overview: Support dragging an overview window from one grid to another

Test: ash_unittests All/SplitViewOverviewSessionInClamshellTestMultiDisplayOnly.DragAndDropIntoAnotherOverviewGrid/0
Test: ash_unittests All/SplitViewOverviewSessionInClamshellTestMultiDisplayOnly.OverviewWidgetStackingOrderWithMultiDisplayDragging/0
Bug: 961170
Change-Id: I56862dfd8094b72ce0abf07a855d058be3d3c3da
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2008237
Commit-Queue: Avery Musbach <amusbach@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#734610}

ash/wm/overview/overview_grid.cc

@@ -549,8 +549,10 @@ void OverviewGrid::AppendItem(aura::Window* window,
           window_list_.size(), use_spawn_animation);
 }
 
-void OverviewGrid::AddItemInMruOrder(aura::Window* window, bool animate) {
-  AddItem(window, /*reposition=*/true, animate, /*ignored_items=*/{},
+void OverviewGrid::AddItemInMruOrder(aura::Window* window,
+                                     bool reposition,
+                                     bool animate) {
+  AddItem(window, reposition, animate, /*ignored_items=*/{},
           FindInsertionIndex(window));
 }
 

ash/wm/overview/overview_grid.h

@@ -106,10 +106,9 @@ class ASH_EXPORT OverviewGrid : public SplitViewObserver,
                   bool animate,
                   bool use_spawn_animation = false);
 
-  // Adds |window| at the correct position according to MRU order. |window|
-  // cannot already be on the grid. Repositions all items. If |animate| is true,
-  // animates the repositioning.
-  void AddItemInMruOrder(aura::Window* window, bool animate);
+  // Like |AddItem|, but adds |window| at the correct position according to MRU
+  // order.
+  void AddItemInMruOrder(aura::Window* window, bool reposition, bool animate);
 
   // Removes |overview_item| from the grid. |overview_item| cannot already be
   // absent from the grid. If |item_destroying| is true, we may want to notify

ash/wm/overview/overview_session.cc

@@ -427,7 +427,7 @@ void OverviewSession::AddItemInMruOrder(aura::Window* window, bool animate) {
   if (!grid || grid->GetOverviewItemContaining(window))
     return;
 
-  grid->AddItemInMruOrder(window, animate);
+  grid->AddItemInMruOrder(window, /*reposition=*/true, animate);
   OnItemAdded(window);
 }
 

ash/wm/overview/overview_session_unittest.cc

@@ -6388,6 +6388,101 @@ TEST_P(SplitViewOverviewSessionInClamshellTestMultiDisplayOnly,
   EXPECT_EQ(root1_drop_target_bounds(item3), root1_drop_target_bounds(item4));
 }
 
