Implementing promise-based commit for driving OffscreenCanvas animations

third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp

Index: third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
diff --git a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
index e9d8b80cc9189fba180c977637e133fcb0250e3f..f3bf65de590eb62a3ff48a819177f24ec29a8c21 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
@@ -712,34 +712,36 @@ ImageBitmap* WebGLRenderingContextBase::transferToImageBitmapBase(
   return ImageBitmap::create(drawingBuffer()->transferToStaticBitmapImage());
 }
 
-void WebGLRenderingContextBase::commit(ScriptState* scriptState,
-                                       ExceptionState& exceptionState) {
+ScriptPromise WebGLRenderingContextBase::commit(
+    ScriptState* scriptState,
+    ExceptionState& exceptionState) {
   UseCounter::Feature feature = UseCounter::OffscreenCanvasCommitWebGL;
   UseCounter::count(scriptState->getExecutionContext(), feature);
-  if (!getOffscreenCanvas()) {
+  if (!offscreenCanvas()) {
     exceptionState.throwDOMException(InvalidStateError,
                                      "Commit() was called on a rendering "
                                      "context that was not created from an "
                                      "OffscreenCanvas.");
-    return;
+    return exceptionState.reject(scriptState);
   }
   // no HTMLCanvas associated, thrown InvalidStateError
-  if (!getOffscreenCanvas()->hasPlaceholderCanvas()) {
+  if (!offscreenCanvas()->hasPlaceholderCanvas()) {
     exceptionState.throwDOMException(InvalidStateError,
                                      "Commit() was called on a context whose "
                                      "OffscreenCanvas is not associated with a "
                                      "canvas element.");
-    return;
+    return exceptionState.reject(scriptState);
+  }
+  if (!drawingBuffer()) {
+    exceptionState.throwDOMException(InvalidStateError,

[xlai (Olivia), 2016/12/21 19:54:25]

Could you add a subtest to OffscreenCanvas-commit-invalid-call.html to validate
this exception?

[Justin Novosad, 2016/12/21 21:15:40]

That is actually really hard to do because it requires faking  some kind of GPU
set-up failure.  This case is really weird because we are forced to return a
promise, and we can't just return a promise that will never be resolved. I think
I was doing the wrong thing here.  I am changing the code to do a silent commit
instead.

+                                     "WebGL context has no drawing buffer.");
+    return exceptionState.reject(scriptState);
   }
-  if (!drawingBuffer())
-    return;
-  double commitStartTime = WTF::monotonicallyIncreasingTime();
   // TODO(crbug.com/646864): Make commit() work correctly with
   // { preserveDrawingBuffer : true }.
-  getOffscreenCanvas()->getOrCreateFrameDispatcher()->dispatchFrame(
+  return offscreenCanvas()->commit(
       std::move(drawingBuffer()->transferToStaticBitmapImage()),
-      commitStartTime,
-      drawingBuffer()->contextProvider()->isSoftwareRendering());
+      drawingBuffer()->contextProvider()->isSoftwareRendering(), scriptState);
 }
 
 PassRefPtr<Image> WebGLRenderingContextBase::getImage(
@@ -780,7 +782,7 @@ ImageData* WebGLRenderingContextBase::toImageData(SnapshotReason reason) const {
             ->transferToStaticBitmapImage()
             ->imageForCurrentFrame(ColorBehavior::transformToGlobalTarget());
     if (snapshot) {
-      imageData = ImageData::create(this->getOffscreenCanvas()->size());
+      imageData = ImageData::create(this->offscreenCanvas()->size());
       SkImageInfo imageInfo = SkImageInfo::Make(
           this->drawingBufferWidth(), this->drawingBufferHeight(),
           kRGBA_8888_SkColorType, kUnpremul_SkAlphaType);
@@ -7384,8 +7386,8 @@ bool WebGLRenderingContextBase::validateDrawElements(const char* functionName,
 void WebGLRenderingContextBase::dispatchContextLostEvent(TimerBase*) {
   WebGLContextEvent* event = WebGLContextEvent::create(
       EventTypeNames::webglcontextlost, false, true, "");
-  if (getOffscreenCanvas())
-    getOffscreenCanvas()->dispatchEvent(event);
+  if (offscreenCanvas())
+    offscreenCanvas()->dispatchEvent(event);
   else
     canvas()->dispatchEvent(event);
   m_restoreAllowed = event->defaultPrevented();
@@ -7431,9 +7433,8 @@ void WebGLRenderingContextBase::maybeRestoreContext(TimerBase*) {
       toPlatformContextAttributes(creationAttributes(), version());
   Platform::GraphicsInfo glInfo;
   std::unique_ptr<WebGraphicsContext3DProvider> contextProvider;
-  const auto& url = canvas()
-                        ? canvas()->document().topDocument().url()
-                        : getOffscreenCanvas()->getExecutionContext()->url();
+  const auto& url = canvas() ? canvas()->document().topDocument().url()
+                             : offscreenCanvas()->getExecutionContext()->url();
   if (isMainThread()) {
     contextProvider = WTF::wrapUnique(
         Platform::current()->createOffscreenGraphicsContext3DProvider(
@@ -7488,7 +7489,7 @@ void WebGLRenderingContextBase::maybeRestoreContext(TimerBase*) {
   if (canvas())
     canvas()->dispatchEvent(event);
   else
-    getOffscreenCanvas()->dispatchEvent(event);
+    offscreenCanvas()->dispatchEvent(event);
 }
 
 String WebGLRenderingContextBase::ensureNotNull(const String& text) const {
@@ -7614,8 +7615,8 @@ IntSize WebGLRenderingContextBase::clampedCanvasSize() const {
     width = canvas()->width();
     height = canvas()->height();
   } else {
-    width = getOffscreenCanvas()->width();
-    height = getOffscreenCanvas()->height();
+    width = offscreenCanvas()->width();
+    height = offscreenCanvas()->height();
   }
   return IntSize(clamp(width, 1, m_maxViewportDims[0]),
                  clamp(height, 1, m_maxViewportDims[1]));
@@ -7777,7 +7778,7 @@ void WebGLRenderingContextBase::getHTMLOrOffscreenCanvas(
   if (canvas())
     result.setHTMLCanvasElement(canvas());
   else
-    result.setOffscreenCanvas(getOffscreenCanvas());
+    result.setOffscreenCanvas(offscreenCanvas());
 }
 
 }  // namespace blink