overview: Show a drop target in the display being dragged in

For multi-display dragging from overview, there shall be a drop target
in the display being dragged in.

Test: manual
Bug: 961170
Change-Id: If8439a301310f82896a776589c3d6be751b9504e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1972297Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Commit-Queue: Avery Musbach <amusbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726184}

ash/wm/overview/overview_grid.cc

@@ -187,6 +187,7 @@ class ShutdownAnimationFpsCounterObserver : public OverviewObserver {
 // Creates |drop_target_widget_|. It's created when a window or overview item is
 // dragged around, and destroyed when the drag ends.
 std::unique_ptr<views::Widget> CreateDropTargetWidget(
+    aura::Window* root_window,
     aura::Window* dragged_window) {
   views::Widget::InitParams params;
   params.type = views::Widget::InitParams::TYPE_WINDOW_FRAMELESS;
@@ -194,7 +195,7 @@ std::unique_ptr<views::Widget> CreateDropTargetWidget(
   params.activatable = views::Widget::InitParams::Activatable::ACTIVATABLE_NO;
   params.opacity = views::Widget::InitParams::WindowOpacity::kTranslucent;
   params.accept_events = false;
-  params.parent = dragged_window->parent();
+  params.parent = desks_util::GetActiveDeskContainerForRoot(root_window);
   params.init_properties_container.SetProperty(kHideInDeskMiniViewKey, true);
   auto widget = std::make_unique<views::Widget>();
   widget->set_focus_on_creation(false);
@@ -655,17 +656,32 @@ void OverviewGrid::RemoveItem(OverviewItem* overview_item,
   }
 }
 
-void OverviewGrid::AddDropTargetForDraggingFromOverview(
+void OverviewGrid::AddDropTargetForDraggingFromThisGrid(
     OverviewItem* dragged_item) {
-  DCHECK_EQ(dragged_item->GetWindow()->GetRootWindow(), root_window_);
   DCHECK(!drop_target_widget_);
-  drop_target_widget_ = CreateDropTargetWidget(dragged_item->GetWindow());
+  drop_target_widget_ =
+      CreateDropTargetWidget(root_window_, dragged_item->GetWindow());
   const size_t position = GetOverviewItemIndex(dragged_item) + 1u;
   overview_session_->AddItem(drop_target_widget_->GetNativeWindow(),
                              /*reposition=*/true, /*animate=*/false,
                              /*ignored_items=*/{dragged_item}, position);
 }
 
+void OverviewGrid::AddDropTargetNotForDraggingFromThisGrid(
+    aura::Window* dragged_window,
+    bool animate) {
+  DCHECK(!drop_target_widget_);
+  drop_target_widget_ = CreateDropTargetWidget(root_window_, dragged_window);
+  aura::Window* drop_target_window = drop_target_widget_->GetNativeWindow();
+  if (animate) {
+    drop_target_widget_->SetOpacity(0.f);
+    ScopedOverviewAnimationSettings settings(
+        OVERVIEW_ANIMATION_DROP_TARGET_FADE, drop_target_window);
+    drop_target_widget_->SetOpacity(1.f);
+  }
+  overview_session_->AddItem(drop_target_window, /*reposition=*/true, animate);
+}
+
 void OverviewGrid::RemoveDropTarget() {
   DCHECK(drop_target_widget_);
   OverviewItem* drop_target = GetDropTarget();
@@ -683,6 +699,7 @@ void OverviewGrid::SetBoundsAndUpdatePositions(
 }
 
 void OverviewGrid::RearrangeDuringDrag(
+    aura::Window* root_window_being_dragged_in,
     aura::Window* dragged_window,
     SplitViewDragIndicators::WindowDraggingState window_dragging_state) {
   OverviewItem* drop_target = GetDropTarget();
@@ -692,11 +709,12 @@ void OverviewGrid::RearrangeDuringDrag(
     ScopedOverviewAnimationSettings settings(
         OVERVIEW_ANIMATION_DROP_TARGET_FADE,
         drop_target_widget_->GetNativeWindow());
-    drop_target->SetOpacity(
-        SplitViewDragIndicators::GetSnapPosition(window_dragging_state) ==
-                SplitViewController::NONE
-            ? 1.f
-            : 0.f);
+    drop_target->SetOpacity(root_window_being_dragged_in == root_window_ &&
+                                    SplitViewDragIndicators::GetSnapPosition(
+                                        window_dragging_state) ==
+                                        SplitViewController::NONE
+                                ? 1.f
+                                : 0.f);
   }
 
