Bento: Support switching between two Alt-Tab modes.

- Add a tab slider and update windows shown in Alt-Tab so that
"Current desk" mode only display windows in the active desk, while
"All desks" display all windows.
- Handle special cases: As before, entering Alt-Tab with less than two
windows aren't allowed. However, if users switch from the all-desks mode
to the current-desk mode resulting in zero or one window,
it should show "no recent items" or show a window consecutively.
- Hide behind Bento flag and make sure to overwrite
kLimitAltTabToActiveDesk in case of conflict, so the old flag works.
- Disable remapping Alt+LeftClick to a right click when using Alt-Tab.
- Ash unittests for switching between modes and special cases.

Bug: 1142726
Test: A manual test (a video in crbug) and unit tests
`ash_unittests --gtest_filter=ModeSelectionWindowCycleControllerTest.*`

Change-Id: Ia203358d0b658529a3090a292ae36850ea60a36a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2581684Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Commit-Queue: Cattalyya Nuengsigkapian <cattalyya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#838709}

ash/BUILD.gn

@@ -1678,6 +1678,10 @@ component("ash") {
     "wm/window_cycle_event_filter.h",
     "wm/window_cycle_list.cc",
     "wm/window_cycle_list.h",
+    "wm/window_cycle_tab_slider.cc",
+    "wm/window_cycle_tab_slider.h",
+    "wm/window_cycle_tab_slider_button.cc",
+    "wm/window_cycle_tab_slider_button.h",
     "wm/window_dimmer.cc",
     "wm/window_dimmer.h",
     "wm/window_finder.cc",

ash/ash_strings.grd

@@ -3125,6 +3125,14 @@ Here are some things you can try to get started.
         Window <ph name="WINDOW_TITLE">$1<ex>Files</ex></ph> moved from Desk <ph name="ACTIVE_DESK">$2</ph> to Desk <ph name="TARGET_DESK">$3</ph>
       </message>
 
+      <!-- Alt Tab -->
+      <message name="IDS_ASH_ALT_TAB_ALL_DESKS_MODE" desc="Alt-tab shows windows from all desks.">
+        All desks
+      </message>
+      <message name="IDS_ASH_ALT_TAB_CURRENT_DESK_MODE" desc="Alt-tab shows only windows from the current desk.">
+        Current desk
+      </message>
+
       <!-- Back gesture -->
       <message name="IDS_ASH_BACK_GESTURE_CONTEXTUAL_NUDGE" desc="Information shown in the suggestion label for the contextual nudge of the back gesture in tablet mode">
         Swipe from the left to go back

ash/ash_strings_grd/IDS_ASH_ALT_TAB_ALL_DESKS_MODE.png.sha1

+a497fea9619c636ff78f2f5bba3724d5e1ad84d4
\ No newline at end of file

ash/ash_strings_grd/IDS_ASH_ALT_TAB_CURRENT_DESK_MODE.png.sha1

+df4b84a84d9cad8a10afc284876e6a4d279435e0
\ No newline at end of file

ash/events/event_rewriter_controller_impl.cc

@@ -60,6 +60,7 @@ void EventRewriterControllerImpl::Initialize(
       std::make_unique<ui::EventRewriterChromeOS>(
           event_rewriter_delegate, Shell::Get()->sticky_keys_controller(),
           privacy_screen_supported);
+  event_rewriter_chromeos_ = event_rewriter_chromeos.get();
 
   std::unique_ptr<AccessibilityEventRewriter> accessibility_event_rewriter =
       std::make_unique<AccessibilityEventRewriter>(
@@ -112,6 +113,12 @@ void EventRewriterControllerImpl::SetSendMouseEvents(bool value) {
   accessibility_event_rewriter_->set_send_mouse_events(value);
 }
 
+void EventRewriterControllerImpl::SetAltLeftClickRemappingEnabled(
+    bool enabled) {
+  if (event_rewriter_chromeos_)
+    event_rewriter_chromeos_->set_alt_left_click_remapping_enabled(enabled);
+}
+
 void EventRewriterControllerImpl::OnHostInitialized(
     aura::WindowTreeHost* host) {
   for (const auto& rewriter : rewriters_)

ash/events/event_rewriter_controller_impl.h

@@ -45,6 +45,11 @@ class ASH_EXPORT EventRewriterControllerImpl : public EventRewriterController,
   // aura::EnvObserver:
   void OnHostInitialized(aura::WindowTreeHost* host) override;
 
+  // Enable/disable Alt + left click mapping in EventRewriterChromeOS. This
+  // only applies if the feature
+  // `chromeos::features::kUseSearchClickForRightClick` is not enabled.
+  void SetAltLeftClickRemappingEnabled(bool enabled);
+
  private:
   // The |EventRewriter|s managed by this controller.
   std::vector<std::unique_ptr<ui::EventRewriter>> rewriters_;
@@ -52,6 +57,7 @@ class ASH_EXPORT EventRewriterControllerImpl : public EventRewriterController,
   // Owned by |rewriters_|.
   AccessibilityEventRewriter* accessibility_event_rewriter_ = nullptr;
   KeyboardDrivenEventRewriter* keyboard_driven_event_rewriter_ = nullptr;
+  ui::EventRewriterChromeOS* event_rewriter_chromeos_ = nullptr;
 
