overview gesture: use scale-in-to-show home screen animation when go home.

When dragging a window from shelf, if the window should be taken to home
screen after the drag ends, use scale-in animation to show home screen.
If overview is active, then fade out overview windows.

Bug: 997885, 1026944
Change-Id: I11b92e152679fe32efc2fae0b30b71dcba4ccc74
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1949276
Commit-Queue: Xiaoqian Dai <xdai@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#721694}

ash/home_screen/drag_window_from_shelf_controller.cc

@@ -217,7 +217,7 @@ DragWindowFromShelfController::EndDrag(const gfx::Point& location_in_screen,
     DCHECK(!in_splitview);
     if (in_overview) {
       overview_controller->EndOverview(
-          OverviewSession::EnterExitOverviewType::kImmediateExit);
+          OverviewSession::EnterExitOverviewType::kFadeOutExit);
     }
     ScaleDownWindowAfterDrag();
     window_drag_result = ShelfWindowDragResult::kGoToHomeScreen;
@@ -229,7 +229,6 @@ DragWindowFromShelfController::EndDrag(const gfx::Point& location_in_screen,
     // dragged window to go to home screen.
     ScaleDownWindowAfterDrag();
     window_drag_result = ShelfWindowDragResult::kGoToHomeScreen;
-
   } else {
     window_drag_result = ShelfWindowDragResult::kGoToOverviewMode;
   }
@@ -350,7 +349,9 @@ void DragWindowFromShelfController::OnDragEnded(
                                              location_in_screen);
   }
 
-  Shell::Get()->home_screen_controller()->OnWindowDragEnded();
+  // Scale-in-to-show home screen if home screen should be shown after drag
+  // ends.
+  Shell::Get()->home_screen_controller()->OnWindowDragEnded(/*animate=*/true);
 
   // Clear the wallpaper dim and blur if not in overview after drag ends.
   // If in overview, the dim and blur will be cleared after overview ends.

ash/home_screen/home_screen_controller.cc

@@ -241,9 +241,13 @@ void HomeScreenController::OnWindowDragStarted() {
   UpdateVisibility();
 }
 
-void HomeScreenController::OnWindowDragEnded() {
+void HomeScreenController::OnWindowDragEnded(bool animate) {
   in_window_dragging_ = false;
   UpdateVisibility();
+  if (ShouldShowHomeScreen()) {
+    home_screen_presenter_.ScheduleOverviewModeAnimation(
+        HomeScreenPresenter::TransitionType::kScaleHomeIn, animate);
+  }
 }
 
 bool HomeScreenController::IsHomeScreenVisible() const {
@@ -359,12 +363,19 @@ void HomeScreenController::UpdateVisibility() {
   if (!window)
     return;
 
+  if (ShouldShowHomeScreen())
+    window->Show();
+  else
+    window->Hide();
+}
+
+bool HomeScreenController::ShouldShowHomeScreen() const {
+  const bool in_tablet_mode =
+      Shell::Get()->tablet_mode_controller()->InTabletMode();
   const bool in_overview =
       Shell::Get()->overview_controller()->InOverviewSession();
-  if (in_overview || in_wallpaper_preview_ || in_window_dragging_)
-    window->Hide();
-  else
-    window->Show();
+  return in_tablet_mode && !in_overview && !in_wallpaper_preview_ &&
+         !in_window_dragging_;
 }
 
 }  // namespace ash

ash/home_screen/home_screen_controller.h

@@ -45,7 +45,9 @@ class ASH_EXPORT HomeScreenController : public OverviewObserver,
   // Called when a window starts/ends dragging. If the home screen is shown, we
   // should hide it during dragging a window and reshow it when the drag ends.
   void OnWindowDragStarted();
-  void OnWindowDragEnded();
+  // If |animate| is true, scale-in-to-show home screen if home screen should
+  // be shown after drag ends.
+  void OnWindowDragEnded(bool animate);
 
   // True if home screen is visible.
   bool IsHomeScreenVisible() const;
@@ -79,6 +81,10 @@ class ASH_EXPORT HomeScreenController : public OverviewObserver,
   // |display_id| - the home screen display ID.
   void NotifyHomeLauncherTransitionEnded(bool shown, int64_t display_id);
 
+  // Returns true if home screen should be shown based on the current
+  // configuration.
+  bool ShouldShowHomeScreen() const;
+
   // Whether the wallpaper is being previewed. The home screen should be hidden
   // during wallpaper preview.
   bool in_wallpaper_preview_ = false;

ash/wm/overview/overview_utils.cc

@@ -75,7 +75,8 @@ void FadeInWidgetAndMaybeSlideOnEnter(views::Widget* widget,
     }
     window->SetTransform(new_transform);
   }
-  window->layer()->SetOpacity(0.0f);
+
+  // Fade in the widget from its current opacity.
   ScopedOverviewAnimationSettings scoped_overview_animation_settings(
       animation_type, window);
   window->layer()->SetOpacity(1.0f);
@@ -100,9 +101,8 @@ void FadeOutWidgetAndMaybeSlideOnExit(std::unique_ptr<views::Widget> widget,
     return;
   }
 
-  widget->SetOpacity(1.f);
-  // Fade out the widget. This animation continues past the lifetime of overview
-  // mode items.
+  // Fade out the widget from its current opacity. This animation continues past
+  // the lifetime of overview mode items.
   ScopedOverviewAnimationSettings animation_settings(animation_type,
                                                      widget->GetNativeWindow());
   // CleanupAnimationObserver will delete itself (and the widget) when the

ash/wm/tablet_mode/tablet_mode_browser_window_drag_delegate.cc

@@ -180,7 +180,8 @@ class TabletModeBrowserWindowDragDelegate::WindowsHider
     DCHECK(!Shell::Get()->overview_controller()->InOverviewSession());
 
     // May reshow the home launcher after dragging.
-    Shell::Get()->home_screen_controller()->OnWindowDragEnded();
+    Shell::Get()->home_screen_controller()->OnWindowDragEnded(
+        /*animate=*/false);
 
     // Clears the background wallpaper blur.
     auto* wallpaper_view =