Separated alt-tab window cycle from overview mode

ash/wm/window_cycle_controller.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ash/wm/window_cycle_controller.h"
+
+#include <algorithm>
+
+#include "ash/session/session_state_delegate.h"
+#include "ash/shell.h"
+#include "ash/shell_window_ids.h"
+#include "ash/wm/mru_window_tracker.h"
+#include "ash/wm/window_cycle_list.h"
+#include "ash/wm/window_util.h"
+#include "ash/wm/workspace_controller.h"
+#include "ui/events/event.h"
+#include "ui/events/event_handler.h"
+
+namespace ash {
+
+namespace {
+
+// Filter to watch for the termination of a keyboard gesture to cycle through
+// multiple windows.
+class WindowCycleEventFilter : public ui::EventHandler {
+ public:
+  WindowCycleEventFilter();
+  virtual ~WindowCycleEventFilter();
+
+  // Overridden from ui::EventHandler:
+  virtual void OnKeyEvent(ui::KeyEvent* event) OVERRIDE;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(WindowCycleEventFilter);
+};
+
+WindowCycleEventFilter::WindowCycleEventFilter() {
+}
+
+WindowCycleEventFilter::~WindowCycleEventFilter() {
+}
+
+void WindowCycleEventFilter::OnKeyEvent(ui::KeyEvent* event) {
+  // Views uses VKEY_MENU for both left and right Alt keys.
+  if (event->key_code() == ui::VKEY_MENU &&
+      event->type() == ui::ET_KEY_RELEASED) {
+    Shell::GetInstance()->window_cycle_controller()->StopCycling();
+    // Warning: |this| will be deleted from here on.
+  }
+}
+
+}  // namespace
+
+
+// WindowCycleController, public:
+
+WindowCycleController::WindowCycleController() {
+}
+
+WindowCycleController::~WindowCycleController() {
+  StopCycling();
+}
+
+// static
+bool WindowCycleController::CanCycle() {
+  // Don't allow window cycling if the screen is locked or a modal dialog is
+  // open.
+  return !Shell::GetInstance()->session_state_delegate()->IsScreenLocked() &&
+         !Shell::GetInstance()->IsSystemModalWindowOpen();
+}
+
+void WindowCycleController::HandleCycleWindow(Direction direction) {
+  if (!CanCycle())
+    return;
+
+  // If this is the start of an alt-tab cycle through multiple windows,
+  // listen for the alt key being released to stop cycling.
+  if (!IsCycling())
+    StartCycling();
+
+  Step(direction);
+}
+
+void WindowCycleController::StartCycling() {
+  window_cycle_list_.reset(new WindowCycleList(ash::Shell::GetInstance()->
+      mru_window_tracker()->BuildMruWindowList()));
+  event_handler_.reset(new WindowCycleEventFilter());
+  Shell::GetInstance()->AddPreTargetHandler(event_handler_.get());
+}
+
+//////////////////////////////////////////////////////////////////////////////
+// WindowCycleController, private:
+
+void WindowCycleController::Step(Direction direction) {
+  DCHECK(window_cycle_list_.get());
+  window_cycle_list_->Step(direction);
+}
+
+void WindowCycleController::StopCycling() {
+  window_cycle_list_.reset();
+  // Remove our key event filter.
+  if (event_handler_) {
+    Shell::GetInstance()->RemovePreTargetHandler(event_handler_.get());
+    event_handler_.reset();
+  }
+}
+
+}  // namespace ash