   DISALLOW_COPY_AND_ASSIGN(EventRewriterControllerImpl);
 };

ash/wm/desks/desks_controller.cc

@@ -697,10 +697,9 @@ void DesksController::ActivateDeskInternal(const Desk* desk,
   // If in the middle of a window cycle gesture, reset the window cycle list
   // contents so it contains the new active desk's windows.
   auto* shell = Shell::Get();
-  if (features::IsAltTabLimitedToActiveDesk()) {
-    auto* window_cycle_controller = shell->window_cycle_controller();
+  auto* window_cycle_controller = shell->window_cycle_controller();
+  if (window_cycle_controller->IsAltTabPerActiveDesk())
     window_cycle_controller->MaybeResetCycleList();
-  }
 
   for (auto& observer : observers_)
     observer.OnDeskActivationChanged(active_desk_, old_active);

ash/wm/window_cycle_controller.cc

@@ -4,6 +4,7 @@
 
 #include "ash/wm/window_cycle_controller.h"
 
+#include "ash/events/event_rewriter_controller_impl.h"
 #include "ash/metrics/task_switch_metrics_recorder.h"
 #include "ash/metrics/task_switch_source.h"
 #include "ash/metrics/user_metrics_recorder.h"
@@ -88,6 +89,8 @@ void WindowCycleController::HandleCycleWindow(Direction direction) {
   if (!IsCycling())
     StartCycling();
 
+  // TODO(crbug.com/1157100): Handle window highlighting after switching
+  // alt-tab mode.
   Step(direction);
 }
 
@@ -107,6 +110,8 @@ void WindowCycleController::StartCycling() {
   // the window view item for the preview is transparent
   // (http://crbug.com/895265).
   Shell::Get()->wallpaper_controller()->MaybeClosePreviewWallpaper();
+  Shell::Get()->event_rewriter_controller()->SetAltLeftClickRemappingEnabled(
+      false);
 
   WindowCycleController::WindowList window_list = CreateWindowList();
   SaveCurrentActiveDeskAndWindow(window_list);
@@ -160,7 +165,7 @@ bool WindowCycleController::IsWindowListVisible() {
 WindowCycleController::WindowList WindowCycleController::CreateWindowList() {
   WindowCycleController::WindowList window_list =
       Shell::Get()->mru_window_tracker()->BuildWindowForCycleWithPipList(
-          features::IsAltTabLimitedToActiveDesk() ? kActiveDesk : kAllDesks);
+          IsAltTabPerActiveDesk() ? kActiveDesk : kAllDesks);
   // Window cycle list windows will handle showing their transient related
   // windows, so if a window in |window_list| has a transient root also in
   // |window_list|, we can remove it as the transient root will handle showing
@@ -169,6 +174,18 @@ WindowCycleController::WindowList WindowCycleController::CreateWindowList() {
   return window_list;
 }
 
+void WindowCycleController::SetAltTabMode(DesksMruType alt_tab_mode) {
+  if (alt_tab_mode_ == alt_tab_mode)
+    return;
+  alt_tab_mode_ = alt_tab_mode;
+  MaybeResetCycleList();
+}
+
+bool WindowCycleController::IsAltTabPerActiveDesk() {
+  return features::IsBentoEnabled() ? alt_tab_mode_ == kActiveDesk
+                                    : features::IsAltTabLimitedToActiveDesk();
+}
+
 void WindowCycleController::SaveCurrentActiveDeskAndWindow(
     const WindowCycleController::WindowList& window_list) {
   active_desk_container_id_before_cycle_ =
@@ -204,6 +221,8 @@ void WindowCycleController::StopCycling() {
 
   active_window_before_window_cycle_ = nullptr;
   active_desk_container_id_before_cycle_ = kShellWindowId_Invalid;
+  Shell::Get()->event_rewriter_controller()->SetAltLeftClickRemappingEnabled(
+      true);
 }
 
 }  // namespace ash

ash/wm/window_cycle_controller.h

@@ -9,6 +9,7 @@
 
 #include "ash/ash_export.h"
 #include "ash/public/cpp/shell_window_ids.h"
+#include "ash/wm/mru_window_tracker.h"
 #include "base/macros.h"
 #include "base/time/time.h"
 
@@ -86,6 +87,14 @@ class ASH_EXPORT WindowCycleController {
     return window_cycle_list_.get();
   }
 
+  // Sets alt-tab mode to all desks (default) or active desk.
+  void SetAltTabMode(DesksMruType alt_tab_mode_);
+
+  // Checks if alt-tab should be per active desk. If Bento is enabled, alt-tab
+  // mode depends on users' alt_tab_mode_ selection. Otherwise, it'll default
+  // to all desk unless LimitAltTabToActiveDesk flag is explicitly enabled.
+  bool IsAltTabPerActiveDesk();
+
  private:
   // Gets a list of windows from the currently open windows, removing windows
   // with transient roots already in the list. The returned list of windows
@@ -115,6 +124,12 @@ class ASH_EXPORT WindowCycleController {
   // Non-null while actively cycling.
   std::unique_ptr<WindowCycleEventFilter> event_filter_;
 
