Basic use implementation for MediaStream from Canvas: captureStream()

third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 260 matching lines @@
 {
     if (rect.isEmpty())
         return;
     m_imageBufferIsClear = false;
     clearCopiedImage();
     if (layoutObject())
         layoutObject()->setMayNeedPaintInvalidation();
     m_dirtyRect.unite(rect);
     if (m_context && m_context->is2d() && hasImageBuffer())
         buffer()->didDraw(rect);
+    notifyListenersCanvasChanged();
 }
 
 void HTMLCanvasElement::didFinalizeFrame()
 {
     if (m_dirtyRect.isEmpty())
         return;
 
     // Propagate the m_dirtyRect accumulated so far to the compositor
     // before restarting with a blank dirty rect.
     FloatRect srcRect(0, 0, size().width(), size().height());
@@ skipping 94 matching lines @@
         }
     }
 }
 
 bool HTMLCanvasElement::paintsIntoCanvasBuffer() const
 {
     ASSERT(m_context);
 
     if (!m_context->isAccelerated())
         return true;
-
     if (layoutBox() && layoutBox()->hasAcceleratedCompositing())
         return false;
 
     return true;
 }
 
+void HTMLCanvasElement::notifyListenersCanvasChanged()
+{
+    for (CanvasDrawListener* listener : m_listeners) {
+        if (listener->needsNewFrameCapture()) {
+            SourceImageStatus status;
+            RefPtr<Image> sourceImage = getSourceImageForCanvas(&status, PreferAcceleration);
+            ASSERT(status == NormalSourceImageStatus);

[Justin Novosad, 2015/11/25 02:38:05]

Are you sure about this? I think you should be doing some error handling here.
For example, what if the size of the canvas gets set to zero?

[emircan, 2015/11/26 01:03:52]

Are you refering to ZeroSizeCanvasSourceImageStatus case? Would (status !=
NormalSourceImageStatus) be enough here or I should check other cases as well?

+            listener->setNewFrameCapture(sourceImage->imageForCurrentFrame());

[Justin Novosad, 2015/11/25 02:38:05]

Before sending the new frame, you need to check the origin-clean flag and mute
the track origin-clean is false.

[emircan, 2015/11/26 01:03:52]

I was planning to leave those checks for later as this CL is growing. I am
adding a check here and one in captureStream () method.

+        }
+    }
+}
+
 void HTMLCanvasElement::paint(GraphicsContext* context, const LayoutRect& r)
 {
     // FIXME: crbug.com/438240; there is a bug with the new CSS blending and compositing feature.
     if (!m_context)
         return;
     if (!paintsIntoCanvasBuffer() && !document().printing())
         return;
 
     m_context->paintRenderingResultsToCanvas(FrontBuffer);
     if (hasImageBuffer()) {
@@ skipping 148 matching lines @@
     RefPtr<DOMUint8ClampedArray> imageDataRef(imageData->data());
 
     RefPtr<CanvasAsyncBlobCreator> asyncCreatorRef = CanvasAsyncBlobCreator::create(imageDataRef.release(), encodingMimeType, imageData->size(), callback);
     if (Platform::current()->isThreadedCompositingEnabled() && (encodingMimeType == DefaultMimeType)) {
         asyncCreatorRef->scheduleAsyncBlobCreation(true);
     } else {
         asyncCreatorRef->scheduleAsyncBlobCreation(false, quality);
     }
 }
 
+void HTMLCanvasElement::addListener(CanvasDrawListener* listener)
+{
+    m_listeners.add(listener);
+    notifyListenersCanvasChanged();
+}
+
+void HTMLCanvasElement::removeListener(CanvasDrawListener* listener)
+{
+    m_listeners.remove(listener);
+}
+
 SecurityOrigin* HTMLCanvasElement::securityOrigin() const
 {
     return document().securityOrigin();
 }
 
 bool HTMLCanvasElement::originClean() const
 {
     if (document().settings() && document().settings()->disableReadingFromCanvas())
         return false;
     return m_originClean;
@@ skipping 352 matching lines @@
 {
     return FloatSize(width(), height());
 }
 
 bool HTMLCanvasElement::isOpaque() const
 {
     return m_context && !m_context->hasAlpha();
 }
 
 } // blink