   // Update the grid's bounds.
@@ -763,22 +781,10 @@ void OverviewGrid::OnSelectorItemDragEnded(bool snap) {
 
 void OverviewGrid::OnWindowDragStarted(aura::Window* dragged_window,
                                        bool animate) {
-  DCHECK_EQ(dragged_window->GetRootWindow(), root_window_);
-  DCHECK(!drop_target_widget_);
   dragged_window_ = dragged_window;
-  drop_target_widget_ = CreateDropTargetWidget(dragged_window);
-  aura::Window* drop_target_window = drop_target_widget_->GetNativeWindow();
-  if (animate) {
-    drop_target_widget_->SetOpacity(0.f);
-    ScopedOverviewAnimationSettings settings(
-        OVERVIEW_ANIMATION_DROP_TARGET_FADE, drop_target_window);
-    drop_target_widget_->SetOpacity(1.f);
-  }
-  overview_session_->AddItem(drop_target_window, /*reposition=*/true, animate);
-
+  AddDropTargetNotForDraggingFromThisGrid(dragged_window, animate);
   // Stack the |dragged_window| at top during drag.
   dragged_window->parent()->StackChildAtTop(dragged_window);
-
   // Called to set caption and title visibility during dragging.
   OnSelectorItemDragStarted(/*item=*/nullptr);
 }
@@ -790,7 +796,7 @@ void OverviewGrid::OnWindowDragContinued(
   DCHECK_EQ(dragged_window_, dragged_window);
   DCHECK_EQ(dragged_window->GetRootWindow(), root_window_);
 
-  RearrangeDuringDrag(dragged_window, window_dragging_state);
+  RearrangeDuringDrag(root_window_, dragged_window, window_dragging_state);
   UpdateDropTargetBackgroundVisibility(nullptr, location_in_screen);
 
   aura::Window* target_window =

ash/wm/overview/overview_grid.h

@@ -128,7 +128,12 @@ class ASH_EXPORT OverviewGrid : public SplitViewObserver,
   // drop target takes the place of |dragged_item|. Does not animate the
   // repositioning or fade in the drop target. The visual effect is that the
   // drop target was already present but was covered by |dragged_item|.
-  void AddDropTargetForDraggingFromOverview(OverviewItem* dragged_item);
+  void AddDropTargetForDraggingFromThisGrid(OverviewItem* dragged_item);
+
+  // Adds a drop target for |dragged_window|. Used for dragging from another
+  // grid, from the top in tablet mode, or from the shelf in tablet mode.
+  void AddDropTargetNotForDraggingFromThisGrid(aura::Window* dragged_window,
+                                               bool animate);
 
   // Removes the drop target from the grid.
   void RemoveDropTarget();
@@ -141,8 +146,9 @@ class ASH_EXPORT OverviewGrid : public SplitViewObserver,
       bool animate);
 
   // Updates overview bounds and hides the drop target when a preview area is
-  // shown.
+  // shown or |root_window_being_dragged_in| does not equal |root_window_|.
   void RearrangeDuringDrag(
+      aura::Window* root_window_being_dragged_in,
       aura::Window* dragged_window,
       SplitViewDragIndicators::WindowDraggingState window_dragging_state);
 

ash/wm/overview/overview_session.cc

@@ -357,15 +357,28 @@ void OverviewSession::UpdateSplitViewDragIndicatorsWindowDraggingStates(
   }
 }
 
-void OverviewSession::RearrangeDuringDrag(aura::Window* dragged_window) {
+void OverviewSession::RearrangeDuringDrag(
+    aura::Window* root_window_being_dragged_in,
+    aura::Window* dragged_window) {
   for (std::unique_ptr<OverviewGrid>& grid : grid_list_) {
     DCHECK(grid->split_view_drag_indicators());
     grid->RearrangeDuringDrag(
-        dragged_window,
+        root_window_being_dragged_in, dragged_window,
         grid->split_view_drag_indicators()->current_window_dragging_state());
   }
 }
 
+void OverviewSession::UpdateDropTargetsBackgroundVisibilities(
+    OverviewItem* dragged_item,
+    const gfx::PointF& location_in_screen) {
+  for (std::unique_ptr<OverviewGrid>& grid : grid_list_) {
+    if (grid->GetDropTarget()) {
+      grid->UpdateDropTargetBackgroundVisibility(dragged_item,
+                                                 location_in_screen);
+    }
+  }
+}
+
 OverviewGrid* OverviewSession::GetGridWithRootWindow(
     aura::Window* root_window) {
   for (std::unique_ptr<OverviewGrid>& grid : grid_list_) {
@@ -431,6 +444,13 @@ void OverviewSession::RemoveItem(OverviewItem* overview_item) {
   UpdateNoWindowsWidget();
 }
 
+void OverviewSession::RemoveDropTargets() {
+  for (std::unique_ptr<OverviewGrid>& grid : grid_list_) {
+    if (grid->GetDropTarget())
+      grid->RemoveDropTarget();
+  }
+}
+
 void OverviewSession::InitiateDrag(OverviewItem* item,
                                    const gfx::PointF& location_in_screen,
                                    bool is_touch_dragging) {

ash/wm/overview/overview_session.h

@@ -145,7 +145,14 @@ class ASH_EXPORT OverviewSession : public display::DisplayObserver,
       SplitViewController::SnapPosition snap_position);
 