+  // Tracks alt-tab mode to display all windows from all desks by default.
+  // An alternative mode is active desk where only windows from the current desk
+  // are shown in alt-tab.
+  // TODO(crbug.com/1157105): Store per-desk mode in primary user pref.
+  DesksMruType alt_tab_mode_ = DesksMruType::kAllDesks;
+
   DISALLOW_COPY_AND_ASSIGN(WindowCycleController);
 };
 

ash/wm/window_cycle_controller_unittest.cc

@@ -124,6 +124,20 @@ class WindowCycleControllerTest : public AshTestBase {
         ->GetWindowCycleItemViewsForTesting();
   }
 
+  const views::View::Views& GetWindowCycleTabSliderViews() const {
+    return Shell::Get()
+        ->window_cycle_controller()
+        ->window_cycle_list()
+        ->GetWindowCycleTabSliderViewsForTesting();
+  }
+
+  const views::Label* GetWindowCycleNoRecentItemsLabel() const {
+    return Shell::Get()
+        ->window_cycle_controller()
+        ->window_cycle_list()
+        ->GetWindowCycleNoRecentItemsLabelForTesting();
+  }
+
   const aura::Window* GetTargetWindow() const {
     return Shell::Get()
         ->window_cycle_controller()
@@ -1337,4 +1351,189 @@ TEST_F(WindowCycleControllerTest, DoubleAltTabWithDeskSwitch) {
   EXPECT_EQ(win0.get(), window_util::GetActiveWindow());
 }
 
