Add TimedCanvasDrawListener

third_party/WebKit/Source/modules/mediacapturefromelement/HTMLCanvasElementCapture.cpp

 // 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.
 
 #include "config.h"
 #include "modules/mediacapturefromelement/HTMLCanvasElementCapture.h"
 
 #include "core/dom/ExceptionCode.h"
 #include "core/html/HTMLCanvasElement.h"
 #include "modules/mediacapturefromelement/CanvasCaptureMediaStreamTrack.h"
 #include "modules/mediastream/MediaStream.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebCanvasCaptureHandler.h"
 #include "public/platform/WebMediaStream.h"
 #include "public/platform/WebMediaStreamTrack.h"
 
 namespace {
 const double kDefaultFrameRate = 60.0;
 } // anonymous namespace
 
 namespace blink {
 
 MediaStream* HTMLCanvasElementCapture::captureStream(HTMLCanvasElement& element, ExceptionState& exceptionState)
 {
+    return HTMLCanvasElementCapture::captureStream(element, false, 0, exceptionState);
+}
+
+MediaStream* HTMLCanvasElementCapture::captureStream(HTMLCanvasElement& element, double frameRate, ExceptionState& exceptionState)
+{
+    return HTMLCanvasElementCapture::captureStream(element, true, frameRate, exceptionState);
+}
+
+MediaStream* HTMLCanvasElementCapture::captureStream(HTMLCanvasElement& element, bool givenFrameRate, double frameRate, ExceptionState& exceptionState)
+{
     if (!element.originClean()) {
         exceptionState.throwDOMException(SecurityError, "Canvas is not origin-clean.");
         return MediaStream::create(element.executionContext());
     }
 
     WebMediaStreamTrack track;
     WebSize size(element.width(), element.height());
-    OwnPtr<WebCanvasCaptureHandler> handler = adoptPtr(Platform::current()->createCanvasCaptureHandler(size, kDefaultFrameRate, &track));
+    OwnPtr<WebCanvasCaptureHandler> handler;
+    if (givenFrameRate)
+        handler = adoptPtr(Platform::current()->createCanvasCaptureHandler(size, frameRate, &track));
+    else
+        handler = adoptPtr(Platform::current()->createCanvasCaptureHandler(size, kDefaultFrameRate, &track));
     ASSERT(handler);
     if (!handler) {
         exceptionState.throwDOMException(NotSupportedError, "No CanvasCapture handler can be created.");
         return MediaStream::create(element.executionContext());
     }
 
     MediaStreamTrackVector tracks;
-    tracks.append(CanvasCaptureMediaStreamTrack::create(track, &element, handler.release()));
+    if (givenFrameRate)
+        tracks.append(CanvasCaptureMediaStreamTrack::create(track, &element, handler.release(), frameRate));
+    else
+        tracks.append(CanvasCaptureMediaStreamTrack::create(track, &element, handler.release()));

[esprehn, 2015/12/19 03:33:04]

I don't understand why we can't use kDefaultFrameRate here?

[emircan, 2015/12/29 22:57:08]

I need a way to distinguish between captureStream(60) and captureStream() calls.
captureStream(60) should lead to TimedCanvasDrawListener and captureStream()
should lead to AutoCanvasDrawListener. kDefaultFrameRate has nothing to do with
blink side classes or CanvasDrawListeners. 

It is just that the Chrome side VideoCapturerSource interface[0] needs to return
some frame_rate information. I decided to have a single
Platform::current()->createCanvasCaptureHandler() signature and define the
kDefaultFrameRate here, see l.46. I can revisit this later as each
captureStream() mode is introduced.

[0]
https://code.google.com/p/chromium/codesearch#chromium/src/media/base/video_c...

     return MediaStream::create(element.executionContext(), tracks);
 }
 
 } // namespace blink