Implement offscreenCanvas.getContext('webgl') on a worker thread

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 a2bd44a75698135a0d48e9ce905cb3a2a639ccbe..6bc0984e7937d893d17741dd5c32e44adb22fa62 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
+++ b/third_party/WebKit/Source/modules/webgl/WebGLRenderingContextBase.cpp
@@ -66,7 +66,6 @@
 #include "modules/webgl/WebGLCompressedTexturePVRTC.h"
 #include "modules/webgl/WebGLCompressedTextureS3TC.h"
 #include "modules/webgl/WebGLContextAttributeHelpers.h"
-#include "modules/webgl/WebGLContextAttributes.h"
 #include "modules/webgl/WebGLContextEvent.h"
 #include "modules/webgl/WebGLContextGroup.h"
 #include "modules/webgl/WebGLDebugRendererInfo.h"
@@ -79,19 +78,18 @@
 #include "modules/webgl/WebGLRenderbuffer.h"
 #include "modules/webgl/WebGLShader.h"
 #include "modules/webgl/WebGLShaderPrecisionFormat.h"
-#include "modules/webgl/WebGLTexture.h"
 #include "modules/webgl/WebGLUniformLocation.h"
 #include "modules/webgl/WebGLVertexArrayObject.h"
 #include "modules/webgl/WebGLVertexArrayObjectOES.h"
 #include "platform/CheckedInt.h"
 #include "platform/RuntimeEnabledFeatures.h"
+#include "platform/ThreadSafeFunctional.h"
+#include "platform/WaitableEvent.h"
 #include "platform/geometry/IntSize.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/UnacceleratedImageBufferSurface.h"
 #include "platform/graphics/gpu/AcceleratedImageBufferSurface.h"
-#include "platform/graphics/gpu/DrawingBuffer.h"
 #include "public/platform/Platform.h"
-#include "public/platform/WebGraphicsContext3DProvider.h"
 #include "public/platform/functional/WebFunction.h"
 #include "wtf/Functional.h"
 #include "wtf/PassOwnPtr.h"
@@ -108,19 +106,24 @@ namespace {
 const double secondsBetweenRestoreAttempts = 1.0;
 const int maxGLErrorsAllowedToConsole = 256;
 const unsigned maxGLActiveContexts = 16;
+const unsigned maxGLActiveContextsOnWorker = 4;
 
 using WebGLRenderingContextBaseSet = PersistentHeapHashSet<WeakMember<WebGLRenderingContextBase>>;
 WebGLRenderingContextBaseSet& activeContexts()
 {
-    DEFINE_STATIC_LOCAL(WebGLRenderingContextBaseSet, activeContexts, ());
-    return activeContexts;
+    DEFINE_THREAD_SAFE_STATIC_LOCAL(ThreadSpecific<WebGLRenderingContextBaseSet>, activeContexts, new ThreadSpecific<WebGLRenderingContextBaseSet>());
+    if (!activeContexts.isSet())
+        activeContexts->registerAsStaticReference();
+    return *activeContexts;
 }
 
 using WebGLRenderingContextBaseMap = PersistentHeapHashMap<WeakMember<WebGLRenderingContextBase>, int>;
 WebGLRenderingContextBaseMap& forciblyEvictedContexts()
 {
-    DEFINE_STATIC_LOCAL(WebGLRenderingContextBaseMap, forciblyEvictedContexts, ());
-    return forciblyEvictedContexts;
+    DEFINE_THREAD_SAFE_STATIC_LOCAL(ThreadSpecific<WebGLRenderingContextBaseMap>, forciblyEvictedContexts, new ThreadSpecific<WebGLRenderingContextBaseMap>());
+    if (!forciblyEvictedContexts.isSet())
+        forciblyEvictedContexts->registerAsStaticReference();
+    return *forciblyEvictedContexts;
 }
 
 } // namespace
@@ -190,8 +193,13 @@ WebGLRenderingContextBase* WebGLRenderingContextBase::oldestEvictedContext()
 
 void WebGLRenderingContextBase::activateContext(WebGLRenderingContextBase* context)
 {
+    unsigned maxGLContexts;

[sof, 2016/05/07 07:21:42]

Could you create a local method for this next to where
maxGLActiveContextsOnWorker is defined & declared?