+class ModeSelectionWindowCycleControllerTest
+    : public WindowCycleControllerTest {
+ public:
+  ModeSelectionWindowCycleControllerTest() = default;
+  ModeSelectionWindowCycleControllerTest(
+      const ModeSelectionWindowCycleControllerTest&) = delete;
+  ModeSelectionWindowCycleControllerTest& operator=(
+      const ModeSelectionWindowCycleControllerTest&) = delete;
+  ~ModeSelectionWindowCycleControllerTest() override = default;
+
+  // WindowCycleControllerTest:
+  void SetUp() override {
+    scoped_feature_list_.InitAndEnableFeature(features::kBento);
+    WindowCycleControllerTest::SetUp();
+    generator_ = GetEventGenerator();
+  }
+
+  void SwitchPerDeskAltTabMode(bool per_desk_mode) {
+    gfx::Point button_center =
+        GetWindowCycleTabSliderViews()[per_desk_mode ? 1 : 0]
+            ->GetBoundsInScreen()
+            .CenterPoint();
+    generator_->MoveMouseTo(button_center);
+    generator_->ClickLeftButton();
+    EXPECT_EQ(per_desk_mode,
+              Shell::Get()->window_cycle_controller()->IsAltTabPerActiveDesk());
+  }
+
+ private:
+  base::test::ScopedFeatureList scoped_feature_list_;
+  ui::test::EventGenerator* generator_;
+};
+
+// Tests that alt-tab shows all windows in an all-desk mode by default and
+// shows only windows in the current desk in a current-desk mode. Switching
+// between two modes should refresh the window list, while re-entering alt-tab
+// should display the most recently selected mode.
+TEST_F(ModeSelectionWindowCycleControllerTest, CycleShowsWindowsPerMode) {
+  WindowCycleController* cycle_controller =
+      Shell::Get()->window_cycle_controller();
+
+  // Create two windows for desk1 and three windows for desk2.
+  auto win0 = CreateAppWindow(gfx::Rect(0, 0, 250, 100));
+  auto win1 = CreateAppWindow(gfx::Rect(50, 50, 200, 200));
+  auto* desks_controller = DesksController::Get();
+  desks_controller->NewDesk(DesksCreationRemovalSource::kButton);
+  ASSERT_EQ(2u, desks_controller->desks().size());
+  const Desk* desk_2 = desks_controller->desks()[1].get();
+  ActivateDesk(desk_2);
+  EXPECT_EQ(desk_2, desks_controller->active_desk());
+  auto win2 = CreateAppWindow(gfx::Rect(0, 0, 300, 200));
+  auto win3 = CreateAppWindow(gfx::Rect(10, 30, 400, 200));
+  auto win4 = CreateAppWindow(gfx::Rect(10, 30, 400, 200));
+
+  // By default should contain windows from all desks.
+  auto* generator = GetEventGenerator();
+  // Press and hold an alt key to test that alt + left clicking a button works.
+  generator->PressKey(ui::VKEY_MENU, ui::EF_NONE);
+  cycle_controller->StartCycling();
+  EXPECT_FALSE(cycle_controller->IsAltTabPerActiveDesk());
+  auto cycle_windows = GetWindows(cycle_controller);
+  EXPECT_EQ(5u, cycle_windows.size());
+  EXPECT_EQ(cycle_windows.size(), GetWindowCycleItemViews().size());
+  EXPECT_TRUE(base::Contains(cycle_windows, win0.get()));
+  EXPECT_TRUE(base::Contains(cycle_windows, win1.get()));
+  EXPECT_TRUE(base::Contains(cycle_windows, win2.get()));
+  EXPECT_TRUE(base::Contains(cycle_windows, win3.get()));
+  EXPECT_TRUE(base::Contains(cycle_windows, win4.get()));
+
+  // Switching alt-tab to the current-desk mode should show windows in the
+  // active desk.
+  SwitchPerDeskAltTabMode(true);
+  cycle_windows = GetWindows(cycle_controller);
+  EXPECT_EQ(3u, GetWindowCycleItemViews().size());
+  EXPECT_EQ(cycle_windows.size(), GetWindowCycleItemViews().size());
+  EXPECT_TRUE(base::Contains(cycle_windows, win2.get()));
+  EXPECT_TRUE(base::Contains(cycle_windows, win3.get()));
+  EXPECT_TRUE(base::Contains(cycle_windows, win4.get()));
+  cycle_controller->CompleteCycling();
+
+  // Activate desk1 and start alt-tab.
+  const Desk* desk_1 = desks_controller->desks()[0].get();
+  ActivateDesk(desk_1);
+  cycle_controller->StartCycling();
+  // Should start alt-tab with the current-desk mode and show only two windows
+  // from desk1.
+  EXPECT_TRUE(cycle_controller->IsAltTabPerActiveDesk());
+  cycle_windows = GetWindows(cycle_controller);
+  EXPECT_EQ(2u, GetWindowCycleItemViews().size());
+  EXPECT_EQ(cycle_windows.size(), GetWindowCycleItemViews().size());
+  EXPECT_TRUE(base::Contains(cycle_windows, win0.get()));
+  EXPECT_TRUE(base::Contains(cycle_windows, win1.get()));
+
+  // Switch to the all-desks mode, check and stop alt-tab.
+  SwitchPerDeskAltTabMode(false);
+  cycle_windows = GetWindows(cycle_controller);
+  EXPECT_EQ(5u, cycle_windows.size());
+  EXPECT_EQ(cycle_windows.size(), GetWindowCycleItemViews().size());
+  cycle_controller->CompleteCycling();
+  generator->ReleaseKey(ui::VKEY_MENU, ui::EF_NONE);
+}
+
+// For one window display, tests that alt-tab does not show up if there is only
+// one window to be shown, but would continue to show a window in alt-tab if
+// switching from the all-desks mode with multiple windows.
+TEST_F(ModeSelectionWindowCycleControllerTest, OneWindowInActiveDesk) {
+  WindowCycleController* cycle_controller =
+      Shell::Get()->window_cycle_controller();
+
+  // Create two windows for desk1 and one window for desk2.
+  auto win0 = CreateAppWindow(gfx::Rect(0, 0, 250, 100));
+  auto win1 = CreateAppWindow(gfx::Rect(50, 50, 200, 200));
+  auto* desks_controller = DesksController::Get();
+  desks_controller->NewDesk(DesksCreationRemovalSource::kButton);
+  ASSERT_EQ(2u, desks_controller->desks().size());
+  const Desk* desk_2 = desks_controller->desks()[1].get();
+  ActivateDesk(desk_2);
+  EXPECT_EQ(desk_2, desks_controller->active_desk());
+  auto win2 = CreateAppWindow(gfx::Rect(0, 0, 300, 200));
+
+  // Starting alt-tab should shows all desks.
+  cycle_controller->StartCycling();
+  auto cycle_windows = GetWindows(cycle_controller);
+  EXPECT_EQ(3u, GetWindowCycleItemViews().size());
+  EXPECT_EQ(cycle_windows.size(), GetWindowCycleItemViews().size());
+
+  // Switching to an active desk mode should shows a single window in desk2.
+  SwitchPerDeskAltTabMode(true);
+  EXPECT_TRUE(cycle_controller->IsCycling());
+  cycle_windows = GetWindows(cycle_controller);
+  EXPECT_EQ(1u, GetWindowCycleItemViews().size());
+  EXPECT_EQ(cycle_windows.size(), GetWindowCycleItemViews().size());
+  EXPECT_TRUE(base::Contains(cycle_windows, win2.get()));
+  cycle_controller->CompleteCycling();
+
+  // Closing alt-tab and trying to re-open again in the current-desk mode
+  // should not work because there's only one window.
+  cycle_controller->StartCycling();
+  EXPECT_TRUE(cycle_controller->IsCycling());
+  EXPECT_FALSE(CycleViewExists());
+  cycle_controller->CompleteCycling();
+}
+
+// Similar to OneWindowInActiveDesk, tests that alt-tab will not work if there
+// is no window to be shown. However, if users already open alt-tab with
+// multiple windows in the all-desks mode and later switch to the current-
+// desk mode, which has no window, it'll display "No recent items".
+TEST_F(ModeSelectionWindowCycleControllerTest, NoWindowInActiveDesk) {
+  WindowCycleController* cycle_controller =
+      Shell::Get()->window_cycle_controller();
+
+  // Create two desks with all two windows in desk1.
+  auto win0 = CreateAppWindow(gfx::Rect(0, 0, 250, 100));
+  auto win1 = CreateAppWindow(gfx::Rect(50, 50, 200, 200));
+  auto* desks_controller = DesksController::Get();
+  desks_controller->NewDesk(DesksCreationRemovalSource::kButton);
+  ASSERT_EQ(2u, desks_controller->desks().size());
+  const Desk* desk_2 = desks_controller->desks()[1].get();
+
+  // Activate desk2.
+  ActivateDesk(desk_2);
+  EXPECT_EQ(desk_2, desks_controller->active_desk());
+
+  // Starting alt-tab should show all windows from all desks.
+  cycle_controller->StartCycling();
+  auto cycle_windows = GetWindows(cycle_controller);
+  EXPECT_EQ(2u, GetWindowCycleItemViews().size());
+  EXPECT_EQ(cycle_windows.size(), GetWindowCycleItemViews().size());
+  EXPECT_FALSE(GetWindowCycleNoRecentItemsLabel()->GetVisible());
+
+  // Switching to an active-desk mode should not show any mirror window
+  // and should display "no recent items" label.
+  SwitchPerDeskAltTabMode(true);
+  EXPECT_TRUE(cycle_controller->IsCycling());
+  cycle_windows = GetWindows(cycle_controller);
+  EXPECT_EQ(0u, GetWindowCycleItemViews().size());
+  EXPECT_EQ(cycle_windows.size(), GetWindowCycleItemViews().size());
+  EXPECT_TRUE(GetWindowCycleNoRecentItemsLabel()->GetVisible());
+
+  // Switching back to an all-desks mode should hide the label.
+  SwitchPerDeskAltTabMode(false);
+  EXPECT_FALSE(GetWindowCycleNoRecentItemsLabel()->GetVisible());
+  cycle_controller->CompleteCycling();
+}
+
 }  // namespace ash

