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";
+
+enum HitTestRegionFlags { 
+
+  // Defines the bounds of the surface ( embedder ).  
+  HIT_TEST_BOUNDS = 0,
+
+  // Region maps to this surface ( me ).  

[rjkroege, 2017/06/07 21:19:06]

It would make sense to me that HIT_TEST_MINE | HIT_TEST_BOUNDS to be set when we
want the smallest HTD whose bounds equal its region? This is elegant.

Perhaps you could write a helper to build HitTestData objects?

[gklassen, 2017/06/12 16:30:41]

The current implementation is using HIT_TEST_MINE only.  Do we need
HIT_TEST_BOUNDS?

And yes, I would like to consider a helper to write these objects.  First I plan
to write them using the auto generated classes and then re-evaluate.  Sound ok?

+  HIT_TEST_MINE,
+
+  // Region maps to child surface ( OOPIF ).  
+  HIT_TEST_CHILD_SURFACE,  
+  
+  // Irregular boundary - send HitTestRequest to resolve. 
+  HIT_TEST_ASK,          
+
+  // No touch event handler exists - no need to send touch events.
+  HIT_TEST_NO_TOUCH_EVENT_HANDLER, 
+
+  // Region ignored for hit testing ( eg. hover:none ).
+  HIT_TEST_IGNORE
+};
+
+struct HitTestRegion {
+
+    // Flags to indicate the type of HitTestRegion.
+    HitTestRegionFlags flags_;
+
+    // SurfaceId for the HIT_TEST_CHILD_SURFACE

[rjkroege, 2017/06/07 21:19:07]

If HIT_TEST_CHILD_SURFACE is set, this is not empty? Must DCHECK that.

[gklassen, 2017/06/12 16:30:41]

Good call.  I have added Validation methods to DCHECK this on submit. Done.

+    cc.mojom.SurfaceId surface_id_;
+
+    // The rect of the region in the current surface coordinate space
+    gfx.mojom.Rect rect_;
+
+    // The transform applied to the child region. 
+    gfx.mojom.Transform transform_;
+};
+
+struct HitTestData {
+
+  // SurfaceId corresponding to this HitTestData.
+  cc.mojom.SurfaceId surface_id_;
+
+  // The clipping bounds of the surface.
+  gfx.mojom.Rect bounds_;
+
+  // The list of sub-regions in this surface.
+  array<HitTestRegion> regions_; // in front to back z-order 
+};