overview gesture: do not start drag if swiping down on hotseat or shelf.

Bug: 997885
Change-Id: I1683b06cc4fd46cdfa46c681cf725157c0fb07f3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1912884
Commit-Queue: Xiaoqian Dai <xdai@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714757}

ash/shelf/shelf_layout_manager.cc

@@ -2194,7 +2194,7 @@ bool ShelfLayoutManager::StartShelfDrag(
     drag_amount_ = 0.f;
   }
 
-  MaybeStartDragWindowFromShelf(event_in_screen);
+  MaybeStartDragWindowFromShelf(event_in_screen, /*scroll_y=*/base::nullopt);
 
   return true;
 }
@@ -2433,7 +2433,8 @@ void ShelfLayoutManager::SendA11yAlertForFullscreenWorkspaceState(
 }
 
 bool ShelfLayoutManager::MaybeStartDragWindowFromShelf(
-    const ui::LocatedEvent& event_in_screen) {
+    const ui::LocatedEvent& event_in_screen,
+    base::Optional<float> scroll_y) {
   if (!features::IsDragFromShelfToHomeOrOverviewEnabled())
     return false;
   if (!IsTabletModeEnabled())
@@ -2467,6 +2468,9 @@ bool ShelfLayoutManager::MaybeStartDragWindowFromShelf(
     const gfx::Rect shelf_bounds = GetVisibleShelfBounds();
     if (event_in_screen.location().y() < shelf_bounds.y())
       return false;
+    // Do not start drag if it's a downward update event.
+    if (scroll_y.has_value() && *scroll_y > 0)
+      return false;
   }
 
   // Do not allow window drag if the previous dragged window is still animating.
@@ -2490,7 +2494,8 @@ void ShelfLayoutManager::MaybeUpdateWindowDrag(
     float scroll_x,
     float scroll_y) {
   if (!IsWindowDragInProgress() &&
-      !MaybeStartDragWindowFromShelf(event_in_screen)) {
+      !MaybeStartDragWindowFromShelf(event_in_screen,
+                                     base::make_optional(scroll_y))) {
     return;
   }
 

ash/shelf/shelf_layout_manager.h

@@ -513,7 +513,8 @@ class ASH_EXPORT ShelfLayoutManager : public AppListControllerObserver,
       WorkspaceWindowState current_workspace_window_state);
 
   // Maybe start/update/end the window drag when swiping up from the shelf.
-  bool MaybeStartDragWindowFromShelf(const ui::LocatedEvent& event_in_screen);
+  bool MaybeStartDragWindowFromShelf(const ui::LocatedEvent& event_in_screen,
+                                     base::Optional<float> scroll_y);
   void MaybeUpdateWindowDrag(const ui::LocatedEvent& event_in_screen,
                              float scroll_x,
                              float scroll_y);

ash/shelf/shelf_layout_manager_unittest.cc

@@ -4494,6 +4494,28 @@ TEST_F(ShelfLayoutManagerWindowDraggingTest, StartsDragAfterHotseatIsUp) {
   EndScroll(/*is_fling=*/false, 0.f);
 }
 
+TEST_F(ShelfLayoutManagerWindowDraggingTest, NoDragForDownwardEvent) {
+  std::unique_ptr<aura::Window> window =
+      AshTestBase::CreateTestWindow(gfx::Rect(0, 0, 400, 400));
+  wm::ActivateWindow(window.get());
+
+  Shelf* shelf = GetPrimaryShelf();
+  shelf->SetAutoHideBehavior(SHELF_AUTO_HIDE_BEHAVIOR_ALWAYS);
+  SwipeUpOnShelf();
+  EXPECT_EQ(SHELF_AUTO_HIDE_SHOWN, shelf->GetAutoHideState());
+  EXPECT_EQ(HotseatState::kExtended, GetShelfLayoutManager()->hotseat_state());
+
+  // Start drag on the extended hotseat.
+  const int hotseat_padding_size = ShelfConfig::Get()->hotseat_bottom_padding();
+  gfx::Rect hotseat_bounds =
+      GetShelfWidget()->hotseat_widget()->GetWindowBoundsInScreen();
+  StartScroll(hotseat_bounds.CenterPoint());
+  EXPECT_FALSE(IsWindowDragInProgress());
+  UpdateScroll(hotseat_bounds.height() + hotseat_padding_size);
+  EXPECT_FALSE(IsWindowDragInProgress());
+  EndScroll(/*is_fling=*/false, 0.f);
+}
+
 class ShelfLayoutManagerKeyboardTest : public AshTestBase {
  public:
   ShelfLayoutManagerKeyboardTest() = default;