Basic use implementation for MediaStream from Canvas: captureStream()

third_party/WebKit/Source/modules/mediacapturefromelement/CanvasCaptureMediaStream.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CanvasCaptureMediaStream_h
+#define CanvasCaptureMediaStream_h
+
+#include "core/html/canvas/CanvasDrawListener.h"
+#include "modules/mediastream/MediaStream.h"
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class HTMLCanvasElement;
+class WebCanvasCaptureHandler;
+
+class CanvasCaptureMediaStream final : public MediaStream {
+    DEFINE_WRAPPERTYPEINFO();
+    USING_GARBAGE_COLLECTED_MIXIN(CanvasCaptureMediaStream);
+
+public:
+    static CanvasCaptureMediaStream* create(MediaStreamDescriptor*, PassRefPtrWillBeRawPtr<HTMLCanvasElement>, const PassOwnPtr<WebCanvasCaptureHandler>);
+    DECLARE_VIRTUAL_TRACE();
+    HTMLCanvasElement* canvas() const;
+    void requestFrame();
+
+private:
+    CanvasCaptureMediaStream(MediaStreamDescriptor*, PassRefPtrWillBeRawPtr<HTMLCanvasElement>, const PassOwnPtr<WebCanvasCaptureHandler>);
+    RefPtrWillBeMember<HTMLCanvasElement> m_canvasElement;

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

This strong ref implies that the canvas, along with its rendering context, will
be kept alive by CanvasCaptureMediaStream. The spec does not specify this
behavior. I don't think it is necessarily bad to hold a strong ref, but I think
it needs to be clarified in the spec.

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

The spec says that HTMLCanvasElement is a readonly attribute. Would it be ok to
return nullptr for it? I will try to clear it with hta.

+    Member<CanvasDrawListener> m_drawListener;
+};
+
+} // namespace blink
+
+#endif