ash/wm/window_cycle_list.cc

@@ -17,7 +17,11 @@
 #include "ash/public/cpp/window_properties.h"
 #include "ash/shell.h"
 #include "ash/shell_delegate.h"
+#include "ash/strings/grit/ash_strings.h"
 #include "ash/style/ash_color_provider.h"
+#include "ash/style/default_colors.h"
+#include "ash/wm/window_cycle_tab_slider.h"
+#include "ash/wm/window_cycle_tab_slider_button.h"
 #include "ash/wm/window_mini_view.h"
 #include "ash/wm/window_preview_view.h"
 #include "ash/wm/window_state.h"
@@ -29,12 +33,15 @@
 #include "ui/aura/scoped_window_targeter.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_targeter.h"
+#include "ui/base/l10n/l10n_util.h"
 #include "ui/compositor/animation_throughput_reporter.h"
 #include "ui/compositor/layer_animation_sequence.h"
 #include "ui/compositor/scoped_layer_animation_settings.h"
 #include "ui/display/display.h"
 #include "ui/gfx/geometry/insets.h"
 #include "ui/views/animation/bounds_animator.h"
+#include "ui/views/background.h"
+#include "ui/views/controls/button/label_button.h"
 #include "ui/views/layout/box_layout.h"
 #include "ui/views/view.h"
 #include "ui/views/widget/widget.h"
@@ -70,9 +77,19 @@ constexpr int kMaxPreviewWidthDp = kFixedPreviewHeightDp * 2;
 constexpr int kInsideBorderHorizontalPaddingDp = 64;
 constexpr int kInsideBorderVerticalPaddingDp = 60;
 
+// Padding between the alt-tab bandshield and the tab slider container.
+constexpr int kMirrorContainerVerticalPaddingDp = 24;
+
 // Padding between the window previews within the alt-tab bandshield.
 constexpr int kBetweenChildPaddingDp = 10;
 
+// Padding between the tab slider button and the tab slider container.
+constexpr int kTabSliderContainerVerticalPaddingDp = 32;
+
+// The font size of "No recent items" string when there's no window in the
+// window cycle list.
+constexpr int kNoRecentItemsLabelFontSizeDp = 14;
+
 // The UMA histogram that logs smoothness of the fade-in animation.
 constexpr char kShowAnimationSmoothness[] =
     "Ash.WindowCycleView.AnimationSmoothness.Show";
@@ -262,6 +279,30 @@ class WindowCycleView : public views::WidgetDelegateView,
     layer->SetBackdropFilterQuality(kBackgroundBlurQuality);
     layer->SetName("WindowCycleView");
 
