Enable WebGL rendering into ImageCHROMIUM, backed by a scanout buffer to enable overlay suppor…

Source/platform/graphics/gpu/DrawingBuffer.cpp

Index: Source/platform/graphics/gpu/DrawingBuffer.cpp
diff --git a/Source/platform/graphics/gpu/DrawingBuffer.cpp b/Source/platform/graphics/gpu/DrawingBuffer.cpp
index 8927cd7eb2ea07757d87929eff452128fe81650e..af0652db00864a5162defd561bb9dd61eef408c2 100644
--- a/Source/platform/graphics/gpu/DrawingBuffer.cpp
+++ b/Source/platform/graphics/gpu/DrawingBuffer.cpp
@@ -32,6 +32,7 @@
 
 #include "platform/graphics/gpu/DrawingBuffer.h"
 
+#include "RuntimeEnabledFeatures.h"
 #include <algorithm>
 #include "platform/TraceEvent.h"
 #include "platform/graphics/GraphicsLayer.h"
@@ -228,7 +229,8 @@ bool DrawingBuffer::prepareMailbox(blink::WebExternalTextureMailbox* outMailbox,
 
     // No buffer available to recycle, create a new one.
     if (!frontColorBufferMailbox) {
-        unsigned newColorBuffer = createColorTexture(m_size);
+        unsigned newColorBuffer = createColorTexture();
+        allocateTextureMemory(newColorBuffer, m_size);
         // Bad things happened, abandon ship.
         if (!newColorBuffer)
             return false;
@@ -262,6 +264,7 @@ bool DrawingBuffer::prepareMailbox(blink::WebExternalTextureMailbox* outMailbox,
     m_context->produceTextureCHROMIUM(GL_TEXTURE_2D, frontColorBufferMailbox->mailbox.name);
     m_context->flush();
     frontColorBufferMailbox->mailbox.syncPoint = m_context->insertSyncPoint();
+    frontColorBufferMailbox->mailbox.allowOverlay = m_textureToImageChromiumMap.find(frontColorBufferMailbox->textureId) != m_textureToImageChromiumMap.end();
     markLayerComposited();
 
     // set m_parentDrawingBuffer to make sure 'this' stays alive as long as it has live mailboxes
@@ -323,7 +326,7 @@ PassRefPtr<DrawingBuffer::MailboxInfo> DrawingBuffer::recycledMailbox()
 
     if (mailboxInfo->size != m_size) {
         m_context->bindTexture(GL_TEXTURE_2D, mailboxInfo->textureId);
-        texImage2DResourceSafe(GL_TEXTURE_2D, 0, m_internalColorFormat, m_size.width(), m_size.height(), 0, m_colorFormat, GL_UNSIGNED_BYTE);
+        allocateTextureMemory(mailboxInfo->textureId, m_size);
         mailboxInfo->size = m_size;
     }
 
@@ -346,6 +349,9 @@ void DrawingBuffer::deleteMailbox(const blink::WebExternalTextureMailbox& mailbo
         if (nameEquals(m_textureMailboxes[i]->mailbox, mailbox)) {
             if (mailbox.syncPoint)
                 m_context->waitSyncPoint(mailbox.syncPoint);
+            if (RuntimeEnabledFeatures::webGLImageChromiumEnabled())
+                deleteChromiumImageForTexture(m_textureMailboxes[i]->textureId);
+
             m_context->deleteTexture(m_textureMailboxes[i]->textureId);
             m_textureMailboxes.remove(i);
             return;
@@ -530,7 +536,8 @@ void DrawingBuffer::paintCompositedResultsToCanvas(ImageBuffer* imageBuffer)
     // We have to make a copy of it here and bind that copy instead.
     // FIXME: That's not true any more, provided we don't change texture
     // parameters.
-    unsigned sourceTexture = createColorTexture(m_size);
+    unsigned sourceTexture = createColorTexture();
+    texImage2DResourceSafe(GL_TEXTURE_2D, 0, m_internalColorFormat, m_size.width(), m_size.height(), 0, m_colorFormat, GL_UNSIGNED_BYTE);
     m_context->copyTextureCHROMIUM(GL_TEXTURE_2D, m_frontColorBuffer, sourceTexture, 0, GL_RGBA, GL_UNSIGNED_BYTE);
 
     // Since we're using the same context as WebGL, we have to restore any state we change (in this case, just the framebuffer binding).
@@ -588,8 +595,12 @@ void DrawingBuffer::beginDestruction()
     if (m_stencilBuffer)
         m_context->deleteRenderbuffer(m_stencilBuffer);
 
