ambient: Show lockscreen contents on detecting user interaction.

In ambient mode, when user interacting with the background image by
mouse or gesture, lock screen contents (login pod and media control
view) need be shown on top for users to either do re-authentication,
or media control.

This CL implements a prototype of this view transaction by:
1. Show the lock screen contents, and
2. Fade-out the current shown image.

Bug: b/149246238
Test: manually.
Change-Id: Ie31c666cdfaddefc863ff8173dc185d73ef19178
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2110689
Commit-Queue: Meilin Wang <meilinw@chromium.org>
Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757120}

ash/ambient/ambient_controller.cc

@@ -11,6 +11,7 @@
 #include "ash/ambient/ui/ambient_container_view.h"
 #include "ash/ambient/util/ambient_util.h"
 #include "ash/assistant/assistant_controller.h"
+#include "ash/assistant/util/animation_util.h"
 #include "ash/login/ui/lock_screen.h"
 #include "ash/public/cpp/ambient/ambient_mode_state.h"
 #include "ash/public/cpp/ambient/ambient_prefs.h"
@@ -93,20 +94,17 @@ void AmbientController::OnAmbientModeEnabled(bool enabled) {
 }
 
 void AmbientController::OnLockStateChanged(bool locked) {
-  if (!locked) {
-    // We should already exit ambient mode at this time, as the ambient
-    // container needs to be closed to uncover the login port for
-    // re-authentication.
+  if (locked) {
+    // Show ambient mode when entering lock screen.
     DCHECK(!container_view_);
-    return;
+    Show();
+  } else {
+    // Destroy ambient mode after user re-login.
+    Destroy();
   }
-
-  // Show the ambient container on top of the lock screen.
-  DCHECK(!container_view_);
-  Start();
 }
 
-void AmbientController::Start() {
+void AmbientController::Show() {
   if (!CanStartAmbientMode()) {
     // TODO(wutao): Show a toast to indicate that Ambient mode is not ready.
     return;
@@ -121,14 +119,34 @@ void AmbientController::Start() {
   ambient_state_.SetAmbientModeEnabled(true);
 }
 
-void AmbientController::Stop() {
+void AmbientController::Destroy() {
   ambient_state_.SetAmbientModeEnabled(false);
 }
+
 void AmbientController::Toggle() {
   if (container_view_)
-    Stop();
+    Destroy();
   else
-    Start();
+    Show();
+}
+
+void AmbientController::OnBackgroundPhotoEvents() {
+  refresh_timer_.Stop();
+
+  // Move the |AmbientModeContainer| beneath the |LockScreenWidget| to show the
+  // lock screen contents on top before the fade-out animation.
+  auto* ambient_window = container_view_->GetWidget()->GetNativeWindow();
+  ambient_window->parent()->StackChildAtBottom(ambient_window);
+
+  // Start fading out the current background photo.
+  StartFadeOutAnimation();
+}
+
+void AmbientController::StartFadeOutAnimation() {
+  // We fade out the |PhotoView| on its own layer instead of using the general
+  // layer of the widget, otherwise it will reveal the color of the lockscreen
+  // wallpaper beneath.
+  container_view_->FadeOutPhotoView();
 }
 
 void AmbientController::CreateContainerView() {
@@ -146,9 +164,6 @@ void AmbientController::DestroyContainerView() {
 }
 
 void AmbientController::RefreshImage() {
-  if (!PhotoController::Get())
-    return;
-
   if (photo_model_.ShouldFetchImmediately()) {
     // TODO(b/140032139): Defer downloading image if it is animating.
     base::SequencedTaskRunnerHandle::Get()->PostDelayedTask(

ash/ambient/ambient_controller.h

@@ -45,12 +45,21 @@ class ASH_EXPORT AmbientController : public views::WidgetObserver,
   // SessionObserver:
   void OnLockStateChanged(bool locked) override;
 
-  void Start();
-  void Stop();
+  // Creates and displays the ambient mode screen on top of the lock screen.
+  void Show();
+  // Destroys the ambient mode screen widget.
+  void Destroy();
+  // Toggle between show and destroy the ambient mode screen.
+  // Should be removed once we delete the shortcut entry point.
   void Toggle();
 
   PhotoModel* photo_model() { return &photo_model_; }
 
+  // Handles user interactions on the background photo. For now the behavior
+  // is showing lock screen contents (login pod and media control view) on top
+  // while fading-out the current shown image.
+  void OnBackgroundPhotoEvents();
+
   AmbientContainerView* get_container_view_for_testing() {
     return container_view_;
   }
@@ -69,6 +78,8 @@ class ASH_EXPORT AmbientController : public views::WidgetObserver,
   void GetNextImage();
   void OnPhotoDownloaded(bool success, const gfx::ImageSkia& image);
 
