Refactor backdrop that is currently used in the maximized mode.

ash/wm/workspace/backdrop_controller.cc

Index: ash/wm/workspace/backdrop_controller.cc
diff --git a/ash/wm/workspace/backdrop_controller.cc b/ash/wm/workspace/backdrop_controller.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ca195433f1022c8a472eec0877ad67762eb9fab4
--- /dev/null
+++ b/ash/wm/workspace/backdrop_controller.cc
@@ -0,0 +1,244 @@
+// 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/workspace/backdrop_controller.h"
+
+#include "ash/accessibility_delegate.h"
+#include "ash/public/cpp/shell_window_ids.h"
+#include "ash/root_window_controller.h"
+#include "ash/shared/app_types.h"
+#include "ash/shell.h"
+#include "ash/system/tray/system_tray_notifier.h"
+#include "ash/wm/window_util.h"
+#include "ash/wm/workspace/backdrop_delegate.h"
+#include "ash/wm_window.h"
+#include "base/auto_reset.h"
+#include "chromeos/audio/chromeos_sounds.h"
+#include "ui/aura/client/aura_constants.h"
+#include "ui/compositor/layer.h"
+#include "ui/compositor/scoped_layer_animation_settings.h"
+#include "ui/views/widget/widget.h"
+#include "ui/wm/core/window_animations.h"
+#include "ui/wm/core/window_util.h"
+
+namespace ash {
+namespace {
+
+class BackdropEventHandler : public ui::EventHandler {
+ public:
+  BackdropEventHandler() = default;
+  ~BackdropEventHandler() override = default;
+
+  // ui::EventHandler:
+  void OnEvent(ui::Event* event) override {
+    // If the event is targeted at the backdrop, it means the user has made an
+    // interaction that is outside the window's bounds and we want to capture
+    // it (usually when in spoken feedback mode). Handle the event (to prevent
+    // behind-windows from receiving it) and play an earcon to notify the user.
+    if (event->IsLocatedEvent()) {
+      switch (event->type()) {
+        case ui::ET_MOUSE_PRESSED:
+        case ui::ET_MOUSEWHEEL:
+        case ui::ET_TOUCH_PRESSED:
+        case ui::ET_POINTER_DOWN:
+        case ui::ET_POINTER_WHEEL_CHANGED:
+        case ui::ET_GESTURE_BEGIN:
+        case ui::ET_SCROLL:
+        case ui::ET_SCROLL_FLING_START:
+          Shell::Get()->accessibility_delegate()->PlayEarcon(
+              chromeos::SOUND_VOLUME_ADJUST);
+          break;
+        default:
+          break;
+      }
+      event->SetHandled();
+    }
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(BackdropEventHandler);
+};
+
+}  // namespace
+
+BackdropController::BackdropController(aura::Window* container)
+    : container_(container), in_restacking_(false) {
+  DCHECK(container_);
+  Shell::Get()->AddShellObserver(this);
+  Shell::Get()->system_tray_notifier()->AddAccessibilityObserver(this);
+}
+
+BackdropController::~BackdropController() {
+  Shell::Get()->system_tray_notifier()->RemoveAccessibilityObserver(this);
+  Shell::Get()->RemoveShellObserver(this);
+  // TODO: animations won't work right with mus: http://crbug.com/548396.
+  Hide();
+}
+
+void BackdropController::OnWindowAddedToLayout(aura::Window* child) {
+  UpdateBackdrop();
+}
+
+void BackdropController::OnWindowRemovedFromLayout(aura::Window* child) {
+  UpdateBackdrop();
+}
+
+void BackdropController::OnChildWindowVisibilityChanged(aura::Window* child,
+                                                        bool visible) {
+  UpdateBackdrop();
+}
+
+void BackdropController::OnWindowStackingChanged(aura::Window* window) {
+  UpdateBackdrop();
+}
+
+void BackdropController::OnPostWindowStateTypeChange(
+    wm::WindowState* window_state,
+    wm::WindowStateType old_type) {
+  UpdateBackdrop();
+}
+
+void BackdropController::SetBackdropDelegate(
+    std::unique_ptr<BackdropDelegate> delegate) {
+  delegate_ = std::move(delegate);
+  UpdateBackdrop();
+}
+
+void BackdropController::UpdateBackdrop() {
+  // Avoid recursive calls.
+  if (in_restacking_ || force_hidden_)
+    return;
+
+  aura::Window* window = GetTopmostWindowWithBackdrop();
+  if (!window) {
+    // Hide backdrop since no suitable window was found.
+    Hide();
+    return;
+  }
+  // We are changing the order of windows which will cause recursion.