-    if (m_colorBuffer)
+    if (m_colorBuffer) {
+        if (RuntimeEnabledFeatures::webGLImageChromiumEnabled())
+            deleteChromiumImageForTexture(m_colorBuffer);
+
         m_context->deleteTexture(m_colorBuffer);
+    }
 
     setSize(IntSize());
 
@@ -607,7 +618,7 @@ void DrawingBuffer::beginDestruction()
         GraphicsLayer::unregisterContentsLayer(m_layer->layer());
 }
 
-unsigned DrawingBuffer::createColorTexture(const IntSize& size)
+unsigned DrawingBuffer::createColorTexture()
 {
     unsigned offscreenColorTexture = m_context->createTexture();
     if (!offscreenColorTexture)
@@ -618,8 +629,6 @@ unsigned DrawingBuffer::createColorTexture(const IntSize& size)
     m_context->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
     m_context->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
     m_context->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-    if (!size.isEmpty())
-        texImage2DResourceSafe(GL_TEXTURE_2D, 0, m_internalColorFormat, size.width(), size.height(), 0, m_colorFormat, GL_UNSIGNED_BYTE);
 
     return offscreenColorTexture;
 }
@@ -641,7 +650,7 @@ bool DrawingBuffer::resizeFramebuffer(const IntSize& size)
 
     m_context->bindTexture(GL_TEXTURE_2D, m_colorBuffer);
 
-    texImage2DResourceSafe(GL_TEXTURE_2D, 0, m_internalColorFormat, size.width(), size.height(), 0, m_colorFormat, GL_UNSIGNED_BYTE);
+    allocateTextureMemory(m_colorBuffer, size);
 
     if (m_multisampleMode == ImplicitResolve)
         m_context->framebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_colorBuffer, 0, m_sampleCount);
@@ -1020,4 +1029,31 @@ void DrawingBuffer::texImage2DResourceSafe(GLenum target, GLint level, GLenum in
     m_context->texImage2D(target, level, internalformat, width, height, border, format, type, 0);
 }
 
+void DrawingBuffer::allocateTextureMemory(Platform3DObject textureId, const IntSize& size)
+{
+    if (RuntimeEnabledFeatures::webGLImageChromiumEnabled()) {
+        deleteChromiumImageForTexture(textureId);
+
+        blink::WGC3Duint newImage = m_context->createImageCHROMIUM(size.width(), size.height(), GL_RGBA8_OES, GC3D_IMAGE_SCANOUT_CHROMIUM);
+        if (newImage) {

[Ken Russell (switch to Gerrit), 2014/05/14 22:11:33]

Under what conditions will createImageCHROMIUM fail? Does the compositor still
render things properly if that happens?

[alexst (slow to review), 2014/05/14 22:29:55]

There may be a limit of memory available to scanout buffers on some hardware,
for example.

But it should fail over gracefully since overlay decisions are made on a per
buffer basis and if no buffer is available above, we'll just make a regular
texture and go on about our business by compositing in GL intead.

+            m_context->bindTexImage2DCHROMIUM(GL_TEXTURE_2D, newImage);
+            m_textureToImageChromiumMap.add(textureId, newImage);

[Ken Russell (switch to Gerrit), 2014/05/14 22:11:33]

The bookkeeping associated with these ImageChromium objects adds more complexity
to already-complex code. Could you think of a way to encapsulate things more?
Maybe add an inner class to DrawingBuffer which would wrap up the texture ID and
any associated ImageChromium object?

[alexst (slow to review), 2014/05/14 22:29:55]

Let me have a look.

+            return;
+        }
+    }
+
+    texImage2DResourceSafe(GL_TEXTURE_2D, 0, m_internalColorFormat, size.width(), size.height(), 0, m_colorFormat, GL_UNSIGNED_BYTE);
+}
+
+void DrawingBuffer::deleteChromiumImageForTexture(Platform3DObject textureId)
+{
+    HashMap<Platform3DObject, blink::WGC3Duint>::iterator imageIter = m_textureToImageChromiumMap.find(textureId);
+    // Release the old buffer if we have any.
+    if (imageIter != m_textureToImageChromiumMap.end()) {
+        m_context->releaseTexImage2DCHROMIUM(GL_TEXTURE_2D, imageIter->value);
+        m_context->destroyImageCHROMIUM(imageIter->value);
+        m_textureToImageChromiumMap.remove(imageIter);
+    }
+}
+
 } // namespace WebCore