Add gesture target fuzzing to views

ui/views/view_constants.h

 // Copyright (c) 2011 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_VIEWS_VIEW_CONSTANTS_H_
 #define UI_VIEWS_VIEW_CONSTANTS_H_
 
 #include "ui/views/views_export.h"
 
 namespace views {
 
 // Size (width or height) within which the user can hold the mouse and the
 // view should scroll.
 VIEWS_EXPORT extern const int kAutoscrollSize;
 
 // Time in milliseconds to autoscroll by a row. This is used during drag and
 // drop.
 VIEWS_EXPORT extern const int kAutoscrollRowTimerMS;
 
 // Used to determine whether a drop is on an item or before/after it. If a drop
 // occurs kDropBetweenPixels from the top/bottom it is considered before/after
 // the item, otherwise it is on the item.
 VIEWS_EXPORT extern const int kDropBetweenPixels;
 
+// A view will only be considered a candidate for touch fuzzing if the touch
+// region covers at least |kFuzzingOverlapPercentage| percent of the area of
+// the view's bounding rectangle.
+VIEWS_EXPORT extern const float kFuzzingOverlapPercentage;

[rjkroege, 2012/07/16 23:35:48]

So... If we have a really huge button, can we fail to hit it?

[tdanderson, 2012/07/17 19:07:07]

This is a good question, and I should have mentioned this in the CL description.
The benefit of fuzzing is for small targets only, and by "small targets" I mean
targets that your finger can cover by at least 70%. The algorithm first tries to
dispatch the tap event to the closest small target; if there are none or if the
target doesn't handle the tap, then the event is dispatched to the center of the
touch region (which is what the code did originally). 

So in the case of a large view such as a tab, assuming that the user's finger
did not sufficiently cover the tab close button, there should be no problem
hitting it because it is large enough for the user to touch without the help of
fuzzing (i.e., it is easy to touch a tab so that the center of the touch region
is contained within the tab).

+
 }  // namespace views
 
 #endif  // UI_VIEWS_VIEW_CONSTANTS_H_