+    if (features::IsBentoEnabled()) {
+      tab_slider_container_ =
+          AddChildView(std::make_unique<WindowCycleTabSlider>());
+
+      no_recent_items_label_ = AddChildView(std::make_unique<views::Label>(
+          l10n_util::GetStringUTF16(IDS_ASH_OVERVIEW_NO_RECENT_ITEMS)));
+
+      no_recent_items_label_->SetPaintToLayer();
+      no_recent_items_label_->layer()->SetFillsBoundsOpaquely(false);
+      no_recent_items_label_->SetHorizontalAlignment(gfx::ALIGN_CENTER);
+      no_recent_items_label_->SetVerticalAlignment(gfx::ALIGN_MIDDLE);
+
+      no_recent_items_label_->SetEnabledColor(
+          AshColorProvider::Get()->GetContentLayerColor(
+              AshColorProvider::ContentLayerType::kIconColorSecondary));
+      no_recent_items_label_->SetFontList(
+          no_recent_items_label_->font_list()
+              .DeriveWithSizeDelta(
+                  kNoRecentItemsLabelFontSizeDp -
+                  no_recent_items_label_->font_list().GetFontSize())
+              .DeriveWithWeight(gfx::Font::Weight::NORMAL));
+      no_recent_items_label_->SetVisible(false);
+    }
+
     // |mirror_container_| may be larger than |this|. In this case, it will be
     // shifted along the x-axis when the user tabs through. It is a container
     // for the previews and has no rendered content.
@@ -271,7 +312,11 @@ class WindowCycleView : public views::WidgetDelegateView,
     views::BoxLayout* layout =
         mirror_container_->SetLayoutManager(std::make_unique<views::BoxLayout>(
             views::BoxLayout::Orientation::kHorizontal,
-            gfx::Insets(kInsideBorderVerticalPaddingDp,
+            gfx::Insets(features::IsBentoEnabled()
+                            ? kMirrorContainerVerticalPaddingDp
+                            : kInsideBorderVerticalPaddingDp,
+                        kInsideBorderHorizontalPaddingDp,
+                        kInsideBorderVerticalPaddingDp,
                         kInsideBorderHorizontalPaddingDp),
             kBetweenChildPaddingDp));
     layout->set_cross_axis_alignment(
@@ -301,6 +346,15 @@ class WindowCycleView : public views::WidgetDelegateView,
   ~WindowCycleView() override = default;
 
   void UpdateWindows(const WindowCycleList::WindowList& windows) {
+    const bool no_windows = windows.empty();
+    if (features::IsBentoEnabled()) {
+      no_recent_items_label_->SetVisible(no_windows);
+    }
+    if (no_windows)
+      return;
+
+    if (features::IsBentoEnabled())
+      no_recent_items_label_->SetVisible(false);
     for (auto* window : windows) {
       auto* view = mirror_container_->AddChildView(
           std::make_unique<WindowCycleItemView>(window));
@@ -394,7 +448,12 @@ class WindowCycleView : public views::WidgetDelegateView,
 
   // views::WidgetDelegateView:
   gfx::Size CalculatePreferredSize() const override {
-    return mirror_container_->GetPreferredSize();
+    gfx::Size size = mirror_container_->GetPreferredSize();
+    if (features::IsBentoEnabled()) {
+      size.Enlarge(0, tab_slider_container_->GetPreferredSize().height() +
+                          kTabSliderContainerVerticalPaddingDp);
+    }
+    return size;
   }
 
   void Layout() override {
@@ -436,6 +495,32 @@ class WindowCycleView : public views::WidgetDelegateView,
     }
     container_bounds.set_x(x_offset);
 
+    // Layout a tab slider if Bento is enabled.
+    if (features::IsBentoEnabled()) {
+      // Layout the tab slider.
+      const gfx::Size tab_slider_size =
+          tab_slider_container_->GetPreferredSize();
+      const gfx::Rect tab_slider_container_bounds(
+          (width() - tab_slider_size.width()) / 2,
+          kTabSliderContainerVerticalPaddingDp, tab_slider_size.width(),
+          tab_slider_size.height());
+      tab_slider_container_->SetBoundsRect(tab_slider_container_bounds);
+
+      // Move window cycle container down.
+      container_bounds.set_y(tab_slider_container_->y() +
+                             tab_slider_container_->height());
+
+      // Unlike the bounds of scrollable mirror container, the bounds of label
+      // should not overflow out of the screen.
+      if (no_previews_set_.empty()) {
+        const gfx::Rect no_recent_item_bounds_(
+            std::max(0, container_bounds.x()), container_bounds.y(),
+            std::min(width(), container_bounds.width()),
+            container_bounds.height());
+        no_recent_items_label_->SetBoundsRect(no_recent_item_bounds_);
+      }
+    }
+
     // Enable animations only after the first Layout() pass.
     std::unique_ptr<ui::ScopedLayerAnimationSettings> settings;
     base::Optional<ui::AnimationThroughputReporter> reporter;
@@ -478,6 +563,13 @@ class WindowCycleView : public views::WidgetDelegateView,
     return mirror_container_->children();
   }
 
+  const views::View::Views& GetTabSliderViewsForTesting() const {
+    return tab_slider_container_->children();
+  }
+
+  const views::Label* GetNoRecentItemsLabelForTesting() const {
+    return no_recent_items_label_;
+  }
   const aura::Window* GetTargetWindowForTesting() const {
     return target_window_;
   }
@@ -491,6 +583,10 @@ class WindowCycleView : public views::WidgetDelegateView,
   std::map<aura::Window*, WindowCycleItemView*> window_view_map_;
   views::View* mirror_container_ = nullptr;
 
+  // Tab slider and no recent items are only used when Bento is enabled.
+  views::View* tab_slider_container_ = nullptr;
+  views::Label* no_recent_items_label_ = nullptr;
+
   // The |target_window_| is the window that has the focus ring. When the user
   // completes cycling the |target_window_| is activated.
   aura::Window* target_window_ = nullptr;
@@ -572,8 +668,6 @@ WindowCycleList::~WindowCycleList() {
 }
 
 void WindowCycleList::ReplaceWindows(const WindowList& windows) {
-  if (windows.empty())
-    return;
 