+    if (isMainThread())
+        maxGLContexts = maxGLActiveContexts;
+    else
+        maxGLContexts = maxGLActiveContextsOnWorker;
     unsigned removedContexts = 0;
-    while (activeContexts().size() >= maxGLActiveContexts && removedContexts < maxGLActiveContexts) {
+    while (activeContexts().size() >= maxGLContexts && removedContexts < maxGLContexts) {
         forciblyLoseOldestContext("WARNING: Too many active WebGL contexts. Oldest context will be lost.");
         removedContexts++;
     }
@@ -223,8 +231,13 @@ void WebGLRenderingContextBase::willDestroyContext(WebGLRenderingContextBase* co
     ASSERT(!forciblyEvictedContexts().contains(context));
     ASSERT(!activeContexts().contains(context));
 
+    unsigned maxGLContexts;
+    if (isMainThread())
+        maxGLContexts = maxGLActiveContexts;
+    else
+        maxGLContexts = maxGLActiveContextsOnWorker;
     // Try to re-enable the oldest inactive contexts.
-    while (activeContexts().size() < maxGLActiveContexts && forciblyEvictedContexts().size()) {
+    while (activeContexts().size() < maxGLContexts && forciblyEvictedContexts().size()) {
         WebGLRenderingContextBase* evictedContext = oldestEvictedContext();
         if (!evictedContext->m_restoreAllowed) {
             forciblyEvictedContexts().remove(evictedContext);
@@ -520,17 +533,38 @@ static String extractWebGLContextCreationError(const Platform::GraphicsInfo& inf
     return statusMessage;
 }
 
-static PassOwnPtr<WebGraphicsContext3DProvider> createWebGraphicsContext3DProviderInternal(HTMLCanvasElement* canvas, ScriptState* scriptState, WebGLContextAttributes attributes, unsigned webGLVersion)
+void WebGLRenderingContextBase::createContextProviderOnMainThread(WebGLRenderingContextBase::ContextProviderCreationInfo* creationInfo, WaitableEvent* waitableEvent)
+{
+    ASSERT(isMainThread());
+    Platform::GraphicsInfo glInfo = creationInfo->glInfo();
+    OwnPtr<WebGraphicsContext3DProvider> provider = adoptPtr(Platform::current()->createOffscreenGraphicsContext3DProvider(
+        creationInfo->contextAttributes(), creationInfo->scriptState()->getExecutionContext()->url(), 0, &glInfo, Platform::DoNotBindToCurrentThread));
+    creationInfo->setContextProvider(provider.release());
+    waitableEvent->signal();
+}
+
+PassOwnPtr<WebGraphicsContext3DProvider> WebGLRenderingContextBase::createContextProviderInternal(HTMLCanvasElement* canvas, ScriptState* scriptState, WebGLContextAttributes attributes, unsigned webGLVersion)
 {
     Platform::ContextAttributes contextAttributes = toPlatformContextAttributes(attributes, webGLVersion);
     Platform::GraphicsInfo glInfo;
     OwnPtr<WebGraphicsContext3DProvider> contextProvider;
     if (canvas) {
         contextProvider = adoptPtr(Platform::current()->createOffscreenGraphicsContext3DProvider(
-            contextAttributes, canvas->document().topDocument().url(), 0, &glInfo));
+            contextAttributes, canvas->document().topDocument().url(), 0, &glInfo, Platform::BindToCurrentThread));
     } else {
-        contextProvider = adoptPtr(Platform::current()->createOffscreenGraphicsContext3DProvider(
-            contextAttributes, scriptState->getExecutionContext()->url(), 0, &glInfo));
+        if (isMainThread()) {
+            contextProvider = adoptPtr(Platform::current()->createOffscreenGraphicsContext3DProvider(
+                contextAttributes, scriptState->getExecutionContext()->url(), 0, &glInfo, Platform::BindToCurrentThread));
+        } else {
+            WaitableEvent waitableEvent;

[sof, 2016/05/07 07:21:42]

Could you abstract this out as createContextProviderFromWorkerThread()? All the
scaffolding code around posting this task obscures reading.

