split view: Reinsert split view window to overview at correct position

When a split view window is reinserted to overview, it shall go to the
correct position to maintain the MRU ordering of the overview grid.

Fixed: 1038396
Change-Id: I4cac7963610eb6a4b7022d2bc0e983e1f587a8cc
Bug: 1038396
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1984723Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Commit-Queue: Avery Musbach <amusbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#728314}

ash/wm/overview/overview_grid.cc

@@ -24,6 +24,7 @@
 #include "ash/wm/desks/desk_mini_view.h"
 #include "ash/wm/desks/desks_bar_view.h"
 #include "ash/wm/desks/desks_util.h"
+#include "ash/wm/mru_window_tracker.h"
 #include "ash/wm/overview/cleanup_animation_observer.h"
 #include "ash/wm/overview/drop_target_view.h"
 #include "ash/wm/overview/overview_constants.h"
@@ -557,6 +558,11 @@ 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=*/{},
+          FindInsertionIndex(window));
+}
+
 void OverviewGrid::RemoveItem(OverviewItem* overview_item,
                               bool item_destroying,
                               bool reposition) {
@@ -1835,6 +1841,24 @@ size_t OverviewGrid::GetOverviewItemIndex(OverviewItem* item) const {
   return iter - window_list_.begin();
 }
 
+size_t OverviewGrid::FindInsertionIndex(const aura::Window* window) {
+  DCHECK(!GetDropTarget());
+  size_t index = 0u;
+  for (aura::Window* mru_window :
+       Shell::Get()->mru_window_tracker()->BuildMruWindowList(kActiveDesk)) {
+    if (index == window_list_.size() || mru_window == window)
+      return index;
+    // As we iterate over the whole MRU window list, the windows in this grid
+    // will be encountered in the same order, but possibly with other windows in
+    // between. Ignore those other windows, and only increment |index| when we
+    // reach the next window in this grid.
+    if (mru_window == window_list_[index]->GetWindow())
+      ++index;
+  }
+  NOTREACHED();
+  return 0u;
+}
+
 void OverviewGrid::AddDraggedWindowIntoOverviewOnDragEnd(
     aura::Window* dragged_window) {
   DCHECK(overview_session_);

ash/wm/overview/overview_grid.h

@@ -93,10 +93,6 @@ class ASH_EXPORT OverviewGrid : public SplitViewObserver,
   // overview is already active, it will use a special spawn animation on its
   // first position in the grid. |use_spawn_animation| has no effect if either
   // |animate| or |reposition| are false.
-  //
-  // Note: This function should only be called by |OverviewSession::AddItem| and
-  // |OverviewGrid::AppendItem|. |overview_session_| keeps count of all overview
-  // items, but this function does not update the tally.
   void AddItem(aura::Window* window,
                bool reposition,
                bool animate,
@@ -105,23 +101,21 @@ class ASH_EXPORT OverviewGrid : public SplitViewObserver,
                bool use_spawn_animation = false);
 
   // Similar to the above function, but adds the window to the end of the grid.
-  // Note: This function should only be called by |OverviewSession::AppendItem|.
-  // |overview_session_| keeps count of all overview items, but this function
-  // does not update the tally.
   void AppendItem(aura::Window* window,
                   bool reposition,
                   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);
+
   // 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
   // |overview_session_| that this grid has become empty. If |item_destroying|
   // and |reposition| are both true, all items are repositioned with animation.
   // |reposition| has no effect if |item_destroying| is false.
-  //
-  // Note: This function should only be called by |OverviewSession::RemoveItem|
-  // and |OverviewGrid::Shutdown|. |overview_session_| keeps count of all
-  // overview items, but this function does not update the tally.
   void RemoveItem(OverviewItem* overview_item,
                   bool item_destroying = false,
                   bool reposition = false);
@@ -419,6 +413,10 @@ class ASH_EXPORT OverviewGrid : public SplitViewObserver,
   // Returns the index of |item| in |window_list_|.
   size_t GetOverviewItemIndex(OverviewItem* item) const;
 
