Basic use implementation for MediaStream from Canvas: captureStream()

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

Index: third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
index 47dfe4296a9a8aeefa3b9b225774817d354caf02..9791b58fd132a4603ab551f1452a7319dfe03dab 100644
--- a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
@@ -278,6 +278,7 @@ void HTMLCanvasElement::didDraw(const FloatRect& rect)
     m_dirtyRect.unite(rect);
     if (m_context && m_context->is2d() && hasImageBuffer())
         buffer()->didDraw(rect);
+    notifyListenersCanvasChanged();
 }
 
 void HTMLCanvasElement::didFinalizeFrame()
@@ -392,13 +393,24 @@ bool HTMLCanvasElement::paintsIntoCanvasBuffer() const
 
     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.
@@ -567,6 +579,17 @@ void HTMLCanvasElement::toBlob(FileCallback* callback, const String& mimeType, c
     }
 }
 
+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();