Is it acceptable for this creation operation to be synchronous, or does that
aspect merit a TODO?

[xidachen, 2016/05/07 17:07:48]

Yes, it is definitely a future work to make this asynchronous. I put a TODO
comment here.

+            WebTaskRunner* taskRunner = Platform::current()->mainThread()->getWebTaskRunner();
+            OwnPtr<WebGLRenderingContextBase::ContextProviderCreationInfo> creationInfo = adoptPtr(new WebGLRenderingContextBase::ContextProviderCreationInfo(contextAttributes, glInfo, scriptState));
+            taskRunner->postTask(BLINK_FROM_HERE, threadSafeBind(&createContextProviderOnMainThread, AllowCrossThreadAccess(creationInfo.get()), AllowCrossThreadAccess(&waitableEvent)));
+            waitableEvent.wait();
+            contextProvider = creationInfo->releaseContextProvider();
+            if (!contextProvider->BindToCurrentThread())
+                return nullptr;
+        }
     }
     if (!contextProvider || shouldFailContextCreationForTesting) {
         shouldFailContextCreationForTesting = false;
@@ -544,7 +578,6 @@ static PassOwnPtr<WebGraphicsContext3DProvider> createWebGraphicsContext3DProvid
             canvas->dispatchEvent(WebGLContextEvent::create(EventTypeNames::webglcontextcreationerror, false, true, "OES_packed_depth_stencil support is required."));
         return nullptr;
     }
-
     return contextProvider.release();
 }
 
@@ -565,12 +598,12 @@ PassOwnPtr<WebGraphicsContext3DProvider> WebGLRenderingContextBase::createWebGra
         return nullptr;
     }
 
-    return createWebGraphicsContext3DProviderInternal(canvas, nullptr, attributes, webGLVersion);
+    return createContextProviderInternal(canvas, nullptr, attributes, webGLVersion);
 }
 
 PassOwnPtr<WebGraphicsContext3DProvider> WebGLRenderingContextBase::createWebGraphicsContext3DProvider(ScriptState* scriptState, WebGLContextAttributes attributes, unsigned webGLVersion)
 {
-    return createWebGraphicsContext3DProviderInternal(nullptr, scriptState, attributes, webGLVersion);
+    return createContextProviderInternal(nullptr, scriptState, attributes, webGLVersion);
 }
 
 void WebGLRenderingContextBase::forceNextWebGLContextCreationToFail()
@@ -1084,6 +1117,11 @@ WebGLRenderingContextBase::~WebGLRenderingContextBase()
 
     destroyContext();
 
+    if (activeContexts().contains(this))
+        activeContexts().remove(this);
+    if (forciblyEvictedContexts().contains(this))
+        forciblyEvictedContexts().remove(this);
+
     willDestroyContext(this);
 }
 
@@ -5968,7 +6006,7 @@ void WebGLRenderingContextBase::maybeRestoreContext(Timer<WebGLRenderingContextB
     Platform::ContextAttributes attributes = toPlatformContextAttributes(m_requestedAttributes, version());
     Platform::GraphicsInfo glInfo;
     OwnPtr<WebGraphicsContext3DProvider> contextProvider = adoptPtr(Platform::current()->createOffscreenGraphicsContext3DProvider(
-        attributes, canvas()->document().topDocument().url(), 0, &glInfo));
+        attributes, canvas()->document().topDocument().url(), 0, &glInfo, Platform::BindToCurrentThread));
     RefPtr<DrawingBuffer> buffer;
     if (contextProvider) {
         // Construct a new drawing buffer with the new GL context.