Serialize a subset of WebInputEvents to protobufs.

blimp/common/proto/input.proto

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // Message definitions for the input subprotocol.
 //
-// Current definitions are just placeholders and are NOT final.
-// Feel free to modify this interface as necessary during feature work.
+// The InputMessage protobuf generally carries web input events.  Currently we
+// just serialize the blink::WebInputEvent POD struct.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
 import "common.proto";
 
 package blimp;
 
-message ClickArgs {
-  optional CoordinatePair target = 1;
+message GestureBaseProperties {

[Wez, 2015/11/23 22:41:41]

nit: I'd rename this GestureBase given the context; each message is inherently a
list of event-specific properties.

However, it would simplify some of the marshalling code if you renamed it
GestureCommon and placed it alongside the Gesture-specific sub-messages - WDYT?

[David Trainor- moved to gerrit, 2015/11/24 20:08:27]

Yeah I think that's a good idea.  Will change.

+  optional int64 x = 1;
+  optional int64 y = 2;
+  optional int64 global_x = 3;
+  optional int64 global_y = 4;
 }
 
-message DragArgs {
-  optional CoordinatePair origin = 1;
-  optional CoordinatePair destination = 2;
-  optional CoordinatePair elastic_overscroll = 3;
+message GestureScrollBegin {
+  optional GestureBaseProperties base = 1;
+  optional float delta_x_hint = 2;
+  optional float delta_y_hint = 3;
+  optional bool target_viewport = 4;
+}
+
+message GestureScrollEnd {
+  optional GestureBaseProperties base = 1;
+}
+
+message GestureScrollUpdate {
+  optional GestureBaseProperties base = 1;
+  optional float delta_x = 2;
+  optional float delta_y = 3;
+  optional float velocity_x = 4;
+  optional float velocity_y = 5;
+  optional bool previous_update_in_sequence_prevented = 6;
+  optional bool prevent_propagation = 7;
+  optional bool inertial = 8;
+}
+
+message GestureFlingStart {
+  optional GestureBaseProperties base = 1;
+  optional float velocity_x = 2;
+  optional float velocity_y = 3;
+  optional bool target_viewport = 4;
+}
+
+message GestureFlingCancel {
+  optional GestureBaseProperties base = 1;
+  optional bool prevent_boosting = 2;
+}
+
+message GestureTap {
+  optional GestureBaseProperties base = 1;
+  optional int32 tap_count = 2;
+  optional float width = 3;
+  optional float height = 4;
+}
+
+message GesturePinchBegin {
+  optional GestureBaseProperties base = 1;
+}
+
+message GesturePinchEnd {
+  optional GestureBaseProperties base = 1;
+}
+
+message GesturePinchUpdate {
+  optional GestureBaseProperties base = 1;
+  optional bool zoom_disabled = 2;
+  optional float scale = 3;
 }
 
 message InputMessage {
   enum Type {
-    CLICK = 1;
-    DRAG = 2;
+    // This is a subset of WebGestureType events.  We only support a small set
+    // of these with the existing protocol.

[Rick Byers, 2015/11/20 03:17:55]

Blink may make assumptions that this subset violates.  For example that a
GestureTap is always preceeded by a GestureTapDown (and a GestureTapDown is
always followed by either a GestureTap or GestureTapCancel, possibly with an
intervening GestureShowPress).  I forget the details of exactly how forgiving we
are here but we'd like to eventually start validating more (at least in DEBUG). 
Anyway, not blocking from my perspective as it doesn't directly affect blink,
but this may cause subtle bugs for you...

+    Type_GestureScrollBegin = 1;
+    Type_GestureScrollEnd = 2;
+    Type_GestureScrollUpdate = 3;
+    Type_GestureFlingStart = 4;
+    Type_GestureFlingCancel = 5;
+    Type_GestureTap = 6;
+    Type_GesturePinchBegin = 7;
+    Type_GesturePinchEnd = 8;
+    Type_GesturePinchUpdate = 9;
   }
+
   optional Type type = 1;
 
-  optional ClickArgs click = 1000;
-  optional DragArgs drag = 1001;
+  // The time this input event happened relative to when the client device was
+  // started.

[Wez, 2015/11/23 22:41:41]

nit: Is this to when the _device_ started, or when the client _app_ was started?

Whichever it is, we're going to need a way of re-basing the timestamp e.g. when
re-connecting to the engine after a device reboot.

[nyquist, 2015/11/24 08:12:43]

In fact, given all the different ways to measure time, it'd be helpful to
specify which method you're using, like for example
http://developer.android.com/reference/android/os/SystemClock.html#elapsedRea...
(or hopefully not
http://developer.android.com/reference/android/os/SystemClock.html#uptimeMill...
), or if it's some other source of time, mention that instead.

It seems like the definition is here:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

The explanatory comment says: "Seconds since platform start with microsecond
resolution."

[David Trainor- moved to gerrit, 2015/11/24 20:08:27]

Sadly it looks like it is SystemCLock#uptimeMillis(), so the resolution for
Android touch events doesn't go to microseconds.  

[nyquist, 2015/11/24 20:33:27]

Oh; that might be unfortunate. That clock is also stopped when the device is
idle, which might potentially screw things up when we are later communicating
with an engine that has stayed alive since last time.

I guess we just have a safe way to rebase the timeline even if the device has
not been rebooted, since being idle also messes it up.

+  optional double timestamp_seconds = 2;
+
+  // Input event specific messages follow.
+  // Only one of these fields may be set per InputMessage.

[Wez, 2015/11/23 22:41:41]

nit: Add a TODO() to make these a oneof if Chromium's protobuf impl ever
supports that?

[David Trainor- moved to gerrit, 2015/11/24 20:08:27]

Done.

+  optional GestureScrollBegin gesture_scroll_begin = 3;
+  optional GestureScrollEnd gesture_scroll_end = 4;
+  optional GestureScrollUpdate gesture_scroll_update = 5;
+  optional GestureFlingStart gesture_fling_start = 6;
+  optional GestureFlingCancel gesture_fling_cancel = 7;
+  optional GestureTap gesture_tap = 8;
+  optional GesturePinchBegin gesture_pinch_begin = 9;
+  optional GesturePinchEnd gesture_pinch_end = 10;
+  optional GesturePinchUpdate gesture_pinch_update = 11;
 }