[aura-mus] Add ui::CursorData, with mojo serialization.

services/ui/public/interfaces/cursor/cursor.mojom

 // 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.
 
 module ui.mojom;
 
+import "ui/gfx/geometry/mojo/geometry.mojom";
+import "skia/public/interfaces/bitmap_array.mojom";
+
 // Standard Cursor numbers. These are the same as Chrome's ui::Cursor and
 // blink's WebCursorInfo.
 enum CursorType {
   // NULL is kept for compatibility with chrome declarations. In chrome code, it
   // is treated exactly like POINTER, the default pointer.
   CURSOR_NULL = 0,
   POINTER,
   CROSS,
   HAND,
   IBEAM,
@@ skipping 31 matching lines @@
   NO_DROP,
   COPY,
   NONE,
   NOT_ALLOWED,
   ZOOM_IN,
   ZOOM_OUT,
   GRAB,
   GRABBING,
   CUSTOM
 };
+
+// A description of a cursor.
+struct CursorData {
+  // The type of cursor. If CUSTOM, the rest of the fields are relevant.
+  CursorType native_type;

[sky, 2017/03/31 04:57:57]

cursor_type?

[Elliot Glaysher, 2017/03/31 21:18:15]

Done.

+
+  // The delay between cursor frames in milliseconds.
+  uint32 frame_delay_ms;
+
+  // The hotspot in cursor frames.
+  gfx.mojom.Point hotspot;

[sky, 2017/03/31 04:57:57]

Is this pixels or dips? Generally if we don't say it's assumed to be dips, but I
suspect this is pixels. I could certainly be wrong.

[Elliot Glaysher, 2017/03/31 21:18:15]

added "_in_pixels" suffix.

+
+  // The frames of the cursor.
+  skia.mojom.BitmapArray cursor_frames;

[sky, 2017/03/31 04:57:57]

Do cursors vary depending upon dpi? Is it expected that cursor_frames is
specific to the dpi of the display?

[sky, 2017/03/31 04:57:57]

Would it be better to use shared memory for the bitmaps? How often do we send
cursors around?

[Tom Sepez, 2017/03/31 16:07:07]

Arbitrarily deep?  Not sure it matters ...

[Elliot Glaysher, 2017/03/31 21:18:15]

Assuming the user is actually checking IsSameAs() before sending a cursor, only
on cursor changes.

As far as I can tell though, we don't have a way to send bitmaps across mojo
pipes using shared memory. This would require modification of the skia bindings.

[Elliot Glaysher, 2017/03/31 21:18:15]

I'm not sure what you're asking here.

[Elliot Glaysher, 2017/03/31 21:18:15]

You're right and I misread this. Added an |image_scale_factor| float to
represent what the scale factor of |cursor_frames| is.

(I had confused this as part of the rotation and display dpi transformation. My
bad.)

+};