   RemoveAllWindows();
   windows_ = windows;
@@ -581,7 +675,7 @@ void WindowCycleList::ReplaceWindows(const WindowList& windows) {
   for (auto* new_window : windows_)
     new_window->AddObserver(this);
 
-  if (ShouldShowUi() && cycle_view_)
+  if (cycle_view_)
     cycle_view_->UpdateWindows(windows_);
 }
 
@@ -819,11 +913,21 @@ int WindowCycleList::GetOffsettedWindowIndex(int offset) const {
 
 const views::View::Views& WindowCycleList::GetWindowCycleItemViewsForTesting()
     const {
-  return cycle_view_->GetPreviewViewsForTesting();
+  return cycle_view_->GetPreviewViewsForTesting();  // IN-TEST
+}
+
+const views::View::Views&
+WindowCycleList::GetWindowCycleTabSliderViewsForTesting() const {
+  return cycle_view_->GetTabSliderViewsForTesting();  // IN-TEST
+}
+
+const views::Label*
+WindowCycleList::GetWindowCycleNoRecentItemsLabelForTesting() const {
+  return cycle_view_->GetNoRecentItemsLabelForTesting();  // IN-TEST
 }
 
 const aura::Window* WindowCycleList::GetTargetWindowForTesting() const {
-  return cycle_view_->GetTargetWindowForTesting();
+  return cycle_view_->GetTargetWindowForTesting();  // IN-TEST
 }
 
 }  // namespace ash

ash/wm/window_cycle_list.h

@@ -15,6 +15,7 @@
 #include "ui/aura/window_observer.h"
 #include "ui/display/display_observer.h"
 #include "ui/display/screen.h"
+#include "ui/views/controls/label.h"
 #include "ui/views/view.h"
 
 namespace aura {
@@ -115,6 +116,12 @@ class ASH_EXPORT WindowCycleList : public aura::WindowObserver,
   // Returns the views for the window cycle list.
   const views::View::Views& GetWindowCycleItemViewsForTesting() const;
 
+  // Returns the views for the window cycle tab slider buttons.
+  const views::View::Views& GetWindowCycleTabSliderViewsForTesting() const;
+
+  // Returns no recent items label.
+  const views::Label* GetWindowCycleNoRecentItemsLabelForTesting() const;
+
   // Returns the window cycle list's target window.
   const aura::Window* GetTargetWindowForTesting() const;
 

ash/wm/window_cycle_tab_slider.cc

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ash/wm/window_cycle_tab_slider.h"
+
+#include "ash/shell.h"
+#include "ash/strings/grit/ash_strings.h"
+#include "ash/style/ash_color_provider.h"
+#include "ash/style/default_colors.h"
+#include "ash/wm/mru_window_tracker.h"
+#include "ash/wm/window_cycle_controller.h"
+#include "base/strings/utf_string_conversions.h"
+#include "ui/base/l10n/l10n_util.h"
+#include "ui/gfx/canvas.h"
+#include "ui/views/background.h"
+#include "ui/views/layout/box_layout.h"
+#include "ui/views/metadata/metadata_impl_macros.h"
+
+namespace ash {
+
+WindowCycleTabSlider::WindowCycleTabSlider()
+    : all_desks_tab_slider_button_(
+          AddChildView(std::make_unique<WindowCycleTabSliderButton>(
+              base::BindRepeating(&WindowCycleTabSlider::OnModeChanged,
+                                  base::Unretained(this),
+                                  false),
+              l10n_util::GetStringUTF16(IDS_ASH_ALT_TAB_ALL_DESKS_MODE)))),
+      current_desk_tab_slider_button_(
+          AddChildView(std::make_unique<WindowCycleTabSliderButton>(
+              base::BindRepeating(&WindowCycleTabSlider::OnModeChanged,
+                                  base::Unretained(this),
+                                  true),
+              l10n_util::GetStringUTF16(IDS_ASH_ALT_TAB_CURRENT_DESK_MODE)))) {
+  SetPaintToLayer();
+  layer()->SetFillsBoundsOpaquely(false);
+  SetLayoutManager(std::make_unique<views::BoxLayout>(
+      views::BoxLayout::Orientation::kHorizontal, gfx::Insets(0, 0), 0));
+
+  // All buttons should have the same width and height.
+  gfx::Size common_size = all_desks_tab_slider_button_->GetPreferredSize();
+  common_size.SetToMax(current_desk_tab_slider_button_->GetPreferredSize());
+  all_desks_tab_slider_button_->SetPreferredSize(common_size);
+  current_desk_tab_slider_button_->SetPreferredSize(common_size);
+
+  const int tab_slider_round_radius = int{common_size.height() / 2};
+  SetBackground(views::CreateRoundedRectBackground(
+      AshColorProvider::Get()->GetControlsLayerColor(
+          AshColorProvider::ControlsLayerType::kControlBackgroundColorInactive),
+      tab_slider_round_radius));
+
+  per_desk_mode_ =
+      Shell::Get()->window_cycle_controller()->IsAltTabPerActiveDesk();
+
+  all_desks_tab_slider_button_->SetToggled(!per_desk_mode_);
+  current_desk_tab_slider_button_->SetToggled(per_desk_mode_);
+}
+
+void WindowCycleTabSlider::OnModeChanged(bool per_desk) {
+  if (per_desk_mode_ == per_desk)
+    return;
+  per_desk_mode_ = per_desk;
+  all_desks_tab_slider_button_->SetToggled(!per_desk_mode_);
+  current_desk_tab_slider_button_->SetToggled(per_desk_mode_);
+  Shell::Get()->window_cycle_controller()->SetAltTabMode(
+      per_desk_mode_ ? DesksMruType::kActiveDesk : DesksMruType::kAllDesks);
+}
+
+BEGIN_METADATA(WindowCycleTabSlider, views::View)
+END_METADATA
+
+}  // namespace ash

