Bug 1982053 - Don't remove pipelines in offscreen transactions. r=emilio

When the async pipeline of a video is removed or swapped, we change the
display list that references it and remove the video's pipeline.
Unfortunately when we are dealing with an offscreen transaction, the
later can race ahead and cause the pipeline to be removed before it is
un-referenced from the main display list. If anthing triggers a scene
build between the offscreen transaction and the next main transaction,
we get a missing pipeline crash.

This patch fixes it by only pusing destroy operations to the transaction
if it isn't offscreen.

Differential Revision: https://phabricator.services.mozilla.com/D261087

Author: nical

gfx/layers/wr/WebRenderBridgeChild.cpp

@@ -76,6 +76,16 @@ void WebRenderBridgeChild::AddWebRenderParentCommand(
   mParentCommands.AppendElement(aCmd);
 }
 
+void WebRenderBridgeChild::AddWebRenderParentDestroyCommand(
+    const WebRenderParentCommand& aCmd) {
+  mParentDestroyCommands.AppendElement(aCmd);
+}
+
+void WebRenderBridgeChild::MergeWebRenderParentCommands() {
+  mParentCommands.AppendElements(std::move(mParentDestroyCommands));
+  mParentDestroyCommands.Clear();
+}
+
 void WebRenderBridgeChild::BeginTransaction() {
   MOZ_ASSERT(!mDestroyed);
 
@@ -114,6 +124,9 @@ bool WebRenderBridgeChild::EndTransaction(
 
   TimeStamp fwdTime = TimeStamp::Now();
 
+  if (!aRenderOffscreen) {
+    MergeWebRenderParentCommands();
+  }
   aDisplayListData.mCommands = std::move(mParentCommands);
   aDisplayListData.mIdNamespace = mIdNamespace;
 
@@ -151,6 +164,7 @@ void WebRenderBridgeChild::EndEmptyTransaction(
   TimeStamp fwdTime = TimeStamp::Now();
 
   if (aTransactionData) {
+    MergeWebRenderParentCommands();
     aTransactionData->mCommands = std::move(mParentCommands);
   }
 
@@ -175,7 +189,8 @@ void WebRenderBridgeChild::EndEmptyTransaction(
 void WebRenderBridgeChild::ProcessWebRenderParentCommands() {
   MOZ_ASSERT(!mDestroyed);
 
-  if (!mParentCommands.IsEmpty()) {
+  if (HasWebRenderParentCommands()) {
+    MergeWebRenderParentCommands();
     this->SendParentCommands(mIdNamespace, mParentCommands);
     mParentCommands.Clear();
   }
@@ -190,7 +205,8 @@ void WebRenderBridgeChild::AddPipelineIdForCompositable(
 
 void WebRenderBridgeChild::RemovePipelineIdForCompositable(
     const wr::PipelineId& aPipelineId) {
-  AddWebRenderParentCommand(OpRemovePipelineIdForCompositable(aPipelineId));
+  AddWebRenderParentDestroyCommand(
+      OpRemovePipelineIdForCompositable(aPipelineId));
 }
 
 wr::ExternalImageId WebRenderBridgeChild::GetNextExternalImageId() {
@@ -201,7 +217,7 @@ wr::ExternalImageId WebRenderBridgeChild::GetNextExternalImageId() {
 }
 
 void WebRenderBridgeChild::ReleaseTextureOfImage(const wr::ImageKey& aKey) {
-  AddWebRenderParentCommand(OpReleaseTextureOfImage(aKey));
+  AddWebRenderParentDestroyCommand(OpReleaseTextureOfImage(aKey));
 }
 
 struct FontFileDataSink {
@@ -412,7 +428,7 @@ void WebRenderBridgeChild::RemoveTextureFromCompositable(
     return;
   }
 
-  AddWebRenderParentCommand(CompositableOperation(
+  AddWebRenderParentDestroyCommand(CompositableOperation(
       aCompositable->GetIPCHandle(),
       OpRemoveTexture(WrapNotNull(aTexture->GetIPDLActor()))));
 }

gfx/layers/wr/WebRenderBridgeChild.h

@@ -65,7 +65,14 @@ class WebRenderBridgeChild final : public PWebRenderBridgeChild,
   explicit WebRenderBridgeChild(const wr::PipelineId& aPipelineId);
 
   void AddWebRenderParentCommand(const WebRenderParentCommand& aCmd);
-  bool HasWebRenderParentCommands() { return !mParentCommands.IsEmpty(); }
+  /// Similar to AddWebRenderParentCommand, with the exception that ops are not
+  /// picked up by off-screen transactions. Typically useful for operations that
+  /// remove resources and should not be applied before we have un-referenced
+  /// the resources from the main display list.
+  void AddWebRenderParentDestroyCommand(const WebRenderParentCommand& aCmd);
+  bool HasWebRenderParentCommands() {
+    return !mParentCommands.IsEmpty() || !mParentDestroyCommands.IsEmpty();
+  }
 
   void UpdateResources(wr::IpcResourceUpdateQueue& aResources);
   void BeginTransaction();
@@ -190,6 +197,8 @@ class WebRenderBridgeChild final : public PWebRenderBridgeChild,
 
   ~WebRenderBridgeChild();
 
+  void MergeWebRenderParentCommands();
+
   wr::ExternalImageId GetNextExternalImageId();
 
   // CompositableForwarder
@@ -236,6 +245,7 @@ class WebRenderBridgeChild final : public PWebRenderBridgeChild,
 
   nsTArray<OpDestroy> mDestroyedActors;
   nsTArray<WebRenderParentCommand> mParentCommands;
+  nsTArray<WebRenderParentCommand> mParentDestroyCommands;
   nsTHashMap<nsUint64HashKey, CompositableClient*> mCompositables;
   bool mIsInTransaction;
   bool mIsInClearCachedResources;