+  // Returns the index where |window| can be inserted into |window_list_| based
+  // on MRU order.
+  size_t FindInsertionIndex(const aura::Window* window);
+
   // Adds the |dragged_window| into overview on drag ended. Might need to update
   // the window's bounds if it has been resized.
   void AddDraggedWindowIntoOverviewOnDragEnd(aura::Window* dragged_window);

ash/wm/overview/overview_session.cc

@@ -403,14 +403,7 @@ void OverviewSession::AddItem(
     return;
 
   grid->AddItem(window, reposition, animate, ignored_items, index);
-  ++num_items_;
-
-  UpdateNoWindowsWidget();
-
-  // Transfer focus from |window| to |overview_focus_widget_| to match the
-  // behavior of entering overview mode in the beginning.
-  DCHECK(overview_focus_widget_);
-  wm::ActivateWindow(GetOverviewFocusWindow());
+  OnItemAdded();
 }
 
 void OverviewSession::AppendItem(aura::Window* window,
@@ -422,14 +415,17 @@ void OverviewSession::AppendItem(aura::Window* window,
     return;
 
   grid->AppendItem(window, reposition, animate, /*use_spawn_animation=*/true);
-  ++num_items_;
+  OnItemAdded();
+}
 
-  UpdateNoWindowsWidget();
+void OverviewSession::AddItemInMruOrder(aura::Window* window, bool animate) {
+  // Early exit if a grid already contains |window|.
+  OverviewGrid* grid = GetGridWithRootWindow(window->GetRootWindow());
+  if (!grid || grid->GetOverviewItemContaining(window))
+    return;
 
-  // Transfer focus from |window| to |overview_focus_widget_| to match the
-  // behavior of entering overview mode in the beginning.
-  DCHECK(overview_focus_widget_);
-  wm::ActivateWindow(GetOverviewFocusWindow());
+  grid->AddItemInMruOrder(window, animate);
+  OnItemAdded();
 }
 
 void OverviewSession::RemoveItem(OverviewItem* overview_item) {
@@ -1097,4 +1093,13 @@ void OverviewSession::RefreshNoWindowsWidgetBounds(bool animate) {
                                           animate);
 }
 
+void OverviewSession::OnItemAdded() {
+  ++num_items_;
+  UpdateNoWindowsWidget();
+  // Transfer focus from |window| to |overview_focus_widget_| to match the
+  // behavior of entering overview mode in the beginning.
+  DCHECK(overview_focus_widget_);
+  wm::ActivateWindow(GetOverviewFocusWindow());
+}
+
 }  // namespace ash

ash/wm/overview/overview_session.h

@@ -174,6 +174,10 @@ class ASH_EXPORT OverviewSession : public display::DisplayObserver,
   // TODO(afakhry): Expose |use_spawn_animation| if needed.
   void AppendItem(aura::Window* window, bool reposition, bool animate);
 
+  // Similar to |AddItem| with reposition=true, but adds the window at the
+  // correct position according to MRU order.
+  void AddItemInMruOrder(aura::Window* window, bool animate);
+
   // Removes |overview_item| from the corresponding grid. No items are
   // repositioned.
   void RemoveItem(OverviewItem* overview_item);
@@ -362,6 +366,8 @@ class ASH_EXPORT OverviewSession : public display::DisplayObserver,
 
   void RefreshNoWindowsWidgetBounds(bool animate);
 
+  void OnItemAdded();
+
   // Tracks observed windows.
   base::flat_set<aura::Window*> observed_windows_;
 

ash/wm/overview/overview_session_unittest.cc

@@ -33,6 +33,7 @@
 #include "ash/test/ash_test_base.h"
 #include "ash/wm/desks/desks_util.h"
 #include "ash/wm/drag_window_resizer.h"
+#include "ash/wm/mru_window_tracker.h"
 #include "ash/wm/overview/overview_constants.h"
 #include "ash/wm/overview/overview_controller.h"
 #include "ash/wm/overview/overview_grid.h"
@@ -5015,6 +5016,74 @@ TEST_P(SplitViewOverviewSessionTest,
   EXPECT_FALSE(wm::IsActiveWindow(window1.get()));
 }
 
