src/ash/wm/window_cycle_controller.cc

   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 #include "ash/wm/window_cycle_controller.h"
   6
   7 #include <algorithm>
   8
   9 #include "ash/session_state_delegate.h"
  10 #include "ash/shell.h"
  11 #include "ash/shell_window_ids.h"
  12 #include "ash/wm/mru_window_tracker.h"
  13 #include "ash/wm/window_cycle_list.h"
  14 #include "ash/wm/window_util.h"
  15 #include "ash/wm/workspace_controller.h"
  16 #include "ui/aura/root_window.h"
  17 #include "ui/events/event.h"
  18 #include "ui/events/event_handler.h"
  19
  20 namespace ash {
  21
  22 namespace {
  23
  24 // Filter to watch for the termination of a keyboard gesture to cycle through
  25 // multiple windows.
  26 class WindowCycleEventFilter : public ui::EventHandler {
  27  public:
  28   WindowCycleEventFilter();
  29   virtual ~WindowCycleEventFilter();
  30
  31   // Overridden from ui::EventHandler:
  32   virtual void OnKeyEvent(ui::KeyEvent* event) OVERRIDE;
  33  private:
  34   DISALLOW_COPY_AND_ASSIGN(WindowCycleEventFilter);
  35 };
  36
  37 // Watch for all keyboard events by filtering the root window.
  38 WindowCycleEventFilter::WindowCycleEventFilter() {
  39 }
  40
  41 WindowCycleEventFilter::~WindowCycleEventFilter() {
  42 }
  43
  44 void WindowCycleEventFilter::OnKeyEvent(ui::KeyEvent* event) {
  45   // Views uses VKEY_MENU for both left and right Alt keys.
  46   if (event->key_code() == ui::VKEY_MENU &&
  47       event->type() == ui::ET_KEY_RELEASED) {
  48     Shell::GetInstance()->window_cycle_controller()->AltKeyReleased();
  49     // Warning: |this| will be deleted from here on.
  50   }
  51 }
  52
  53 }  // namespace
  54
  55 //////////////////////////////////////////////////////////////////////////////
  56 // WindowCycleController, public:
  57
  58 WindowCycleController::WindowCycleController() {
  59 }
  60
  61 WindowCycleController::~WindowCycleController() {
  62   StopCycling();
  63 }
  64
  65 // static
  66 bool WindowCycleController::CanCycle() {
  67   // Don't allow window cycling if the screen is locked or a modal dialog is
  68   // open.
  69   return !Shell::GetInstance()->session_state_delegate()->IsScreenLocked() &&
  70          !Shell::GetInstance()->IsSystemModalWindowOpen();
  71 }
  72
  73 void WindowCycleController::HandleCycleWindow(Direction direction,
  74                                               bool is_alt_down) {
  75   if (!CanCycle())
  76     return;
  77
  78   if (is_alt_down) {
  79     if (!IsCycling()) {
  80       // This is the start of an alt-tab cycle through multiple windows, so
  81       // listen for the alt key being released to stop cycling.
  82       StartCycling();
  83       Step(direction);
  84       InstallEventFilter();
  85     } else {
  86       // We're in the middle of an alt-tab cycle, just step forward.
  87       Step(direction);
  88     }
  89   } else {
  90     // This is a simple, single-step window cycle.
  91     StartCycling();
  92     Step(direction);
  93     StopCycling();
  94   }
  95 }
  96
  97 void WindowCycleController::HandleLinearCycleWindow() {
  98   if (!CanCycle() || IsCycling())
  99     return;
 100
 101   // Use the reversed list of windows to prevent a 2-cycle of the most recent
 102   // windows occurring.
 103   WindowCycleList cycle_list(MruWindowTracker::BuildWindowList(true));
 104   cycle_list.Step(WindowCycleList::FORWARD);
 105 }
 106
 107 void WindowCycleController::AltKeyReleased() {
 108   StopCycling();
 109 }
 110
 111 //////////////////////////////////////////////////////////////////////////////
 112 // WindowCycleController, private:
 113
 114 void WindowCycleController::StartCycling() {
 115   windows_.reset(new WindowCycleList(ash::Shell::GetInstance()->
 116       mru_window_tracker()->BuildMruWindowList()));
 117 }
 118
 119 void WindowCycleController::Step(Direction direction) {
 120   DCHECK(windows_.get());
 121   windows_->Step(direction == FORWARD ? WindowCycleList::FORWARD :
 122                  WindowCycleList::BACKWARD);
 123 }
 124
 125 void WindowCycleController::StopCycling() {
 126   windows_.reset();
 127   // Remove our key event filter.
 128   if (event_handler_) {
 129     Shell::GetInstance()->RemovePreTargetHandler(event_handler_.get());
 130     event_handler_.reset();
 131   }
 132 }
 133
 134 void WindowCycleController::InstallEventFilter() {
 135   event_handler_.reset(new WindowCycleEventFilter());
 136   Shell::GetInstance()->AddPreTargetHandler(event_handler_.get());
 137 }
 138
 139 }  // namespace ash