.width, size.height);
 
   gfx::Rect clipRect = GetWrClipRect(rect);
-  Maybe<WrImageMask> mask = BuildWrMaskLayer();
+  Maybe<WrImageMask> mask = BuildWrMaskLayer(true);
   WrClipRegion clip = aBuilder.BuildClipRegion(wr::ToWrRect(clipRect), mask.ptrOr(nullptr));
 
   wr::MixBlendMode mixBlendMode = wr::ToWrMixBlendMode(GetMixBlendMode());