Bug 998916 - check the visibility change event to defer the webgl context restore. r=jgilbert,smaug

content/canvas/src/WebGLContext.cpp

@@ -52,6 +52,7 @@
 #include "mozilla/Telemetry.h"
 
 #include "nsIObserverService.h"
+#include "nsIDOMEvent.h"
 #include "mozilla/Services.h"
 #include "mozilla/dom/WebGLRenderingContextBinding.h"
 #include "mozilla/dom/BindingUtils.h"
@@ -71,24 +72,111 @@ using namespace mozilla::gfx;
 using namespace mozilla::gl;
 using namespace mozilla::layers;
 
+WebGLObserver::WebGLObserver(WebGLContext* aContext)
+    : mContext(aContext)
+{
+}
+
+WebGLObserver::~WebGLObserver()
+{
+}
+
+void
+WebGLObserver::Destroy()
+{
+    UnregisterMemoryPressureEvent();
+    UnregisterVisibilityChangeEvent();
+    mContext = nullptr;
+}
+
+void
+WebGLObserver::RegisterVisibilityChangeEvent()
+{
+    if (!mContext) {
+        return;
+    }
+
+    HTMLCanvasElement* canvasElement = mContext->GetCanvas();
+
+    MOZ_ASSERT(canvasElement);
+
+    if (canvasElement) {
+        nsIDocument* document = canvasElement->OwnerDoc();
+
+        document->AddSystemEventListener(NS_LITERAL_STRING("visibilitychange"),
+                                         this,
+                                         true,
+                                         false);
+    }
+}
+
+void
+WebGLObserver::UnregisterVisibilityChangeEvent()
+{
+    if (!mContext) {
+        return;
+    }
+
+    HTMLCanvasElement* canvasElement = mContext->GetCanvas();
+
+    if (canvasElement) {
+        nsIDocument* document = canvasElement->OwnerDoc();
+
+        document->RemoveSystemEventListener(NS_LITERAL_STRING("visibilitychange"),
+                                            this,
+                                            true);
+    }
+}
+
+void
+WebGLObserver::RegisterMemoryPressureEvent()
+{
+    if (!mContext) {
+        return;
+    }
+
+    nsCOMPtr<nsIObserverService> observerService =
+        mozilla::services::GetObserverService();
+
+    MOZ_ASSERT(observerService);
+
+    if (observerService) {
+        observerService->AddObserver(this, "memory-pressure", false);
+    }
+}
+
+void
+WebGLObserver::UnregisterMemoryPressureEvent()
+{
+    if (!mContext) {
+        return;
+    }
+
+    nsCOMPtr<nsIObserverService> observerService =
+        mozilla::services::GetObserverService();
+
+    MOZ_ASSERT(observerService);
+
+    if (observerService) {
+        observerService->RemoveObserver(this, "memory-pressure");
+    }
+}
+
 NS_IMETHODIMP
-WebGLMemoryPressureObserver::Observe(nsISupports* aSubject,
+WebGLObserver::Observe(nsISupports* aSubject,
                        const char* aTopic,
                        const char16_t* aSomeData)
 {
-    if (strcmp(aTopic, "memory-pressure"))
+    if (!mContext || strcmp(aTopic, "memory-pressure")) {
         return NS_OK;
+    }
 
-    bool wantToLoseContext = true;
+    bool wantToLoseContext = mContext->mLoseContextOnMemoryPressure;
 
     if (!mContext->mCanLoseContextInForeground &&
         ProcessPriorityManager::CurrentProcessIsForeground())
     {
         wantToLoseContext = false;
-    } else if (!nsCRT::strcmp(aSomeData,
-                              MOZ_UTF16("heap-minimize")))
-    {
-        wantToLoseContext = mContext->mLoseContextOnHeapMinimize;
     }
 
     if (wantToLoseContext) {
@@ -98,6 +186,26 @@ WebGLMemoryPressureObserver::Observe(nsISupports* aSubject,
     return NS_OK;
 }
 
+NS_IMETHODIMP
+WebGLObserver::HandleEvent(nsIDOMEvent* aEvent)
+{
+    nsAutoString type;
+    aEvent->GetType(type);
+    if (!mContext || !type.EqualsLiteral("visibilitychange")) {
+        return NS_OK;
+    }
+
+    HTMLCanvasElement* canvasElement = mContext->GetCanvas();
+
+    MOZ_ASSERT(canvasElement);
+
+    if (canvasElement && !canvasElement->OwnerDoc()->Hidden()) {
+        mContext->ForceRestoreContext();
+    }
+
+    return NS_OK;
+}
+
 WebGLContextOptions::WebGLContextOptions()
     : alpha(true), depth(true), stencil(false),
       premultipliedAlpha(true), antialias(true),
@@ -177,8 +285,9 @@ WebGLContext::WebGLContext()
     mRunContextLossTimerAgain = false;
     mContextRestorer = do_CreateInstance("@mozilla.org/timer;1");
     mContextStatus = ContextNotLost;
-    mLoseContextOnHeapMinimize = false;
+    mLoseContextOnMemoryPressure = false;
     mCanLoseContextInForeground = true;
+    mRestoreWhenVisible = false;
 
     mAlreadyGeneratedWarnings = 0;
     mAlreadyWarnedAboutFakeVertexAttrib0 = false;
@@ -190,6 +299,9 @@ WebGLContext::WebGLContext()
         mMaxWarnings = 0;
     }
 