+  base::AutoReset<bool> lock(&in_restacking_, true);
+  EnsureBackdropWidget();
+  UpdateAccessibilityMode();
+
+  if (window == backdrop_window_ && backdrop_->IsVisible())
+    return;
+  if (window->GetRootWindow() != backdrop_window_->GetRootWindow())
+    return;
+
+  if (!backdrop_->IsVisible())
+    Show();
+
+  // Since the backdrop needs to be immediately behind the window and the
+  // stacking functions only guarantee a "it's above or below", we need
+  // to re-arrange the two windows twice.
+  container_->StackChildAbove(backdrop_window_, window);
+  container_->StackChildAbove(window, backdrop_window_);
+}
+
+void BackdropController::OnOverviewModeStarting() {
+  force_hidden_ = true;
+  Hide();
+}
+
+void BackdropController::OnOverviewModeEnded() {
+  force_hidden_ = false;
+  UpdateBackdrop();
+}
+
+void BackdropController::OnAccessibilityModeChanged(
+    AccessibilityNotificationVisibility notify) {
+  UpdateBackdrop();
+}
+
+void BackdropController::EnsureBackdropWidget() {
+  if (backdrop_)
+    return;
+
+  backdrop_ = new views::Widget;
+  views::Widget::InitParams params(
+      views::Widget::InitParams::TYPE_WINDOW_FRAMELESS);
+  params.bounds = container_->GetBoundsInScreen();
+  params.layer_type = ui::LAYER_SOLID_COLOR;
+  params.name = "WorkspaceBackdropDelegate";
+  // To disallow the MRU list from picking this window up it should not be
+  // activateable.
+  params.activatable = views::Widget::InitParams::ACTIVATABLE_NO;
+  DCHECK_NE(kShellWindowId_Invalid, container_->id());
+  RootWindowController::ForWindow(container_)
+      ->ConfigureWidgetInitParamsForContainer(backdrop_, container_->id(),
+                                              &params);
+  backdrop_->Init(params);
+  backdrop_window_ = backdrop_->GetNativeWindow();
+  backdrop_window_->SetName("Backdrop");
+  ::wm::SetWindowVisibilityAnimationType(
+      backdrop_window_, ::wm::WINDOW_VISIBILITY_ANIMATION_TYPE_FADE);
+  backdrop_window_->layer()->SetColor(SK_ColorBLACK);
+}
+
+void BackdropController::UpdateAccessibilityMode() {
+  if (!backdrop_)
+    return;
+
+  bool enabled =
+      Shell::Get()->accessibility_delegate()->IsSpokenFeedbackEnabled();
+  if (enabled) {
+    if (!backdrop_event_handler_) {
+      backdrop_event_handler_ = base::MakeUnique<BackdropEventHandler>();
+      original_event_handler_ =
+          backdrop_window_->SetTargetHandler(backdrop_event_handler_.get());
+    }
+  } else if (backdrop_event_handler_) {
+    backdrop_window_->SetTargetHandler(original_event_handler_);
+    backdrop_event_handler_.reset();
+  }
+}
+
+aura::Window* BackdropController::GetTopmostWindowWithBackdrop() {
+  // ARC app should always have a backdrop when spoken feedback is enabled.
+  if (Shell::Get()->accessibility_delegate()->IsSpokenFeedbackEnabled()) {
+    aura::Window* active_window = wm::GetActiveWindow();
+    if (active_window && active_window->parent() == container_ &&
+        active_window->GetProperty(aura::client::kAppType) ==
+            static_cast<int>(AppType::ARC_APP)) {
+      return active_window;
+    }
+  }
+
+  const aura::Window::Windows windows = container_->children();
+  for (auto window_iter = windows.rbegin(); window_iter != windows.rend();
+       ++window_iter) {
+    aura::Window* window = *window_iter;
+    if (window != backdrop_window_ && window->layer()->GetTargetVisibility() &&
+        window->type() == ui::wm::WINDOW_TYPE_NORMAL &&
+        ::wm::CanActivateWindow(window) && WindowShouldHaveBackdrop(window)) {
+      return window;
+    }
+  }
+  return nullptr;
+}
+
+bool BackdropController::WindowShouldHaveBackdrop(aura::Window* window) {
+  if (window->GetAllPropertyKeys().count(aura::client::kHasBackdrop) &&
+      window->GetProperty(aura::client::kHasBackdrop)) {
+    return true;
+  }
+  return delegate_ ? delegate_->HasBackdrop(window) : false;
+}
+
+void BackdropController::Show() {
+  backdrop_->Show();
+  backdrop_->SetFullscreen(true);
+}
+
+void BackdropController::Hide() {
+  if (!backdrop_)
+    return;
+  backdrop_->Close();
+  backdrop_ = nullptr;
+  backdrop_window_ = nullptr;
+  original_event_handler_ = nullptr;
+  backdrop_event_handler_.reset();
+}
+
+}  // namespace ash