+// Verify that if overview mode is active and the split view divider is dragged
+// all the way to the opposite edge, then the split view window is reinserted
+// into the overview grid at the correct position according to MRU order.
+TEST_P(
+    SplitViewOverviewSessionTest,
+    SplitViewWindowReinsertedToOverviewAtCorrectPositionWhenSplitViewIsEnded) {
+  const gfx::Rect bounds(400, 400);
+  std::unique_ptr<aura::Window> window1(CreateWindow(bounds));
+  std::unique_ptr<aura::Window> window2(CreateWindow(bounds));
+  ToggleOverview();
+  DragWindowTo(GetOverviewItemForWindow(window1.get()), gfx::PointF());
+  DragWindowTo(GetOverviewItemForWindow(window2.get()),
+               gfx::PointF(799.f, 0.f));
+  EXPECT_EQ(window1.get(), split_view_controller()->left_window());
+  EXPECT_EQ(window2.get(), split_view_controller()->right_window());
+  ToggleOverview();
+  // Drag the divider to the left edge.
+  const gfx::Rect divider_bounds =
+      GetSplitViewDividerBounds(/*is_dragging=*/false);
+  GetEventGenerator()->set_current_screen_location(
+      divider_bounds.CenterPoint());
+  GetEventGenerator()->DragMouseTo(0, 0);
+  SkipDividerSnapAnimation();
+
+  ASSERT_TRUE(InOverviewSession());
+  const std::vector<aura::Window*> expected_mru_list = {window2.get(),
+                                                        window1.get()};
+  const std::vector<aura::Window*> expected_overview_list = {window2.get(),
+                                                             window1.get()};
+  EXPECT_EQ(
+      expected_mru_list,
+      Shell::Get()->mru_window_tracker()->BuildMruWindowList(kActiveDesk));
+  EXPECT_EQ(expected_overview_list,
+            overview_controller()->GetWindowsListInOverviewGridsForTest());
+}
+
+// Verify that if a window is dragged from overview and snapped in place of
+// another split view window, then the old split view window is reinserted into
+// the overview grid at the correct position according to MRU order.
+TEST_P(
+    SplitViewOverviewSessionTest,
+    SplitViewWindowReinsertedToOverviewAtCorrectPositionWhenAnotherWindowTakesItsPlace) {
+  const gfx::Rect bounds(400, 400);
+  std::unique_ptr<aura::Window> window1(CreateWindow(bounds));
+  std::unique_ptr<aura::Window> window2(CreateWindow(bounds));
+  std::unique_ptr<aura::Window> window3(CreateWindow(bounds));
+  ToggleOverview();
+  DragWindowTo(GetOverviewItemForWindow(window1.get()), gfx::PointF());
+  DragWindowTo(GetOverviewItemForWindow(window2.get()),
+               gfx::PointF(799.f, 0.f));
+  EXPECT_EQ(window1.get(), split_view_controller()->left_window());
+  EXPECT_EQ(window2.get(), split_view_controller()->right_window());
+  ToggleOverview();
+  DragWindowTo(GetOverviewItemForWindow(window3.get()), gfx::PointF());
+  EXPECT_EQ(window3.get(), split_view_controller()->left_window());
+
+  ASSERT_TRUE(InOverviewSession());
+  const std::vector<aura::Window*> expected_mru_list = {
+      window3.get(), window2.get(), window1.get()};
+  const std::vector<aura::Window*> expected_overview_list = {window2.get(),
+                                                             window1.get()};
+  EXPECT_EQ(
+      expected_mru_list,
+      Shell::Get()->mru_window_tracker()->BuildMruWindowList(kActiveDesk));
+  EXPECT_EQ(expected_overview_list,
+            overview_controller()->GetWindowsListInOverviewGridsForTest());
+}
+
 // Verify that if the split view divider is dragged close to the edge, the grid
 // bounds will be fixed to a third of the work area width and start sliding off
 // the screen instead of continuing to shrink.

ash/wm/splitview/split_view_controller.cc

@@ -1749,7 +1749,7 @@ void SplitViewController::InsertWindowToOverview(aura::Window* window,
                                                  bool animate) {
   if (!window || !GetOverviewSession())
     return;
-  GetOverviewSession()->AddItem(window, /*reposition=*/true, animate);
+  GetOverviewSession()->AddItemInMruOrder(window, animate);
 }
 
 void SplitViewController::FinishWindowResizing(aura::Window* window) {