+    mContextObserver = new WebGLObserver(this);
+    MOZ_RELEASE_ASSERT(mContextObserver, "Can't alloc WebGLContextObserver");
+
     mLastUseIndex = 0;
 
     InvalidateBufferFetching();
@@ -203,6 +315,8 @@ WebGLContext::WebGLContext()
 
 WebGLContext::~WebGLContext()
 {
+    mContextObserver->Destroy();
+
     DestroyResourcesAndContext();
     WebGLMemoryTracker::RemoveWebGLContext(this);
     TerminateContextLossTimer();
@@ -212,15 +326,7 @@ WebGLContext::~WebGLContext()
 void
 WebGLContext::DestroyResourcesAndContext()
 {
-    if (mMemoryPressureObserver) {
-        nsCOMPtr<nsIObserverService> observerService
-            = mozilla::services::GetObserverService();
-        if (observerService) {
-            observerService->RemoveObserver(mMemoryPressureObserver,
-                                            "memory-pressure");
-        }
-        mMemoryPressureObserver = nullptr;
-    }
+    mContextObserver->UnregisterMemoryPressureEvent();
 
     if (!gl)
         return;
@@ -1281,6 +1387,10 @@ WebGLContext::UpdateContextLossStatus()
         if (mLastLossWasSimulated)
             return;
 
+        // Restore when the app is visible
+        if (mRestoreWhenVisible)
+            return;
+
         ForceRestoreContext();
         return;
     }
@@ -1314,16 +1424,22 @@ WebGLContext::UpdateContextLossStatus()
 }
 
 void
-WebGLContext::ForceLoseContext()
+WebGLContext::ForceLoseContext(bool simulateLosing)
 {
     printf_stderr("WebGL(%p)::ForceLoseContext\n", this);
     MOZ_ASSERT(!IsContextLost());
     mContextStatus = ContextLostAwaitingEvent;
     mContextLostErrorSet = false;
-    mLastLossWasSimulated = false;
 
     // Burn it all!
     DestroyResourcesAndContext();
+    mLastLossWasSimulated = simulateLosing;
+
+    // Register visibility change observer to defer the context restoring.
+    // Restore the context when the app is visible.
+    if (mRestoreWhenVisible && !mLastLossWasSimulated) {
+        mContextObserver->RegisterVisibilityChangeEvent();
+    }
 
     // Queue up a task, since we know the status changed.
     EnqueueUpdateContextLossStatus();
@@ -1336,6 +1452,8 @@ WebGLContext::ForceRestoreContext()
     mContextStatus = ContextLostAwaitingRestore;
     mAllowContextRestore = true; // Hey, you did say 'force'.
 
+    mContextObserver->UnregisterVisibilityChangeEvent();
+
     // Queue up a task, since we know the status changed.
     EnqueueUpdateContextLossStatus();
 }

content/canvas/src/WebGLContext.h

@@ -21,6 +21,7 @@
 #include "mozilla/dom/HTMLCanvasElement.h"
 #include "nsWrapperCache.h"
 #include "nsIObserver.h"
+#include "nsIDOMEventListener.h"
 #include "nsLayoutUtils.h"
 
 #include "GLContextProvider.h"
@@ -60,7 +61,7 @@ class nsIDocShell;
 
 namespace mozilla {
 
-class WebGLMemoryPressureObserver;
+class WebGLObserver;
 class WebGLContextBoundObject;
 class WebGLActiveInfo;
 class WebGLExtensionBase;
@@ -146,7 +147,7 @@ class WebGLContext :
     friend class WebGLExtensionDrawBuffers;
     friend class WebGLExtensionLoseContext;
     friend class WebGLExtensionVertexArray;
-    friend class WebGLMemoryPressureObserver;
+    friend class WebGLObserver;
     friend class WebGLMemoryTracker;
 
     enum {
@@ -917,8 +918,9 @@ protected:
     bool mMinCapability;
     bool mDisableExtensions;
     bool mIsMesa;
-    bool mLoseContextOnHeapMinimize;
+    bool mLoseContextOnMemoryPressure;
     bool mCanLoseContextInForeground;
+    bool mRestoreWhenVisible;
     bool mShouldPresent;
     bool mBackbufferNeedsClear;
     bool mDisableFragHighP;
@@ -1162,7 +1164,7 @@ protected:
                              GLenum type,
                              const GLvoid *data);
 
