ash/wm/window_cycle_controller.cc

   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 #include "ash/wm/window_cycle_controller.h"
   6
   7 #include "ash/metrics/user_metrics_recorder.h"
   8 #include "ash/session/session_state_delegate.h"
   9 #include "ash/shell.h"
  10 #include "ash/wm/mru_window_tracker.h"
  11 #include "ash/wm/window_cycle_list.h"
  12 #include "base/metrics/histogram.h"
  13 #include "ui/aura/window.h"
  14 #include "ui/events/event.h"
  15 #include "ui/events/event_handler.h"
  16
  17 namespace ash {
  18
  19 namespace {
  20
  21 // Returns the most recently active window from the |window_list| or nullptr
  22 // if the list is empty.
  23 aura::Window* GetActiveWindow(const MruWindowTracker::WindowList& window_list) {
  24   return window_list.empty() ? nullptr : window_list[0];
  25 }
  26
  27 // Filter to watch for the termination of a keyboard gesture to cycle through
  28 // multiple windows.
  29 class WindowCycleEventFilter : public ui::EventHandler {
  30  public:
  31   WindowCycleEventFilter();
  32   ~WindowCycleEventFilter() override;
  33
  34   // Overridden from ui::EventHandler:
  35   void OnKeyEvent(ui::KeyEvent* event) override;
  36
  37  private:
  38   DISALLOW_COPY_AND_ASSIGN(WindowCycleEventFilter);
  39 };
  40
  41 WindowCycleEventFilter::WindowCycleEventFilter() {
  42   Shell::GetInstance()->AddPreTargetHandler(this);
  43 }
  44
  45 WindowCycleEventFilter::~WindowCycleEventFilter() {
  46   Shell::GetInstance()->RemovePreTargetHandler(this);
  47 }
  48
  49 void WindowCycleEventFilter::OnKeyEvent(ui::KeyEvent* event) {
  50   // Views uses VKEY_MENU for both left and right Alt keys.
  51   if (event->key_code() == ui::VKEY_MENU &&
  52       event->type() == ui::ET_KEY_RELEASED) {
  53     Shell::GetInstance()->window_cycle_controller()->StopCycling();
  54     // Warning: |this| will be deleted from here on.
  55   }
  56 }
  57
  58 }  // namespace
  59
  60 //////////////////////////////////////////////////////////////////////////////
  61 // WindowCycleController, public:
  62
  63 WindowCycleController::WindowCycleController() {
  64 }
  65
  66 WindowCycleController::~WindowCycleController() {
  67 }
  68
  69 // static
  70 bool WindowCycleController::CanCycle() {
  71   // Don't allow window cycling if the screen is locked or a modal dialog is
  72   // open.
  73   return !Shell::GetInstance()->session_state_delegate()->IsScreenLocked() &&
  74          !Shell::GetInstance()->IsSystemModalWindowOpen();
  75 }
  76
  77 void WindowCycleController::HandleCycleWindow(Direction direction) {
  78   if (!CanCycle())
  79     return;
  80
  81   if (!IsCycling())
  82     StartCycling();
  83
  84   Step(direction);
  85 }
  86
  87 void WindowCycleController::StartCycling() {
  88   MruWindowTracker::WindowList window_list =
  89       Shell::GetInstance()->mru_window_tracker()->BuildMruWindowList();
  90
  91   active_window_before_window_cycle_ = GetActiveWindow(window_list);
  92
  93   window_cycle_list_.reset(new WindowCycleList(window_list));
  94   event_handler_.reset(new WindowCycleEventFilter());
  95   cycle_start_time_ = base::Time::Now();
  96   Shell::GetInstance()->metrics()->RecordUserMetricsAction(UMA_WINDOW_CYCLE);
  97 }
  98
  99 //////////////////////////////////////////////////////////////////////////////
 100 // WindowCycleController, private:
 101
 102 void WindowCycleController::Step(Direction direction) {
 103   DCHECK(window_cycle_list_.get());
 104   window_cycle_list_->Step(direction);
 105 }
 106
 107 void WindowCycleController::StopCycling() {
 108   window_cycle_list_.reset();
 109
 110   aura::Window* active_window_after_window_cycle = GetActiveWindow(
 111       Shell::GetInstance()->mru_window_tracker()->BuildMruWindowList());
 112
 113   // Remove our key event filter.
 114   event_handler_.reset();
 115   UMA_HISTOGRAM_MEDIUM_TIMES("Ash.WindowCycleController.CycleTime",
 116                              base::Time::Now() - cycle_start_time_);
 117
 118   if (active_window_after_window_cycle != nullptr &&
 119       active_window_before_window_cycle_ != active_window_after_window_cycle) {
 120     Shell::GetInstance()
 121         ->metrics()
 122         ->task_switch_metrics_recorder()
 123         .OnTaskSwitch(TaskSwitchMetricsRecorder::kWindowCycleController);
 124   }
 125   active_window_before_window_cycle_ = nullptr;
 126 }
 127
 128 }  // namespace ash