Bug 1167235 - Part 4 - Forward the shutdown notification to CanvasRenderingContext2D. r=Bas

dom/canvas/CanvasRenderingContext2D.cpp

@@ -745,6 +745,36 @@ NS_IMPL_CYCLE_COLLECTION_UNROOT_NATIVE(CanvasPattern, Release)
 
 NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(CanvasPattern, mContext)
 
+class CanvasShutdownObserver final : public nsIObserver
+{
+public:
+  explicit CanvasShutdownObserver(CanvasRenderingContext2D* aCanvas)
+  : mCanvas(aCanvas)
+  {}
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+private:
+  ~CanvasShutdownObserver() {}
+
+  CanvasRenderingContext2D* mCanvas;
+};
+
+NS_IMPL_ISUPPORTS(CanvasShutdownObserver, nsIObserver)
+
+NS_IMETHODIMP
+CanvasShutdownObserver::Observe(nsISupports *aSubject,
+                                const char *aTopic,
+                                const char16_t *aData)
+{
+  if (mCanvas && strcmp(aTopic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) == 0) {
+    mCanvas->OnShutdown();
+    nsContentUtils::UnregisterShutdownObserver(this);
+  }
+
+  return NS_OK;
+}
+
 class CanvasDrawObserver
 {
 public:
@@ -1044,6 +1074,9 @@ CanvasRenderingContext2D::CanvasRenderingContext2D()
 {
   sNumLivingContexts++;
 
+  mShutdownObserver = new CanvasShutdownObserver(this);
+  nsContentUtils::RegisterShutdownObserver(mShutdownObserver);
+
   // The default is to use OpenGL mode
   if (gfxPlatform::GetPlatform()->UseAcceleratedCanvas()) {
     mDrawObserver = new CanvasDrawObserver(this);
@@ -1056,6 +1089,7 @@ CanvasRenderingContext2D::~CanvasRenderingContext2D()
 {
   RemoveDrawObserver();
   RemovePostRefreshObserver();
+  RemoveShutdownObserver();
   Reset();
   // Drop references from all CanvasRenderingContext2DUserData to this context
   for (uint32_t i = 0; i < mUserDatas.Length(); ++i) {
@@ -1148,6 +1182,29 @@ CanvasRenderingContext2D::Reset()
   return NS_OK;
 }
 
+void
+CanvasRenderingContext2D::OnShutdown()
+{
+  mShutdownObserver = nullptr;
+
+  RefPtr<PersistentBufferProvider> provider = mBufferProvider;
+
+  Reset();
+
+  if (provider) {
+    provider->OnShutdown();
+  }
+}
+
+void
+CanvasRenderingContext2D::RemoveShutdownObserver()
+{
+  if (mShutdownObserver) {
+    nsContentUtils::UnregisterShutdownObserver(mShutdownObserver);
+    mShutdownObserver = nullptr;
+  }
+}
+
 void
 CanvasRenderingContext2D::SetStyleFromString(const nsAString& aStr,
                                              Style aWhichStyle)
@@ -1456,6 +1513,13 @@ CanvasRenderingContext2D::RenderingMode
 CanvasRenderingContext2D::EnsureTarget(const gfx::Rect* aCoveredRect,
                                        RenderingMode aRenderingMode)
 {
+  if (AlreadyShutDown()) {
+    gfxCriticalError() << "Attempt to render into a Canvas2d after shutdown.";
+    EnsureErrorTarget();
+    mTarget = sErrorTarget;
+    return aRenderingMode;
+  }
+
   // This would make no sense, so make sure we don't get ourselves in a mess
   MOZ_ASSERT(mRenderingMode != RenderingMode::DefaultBackendMode);
 
@@ -5691,6 +5755,10 @@ void CanvasRenderingContext2D::RemoveDrawObserver()
 PersistentBufferProvider*
 CanvasRenderingContext2D::GetBufferProvider(LayerManager* aManager)
 {
+  if (AlreadyShutDown()) {
+    return nullptr;
+  }
+
   if (mBufferProvider) {
     return mBufferProvider;
   }

dom/canvas/CanvasRenderingContext2D.h

@@ -54,6 +54,7 @@ template<typename T> class Optional;
 struct CanvasBidiProcessor;
 class CanvasRenderingContext2DUserData;
 class CanvasDrawObserver;
+class CanvasShutdownObserver;
 
