Basic use implementation for MediaStream from Canvas: captureStream()

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/CanvasCaptureMediaStream.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 {
+
+CanvasCaptureMediaStream* HTMLCanvasElementCapture::captureStream(HTMLCanvasElement& element, ExceptionState& exceptionState)
+{
+    WebMediaStream stream;
+    stream.initialize(WebVector<WebMediaStreamTrack>(), Vector<WebMediaStreamTrack>());
+    WebSize size(element.width(), element.height());
+
+    if (!element.originClean()) {
+        exceptionState.throwDOMException(SecurityError, "Canvas is not origin-clean.");
+        return CanvasCaptureMediaStream::create(stream, &element);
+    }
+
+    OwnPtr<WebCanvasCaptureHandler> handler = adoptPtr(Platform::current()->createCanvasCaptureHandler(size, kDefaultFrameRate, &stream));
+    ASSERT(handler);
+    if (!handler) {
+        exceptionState.throwDOMException(NotSupportedError, "No CanvasCapture handler can be created.");
+        return CanvasCaptureMediaStream::create(stream, &element);
+    }
+
+    return CanvasCaptureMediaStream::create(stream, &element, handler.release());
+}
+
+} // namespace blink