Do not cancel overview if the to-be-snapped window is activated

Background: For client-controlled windows, because all window state
changes need to be asynchronously ack’ed by its client (e.g. ARC), there
is always a very short transitional state between “ash sends a request
to the client” and “ash receives an ack from the client”. We
particularly call the transitional state for a snapped state as
“to-be-snapped”.

In overview mode, if a to-be-snapped window is activated just before the
new snapped state is applied, we don’t want to end the overview.

BUG=b:269689567
BUG=b:237743541
TEST=ClientControlledStateTestClamshellAndTablet.DragOverviewWindowToSnap

Change-Id: Id353bcf5fe247340081517329ee39591a27da19f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4263452
Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Commit-Queue: Toshiki Kikuchi <toshikikikuchi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1107298}

ash/wm/client_controlled_state_unittest.cc

@@ -13,6 +13,9 @@
 #include "ash/test/ash_test_base.h"
 #include "ash/wm/desks/desks_util.h"
 #include "ash/wm/float/float_controller.h"
+#include "ash/wm/overview/overview_controller.h"
+#include "ash/wm/overview/overview_item.h"
+#include "ash/wm/overview/overview_test_util.h"
 #include "ash/wm/pip/pip_positioner.h"
 #include "ash/wm/screen_pinning_controller.h"
 #include "ash/wm/splitview/split_view_controller.h"
@@ -32,6 +35,7 @@
 #include "ui/aura/client/aura_constants.h"
 #include "ui/events/test/event_generator.h"
 #include "ui/gfx/geometry/point.h"
+#include "ui/gfx/geometry/point_conversions.h"
 #include "ui/gfx/geometry/vector2d.h"
 #include "ui/views/widget/widget.h"
 #include "ui/views/widget/widget_delegate.h"
@@ -965,4 +969,48 @@ TEST_P(ClientControlledStateTestClamshellAndTablet, FloatWindow) {
   EXPECT_NE(kShellWindowId_FloatContainer, window()->parent()->GetId());
 }
 
+TEST_P(ClientControlledStateTestClamshellAndTablet, DragOverviewWindowToSnap) {
+  auto* const overview_controller = Shell::Get()->overview_controller();
+  auto* const split_view_controller = SplitViewController::Get(window());
+
+  widget_delegate()->EnableSnap();
+
+  // Create a fake normal window in addition to `window()` (client-controlled
+  // window) because we need at least two windows to keep overview mode active
+  // after snapping one of them.
+  auto fake_uninterested_window = CreateAppWindow();
+
+  // Enter overview.
+  ToggleOverview();
+  EXPECT_TRUE(overview_controller->InOverviewSession());
+  EXPECT_FALSE(split_view_controller->InSplitViewMode());
+
+  // Drag `window()`'s overview item to snap to left.
+  auto* const overview_item = GetOverviewItemForWindow(window());
+  auto* const event_generator = GetEventGenerator();
+  event_generator->set_current_screen_location(
+      gfx::ToRoundedPoint(overview_item->target_bounds().CenterPoint()));
+  event_generator->DragMouseTo(0, 0);
+
+  // Ensures the window is in a transitional snapped state.
+  EXPECT_TRUE(split_view_controller->IsWindowInTransitionalState(window()));
+  EXPECT_EQ(WindowStateType::kPrimarySnapped, delegate()->new_state());
+  EXPECT_FALSE(window_state()->IsSnapped());
+
+  // Activating window just before accepting the request shouldn't end the
+  // overview.
+  widget()->Activate();
+  EXPECT_TRUE(overview_controller->InOverviewSession());
+
+  // Accept the snap request.
+  state()->EnterNextState(window_state(), delegate()->new_state());
+  ApplyPendingRequestedBounds();
+  EXPECT_TRUE(window_state()->IsSnapped());
+  EXPECT_TRUE(split_view_controller->InSplitViewMode());
+  EXPECT_EQ(split_view_controller->state(),
+            SplitViewController::State::kPrimarySnapped);
+  EXPECT_EQ(split_view_controller->primary_window(), window());
+  EXPECT_TRUE(overview_controller->InOverviewSession());
+}
+
 }  // namespace ash

ash/wm/overview/overview_session.cc

@@ -875,10 +875,14 @@ void OverviewSession::OnWindowActivating(
   // handle the window activation change. Check for split view mode without
   // using |SplitViewController::state_| which is updated asynchronously when
   // snapping an ARC window.
+  // We also check if `gained_active` is to-be-snapped transitional state. In
+  // the case, the window has not been attached to SplitViewController yet but
+  // will be very soon.
   SplitViewController* split_view_controller =
       SplitViewController::Get(gained_active);
   if (split_view_controller->primary_window() ||
-      split_view_controller->secondary_window()) {
+      split_view_controller->secondary_window() ||
+      split_view_controller->IsWindowInTransitionalState(gained_active)) {
     RestoreWindowActivation(false);
     return;
   }