WIP Hittest Component.

components/viz/hit_test/public/interfaces/hit_test_data.mojom

+// Copyright 2017 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 viz.hit_test.mojom;
+
+import "cc/ipc/surface_id.mojom";
+import "ui/gfx/geometry/mojo/geometry.mojom";
+import "ui/gfx/mojo/transform.mojom";
+
+// Region maps to this surface ( me ).  
+const uint32 kHitTestMine = 0x01;
+
+// Region ignored for hit testing ( transparent backgrounds & hover:none ).
+const uint32 kHitTestIgnore = 0x02;
+
+// Region maps to child surface ( OOPIF ).  
+const uint32 kHitTestChildSurface = 0x04;  
+
+// Irregular boundary - send HitTestRequest to resolve. 
+const uint32 kHitTestAsk = 0x08;          
+
+// No touch event handler exists - no need to send touch events.
+const uint32 kHitTestNoTouchEventHandler = 0x10; 

[sadrul, 2017/06/16 17:07:56]

Instead of saying 'no touch handler', I would rather go with a 'touch handler'
enum (i.e. the default is the client does not receive touch events, and would
need to explicitly turn the flag on to receive touch events).

[gklassen, 2017/06/27 19:29:02]

Done.

+
+struct HitTestRegion {
+
+    // Flags to indicate the type of HitTestRegion.
+    uint32 flags;
+
+    // SurfaceId is required when flags = kHitTestChildSurface.
+    cc.mojom.SurfaceId surface_id;
+
+    // The rect of the region in the coordinate space of the embedder.
+    gfx.mojom.Rect rect;
+
+    // The transform applied to the child region. 

[sadrul, 2017/06/16 17:07:56]

Do you mean the transform of the region with respect to the embedder? Because
it's not clear what 'child region' is referring to.

[gklassen, 2017/06/27 19:29:02]

Done.

+    gfx.mojom.Transform transform;
+};
+
+struct HitTestData {
+
+  // SurfaceId corresponding to this HitTestData.
+  cc.mojom.SurfaceId surface_id;
+
+  // The list of sub-regions in this surface.
+  array<HitTestRegion> regions; // in front to back z-order 
+};