   // See |OverviewGrid::RearrangeDuringDrag|.
-  void RearrangeDuringDrag(aura::Window* dragged_window);
+  void RearrangeDuringDrag(aura::Window* root_window_being_dragged_in,
+                           aura::Window* dragged_window);
+
+  // Updates the appearance of each drop target to visually indicate when the
+  // dragged window is being dragged over it.
+  void UpdateDropTargetsBackgroundVisibilities(
+      OverviewItem* dragged_item,
+      const gfx::PointF& location_in_screen);
 
   // Retrieves the window grid whose root window matches |root_window|. Returns
   // nullptr if the window grid is not found.
@@ -172,6 +179,8 @@ class ASH_EXPORT OverviewSession : public display::DisplayObserver,
   // repositioned.
   void RemoveItem(OverviewItem* overview_item);
 
+  void RemoveDropTargets();
+
   void InitiateDrag(OverviewItem* item,
                     const gfx::PointF& location_in_screen,
                     bool is_touch_dragging);

ash/wm/overview/overview_window_drag_controller.cc

@@ -237,7 +237,7 @@ void OverviewWindowDragController::StartNormalDragMode(
       OVERVIEW_ANIMATION_LAYOUT_OVERVIEW_ITEMS_IN_OVERVIEW);
   original_scaled_size_ = item_->target_bounds().size();
   auto* overview_grid = item_->overview_grid();
-  overview_grid->AddDropTargetForDraggingFromOverview(item_);
+  overview_grid->AddDropTargetForDraggingFromThisGrid(item_);
 
   if (should_allow_split_view_) {
     overview_session_->SetSplitViewDragIndicatorsDraggedWindow(
@@ -336,7 +336,7 @@ void OverviewWindowDragController::ResetGesture() {
       Shell::Get()->mouse_cursor_filter()->HideSharedEdgeIndicator();
       item_->DestroyPhantomsForDragging();
     }
-    item_->overview_grid()->RemoveDropTarget();
+    overview_session_->RemoveDropTargets();
     if (should_allow_split_view_) {
       SplitViewController::Get(Shell::GetPrimaryRootWindow())
           ->OnWindowDragCanceled();
@@ -493,8 +493,21 @@ void OverviewWindowDragController::ContinueNormalDrag(
     // portrait mode.
     overview_grid->MaybeUpdateDesksWidgetBounds();
   }
-  overview_grid->UpdateDropTargetBackgroundVisibility(item_,
-                                                      location_in_screen);
+  if (AreMultiDisplayOverviewAndSplitViewEnabled()) {
+    OverviewGrid* grid_being_dragged_in =
+        overview_session_->GetGridWithRootWindow(GetRootWindowBeingDraggedIn());
+    if (!grid_being_dragged_in->GetDropTarget() &&
+        (!should_allow_split_view_ ||
+         SplitViewDragIndicators::GetSnapPosition(
+             grid_being_dragged_in->split_view_drag_indicators()
+                 ->current_window_dragging_state()) ==
+             SplitViewController::NONE)) {
+      grid_being_dragged_in->AddDropTargetNotForDraggingFromThisGrid(
+          item_->GetWindow(), /*animate=*/true);
+    }
+  }
+  overview_session_->UpdateDropTargetsBackgroundVisibilities(
+      item_, location_in_screen);
 
   bounds.set_x(centerpoint.x() - bounds.width() / 2.f);
   bounds.set_y(centerpoint.y() - bounds.height() / 2.f);
@@ -513,7 +526,7 @@ OverviewWindowDragController::CompleteNormalDrag(
     Shell::Get()->mouse_cursor_filter()->HideSharedEdgeIndicator();
     item_->DestroyPhantomsForDragging();
   }
-  overview_grid->RemoveDropTarget();
+  overview_session_->RemoveDropTargets();
 
   const gfx::Point rounded_screen_point =
       gfx::ToRoundedPoint(location_in_screen);
@@ -576,6 +589,7 @@ OverviewWindowDragController::CompleteNormalDrag(
     }
 
     SnapWindow(snap_position_);
+    overview_session_->PositionWindows(/*animate=*/true);
     return DragResult::kSuccessfulDragToSnap;
   }
 
@@ -591,11 +605,12 @@ void OverviewWindowDragController::UpdateDragIndicatorsAndOverviewGrid(
     return;
 
   snap_position_ = GetSnapPosition(location_in_screen);
+  aura::Window* root_window = GetRootWindowBeingDraggedIn();
   overview_session_->UpdateSplitViewDragIndicatorsWindowDraggingStates(
-      GetRootWindowBeingDraggedIn(), /*is_dragging=*/true,
+      root_window, /*is_dragging=*/true,
       SplitViewDragIndicators::WindowDraggingState::kFromOverview,
       snap_position_);
-  overview_session_->RearrangeDuringDrag(item_->GetWindow());
+  overview_session_->RearrangeDuringDrag(root_window, item_->GetWindow());
 }
 
 aura::Window* OverviewWindowDragController::GetRootWindowBeingDraggedIn()