Fix WebGL context restoration logic. The retry mechanism was broken when the ownership of the WebGr…

Source/platform/graphics/gpu/DrawingBuffer.cpp

 /*
  * Copyright (c) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 63 matching lines @@
 
 private:
     blink::WebGraphicsContext3D* m_context;
     GLenum m_oldActiveTextureUnit;
     Platform3DObject m_oldTextureUnitZeroId;
 };
 
 PassRefPtr<DrawingBuffer> DrawingBuffer::create(PassOwnPtr<blink::WebGraphicsContext3D> context, const IntSize& size, PreserveDrawingBuffer preserve, PassRefPtr<ContextEvictionManager> contextEvictionManager)
 {
     ASSERT(context);
-    Extensions3DUtil extensionsUtil(context.get());
-    bool multisampleSupported = extensionsUtil.supportsExtension("GL_CHROMIUM_framebuffer_multisample")
-        && extensionsUtil.supportsExtension("GL_OES_rgb8_rgba8");
+    OwnPtr<Extensions3DUtil> extensionsUtil = Extensions3DUtil::create(context.get());

[bajones, 2014/04/23 23:52:52]

I wonder if the patch couldn't be made cleaner by:

- Leaving the Extensions3DUtil as it was
- Adding an explicit check for context->makeCurrentContext() at the start of
DrawingBuffer::create (we know it's going to happen anyway)
- Querying "GL_EXT_multisampled_render_to_texture" in DrawingBuffer::create with
all the other extensions and passing it as a bool to drawingBuffer->initialize()
to prevent a second construction on Extensions3DUtil

That said I think the code changes in the CL work as-is, so it's your call.
LGTM.

+    if (!extensionsUtil) {
+        // This might be the first time we notice that the WebGraphicsContext3D is lost.
+        return nullptr;
+    }
+    bool multisampleSupported = extensionsUtil->supportsExtension("GL_CHROMIUM_framebuffer_multisample")
+        && extensionsUtil->supportsExtension("GL_OES_rgb8_rgba8");
     if (multisampleSupported) {
-        extensionsUtil.ensureExtensionEnabled("GL_CHROMIUM_framebuffer_multisample");
-        extensionsUtil.ensureExtensionEnabled("GL_OES_rgb8_rgba8");
+        extensionsUtil->ensureExtensionEnabled("GL_CHROMIUM_framebuffer_multisample");
+        extensionsUtil->ensureExtensionEnabled("GL_OES_rgb8_rgba8");
     }
-    bool packedDepthStencilSupported = extensionsUtil.supportsExtension("GL_OES_packed_depth_stencil");
+    bool packedDepthStencilSupported = extensionsUtil->supportsExtension("GL_OES_packed_depth_stencil");
     if (packedDepthStencilSupported)
-        extensionsUtil.ensureExtensionEnabled("GL_OES_packed_depth_stencil");
+        extensionsUtil->ensureExtensionEnabled("GL_OES_packed_depth_stencil");
 
-    RefPtr<DrawingBuffer> drawingBuffer = adoptRef(new DrawingBuffer(context, multisampleSupported, packedDepthStencilSupported, preserve, contextEvictionManager));
+    RefPtr<DrawingBuffer> drawingBuffer = adoptRef(new DrawingBuffer(context, extensionsUtil.release(), multisampleSupported, packedDepthStencilSupported, preserve, contextEvictionManager));
     if (!drawingBuffer->initialize(size))
         return PassRefPtr<DrawingBuffer>();
     return drawingBuffer.release();
 }
 
 DrawingBuffer::DrawingBuffer(PassOwnPtr<blink::WebGraphicsContext3D> context,
+    PassOwnPtr<Extensions3DUtil> extensionsUtil,
     bool multisampleExtensionSupported,
     bool packedDepthStencilExtensionSupported,
     PreserveDrawingBuffer preserve,
     PassRefPtr<ContextEvictionManager> contextEvictionManager)
     : m_preserveDrawingBuffer(preserve)
     , m_scissorEnabled(false)
     , m_texture2DBinding(0)
     , m_framebufferBinding(0)
     , m_activeTextureUnit(GL_TEXTURE0)
     , m_context(context)
+    , m_extensionsUtil(extensionsUtil)
     , m_size(-1, -1)
     , m_multisampleExtensionSupported(multisampleExtensionSupported)
     , m_packedDepthStencilExtensionSupported(packedDepthStencilExtensionSupported)
     , m_fbo(0)
     , m_colorBuffer(0)
     , m_frontColorBuffer(0)
     , m_depthStencilBuffer(0)
     , m_depthBuffer(0)
     , m_stencilBuffer(0)
     , m_multisampleFBO(0)
@@ skipping 152 matching lines @@
     RefPtr<MailboxInfo> returnMailbox = adoptRef(new MailboxInfo());
     m_context->genMailboxCHROMIUM(returnMailbox->mailbox.name);
     returnMailbox->textureId = textureId;
     returnMailbox->size = m_size;
     m_textureMailboxes.append(returnMailbox);
     return returnMailbox.release();
 }
 
 bool DrawingBuffer::initialize(const IntSize& size)
 {
+    if (!m_context->makeContextCurrent()) {
+        // The new context is lost; it wasn't allocated successfully.
+        // Need to try to restore the context again later.
+        return false;
+    }
+
     m_attributes = m_context->getContextAttributes();
-    Extensions3DUtil extensionsUtil(m_context.get());
 
     if (m_attributes.alpha) {
         m_internalColorFormat = GL_RGBA;
         m_colorFormat = GL_RGBA;
         m_internalRenderbufferFormat = GL_RGBA8_OES;
     } else {
         m_internalColorFormat = GL_RGB;
         m_colorFormat = GL_RGB;
         m_internalRenderbufferFormat = GL_RGB8_OES;
     }
 
     m_context->getIntegerv(GL_MAX_TEXTURE_SIZE, &m_maxTextureSize);
 
     int maxSampleCount = 0;
     m_multisampleMode = None;
     if (m_attributes.antialias && m_multisampleExtensionSupported) {
         m_context->getIntegerv(GL_MAX_SAMPLES_ANGLE, &maxSampleCount);
         m_multisampleMode = ExplicitResolve;
-        if (extensionsUtil.supportsExtension("GL_EXT_multisampled_render_to_texture"))
+        if (m_extensionsUtil->supportsExtension("GL_EXT_multisampled_render_to_texture"))
             m_multisampleMode = ImplicitResolve;
     }
     m_sampleCount = std::min(4, maxSampleCount);
 
     m_fbo = m_context->createFramebuffer();
 
     m_context->bindFramebuffer(GL_FRAMEBUFFER, m_fbo);
     m_colorBuffer = createColorTexture();
     if (m_multisampleMode == ImplicitResolve)
         m_context->framebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_colorBuffer, 0, m_sampleCount);
@@ skipping 614 matching lines @@
     }
 }
 
 void DrawingBuffer::texImage2DResourceSafe(GLenum target, GLint level, GLenum internalformat, GLsizei width, GLsizei height, GLint border, GLenum format, GLenum type, GLint unpackAlignment)
 {
     ASSERT(unpackAlignment == 1 || unpackAlignment == 2 || unpackAlignment == 4 || unpackAlignment == 8);
     m_context->texImage2D(target, level, internalformat, width, height, border, format, type, 0);
 }
 
 } // namespace WebCore