client-side wheel mouse support

remoting/proto/event.proto

 // Copyright (c) 2010 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.
 
 // Protocol for event messages.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
 package remoting.protocol;
 
 // Defines a keyboard event.
-// NEXT ID: 3
 message KeyEvent {
   // The POSIX key code.
   required int32 keycode = 1;
   required bool pressed = 2;
 }
 
 // Defines a mouse event message on the event channel. 
 message MouseEvent {
 
   enum MouseButton {
     BUTTON_UNDEFINED = 0;
     BUTTON_LEFT = 1;
     BUTTON_MIDDLE = 2;
     BUTTON_RIGHT = 3;
   }
 
   // Mouse position information.
   optional int32 x = 1;
   optional int32 y = 2;
 
   // Mouse wheel information.
+  // In general, the |offset| values are the most useful, but the raw |clicks|
+  // value can be useful when cycling through a small set of items.

[Jamie, 2011/03/16 11:59:29]

I don't understand what this comment means. How would a host decide which of the
values to use?

[garykac, 2011/03/16 20:43:43]

If you're doing scrolling, then you should use the offsets.

If you're not doing traditional scrolling, then you can consider using the
clicks instead. An example of when you might want to do this would be when
cycling through the set of tabs in Chrome. This isn't really scrolling, but you
can use the wheel clicks to select the previous/next tabs.

+  // The number of pixels to scroll.
   optional int32 wheel_offset_x = 3;
   optional int32 wheel_offset_y = 4;
+  // The number of wheel clicks.
+  optional int32 wheel_clicks_x = 7;
+  optional int32 wheel_clicks_y = 8;
+  // True if |offset| values mean scroll by page (rather than by pixel or line).

[Jamie, 2011/03/16 11:59:29]

Why do we have a bool to indicate scrolling by a page, but not one to
distinguish between pixels vs. lines if wheel_by_page is false?

[garykac, 2011/03/16 20:43:43]

The pixel vs. line distinction is app-specific.

I understand this as:

If false, then scroll by the smallest unit of scrolliness that you (the app)
understand. This is most commonly either pixels or lines.

If true, then scroll by an entire page of content.

+  optional bool wheel_by_page = 9;
 
   // Mouse button event.
   optional MouseButton button = 5;
   optional bool button_down = 6;
 }