 /**
  ** CanvasRenderingContext2D
@@ -545,6 +546,7 @@ public:
   // return true and fills in the bound rect if element has a hit region.
   bool GetHitRegionRect(Element* aElement, nsRect& aRect) override;
 
+  void OnShutdown();
 protected:
   nsresult GetImageDataArray(JSContext* aCx, int32_t aX, int32_t aY,
                              uint32_t aWidth, uint32_t aHeight,
@@ -749,6 +751,10 @@ protected:
   CanvasDrawObserver* mDrawObserver;
   void RemoveDrawObserver();
 
+  RefPtr<CanvasShutdownObserver> mShutdownObserver;
+  void RemoveShutdownObserver();
+  bool AlreadyShutDown() const { return !mShutdownObserver; }
+
   /**
     * Flag to avoid duplicate calls to InvalidateFrame. Set to true whenever
     * Redraw is called, reset to false when Render is called.

dom/html/HTMLCanvasElement.cpp

@@ -353,8 +353,7 @@ HTMLCanvasElement::HTMLCanvasElement(already_AddRefed<mozilla::dom::NodeInfo>& a
   : nsGenericHTMLElement(aNodeInfo),
     mResetLayer(true) ,
     mWriteOnly(false)
-{
-}
+{}
 
 HTMLCanvasElement::~HTMLCanvasElement()
 {

gfx/layers/PersistentBufferProvider.cpp

@@ -126,16 +126,7 @@ PersistentBufferProviderShared::~PersistentBufferProviderShared()
     mFwd->GetActiveResourceTracker().RemoveObject(this);
   }
 
-  mDrawTarget = nullptr;
-  if (mBack && mBack->IsLocked()) {
-    mBack->Unlock();
-  }
-  if (mFront && mFront->IsLocked()) {
-    mFront->Unlock();
-  }
-  if (mBuffer && mBuffer->IsLocked()) {
-    mBuffer->Unlock();
-  }
+  Destroy();
 }
 
 already_AddRefed<gfx::DrawTarget>
@@ -276,5 +267,28 @@ PersistentBufferProviderShared::NotifyInactive()
   mBuffer = nullptr;
 }
 
+void
+PersistentBufferProviderShared::Destroy()
+{
+  mSnapshot = nullptr;
+  mDrawTarget = nullptr;
+
+  if (mFront && mFront->IsLocked()) {
+    mFront->Unlock();
+  }
+
+  if (mBack && mBack->IsLocked()) {
+    mBack->Unlock();
+  }
+
+  if (mBuffer && mBuffer->IsLocked()) {
+    mBuffer->Unlock();
+  }
+
+  mFront = nullptr;
+  mBack = nullptr;
+  mBuffer = nullptr;
+}
+
 } // namespace layers
 } // namespace mozilla

gfx/layers/PersistentBufferProvider.h

@@ -60,6 +60,8 @@ public:
   virtual void ReturnSnapshot(already_AddRefed<gfx::SourceSurface> aSnapshot) = 0;
 
   virtual TextureClient* GetTextureClient() { return nullptr; }
+
+  virtual void OnShutdown() {}
 };
 
 
@@ -121,6 +123,8 @@ public:
 
   virtual void NotifyInactive() override;
 
+  virtual void OnShutdown() override { Destroy(); }
+
 protected:
   PersistentBufferProviderShared(gfx::IntSize aSize, gfx::SurfaceFormat aFormat,
                                  CompositableForwarder* aFwd,
@@ -128,6 +132,8 @@ protected:
 
   ~PersistentBufferProviderShared();
 
+  void Destroy();
+
   gfx::IntSize mSize;
   gfx::SurfaceFormat mFormat;
   RefPtr<CompositableForwarder> mFwd;

gfx/layers/client/TextureClient.cpp

@@ -364,6 +364,8 @@ void TextureClient::Destroy(bool aForceSync)
     mActor->Lock();
   }
 
+  mReadLock = nullptr;
+
   CancelWaitFenceHandleOnImageBridge();
   RefPtr<TextureChild> actor = mActor;
   mActor = nullptr;