ui/views/view_targeter_delegate.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef UI_VIEWS_VIEW_TARGETER_DELEGATE_H_
   6 #define UI_VIEWS_VIEW_TARGETER_DELEGATE_H_
   7
   8 #include "base/macros.h"
   9 #include "ui/views/views_export.h"
  10
  11 namespace gfx {
  12 class Rect;
  13 }
  14
  15 namespace views {
  16 class View;
  17
  18 // Defines the default behaviour for hit-testing and event-targeting against a
  19 // View using a rectangular region representing an event's location. Views
  20 // wishing to define custom hit-testing or event-targeting behaviour do so by
  21 // extending ViewTargeterDelegate and then installing a ViewTargeter on
  22 // themselves.
  23 class VIEWS_EXPORT ViewTargeterDelegate {
  24  public:
  25   ViewTargeterDelegate() {}
  26   virtual ~ViewTargeterDelegate() {}
  27
  28   // Returns true if the bounds of |target| intersects |rect|, where |rect|
  29   // is in the local coodinate space of |target|. Overrides of this method by
  30   // a View subclass should enforce DCHECK_EQ(this, target).
  31   virtual bool DoesIntersectRect(const View* target,
  32                                  const gfx::Rect& rect) const;
  33
  34   // If point-based targeting should be used, return the deepest visible
  35   // descendant of |root| that contains the center point of |rect|.
  36   // If rect-based targeting (i.e., fuzzing) should be used, return the
  37   // closest visible descendant of |root| having at least kRectTargetOverlap of
  38   // its area covered by |rect|. If no such descendant exists, return the
  39   // deepest visible descendant of |root| that contains the center point of
  40   // |rect|. See http://goo.gl/3Jp2BD for more information about rect-based
  41   // targeting.
  42   virtual View* TargetForRect(View* root, const gfx::Rect& rect);
  43
  44  private:
  45   DISALLOW_COPY_AND_ASSIGN(ViewTargeterDelegate);
  46 };
  47
  48 }  // namespace views
  49
  50 #endif  // UI_VIEWS_VIEW_TARGETER_DELEGATE_H_