Bug 1398706 - Always create new clip ids in ScrollingLayersHelper if it's inside a mask. r=kats

MozReview-Commit-ID: Hhsbgpqddo1

--HG--
extra : rebase_source : 40507644148da5bfe6ca3dd5f1f438ac9e7e10ff

gfx/layers/wr/ScrollingLayersHelper.cpp

@@ -226,7 +226,7 @@ ScrollingLayersHelper::DefineAndPushChain(const DisplayItemClipChain* aChain,
     // This item in the chain is a no-op, skip over it
     return;
   }
-  if (!clipId) {
+  if (!clipId || aBuilder.HasMaskClip()) {
     // If we don't have a clip id for this chain item yet, define the clip in WR
     // and save the id
     LayoutDeviceRect clip = LayoutDeviceRect::FromAppUnits(
@@ -234,7 +234,9 @@ ScrollingLayersHelper::DefineAndPushChain(const DisplayItemClipChain* aChain,
     nsTArray<wr::WrComplexClipRegion> wrRoundedRects;
     aChain->mClip.ToWrComplexClipRegions(aAppUnitsPerDevPixel, aStackingContext, wrRoundedRects);
     clipId = Some(aBuilder.DefineClip(aStackingContext.ToRelativeLayoutRect(clip), &wrRoundedRects));
-    aCache[aChain] = clipId.value();
+    if (!aBuilder.HasMaskClip()) {
+      aCache[aChain] = clipId.value();
+    }
   }
   // Finally, push the clip onto the WR stack
   MOZ_ASSERT(clipId);

gfx/webrender_bindings/WebRenderAPI.cpp

@@ -622,6 +622,7 @@ WebRenderAPI::RunOnRenderThread(UniquePtr<RendererEvent> aEvent)
 
 DisplayListBuilder::DisplayListBuilder(PipelineId aId,
                                        const wr::LayoutSize& aContentSize)
+  : mMaskClipCount(0)
 {
   MOZ_COUNT_CTOR(DisplayListBuilder);
   mWrState = wr_state_new(aId, aContentSize);
@@ -707,21 +708,25 @@ DisplayListBuilder::DefineClip(const wr::LayoutRect& aClipRect,
 }
 
 void
-DisplayListBuilder::PushClip(const wr::WrClipId& aClipId, bool aRecordInStack)
+DisplayListBuilder::PushClip(const wr::WrClipId& aClipId, bool aMask)
 {
   wr_dp_push_clip(mWrState, aClipId.id);
   WRDL_LOG("PushClip id=%" PRIu64 "\n", mWrState, aClipId.id);
-  if (aRecordInStack) {
+  if (!aMask) {
     mClipIdStack.push_back(aClipId);
+  } else {
+    mMaskClipCount++;
   }
 }
 
 void
-DisplayListBuilder::PopClip(bool aRecordInStack)
+DisplayListBuilder::PopClip(bool aMask)
 {
   WRDL_LOG("PopClip id=%" PRIu64 "\n", mWrState, mClipIdStack.back().id);
-  if (aRecordInStack) {
+  if (!aMask) {
     mClipIdStack.pop_back();
+  } else {
+    mMaskClipCount--;
   }
   wr_dp_pop_clip(mWrState);
 }

gfx/webrender_bindings/WebRenderAPI.h

@@ -226,8 +226,8 @@ public:
   wr::WrClipId DefineClip(const wr::LayoutRect& aClipRect,
                           const nsTArray<wr::WrComplexClipRegion>* aComplex = nullptr,
                           const wr::WrImageMask* aMask = nullptr);
-  void PushClip(const wr::WrClipId& aClipId, bool aRecordInStack = true);
-  void PopClip(bool aRecordInStack = true);
+  void PushClip(const wr::WrClipId& aClipId, bool aMask = false);
+  void PopClip(bool aMask = false);
 
   wr::WrStickyId DefineStickyFrame(const wr::LayoutRect& aContentRect,
                                    const wr::StickySideConstraint* aTop,
@@ -401,6 +401,10 @@ public:
 
   // Try to avoid using this when possible.
   wr::WrState* Raw() { return mWrState; }
+
+  // Return true if the current clip stack has any mask type clip.
+  bool HasMaskClip() { return mMaskClipCount > 0; }
+
 protected:
   wr::WrState* mWrState;
 
@@ -416,6 +420,9 @@ protected:
   // ensure that we don't define a particular scroll layer multiple times.
   std::unordered_map<layers::FrameMetrics::ViewID, Maybe<layers::FrameMetrics::ViewID>> mScrollParents;
 
+  // The number of mask clips that are in the stack.
+  uint32_t mMaskClipCount;
+
   friend class WebRenderAPI;
 };
 

layout/painting/nsDisplayList.cpp

@@ -9155,13 +9155,13 @@ nsDisplayMask::CreateWebRenderCommands(mozilla::wr::DisplayListBuilder& aBuilder
     // Don't record this clip push in aBuilder's internal clip stack, because
     // otherwise any nested ScrollingLayersHelper instances that are created
     // will get confused about which clips are pushed.
-    aBuilder.PushClip(clipId, /*aRecordInStack*/ false);
+    aBuilder.PushClip(clipId, /*aMask*/ true);
   }
 
   nsDisplaySVGEffects::CreateWebRenderCommands(aBuilder, aResources, aSc, aManager, aDisplayListBuilder);
 
   if (mask) {
-    aBuilder.PopClip(/*aRecordInStack*/ false);
+    aBuilder.PopClip(/*aMask*/ true);
   }
 
   return true;