+// Test dragging from one overview grid and dropping into another overview grid.
+TEST_P(SplitViewOverviewSessionInClamshellTestMultiDisplayOnly,
+       DragAndDropIntoAnotherOverviewGrid) {
+  UpdateDisplay("800x600,800x600");
+  aura::Window::Windows root_windows = Shell::GetAllRootWindows();
+  ASSERT_EQ(2u, root_windows.size());
+  std::unique_ptr<aura::Window> window = CreateTestWindow();
+  ASSERT_EQ(root_windows[0], window->GetRootWindow());
+  ToggleOverview();
+  OverviewGrid* grid1 =
+      overview_session()->GetGridWithRootWindow(root_windows[0]);
+  OverviewGrid* grid2 =
+      overview_session()->GetGridWithRootWindow(root_windows[1]);
+
+  // Drag |window| from |grid1| and drop into |grid2|.
+  ui::test::EventGenerator* generator = GetEventGenerator();
+  generator->MoveMouseTo(
+      gfx::ToRoundedPoint(grid1->GetOverviewItemContaining(window.get())
+                              ->target_bounds()
+                              .CenterPoint()));
+  generator->PressLeftButton();
+  Shell::Get()->cursor_manager()->SetDisplay(
+      display::Screen::GetScreen()->GetDisplayNearestWindow(root_windows[1]));
+  generator->MoveMouseTo(1200, 300);
+  generator->ReleaseLeftButton();
+
+  EXPECT_EQ(root_windows[1], window->GetRootWindow());
+  EXPECT_TRUE(grid1->empty());
+  OverviewItem* item = grid2->GetOverviewItemContaining(window.get());
+  ASSERT_TRUE(item);
+  EXPECT_EQ(root_windows[1], item->root_window());
+}
+
+// Test that overview widgets are stacked in the correct order after an overview
+// window is dragged from one overview grid and dropped into another.
+TEST_P(SplitViewOverviewSessionInClamshellTestMultiDisplayOnly,
+       OverviewWidgetStackingOrderWithMultiDisplayDragging) {
+  UpdateDisplay("800x600,800x600");
+  aura::Window::Windows root_windows = Shell::GetAllRootWindows();
+  ASSERT_EQ(2u, root_windows.size());
+  const gfx::Rect bounds_within_root1(0, 0, 400, 400);
+  const gfx::Rect bounds_within_root2(800, 0, 400, 400);
+  std::unique_ptr<aura::Window> window3 = CreateTestWindow(bounds_within_root2);
+  std::unique_ptr<aura::Window> window2 = CreateTestWindow(bounds_within_root1);
+  std::unique_ptr<aura::Window> window1 = CreateTestWindow(bounds_within_root2);
+  aura::Window* parent_on_root1 = window2->parent();
+  aura::Window* parent_on_root2 = window1->parent();
+  ASSERT_NE(parent_on_root1, parent_on_root2);
+  ASSERT_EQ(window3->parent(), parent_on_root2);
+  ToggleOverview();
+  OverviewItem* item1 = GetOverviewItemForWindow(window1.get());
+  OverviewItem* item2 = GetOverviewItemForWindow(window2.get());
+  OverviewItem* item3 = GetOverviewItemForWindow(window3.get());
+
+  ASSERT_EQ(root_windows[0], item2->root_window());
+  // Verify that |item1| is stacked above |item3| (because we created |window1|
+  // after |window3|).
+  EXPECT_GT(IndexOf(item1->item_widget()->GetNativeWindow(), parent_on_root2),
+            IndexOf(item3->item_widget()->GetNativeWindow(), parent_on_root2));
+  // Verify that the item widget for each window is stacked below that window.
+  EXPECT_LT(IndexOf(item1->item_widget()->GetNativeWindow(), parent_on_root2),
+            IndexOf(window1.get(), parent_on_root2));
+  EXPECT_LT(IndexOf(item2->item_widget()->GetNativeWindow(), parent_on_root1),
+            IndexOf(window2.get(), parent_on_root1));
+  EXPECT_LT(IndexOf(item3->item_widget()->GetNativeWindow(), parent_on_root2),
+            IndexOf(window3.get(), parent_on_root2));
+
+  // Drag |item2| from the left display and drop into the right display.
+  ui::test::EventGenerator* generator = GetEventGenerator();
+  generator->MoveMouseTo(
+      gfx::ToRoundedPoint(item2->target_bounds().CenterPoint()));
+  generator->PressLeftButton();
+  Shell::Get()->cursor_manager()->SetDisplay(
+      display::Screen::GetScreen()->GetDisplayNearestWindow(root_windows[1]));
+  generator->MoveMouseTo(1200, 300);
+  generator->ReleaseLeftButton();
+  // |item2| is now a dangling pointer and we have to refresh it, because when
+  // an overview window is dragged from one grid and dropped into another, the
+  // original item is destroyed and a new one is created.
+  item2 = GetOverviewItemForWindow(window2.get());
+
+  ASSERT_EQ(window2->parent(), parent_on_root2);
+  ASSERT_EQ(root_windows[1], item2->root_window());
+  // With all three items on one grid, verify that their stacking order
+  // corresponds to the MRU order of the windows. The new |item2| is sandwiched
+  // between |item1| and |item3|.
+  EXPECT_GT(IndexOf(item1->item_widget()->GetNativeWindow(), parent_on_root2),
+            IndexOf(item2->item_widget()->GetNativeWindow(), parent_on_root2));
+  EXPECT_GT(IndexOf(item2->item_widget()->GetNativeWindow(), parent_on_root2),
+            IndexOf(item3->item_widget()->GetNativeWindow(), parent_on_root2));
+  // Verify that the item widget for the new |item2| is stacked below |window2|.
+  EXPECT_LT(IndexOf(item2->item_widget()->GetNativeWindow(), parent_on_root2),
+            IndexOf(window2.get(), parent_on_root2));
+}
+
 // Test dragging from one display to another and then snapping.
 TEST_P(SplitViewOverviewSessionInClamshellTestMultiDisplayOnly,
        DragFromOneDisplayToAnotherAndSnap) {

ash/wm/overview/overview_window_drag_controller.cc

@@ -582,6 +582,36 @@ OverviewWindowDragController::CompleteNormalDrag(
 
   // Drop a window into overview because we have not done anything else with it.
   DCHECK(item_);
+  aura::Window* target_root = GetRootWindowBeingDraggedIn();
+  if (AreMultiDisplayOverviewAndSplitViewEnabled() &&
+      target_root != item_->root_window()) {
+    // Get the window and bounds from |item_| before removing it from its grid.
+    aura::Window* window = item_->GetWindow();
+    const gfx::RectF bounds = item_->target_bounds();
+    item_->overview_grid()->RemoveItem(item_);
+    item_ = nullptr;
+    // Use |OverviewSession::set_ignore_window_hierarchy_changes| to prevent
+    // |OverviewSession::OnWindowHierarchyChanged| from ending overview as we
+    // move |window| to |target_root|.
+    overview_session_->set_ignore_window_hierarchy_changes(true);
+    window_util::MoveWindowToDisplay(window,
+                                     display::Screen::GetScreen()
+                                         ->GetDisplayNearestWindow(target_root)
+                                         .id());
+    overview_session_->set_ignore_window_hierarchy_changes(false);
+
+    OverviewGrid* target_grid =
+        overview_session_->GetGridWithRootWindow(target_root);
+    // Add |window| to |target_grid| with reposition=false because soon we will
+    // call |OverviewSession::PositionWindows| anyway.
+    target_grid->AddItemInMruOrder(window, /*reposition=*/false,
+                                   /*animate=*/false);
+    item_ = target_grid->GetOverviewItemContaining(window);
+    // Put the new item where the old item ended, so it looks like it is the
+    // same item. The following call to |OverviewSession::PositionWindows| will
+    // animate it from there.
+    item_->SetBounds(bounds, OVERVIEW_ANIMATION_NONE);
+  }
   item_->set_should_restack_on_animation_end(true);
   overview_session_->PositionWindows(/*animate=*/true);
   return DragResult::kDropIntoOverview;