Separated alt-tab window cycle from overview mode

ash/wm/window_cycle_controller.cc

+// Copyright (c) 2012 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;

[tdanderson, 2014/05/01 18:51:39]

newline after 31

[Nina, 2014/05/01 20:41:16]

Done.

+ private:
+  DISALLOW_COPY_AND_ASSIGN(WindowCycleEventFilter);
+};
+
+// Watch for all keyboard events by filtering the root window.
+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()->AltKeyReleased();
+    // 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 (!IsCycling()) {
+    // This is the start of an alt-tab cycle through multiple windows, so
+    // listen for the alt key being released to stop cycling.
+    StartCycling();
+    Step(direction);

[tdanderson, 2014/05/01 18:51:39]

Can you factor out the call to Step(direction) here and at line 84 and just call
it at the end of this function?

[Nina, 2014/05/01 20:41:16]

Done.

+    InstallEventFilter();
+  } else {
+    // We're in the middle of an alt-tab cycle, just step forward.

[tdanderson, 2014/05/01 18:51:39]

"forward" -> |direction| is not necessarily FORWARD, so update the comment here.

[Nina, 2014/05/01 20:41:16]

Done.

+    Step(direction);
+  }
+}
+
+void WindowCycleController::HandleLinearCycleWindow() {
+  if (!CanCycle() || IsCycling())
+    return;
+
+  // Use the reversed list of windows to prevent a 2-cycle of the most recent
+  // windows occurring.
+  WindowCycleList cycle_list(MruWindowTracker::BuildWindowList(true));
+  cycle_list.Step(WindowCycleList::FORWARD);
+}
+
+void WindowCycleController::AltKeyReleased() {
+  StopCycling();
+}
+
+//////////////////////////////////////////////////////////////////////////////
+// WindowCycleController, private:
+
+void WindowCycleController::StartCycling() {
+  windows_.reset(new WindowCycleList(ash::Shell::GetInstance()->
+      mru_window_tracker()->BuildMruWindowList()));
+}
+
+void WindowCycleController::Step(Direction direction) {
+  DCHECK(windows_.get());
+  windows_->Step(direction == FORWARD ? WindowCycleList::FORWARD :
+                 WindowCycleList::BACKWARD);
+}
+
+void WindowCycleController::StopCycling() {
+  windows_.reset();
+  // Remove our key event filter.
+  if (event_handler_) {
+    Shell::GetInstance()->RemovePreTargetHandler(event_handler_.get());
+    event_handler_.reset();
+  }
+}
+
+void WindowCycleController::InstallEventFilter() {

[tdanderson, 2014/05/01 18:51:39]

I don't think this needs to be its own helper. I'd remove it and instead move
lines 126-127 to the bottom of StartCycling(). This would be consistent with the
fact you're removing the handler at the end of StopCycling().

[Nina, 2014/05/01 20:41:16]

Done.

+  event_handler_.reset(new WindowCycleEventFilter());
+  Shell::GetInstance()->AddPreTargetHandler(event_handler_.get());
+}
+
+}  // namespace ash