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
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+ * in the documentation and/or other materials provided with the
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+ * 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
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+ * 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 "core/platform/NotImplemented.h"
+#include "modules/device_orientation/DeviceMotionController.h"
+#include "modules/device_orientation/DeviceMotionData.h"
+#include <public/Platform.h>
+#include <public/WebDeviceMotionData.h>
+
+namespace WebCore {
+
+// static
+DeviceMotionDispatcher& DeviceMotionDispatcher::shared()

[darin (slow to review), 2013/05/23 19:08:09]

nit: "shared()" seems a little awkward for this method name.  it seems like you
want to use a noun (like "instance"?) here.  i'm not sure what the convention in
Blink is if any for methods like this that return a shared instance.

  sharedInstance() ?

[timvolodine, 2013/05/23 19:30:31]

it is a former convention in WebKit, static methods like this should be called
shared().

+{
+    DEFINE_STATIC_LOCAL(DeviceMotionDispatcher, deviceMotionDispatcher, ());
+    return deviceMotionDispatcher;
+}
+
+DeviceMotionDispatcher::DeviceMotionDispatcher()
+{
+}
+
+DeviceMotionDispatcher::~DeviceMotionDispatcher()
+{
+}
+
+void DeviceMotionDispatcher::addController(DeviceMotionController* controller)

[darin (slow to review), 2013/05/23 19:08:09]

just an observation:

you could easily make DeviceMotionController also implement
WebDeviceMotionListener, and then DeviceMotionDispatcher could just support
adding and removing listeners.  i'm not sure if that level of abstraction is
valuable.

[timvolodine, 2013/05/23 19:30:31]

note taken,
doesn't seem to add much functionality though, can explore in a follow-up CL.

+{
+    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.
+    size_t index = m_controllers.find(controller);
+    if (index != notFound)
+        m_controllers[index] = 0;
+}
+
+void DeviceMotionDispatcher::startListening()
+{
+    WebKit::Platform::current()->setDeviceMotionListener(this);
+}
+
+void DeviceMotionDispatcher::stopListening()
+{
+    WebKit::Platform::current()->setDeviceMotionListener(0);
+}
+
+void DeviceMotionDispatcher::didChangeDeviceMotion(const WebKit::WebDeviceMotionData& motion)
+{
+    m_lastDeviceMotionData = DeviceMotionData::create(motion);
+    bool needsPurge = false;
+    for (size_t i = 0; i < m_controllers.size(); ++i) {
+        if (m_controllers[i])
+            m_controllers[i]->didChangeDeviceMotion(m_lastDeviceMotionData.get());
+        else
+            needsPurge = true;
+    }
+
+    if (needsPurge)
+        purgeControllers();
+}
+
+DeviceMotionData* DeviceMotionDispatcher::latestDeviceMotionData()
+{
+    return m_lastDeviceMotionData.get();
+}
+
+void DeviceMotionDispatcher::purgeControllers()
+{
+    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 WebCore