Pass mouse scrolling over empty area to Shelf

Bug: 1071218
Change-Id: I79da1693562db63262084853b1d3c35cdb97518e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2537936
Commit-Queue: Angus McLean <angusmclean@chromium.org>
Reviewed-by: Toni Baržić <tbarzic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827869}

ash/shelf/scrollable_shelf_view.cc

@@ -1649,6 +1649,15 @@ bool ScrollableShelfView::ProcessGestureEvent(const ui::GestureEvent& event) {
 
 void ScrollableShelfView::HandleMouseWheelEvent(ui::MouseWheelEvent* event) {
   // Note that the scrolling from touchpad is propagated as mouse wheel event.
+  // Let the shelf handle mouse wheel events over the empty area of the shelf
+  // view, as these events would be ignored by the scrollable shelf view.
+  gfx::Point location_in_shelf_view = event->location();
+  View::ConvertPointToTarget(this, shelf_view_, &location_in_shelf_view);
+  if (!shelf_view_->LocationInsideVisibleShelfItemBounds(
+          location_in_shelf_view)) {
+    GetShelf()->ProcessMouseWheelEvent(event, false);
+    return;
+  }
 
   if (!ShouldHandleScroll(gfx::Vector2dF(event->x_offset(), event->y_offset()),
                           /*is_gesture_fling=*/false)) {

ash/shelf/scrollable_shelf_view_unittest.cc

@@ -871,6 +871,55 @@ TEST_F(ScrollableShelfViewTest, RipOffShelfItem) {
 }
 
 // Verifies that the scrollable shelf handles the mouse wheel event as expected.
+TEST_F(ScrollableShelfViewTest, MouseWheelOnEmptyShelfShouldExpandAppList) {
+  // First mouse wheel over apps and then over empty shelf. When apps are not
+  // overflowing, and we mouse wheel over the app icons, the launcher should
+  // stay hidden. When we mouse wheel over the empty area of the shelf, the
+  // launcher should expand. https://crbug.com/1071218
+
+  // Add a couple of apps to start, so we have some to put the cursor over for
+  // testing.
+  AddAppShortcut();
+  AddAppShortcut();
+
+  int shelf_scroll_threshold =
+      ShelfConfig::Get()->mousewheel_scroll_offset_threshold();
+  GetEventGenerator()->MoveMouseTo(
+      scrollable_shelf_view_->GetBoundsInScreen().CenterPoint());
+  GetEventGenerator()->MoveMouseWheel(0, shelf_scroll_threshold + 1);
+
+  // The app list's view is lazily loaded. Since this is the first time, and we
+  // didn't scroll in the right spot, it shouldn't have been created yet.
+  EXPECT_EQ(nullptr,
+            Shell::Get()->app_list_controller()->presenter()->GetView());
+
+  auto empty_shelf_point = scrollable_shelf_view_->GetBoundsInScreen().origin();
+  empty_shelf_point.Offset(10, 10);
+  GetEventGenerator()->MoveMouseTo(empty_shelf_point);
+  GetEventGenerator()->MoveMouseWheel(0, shelf_scroll_threshold + 1);
+  EXPECT_EQ(AppListViewState::kPeeking, Shell::Get()
+                                            ->app_list_controller()
+                                            ->presenter()
+                                            ->GetView()
+                                            ->app_list_state());
+
+  // Scrolling again should expand to all apps.
+  GetEventGenerator()->MoveMouseWheel(0, shelf_scroll_threshold + 1);
+  EXPECT_EQ(AppListViewState::kFullscreenAllApps, Shell::Get()
+                                                      ->app_list_controller()
+                                                      ->presenter()
+                                                      ->GetView()
+                                                      ->app_list_state());
+
+  // Scrolling again will close the app list.
+  GetEventGenerator()->MoveMouseWheel(0, shelf_scroll_threshold + 1);
+  EXPECT_EQ(AppListViewState::kClosed, Shell::Get()
+                                           ->app_list_controller()
+                                           ->presenter()
+                                           ->GetView()
+                                           ->app_list_state());
+}
+
 TEST_F(ScrollableShelfViewTest, ScrollsByMouseWheelEvent) {
   AddAppShortcutsUntilOverflow();
   ASSERT_EQ(ScrollableShelfView::kShowRightArrowButton,

ash/shelf/shelf_view.cc

@@ -497,12 +497,16 @@ void ShelfView::AnnounceShelfItemNotificationBadge(views::View* button) {
                                                /*send_native_event=*/true);
 }
 
+bool ShelfView::LocationInsideVisibleShelfItemBounds(
+    const gfx::Point& location) const {
+  return visible_shelf_item_bounds_union_.Contains(location);
+}
+
 bool ShelfView::ShouldHideTooltip(const gfx::Point& cursor_location) const {
   // There are thin gaps between launcher buttons but the tooltip shouldn't hide
   // in the gaps, but the tooltip should hide if the mouse moved totally outside
   // of the buttons area.
-
-  return !visible_shelf_item_bounds_union_.Contains(cursor_location);
+  return !LocationInsideVisibleShelfItemBounds(cursor_location);
 }
 
 const std::vector<aura::Window*> ShelfView::GetOpenWindowsForView(

ash/shelf/shelf_view.h

@@ -117,6 +117,10 @@ class ASH_EXPORT ShelfView : public views::AccessiblePaneView,
   // for showing tooltips without stuttering over gaps.
   void UpdateVisibleShelfItemBoundsUnion();
 
+  // Returns true if the given location is within the bounds of all visiable app
+  // icons. Used for tool tip visibility and scrolling event propogation.
+  bool LocationInsideVisibleShelfItemBounds(const gfx::Point& location) const;
+
   // ShelfTooltipDelegate:
   bool ShouldShowTooltipForView(const views::View* view) const override;
   bool ShouldHideTooltip(const gfx::Point& cursor_location) const override;