-    void ForceLoseContext();
+    void ForceLoseContext(bool simulateLosing = false);
     void ForceRestoreContext();
 
     nsTArray<WebGLRefPtr<WebGLTexture> > mBound2DTextures;
@@ -1273,7 +1275,7 @@ protected:
     ForceDiscreteGPUHelperCGL mForceDiscreteGPUHelper;
 #endif
 
-    nsRefPtr<WebGLMemoryPressureObserver> mMemoryPressureObserver;
+    nsRefPtr<WebGLObserver> mContextObserver;
 
 public:
     // console logging helpers
@@ -1371,19 +1373,29 @@ WebGLContext::ValidateObject(const char* info, ObjectType *aObject)
     return ValidateObjectAssumeNonNull(info, aObject);
 }
 
-class WebGLMemoryPressureObserver MOZ_FINAL
+// Listen visibilitychange and memory-pressure event for context lose/restore
+class WebGLObserver MOZ_FINAL
     : public nsIObserver
+    , public nsIDOMEventListener
 {
 public:
     NS_DECL_ISUPPORTS
     NS_DECL_NSIOBSERVER
+    NS_DECL_NSIDOMEVENTLISTENER
 
-  WebGLMemoryPressureObserver(WebGLContext *context)
-    : mContext(context)
-  {}
+    WebGLObserver(WebGLContext* aContext);
+    ~WebGLObserver();
+
+    void Destroy();
+
+    void RegisterVisibilityChangeEvent();
+    void UnregisterVisibilityChangeEvent();
+
+    void RegisterMemoryPressureEvent();
+    void UnregisterMemoryPressureEvent();
 
 private:
-  WebGLContext *mContext;
+    WebGLContext* mContext;
 };
 
 } // namespace mozilla

content/canvas/src/WebGLContextGL.cpp

@@ -3878,8 +3878,7 @@ WebGLContext::LoseContext()
     if (IsContextLost())
         return ErrorInvalidOperation("loseContext: Context is already lost.");
 
-    ForceLoseContext();
-    mLastLossWasSimulated = true;
+    ForceLoseContext(true);
 }
 
 void

content/canvas/src/WebGLContextReporter.cpp

@@ -8,7 +8,7 @@
 
 using namespace mozilla;
 
-NS_IMPL_ISUPPORTS(WebGLMemoryPressureObserver, nsIObserver)
+NS_IMPL_ISUPPORTS(WebGLObserver, nsIObserver)
 
 NS_IMETHODIMP
 WebGLMemoryTracker::CollectReports(nsIHandleReportCallback* aHandleReport,

content/canvas/src/WebGLContextValidate.cpp

@@ -1553,8 +1553,9 @@ WebGLContext::InitAndValidateGL()
 
     mMinCapability = Preferences::GetBool("webgl.min_capability_mode", false);
     mDisableExtensions = Preferences::GetBool("webgl.disable-extensions", false);
-    mLoseContextOnHeapMinimize = Preferences::GetBool("webgl.lose-context-on-heap-minimize", false);
+    mLoseContextOnMemoryPressure = Preferences::GetBool("webgl.lose-context-on-memory-preasure", false);
     mCanLoseContextInForeground = Preferences::GetBool("webgl.can-lose-context-in-foreground", true);
+    mRestoreWhenVisible = Preferences::GetBool("webgl.restore-context-when-visible", true);
 
     if (MinCapabilityMode()) {
       mDisableFragHighP = true;
@@ -1778,19 +1779,13 @@ WebGLContext::InitAndValidateGL()
         VertexAttrib4f(index, 0, 0, 0, 1);
     }
 
-    mMemoryPressureObserver
-        = new WebGLMemoryPressureObserver(this);
-    nsCOMPtr<nsIObserverService> observerService
-        = mozilla::services::GetObserverService();
-    if (observerService) {
-        observerService->AddObserver(mMemoryPressureObserver,
-                                     "memory-pressure",
-                                     false);
-    }
-
     mDefaultVertexArray = WebGLVertexArray::Create(this);
     mDefaultVertexArray->mAttribs.SetLength(mGLMaxVertexAttribs);
     mBoundVertexArray = mDefaultVertexArray;
 
+    if (mLoseContextOnMemoryPressure) {
+        mContextObserver->RegisterMemoryPressureEvent();
+    }
+
     return true;
 }

modules/libpref/src/init/all.js

@@ -3716,8 +3716,9 @@ pref("webgl.msaa-force", false);
 pref("webgl.prefer-16bpp", false);
 pref("webgl.default-no-alpha", false);
 pref("webgl.force-layers-readback", false);
-pref("webgl.lose-context-on-heap-minimize", false);
+pref("webgl.lose-context-on-memory-preasure", false);
 pref("webgl.can-lose-context-in-foreground", true);
+pref("webgl.restore-context-when-visible", true);
 pref("webgl.max-warnings-per-context", 32);
 pref("webgl.enable-draft-extensions", false);
 pref("webgl.enable-privileged-extensions", false);