Add touch events to the protocol, the stub layer, and to the client plugin.

- Add TouchEvent and TouchEventPoint messages to the input event protocol.
- Extend the InputStub interface with an InjectTouchEvent() method.
- Update InputEventTracker to track touch points, and to cancel them
  when ReleaseAll() is called.
- Implement touch handling in the client plugin, but off by default.
  The web-app may choose to enable touch handling if desired.
- Add a TouchInputScaler that scales and clamps touch points, similarly to
  the MouseInputFilter, for use by both client and host.

BUG=314515

Review URL: https://codereview.chromium.org/799233004

Cr-Commit-Position: refs/heads/master@{#318284}

2 files changed, 52 insertions, 0 deletions

diff --git a/remoting/proto/event.proto b/remoting/proto/event.proto
index dd15094..37df684 100644
--- a/remoting/proto/event.proto
+++ b/remoting/proto/event.proto
@@ -79,3 +79,54 @@ message ClipboardEvent {
   // The data being sent.
   optional bytes data = 2;
 }
+
+message TouchEventPoint {
+  // The ID for the touch point.
+  optional uint32 id = 1;
+
+  // The position of the touch point.
+  // These values on-the-wire are host coordinates.
+  optional float x = 2;
+  optional float y = 3;
+
+  // The size of the touch point, used to aid hit-testing.
+  // Scaled to match the size on host.
+  optional float radius_x = 4;
+  optional float radius_y = 5;
+
+  // Angle in degrees from the y-axis of the touch point.
+  optional float angle = 6;
+
+  // The pressure of the touch point.
+  // The value should be in [0.0, 1.0].
+  optional float pressure = 7;
+}
+
+message TouchEvent {
+  // A START event means that this event reports all the touch points that were
+  // just added, e.g. a finger started touching the display.
+  // A MOVE event means that the touch points that have been STARTed moved,
+  // e.g. multiple fingers on the screen moved.
+  // An END event means that the touch points that have been STARTed ended.
+  // e.g. a finger went off the screen.
+  // A CANCEL event means that the touch points that have been STARTed were
+  // canceled, e.g. a finger went off the screen.
+  // Cancel event is simlar to END but slighly different. For example, Android
+  // MotionEvent's ACTION_CANCEL documentation mentions that a cancel should be
+  // treated as an ACTION_UP (END) event but might not perform the exact same
+  // actions as a normal ACTION_UP event.
+  enum TouchEventType {
+    TOUCH_POINT_START = 1;
+    TOUCH_POINT_MOVE = 2;
+    TOUCH_POINT_END = 3;
+    TOUCH_POINT_CANCEL = 4;
+  };
+
+  optional TouchEventType event_type = 1;
+
+  // Only the changed touch points are added to this field.
+  // Given the existing touch point APIs (e.g. Android and PPAPI)
+  // for START, END, and CANCEL events the size of this field will typically be
+  // 1, but for MOVE events it is likely to have multiple points.
+  repeated TouchEventPoint touch_points = 2;
+}
diff --git a/remoting/proto/internal.proto b/remoting/proto/internal.proto
index 482d9fa..3041646 100644
--- a/remoting/proto/internal.proto
+++ b/remoting/proto/internal.proto
@@ -35,4 +35,5 @@ message EventMessage {
   optional KeyEvent key_event = 3;
   optional MouseEvent mouse_event = 4;
   optional TextEvent text_event = 5;
+  optional TouchEvent touch_event = 6;
 }