WebKit & WebCore part of the device motion implementation using the platform layer.

Source/Platform/chromium/public/WebDeviceMotionData.h

+/*
+ * 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.
+ */
+
+#ifndef WebDeviceMotionData_h
+#define WebDeviceMotionData_h
+
+#if WEBKIT_IMPLEMENTATION
+namespace WTF { template <typename T> class PassRefPtr; }
+namespace WebCore { class DeviceMotionData; }
+#endif
+
+namespace WebKit {
+
+#pragma pack(push, 1)

[abarth-chromium, 2013/04/23 21:36:26]

Why is this needed?

[timvolodine, 2013/04/24 12:36:03]

Here I am using a similar approach as the Gamepad API. We basically want the
shared memory buffer to be as small as possible.

+
+class WebDeviceMotionData {
+public:
+    WebDeviceMotionData();
+    ~WebDeviceMotionData() { }
+
+    void setAccelerationX(double);
+    void setAccelerationY(double);
+    void setAccelerationZ(double);
+
+    void setAccelerationIncludingGravityX(double);
+    void setAccelerationIncludingGravityY(double);
+    void setAccelerationIncludingGravityZ(double);
+
+    void setRotationRateAlpha(double);
+    void setRotationRateBeta(double);
+    void setRotationRateGamma(double);
+
+#if WEBKIT_IMPLEMENTATION
+    operator WTF::PassRefPtr<WebCore::DeviceMotionData>() const;
+#endif
+
+private:
+    double m_accelerationX;
+    double m_accelerationY;
+    double m_accelerationZ;
+
+    double m_accelerationIncludingGravityX;
+    double m_accelerationIncludingGravityY;
+    double m_accelerationIncludingGravityZ;
+
+    double m_rotationRateAlpha;
+    double m_rotationRateBeta;
+    double m_rotationRateGamma;
+
+    char m_hasAccelerationX : 1;
+    char m_hasAccelerationY : 1;
+    char m_hasAccelerationZ : 1;
+
+    char m_hasAccelerationIncludingGravityX : 1;
+    char m_hasAccelerationIncludingGravityY : 1;
+    char m_hasAccelerationIncludingGravityZ : 1;
+
+    char m_hasRotationRateAlpha : 1;
+    char m_hasRotationRateBeta : 1;
+    char m_hasRotationRateGamma : 1;
+};
+
+#if WEBKIT_IMPLEMENTATION
+COMPILE_ASSERT(sizeof(WebDeviceMotionData) == (9*8 + 2), WebDeviceMotionData_has_wrong_size);

[abarth-chromium, 2013/04/23 21:36:26]

Where does this magic number come from?

[timvolodine, 2013/04/24 12:36:03]

8 doubles + 2 bytes for the bit-packed booleans.

+#endif
+
+#pragma pack(pop)
+
+} // namespace WebKit
+
+#endif // WebDeviceMotionData_h