+  void StartFadeOutAnimation();
+
   AmbientViewDelegateImpl delegate_{this};
   AmbientContainerView* container_view_ = nullptr;   // Owned by view hierarchy.
   PhotoModel photo_model_;

ash/ambient/ambient_view_delegate_impl.cc

@@ -21,18 +21,7 @@ PhotoModel* AmbientViewDelegateImpl::GetPhotoModel() {
 }
 
 void AmbientViewDelegateImpl::OnBackgroundPhotoEvents() {
-  // Exit ambient mode by closing the widget when user interacts with the
-  // background photo using mouse or gestures. We do this asynchronously to
-  // ensure that for a mouse moved event, the widget will be destroyed *after*
-  // its cursor has been updated in |RootView::OnMouseMoved|.
-  base::SequencedTaskRunnerHandle::Get()->PostTask(
-      FROM_HERE,
-      base::BindOnce(
-          [](const base::WeakPtr<AmbientViewDelegateImpl>& weak_ptr) {
-            if (weak_ptr)
-              weak_ptr->ambient_controller_->Stop();
-          },
-          weak_factory_.GetWeakPtr()));
+  ambient_controller_->OnBackgroundPhotoEvents();
 }
 
 }  // namespace ash

ash/ambient/ui/ambient_container_view.cc

@@ -12,6 +12,7 @@
 #include "ash/ambient/ui/photo_view.h"
 #include "ash/ambient/util/ambient_util.h"
 #include "ash/assistant/assistant_controller.h"
+#include "ash/assistant/util/animation_util.h"
 #include "ash/login/ui/lock_screen.h"
 #include "ash/public/cpp/shell_window_ids.h"
 #include "ash/shell.h"
@@ -27,6 +28,12 @@ namespace {
 // Ambient Assistant container view appearance.
 constexpr int kAmbientAssistantContainerViewPreferredHeightDip = 128;
 
+// TODO(meilinw): temporary values for dev purpose, need to be updated with the
+// final spec.
+constexpr float kBackgroundPhotoOpacity = 0.5f;
+constexpr base::TimeDelta kBackgroundPhotoFadeOutAnimationDuration =
+    base::TimeDelta::FromMilliseconds(500);
+
 aura::Window* GetContainer() {
   aura::Window* container = nullptr;
   if (ambient::util::IsShowing(LockScreen::ScreenType::kLock))
@@ -41,7 +48,7 @@ void CreateWidget(AmbientContainerView* view) {
   params.parent = GetContainer();
   params.type = views::Widget::InitParams::TYPE_WINDOW_FRAMELESS;
   params.delegate = view;
-  params.name = view->GetClassName();
+  params.name = "AmbientModeContainer";
 
   views::Widget* widget = new views::Widget;
   widget->Init(std::move(params));
@@ -76,6 +83,16 @@ void AmbientContainerView::Layout() {
                 kAmbientAssistantContainerViewPreferredHeightDip));
 }
 
+void AmbientContainerView::FadeOutPhotoView() {
+  DCHECK(photo_view_);
+
+  photo_view_->layer()->GetAnimator()->StartAnimation(
+      assistant::util::CreateLayerAnimationSequence(
+          assistant::util::CreateOpacityElement(
+              kBackgroundPhotoOpacity,
+              kBackgroundPhotoFadeOutAnimationDuration)));
+}
+
 void AmbientContainerView::Init() {
   CreateWidget(this);
   // TODO(b/139954108): Choose a better dark mode theme color.

ash/ambient/ui/ambient_container_view.h

@@ -26,6 +26,9 @@ class ASH_EXPORT AmbientContainerView : public views::WidgetDelegateView {
   gfx::Size CalculatePreferredSize() const override;
   void Layout() override;
 
+  // Fade out the background photo.
+  void FadeOutPhotoView();
+
  private:
   void Init();
 

ash/ambient/ui/ambient_view_delegate.h

@@ -17,7 +17,7 @@ class ASH_EXPORT AmbientViewDelegate {
 
   virtual PhotoModel* GetPhotoModel() = 0;
 
-  // Invoked when user interacts with the background photo using mouse,
+  // Invoked when user interacting with the background photo using mouse,
   // touchpad, or touchscreen.
   virtual void OnBackgroundPhotoEvents() = 0;
 };