Implement app list rounded rect background

1. Set a mask layer to create a rounded rect background.
2. Change the corner radius based on app list height.

Specs: https://screenshot.googleplex.com/xVbKhQhE9xf

Bug: 860822
Change-Id: I3db9f1ebb29978b1dd0804afbb8accf253db2751
Reviewed-on: https://chromium-review.googlesource.com/1138636Reviewed-by: Yury Khmel <khmel@chromium.org>
Commit-Queue: Weidong Guo <weidongg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576248}

ash/app_list/views/app_list_view.cc

@@ -98,6 +98,13 @@ constexpr float kAppListAnimationDurationFromFullscreenMs = 250;
 // The app list opacity when the tablet mode is enabled.
 constexpr float kAppListOpacityInTabletMode = 0.1;
 
+// The background corner radius in peeking and fullscreen state.
+constexpr int kAppListPeekingBackgroundRadius = 28;
+constexpr int kAppListFullscreenBackgroundRadius = 0;
+
+// The threshold beyond which the background radius starts transition.
+constexpr int kAppListBackgroundTransitionThreshold = 156;
+
 // Set animation durations to 0 for testing.
 static bool short_animations_for_testing;
 
@@ -279,6 +286,7 @@ AppListView::AppListView(AppListViewDelegate* delegate)
       state_animation_metrics_reporter_(
           std::make_unique<StateAnimationMetricsReporter>()),
       is_home_launcher_enabled_(app_list::features::IsHomeLauncherEnabled()),
+      is_new_style_launcher_enabled_(features::IsNewStyleLauncherEnabled()),
       weak_ptr_factory_(this) {
   CHECK(delegate);
 
@@ -1062,6 +1070,7 @@ void AppListView::Layout() {
 
   contents_view->Layout();
   app_list_background_shield_->SetBoundsRect(contents_bounds);
+  UpdateBackgroundRadius();
 }
 
 void AppListView::GetAccessibleNodeData(ui::AXNodeData* node_data) {
@@ -1497,4 +1506,36 @@ bool AppListView::ShouldIgnoreScrollEvents() {
          GetRootAppsGridView()->pagination_model()->has_transition();
 }
 
+void AppListView::UpdateBackgroundRadius() {
+  if (!is_new_style_launcher_enabled_)
+    return;
+
+  const int current_height = GetCurrentAppListHeight();
+  const int fullscreen_height = GetDisplayNearestView().size().height();
+  const int threshold_height =
+      fullscreen_height - kAppListBackgroundTransitionThreshold;
+  int background_radius = kAppListPeekingBackgroundRadius;
+  if (current_height > threshold_height) {
+    background_radius = gfx::Tween::IntValueBetween(
+        static_cast<double>(current_height - threshold_height) /
+            kAppListBackgroundTransitionThreshold,
+        kAppListPeekingBackgroundRadius, kAppListFullscreenBackgroundRadius);
+  }
+
+  // Resetting mask layer is heavy operation, so avoid doing so if radius does
+  // not change.
+  static int previous_background_radius = -1;
+  if (previous_background_radius == background_radius)
+    return;
+
+  app_list_background_mask_ = views::Painter::CreatePaintedLayer(
+      views::Painter::CreateSolidRoundRectPainter(SK_ColorBLACK,
+                                                  background_radius));
+  app_list_background_mask_->layer()->SetFillsBoundsOpaquely(false);
+  app_list_background_mask_->layer()->SetBounds(GetContentsBounds());
+  app_list_background_shield_->layer()->SetMaskLayer(
+      app_list_background_mask_->layer());
+  previous_background_radius = background_radius;
+}
+
 }  // namespace app_list

ash/app_list/views/app_list_view.h

@@ -324,6 +324,9 @@ class APP_LIST_EXPORT AppListView : public views::WidgetDelegateView,
   // Returns true if scroll events should be ignored.
   bool ShouldIgnoreScrollEvents();
 
+  // Updates corner radius of the app list background.
+  void UpdateBackgroundRadius();
+
   AppListViewDelegate* delegate_;    // Weak. Owned by AppListService.
   AppListModel* const model_;        // Not Owned.
   SearchModel* const search_model_;  // Not Owned.
@@ -340,6 +343,10 @@ class APP_LIST_EXPORT AppListView : public views::WidgetDelegateView,
   // Owned by the app list's widget. Null if the fullscreen app list is not
   // enabled.
   views::View* app_list_background_shield_ = nullptr;
+
+  // The mask layer to create rounded corner of the app list background.
+  std::unique_ptr<ui::LayerOwner> app_list_background_mask_ = nullptr;
+
   // Whether tablet mode is active.
   bool is_tablet_mode_ = false;
   // Whether the shelf is oriented on the side.
@@ -404,6 +411,9 @@ class APP_LIST_EXPORT AppListView : public views::WidgetDelegateView,
   // Whether the home launcher feature is enabled.
   const bool is_home_launcher_enabled_;
 
+  // True if new style launcher feature is enabled.
+  const bool is_new_style_launcher_enabled_;
+
   base::WeakPtrFactory<AppListView> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AppListView);