window_cycle_controller.cc revision a36e5920737c6adbddd3e43b760e5de8431db6e0 
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/base/events/event.h"
18#include "ui/base/events/event_handler.h"
19
20namespace ash {
21
22namespace {
23
24// Filter to watch for the termination of a keyboard gesture to cycle through
25// multiple windows.
26class 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.
38WindowCycleEventFilter::WindowCycleEventFilter() {
39}
40
41WindowCycleEventFilter::~WindowCycleEventFilter() {
42}
43
44void 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
58WindowCycleController::WindowCycleController() {
59}
60
61WindowCycleController::~WindowCycleController() {
62  StopCycling();
63}
64
65// static
66bool 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
73void 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
97void 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
107void WindowCycleController::AltKeyReleased() {
108  StopCycling();
109}
110
111//////////////////////////////////////////////////////////////////////////////
112// WindowCycleController, private:
113
114void WindowCycleController::StartCycling() {
115  windows_.reset(new WindowCycleList(ash::Shell::GetInstance()->
116      mru_window_tracker()->BuildMruWindowList()));
117}
118
119void WindowCycleController::Step(Direction direction) {
120  DCHECK(windows_.get());
121  windows_->Step(direction == FORWARD ? WindowCycleList::FORWARD :
122                 WindowCycleList::BACKWARD);
123}
124
125void 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
134void WindowCycleController::InstallEventFilter() {
135  event_handler_.reset(new WindowCycleEventFilter());
136  Shell::GetInstance()->AddPreTargetHandler(event_handler_.get());
137}
138
139}  // namespace ash
140