Bug 736481 - 2/7 - lose WebGL context on memory-pressure events - r=jgilbert, a=blocking-fennec

content/canvas/src/WebGLContext.cpp

@@ -71,10 +71,25 @@
 #include "mozilla/Preferences.h"
 #include "mozilla/Telemetry.h"
 
+#include "nsIObserverService.h"
+
+
 using namespace mozilla;
 using namespace mozilla::gl;
 using namespace mozilla::layers;
 
+NS_IMPL_ISUPPORTS1(WebGLMemoryPressureObserver, nsIObserver)
+
+NS_IMETHODIMP
+WebGLMemoryPressureObserver::Observe(nsISupports* aSubject,
+                                     const char* aTopic,
+                                     const PRUnichar* aSomeData)
+{
+  if (strcmp(aTopic, "memory-pressure") == 0)
+    mContext->ForceLoseContext();
+  return NS_OK;
+}
+
 
 nsresult NS_NewCanvasRenderingContextWebGL(nsIDOMWebGLRenderingContext** aResult);
 
@@ -172,6 +187,16 @@ WebGLContext::WebGLContext()
     mContextRestorer = do_CreateInstance("@mozilla.org/timer;1");
     mContextStatus = ContextStable;
     mContextLostErrorSet = false;
+
+    nsRefPtr<WebGLMemoryPressureObserver> memoryPressureObserver
+        = new WebGLMemoryPressureObserver(this);
+    nsCOMPtr<nsIObserverService> observerService
+        = mozilla::services::GetObserverService();
+    if (observerService) {
+        observerService->AddObserver(memoryPressureObserver,
+                                     "memory-pressure",
+                                     false);
+    }
 }
 
 WebGLContext::~WebGLContext()

content/canvas/src/WebGLContext.h

@@ -59,6 +59,7 @@
 #include "nsIJSNativeInitializer.h"
 #include "nsContentUtils.h"
 #include "nsWrapperCache.h"
+#include "nsIObserver.h"
 
 #include "GLContextProvider.h"
 #include "Layers.h"
@@ -526,6 +527,7 @@ class WebGLContext :
     friend class WebGLMemoryMultiReporterWrapper;
     friend class WebGLExtensionLoseContext;
     friend class WebGLContextUserData;
+    friend class WebGLMemoryPressureObserver;
 
 public:
     WebGLContext();
@@ -2887,6 +2889,21 @@ class WebGLMemoryMultiReporterWrapper
     }
 };
 
+class WebGLMemoryPressureObserver MOZ_FINAL
+    : public nsIObserver
+{
+public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+
+  WebGLMemoryPressureObserver(WebGLContext *context)
+    : mContext(context)
+  {}
+
+private:
+  WebGLContext *mContext;
+};
+
 }
 
 #endif