1// Copyright (c) 2012 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_WM_CORE_FOCUS_RULES_H_
6#define UI_WM_CORE_FOCUS_RULES_H_
7
8#include "ui/wm/wm_export.h"
9
10namespace aura {
11class Window;
12}
13
14namespace wm {
15
16// Implemented by an object that establishes the rules about what can be
17// focused or activated.
18class WM_EXPORT FocusRules {
19 public:
20  virtual ~FocusRules() {}
21
22  // Returns true if |window| is a toplevel window. Whether or not a window
23  // is considered toplevel is determined by a similar set of rules that
24  // govern activation and focus. Not all toplevel windows are activatable,
25  // call CanActivateWindow() to determine if a window can be activated.
26  virtual bool IsToplevelWindow(aura::Window* window) const = 0;
27  // Returns true if |window| can be activated or focused.
28  virtual bool CanActivateWindow(aura::Window* window) const = 0;
29  // For CanFocusWindow(), NULL is supported, because NULL is a valid focusable
30  // window (in the case of clearing focus).
31  virtual bool CanFocusWindow(aura::Window* window) const = 0;
32
33  // Returns the toplevel window containing |window|. Not all toplevel windows
34  // are activatable, call GetActivatableWindow() instead to return the
35  // activatable window, which might be in a different hierarchy.
36  // Will return NULL if |window| is not contained by a window considered to be
37  // a toplevel window.
38  virtual aura::Window* GetToplevelWindow(aura::Window* window) const = 0;
39  // Returns the activatable or focusable window given an attempt to activate or
40  // focus |window|. Some possible scenarios (not intended to be exhaustive):
41  // - |window| is a child of a non-focusable window and so focus must be set
42  //   according to rules defined by the delegate, e.g. to a parent.
43  // - |window| is an activatable window that is the transient parent of a modal
44  //   window, so attempts to activate |window| should result in the modal
45  //   transient being activated instead.
46  // These methods may return NULL if they are unable to find an activatable
47  // or focusable window given |window|.
48  virtual aura::Window* GetActivatableWindow(aura::Window* window) const = 0;
49  virtual aura::Window* GetFocusableWindow(aura::Window* window) const = 0;
50
51  // Returns the next window to activate in the event that |ignore| is no longer
52  // activatable. This function is called when something is happening to
53  // |ignore| that means it can no longer have focus or activation, including
54  // but not limited to:
55  // - it or its parent hierarchy is being hidden, or removed from the
56  //   RootWindow.
57  // - it is being destroyed.
58  // - it is being explicitly deactivated.
59  // |ignore| cannot be NULL.
60  virtual aura::Window* GetNextActivatableWindow(
61      aura::Window* ignore) const = 0;
62};
63
64}  // namespace wm
65
66#endif  // UI_WM_CORE_FOCUS_RULES_H_
67