Add TimedCanvasDrawListener

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

Index: third_party/WebKit/Source/modules/mediacapturefromelement/TimedCanvasDrawListener.cpp
diff --git a/third_party/WebKit/Source/modules/mediacapturefromelement/TimedCanvasDrawListener.cpp b/third_party/WebKit/Source/modules/mediacapturefromelement/TimedCanvasDrawListener.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..a7257c9b84ccebce45c78180dcf33af9cd981620
--- /dev/null
+++ b/third_party/WebKit/Source/modules/mediacapturefromelement/TimedCanvasDrawListener.cpp
@@ -0,0 +1,49 @@
+// 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/TimedCanvasDrawListener.h"
+
+#include "platform/Task.h"
+#include "public/platform/Platform.h"
+#include "public/platform/WebSkImage.h"
+#include "public/platform/WebTaskRunner.h"
+#include "public/platform/WebTraceLocation.h"
+
+namespace blink {
+
+// static
+TimedCanvasDrawListener* TimedCanvasDrawListener::create(const PassOwnPtr<WebCanvasCaptureHandler>& handler, double frameRate)
+{
+    return new TimedCanvasDrawListener(handler, frameRate);
+}
+
+bool TimedCanvasDrawListener::needsNewFrame() const
+{
+    if (m_requestFrame) {
+        return CanvasDrawListener::needsNewFrame();

[esprehn, 2015/12/11 10:38:24]

return m_requestFrame && CanvasDrawListener::needsNewFrame();

[emircan, 2015/12/11 19:25:16]

Done.

+    }
+    return false;
+}
+
+void TimedCanvasDrawListener::sendNewFrame(const WTF::PassRefPtr<SkImage>& image)
+{
+    m_requestFrame = false;
+    Platform::current()->currentThread()->taskRunner()->postDelayedTask(BLINK_FROM_HERE, new Task(bind(&TimedCanvasDrawListener::requestNewFrame, this)), m_frameInterval);

[esprehn, 2015/12/11 10:38:24]

I have to admit this feels suuuper weird. It means we randomly sample the canvas
in a task at the frame interval. I think the spec actually should tell us to
pick the nearest frame boundary that's after that time, so the requestNewFrame
thing should actually do:

setNeedsBeginFrame()

and at the end of the BeginFrame work we should sample the canvas. That gives
you predictable timing for when the canvas is sampled.

This is okay to land for now, but we should probably fix the spec.

[emircan, 2015/12/11 19:25:16]

I totally see your point. I am going to explain it to hta@ to bring it up in the
spec discussion. 

For now, I am changing it such that we are listening every interval. This should
work similar to what you explained.

+    CanvasDrawListener::sendNewFrame(image);
+}
+
+TimedCanvasDrawListener::TimedCanvasDrawListener(const PassOwnPtr<WebCanvasCaptureHandler>& handler, double frameRate)
+    :CanvasDrawListener(handler)

[esprehn, 2015/12/11 10:38:24]

missing space, also lets move this to the top near create

[emircan, 2015/12/11 19:25:16]

Done.

+{
+    m_frameInterval = 1000 / frameRate;
+    m_requestFrame = true;
+}
+
+void TimedCanvasDrawListener::requestNewFrame()
+{
+    m_requestFrame = true;
+}
+
+} // namespace blink