Add support for rect-based event targeting in views

ui/views/rect_based_targeting_utils.h

+// Copyright (c) 2013 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.
+
+#ifndef UI_RECT_BASED_TARGETING_UTILS_H_

[sky, 2013/10/08 20:01:12]

Since this is all touch based, how about touch_targetting_utils or
touch_hit_test_utils?

[tdanderson, 2013/10/09 21:42:06]

My preference would be to use point/rect instead of mouse/touch where possible
since it stays consistent with the naming of HitTestPoint()/HitTestRect() and
GetEventHandlerForPoint()/GetEventHandlerForRect(). 

I recognize that for the time being "rect-based targeting" and "touch-based
targeting" are the same thing (which is why the HitTestSource enum in view.h
makes sense) but my opinion for the longer term is that the size/shape of the
region used for the hit test shouldn't necessarily imply that the hit test was
requested as a result of using a specific input device.

+#define UI_RECT_BASED_TARGETING_UTILS_H_
+
+#include "ui/gfx/point.h"
+#include "ui/gfx/rect.h"
+#include "ui/views/views_export.h"
+
+namespace views {
+
+// Returns true if |rect| is 1x1.
+VIEWS_EXPORT bool UsePointBasedTargeting(const gfx::Rect& rect);
+
+// Returns the percentage of |rect_1|'s area that is covered by |rect_2|.
+VIEWS_EXPORT float PercentCoveredBy(const gfx::Rect& rect_1,
+                                    const gfx::Rect& rect_2);
+
+// Returns the square of the distance from |point| to the center line of
+// |rect|. The center line of a rectangle is obtained by repeatedly
+// stripping away 1px borders around the rectangle until a line remains.
+VIEWS_EXPORT int DistanceSquaredFromCenterLineToPoint(const gfx::Point& point,
+                                                      const gfx::Rect& rect);
+
+}  // namespace views
+
+#endif  // UI_RECT_BASED_TARGETING_UTILS_H_