Implement the Blink part of the Device Motion API.

Source/modules/device_orientation/DeviceMotionDispatcher.cpp

+/*
+ * Copyright (C) 2013 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "DeviceMotionDispatcher.h"
+
+#include <public/Platform.h>
+#include <public/WebDeviceMotionData.h>
+#include <public/WebDeviceMotionHandler.h>
+#include "modules/device_orientation/DeviceMotionController.h"
+#include "modules/device_orientation/DeviceMotionData.h"
+
+namespace WebCore {
+
+// static
+DeviceMotionDispatcher& DeviceMotionDispatcher::shared()
+{
+    DEFINE_STATIC_LOCAL(DeviceMotionDispatcher, deviceMotionDispatcher, ());
+    return deviceMotionDispatcher;
+}
+
+DeviceMotionDispatcher::DeviceMotionDispatcher()
+{
+}
+
+DeviceMotionDispatcher::~DeviceMotionDispatcher()
+{
+}
+
+void DeviceMotionDispatcher::addController(DeviceMotionController* controller)
+{
+    bool wasEmpty = m_controllers.isEmpty();
+    if (!m_controllers.contains(controller))
+        m_controllers.append(controller);
+    if (wasEmpty)
+        startListening();
+}
+
+void DeviceMotionDispatcher::removeController(DeviceMotionController* controller)
+{
+    // Do not actually remove controller from the vector, instead zero them out.
+    // The zeros are removed after didChangeDeviceMotion has dispatched all events.
+    // This is to prevent re-entrancy case when a controller is destroyed while in the
+    // didChangeDeviceMotion method.

[Peter Beverloo, 2013/05/08 13:15:01]

Can we test this with a layout test?

[timvolodine, 2013/05/09 10:08:28]

I'll try to add this to the tests as abarth commented.

+    size_t index = m_controllers.find(controller);
+    if (index != notFound)
+        m_controllers[index] = 0;
+}
+
+void DeviceMotionDispatcher::startListening()
+{
+    if (WebKit::WebDeviceMotionHandler* handler = WebKit::Platform::current()->deviceMotionHandler())
+        handler->startListeningToDeviceMotion(this);
+}
+
+void DeviceMotionDispatcher::stopListening()
+{
+    if (WebKit::WebDeviceMotionHandler* handler = WebKit::Platform::current()->deviceMotionHandler())
+        handler->stopListeningToDeviceMotion();
+}
+
+void DeviceMotionDispatcher::didChangeDeviceMotion(const WebKit::WebDeviceMotionData& motion)
+{
+    m_lastDeviceMotionData = PassRefPtr<WebCore::DeviceMotionData>(motion);
+    bool needsCompactify = false;

[Peter Beverloo, 2013/05/08 13:15:01]

I'm not thrilled about the "compactify" name.  Can we go with "needsPurge"
instead?  That way, "compactifyControllers" can be named "purgeControllers".

[timvolodine, 2013/05/09 10:08:28]

Done.

+    for (size_t i = 0; i < m_controllers.size(); ++i) {
+        if (m_controllers[i])
+            m_controllers[i]->didChangeDeviceMotion(m_lastDeviceMotionData.get());
+        else
+            needsCompactify = true;
+    }
+
+    if (needsCompactify)
+        compactifyControllers();
+}
+
+DeviceMotionData* DeviceMotionDispatcher::latestDeviceMotionData()
+{
+    return m_lastDeviceMotionData.get();
+}
+
+void DeviceMotionDispatcher::compactifyControllers()
+{
+    size_t i = 0;
+    while (i < m_controllers.size()) {
+        if (!m_controllers[i]) {
+            m_controllers[i] = m_controllers.last();
+            m_controllers.removeLast();
+        } else
+            ++i;
+    }
+
+    if (m_controllers.isEmpty())
+        stopListening();
+}
+
+}  // namespace WebKit

[Peter Beverloo, 2013/05/08 13:15:01]

This comment should read "namespace WebCore" now.

[timvolodine, 2013/05/09 10:08:28]

Done.