Add struct_traits and typemap for blink::WebGamepad

device/gamepad/public/interfaces/gamepad.mojom

Index: device/gamepad/public/interfaces/gamepad.mojom
diff --git a/device/gamepad/public/interfaces/gamepad.mojom b/device/gamepad/public/interfaces/gamepad.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..dc12aab9de905127ce94c1ca66468dc87a77eeef
--- /dev/null
+++ b/device/gamepad/public/interfaces/gamepad.mojom
@@ -0,0 +1,54 @@
+module device.mojom;

[yzshen1, 2016/11/14 21:13:17]

Please add the copyright boilerplate.

[ke.he, 2016/11/15 10:55:18]

Done.

+
+struct WebGamepadQuaternion{

[blundell, 2016/11/14 12:33:16]

nit: "Web" is a Blink-ism that shouldn't be part of the Mojo descriptions of any
of these.

[ke.he, 2016/11/15 10:55:18]

I changed all the "WebGamepadxxx" into "Gamepadxxx", only keep some functions
names in unittests which are really closed to blink::WebGamepad.
Done.

+  bool notNull;

[yzshen1, 2016/11/14 21:13:17]

please use naming format like this: not_null. (Here and below.)

There are other coding style issues. For example,
- there should be a space between WebGamepadQuaternion and "{".
- two spaces between code and same-line comment.

It is probably useful to review the coding style doc:
https://chromium.googlesource.com/chromium/src/+/master/styleguide/c++/c++.md

[yzshen1, 2016/11/14 21:13:17]

Could we use the nullable feature instead of an explicit notNull field?

For example, 

struct WebGamepadPose {
  ...
  WebGamepadQuaternion? orientation;
};

If you want, you could still make nullable/non-nullable WebGamepadQuaternion to
the same custom type.

Please see:
nullable: https://www.chromium.org/developers/design-documents/mojo/mojom-syntax
nullable_is_same_type:
https://www.chromium.org/developers/design-documents/mojo/type-mapping

[ke.he, 2016/11/15 10:55:18]

Done.

[ke.he, 2016/11/15 10:55:18]

Oh, it is not correct to just copy those webxxx structs which
are in blink style directly into mojom file. In mojom it should follow the
chromium style. Thanks for reminding me this.
So besides "notNull" to "not_null", other members like "hasPosition" should be
changed as "has_position". I'll change all of them.
Thanks!
Done.

+  float x;
+  float y;
+  float z;
+  float w;
+};
+
+struct WebGamepadVector{
+  bool notNull;
+  float x;
+  float y;
+  float z;
+};
+
+struct WebGamepadButton{
+  bool pressed;
+  bool touched;
+  double value;
+};
+
+struct WebGamepadPose{
+  bool notNull;
+  bool hasOrientation;
+  bool hasPosition;
+  WebGamepadQuaternion orientation;
+  WebGamepadVector position;
+  WebGamepadVector angularVelocity;
+  WebGamepadVector linearVelocity;
+  WebGamepadVector angularAcceleration;
+  WebGamepadVector linearAcceleration;
+};
+
+enum WebGamepadHand {
+  GamepadHandNone = 0,
+  GamepadHandLeft = 1,
+  GamepadHandRight = 2
+};
+
+struct WebGamepad {
+  bool connected;
+  array<uint16, 128> id; //blink::WebGamepad::idLengthCap = 128
+  uint64 timestamp;
+  uint32 axesLength;
+  array<double, 16> axes; //blink::WebGamepad::axesLengthCap = 16
+  uint32 buttonsLength;
+  array<WebGamepadButton, 32> buttons; //blink::WebGamepad::buttonLengthCap = 32
+  array<uint16, 16> mapping; //blink::WebGamepad::mappingLengthCap = 16
+  WebGamepadPose pose;
+  WebGamepadHand hand;
+  uint32 displayId;
+};