ash/wm/overlay_event_filter.h

   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 ASH_WM_OVERLAY_EVENT_FILTER_H_
   6 #define ASH_WM_OVERLAY_EVENT_FILTER_H_
   7
   8 #include "ash/ash_export.h"
   9 #include "ash/shell_observer.h"
  10 #include "base/compiler_specific.h"
  11 #include "ui/aura/window.h"
  12 #include "ui/events/event_handler.h"
  13
  14 namespace ash {
  15
  16 // EventFilter for the "overlay window", which intercepts events before they are
  17 // processed by the usual path (e.g. the partial screenshot UI, the keyboard
  18 // overlay).  It does nothing the first time, but works when |Activate()| is
  19 // called.  The main task of this event filter is just to stop propagation
  20 // of any key events during activation, and also signal cancellation when keys
  21 // for canceling are pressed.
  22 class ASH_EXPORT OverlayEventFilter : public ui::EventHandler,
  23                                       public ShellObserver {
  24  public:
  25   // Windows that need to receive events from OverlayEventFilter implement this.
  26   class ASH_EXPORT Delegate {
  27    public:
  28     // Invoked when OverlayEventFilter needs to stop handling events.
  29     virtual void Cancel() = 0;
  30
  31     // Returns true if the overlay should be canceled in response to |event|.
  32     virtual bool IsCancelingKeyEvent(ui::KeyEvent* event) = 0;
  33
  34     // Returns the window that needs to receive events. NULL if no window needs
  35     // to receive key events from OverlayEventFilter.
  36     virtual aura::Window* GetWindow() = 0;
  37   };
  38
  39   OverlayEventFilter();
  40   virtual ~OverlayEventFilter();
  41
  42   // Starts the filtering of events.  It also notifies the specified
  43   // |delegate| when a key event means cancel (like Esc).  It holds the
  44   // pointer to the specified |delegate| until Deactivate() is called, but
  45   // does not take ownership.
  46   void Activate(Delegate* delegate);
  47
  48   // Ends the filtering of events.
  49   void Deactivate();
  50
  51   // Cancels the partial screenshot UI.  Do nothing if it's not activated.
  52   void Cancel();
  53
  54   // ui::EventHandler overrides:
  55   virtual void OnKeyEvent(ui::KeyEvent* event) OVERRIDE;
  56
  57   // ShellObserver overrides:
  58   virtual void OnLoginStateChanged(user::LoginStatus status) OVERRIDE;
  59   virtual void OnAppTerminating() OVERRIDE;
  60   virtual void OnLockStateChanged(bool locked) OVERRIDE;
  61
  62  private:
  63   Delegate* delegate_;
  64
  65   DISALLOW_COPY_AND_ASSIGN(OverlayEventFilter);
  66 };
  67
  68 }  // namespace ash
  69
  70 #endif  // ASH_WM_OVERLAY_EVENT_FILTER_H_