[reland] In tablet mode, tap on overview background should go to home screen.

Clamshell mode behavior will remain the same, i.e., tapping on the
overview background will return to its previous state, it can either be
in-app or home screen.

Bug: 997885

Change-Id: I2dae82657d4d92876c834c78dd62d53830fbe6cf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1865264
Commit-Queue: Xiaoqian Dai <xdai@chromium.org>
Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707036}

ash/wm/overview/overview_grid_event_handler.cc

@@ -4,6 +4,8 @@
 
 #include "ash/wm/overview/overview_grid_event_handler.h"
 
+#include "ash/home_screen/home_screen_controller.h"
+#include "ash/public/cpp/ash_features.h"
 #include "ash/root_window_controller.h"
 #include "ash/shell.h"
 #include "ash/wallpaper/wallpaper_view.h"
@@ -12,6 +14,7 @@
 #include "ash/wm/overview/overview_grid.h"
 #include "ash/wm/overview/overview_utils.h"
 #include "ui/compositor/compositor.h"
+#include "ui/display/screen.h"
 #include "ui/events/event.h"
 #include "ui/events/gestures/fling_curve.h"
 
@@ -128,8 +131,20 @@ void OverviewGridEventHandler::HandleClickOrTap(ui::Event* event) {
   CHECK_EQ(ui::EP_PRETARGET, event->phase());
   // Events that happen while app list is sliding out during overview should
   // be ignored to prevent overview from disappearing out from under the user.
-  if (!IsSlidingOutOverviewFromShelf())
-    Shell::Get()->overview_controller()->EndOverview();
+  if (!IsSlidingOutOverviewFromShelf()) {
+    if (Shell::Get()->tablet_mode_controller()->InTabletMode() &&
+        features::IsDragFromShelfToHomeOrOverviewEnabled()) {
+      // In tablet mode, clicking on tapping on the wallpaper background will
+      // always head back to home launcher screen.
+      int64_t display_id = display::Screen::GetScreen()
+                               ->GetDisplayNearestWindow(
+                                   static_cast<aura::Window*>(event->target()))
+                               .id();
+      Shell::Get()->home_screen_controller()->GoHome(display_id);
+    } else {
+      Shell::Get()->overview_controller()->EndOverview();
+    }
+  }
   event->StopPropagation();
 }
 

ash/wm/overview/overview_session_unittest.cc

@@ -17,11 +17,13 @@
 #include "ash/display/screen_orientation_controller.h"
 #include "ash/display/screen_orientation_controller_test_api.h"
 #include "ash/drag_drop/drag_drop_controller.h"
+#include "ash/home_screen/home_screen_controller.h"
 #include "ash/magnifier/docked_magnifier_controller_impl.h"
 #include "ash/public/cpp/app_types.h"
 #include "ash/public/cpp/ash_features.h"
 #include "ash/public/cpp/fps_counter.h"
 #include "ash/public/cpp/shelf_config.h"
+#include "ash/public/cpp/test/shell_test_api.h"
 #include "ash/public/cpp/window_properties.h"
 #include "ash/screen_util.h"
 #include "ash/shelf/shelf.h"
@@ -2790,6 +2792,50 @@ TEST_P(OverviewSessionTest, ShelfAlignmentChangeWhileInOverview) {
   EXPECT_FALSE(InOverviewSession());
 }
 
+// The class to test overview behavior with kDragFromShelfToHomeOrOverview flag
+// enabled.
+class OverviewSessionWithDragFromShelfFeatureTest : public OverviewSessionTest {
+ public:
+  OverviewSessionWithDragFromShelfFeatureTest() = default;
+  ~OverviewSessionWithDragFromShelfFeatureTest() override = default;
+
+  void SetUp() override {
+    scoped_feature_list_.InitAndEnableFeature(
+        features::kDragFromShelfToHomeOrOverview);
+    OverviewSessionTest::SetUp();
+    EnterTabletMode();
+  }
+
+ private:
+  base::test::ScopedFeatureList scoped_feature_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(OverviewSessionWithDragFromShelfFeatureTest);
+};
+
+// Tests that in tablet mode, tapping on the background will always go to home
+// screen.
+TEST_P(OverviewSessionWithDragFromShelfFeatureTest, TapOnBackgroundGoToHome) {
+  UpdateDisplay("800x600");
+  std::unique_ptr<aura::Window> window(CreateTestWindow());
+  WindowState* window_state = WindowState::Get(window.get());
+
+  EXPECT_FALSE(window_state->IsMinimized());
+  EXPECT_FALSE(Shell::Get()->home_screen_controller()->IsHomeScreenVisible());
+  ToggleOverview();
+  EXPECT_TRUE(InOverviewSession());
+
+  // Tap on the background.
+  ui::ScopedAnimationDurationScaleMode test_duration_mode(
+      ui::ScopedAnimationDurationScaleMode::NON_ZERO_DURATION);
+  GetEventGenerator()->GestureTapAt(gfx::Point(10, 10));
+  ShellTestApi().WaitForOverviewAnimationState(
+      OverviewAnimationState::kExitAnimationComplete);
+
+  EXPECT_FALSE(InOverviewSession());
+  EXPECT_TRUE(window_state->IsMinimized());
+  EXPECT_TRUE(Shell::Get()->home_screen_controller()->IsHomeScreenVisible());
+}
+
 // TODO(sammiequon): Merge this into SplitViewOverviewSessionTest and rename
 // that to TabletModeOverviewSessionTest.
 class OverviewSessionNewLayoutTest : public OverviewSessionTest {
@@ -5251,5 +5297,8 @@ INSTANTIATE_TEST_SUITE_P(
     ,
     SplitViewOverviewSessionInClamshellTestMultiDisplayOnly,
     testing::Values(true));
+INSTANTIATE_TEST_SUITE_P(,
+                         OverviewSessionWithDragFromShelfFeatureTest,
+                         testing::Bool());
 
 }  // namespace ash