ash/wm/window_cycle_tab_slider.h

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ASH_WM_WINDOW_CYCLE_TAB_SLIDER_H_
+#define ASH_WM_WINDOW_CYCLE_TAB_SLIDER_H_
+
+#include "ash/ash_export.h"
+#include "ash/wm/window_cycle_tab_slider_button.h"
+#include "ui/views/metadata/metadata_header_macros.h"
+
+namespace ash {
+
+// A WindowCycleTabSlider containing two buttons to switch between
+// all desks and current desks mode.
+class ASH_EXPORT WindowCycleTabSlider : public views::View {
+ public:
+  METADATA_HEADER(WindowCycleTabSlider);
+
+  WindowCycleTabSlider();
+  WindowCycleTabSlider(const WindowCycleTabSlider&) = delete;
+  WindowCycleTabSlider& operator=(const WindowCycleTabSlider&) = delete;
+  ~WindowCycleTabSlider() override = default;
+
+  void OnModeChanged(bool per_desk);
+
+  // TODO(crbug.com/1157087): Add tab slider animation.
+
+ private:
+  bool per_desk_mode_ = false;
+
+  WindowCycleTabSliderButton* all_desks_tab_slider_button_;
+  WindowCycleTabSliderButton* current_desk_tab_slider_button_;
+};
+
+}  // namespace ash
+
+#endif  // ASH_WM_WINDOW_CYCLE_TAB_SLIDER_H_

ash/wm/window_cycle_tab_slider_button.cc

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ash/wm/window_cycle_tab_slider_button.h"
+
+#include "ash/style/ash_color_provider.h"
+#include "base/strings/utf_string_conversions.h"
+#include "ui/gfx/canvas.h"
+#include "ui/views/background.h"
+#include "ui/views/controls/label.h"
+#include "ui/views/layout/box_layout.h"
+#include "ui/views/metadata/metadata_impl_macros.h"
+
+namespace ash {
+
+namespace {
+
+// The height of the tab slider button.
+constexpr int kTabSliderButtonHeight = 32;
+
+// The round radius of the slider, which is half of its diameter (height).
+constexpr int kTabSliderRoundRadius = int{kTabSliderButtonHeight / 2};
+
+// The horizontal insets between the label and the button.
+constexpr int kTabSliderButtonHorizontalInsets = 20;
+
+// The font size of the button label.
+constexpr int kTabSliderButtonLabelFontSizeDp = 13;
+
+}  // namespace
+
+WindowCycleTabSliderButton::WindowCycleTabSliderButton(
+    views::Button::PressedCallback callback,
+    const base::string16& label_text)
+    : LabelButton(std::move(callback), label_text) {
+  SetHorizontalAlignment(gfx::ALIGN_CENTER);
+
+  label()->SetFontList(
+      label()
+          ->font_list()
+          .DeriveWithSizeDelta(kTabSliderButtonLabelFontSizeDp -
+                               label()->font_list().GetFontSize())
+          .DeriveWithWeight(gfx::Font::Weight::MEDIUM));
+
+  SetEnabledTextColors(AshColorProvider::Get()->GetContentLayerColor(
+      AshColorProvider::ContentLayerType::kTextColorPrimary));
+
+  SetBorder(views::CreateEmptyBorder(gfx::Insets()));
+}
+
+void WindowCycleTabSliderButton::SetToggled(bool is_toggled) {
+  if (is_toggled == toggled_)
+    return;
+  toggled_ = is_toggled;
+  SetEnabledTextColors(AshColorProvider::Get()->GetContentLayerColor(
+      toggled_ ? AshColorProvider::ContentLayerType::kButtonLabelColorPrimary
+               : AshColorProvider::ContentLayerType::kTextColorPrimary));
+  // SchedulePaint triggers OnPaintBackground
+  SchedulePaint();
+}
+
+void WindowCycleTabSliderButton::OnPaintBackground(gfx::Canvas* canvas) {
+  if (!toggled_)
+    return;
+
+  cc::PaintFlags flags;
+  flags.setAntiAlias(true);
+  flags.setStyle(cc::PaintFlags::kFill_Style);
+  flags.setColor(AshColorProvider::Get()->GetControlsLayerColor(
+      AshColorProvider::ControlsLayerType::kControlBackgroundColorActive));
+  canvas->DrawRoundRect(GetContentsBounds(), kTabSliderRoundRadius, flags);
+}
+
+gfx::Size WindowCycleTabSliderButton::CalculatePreferredSize() const {
+  return gfx::Size(label()->GetPreferredSize().width() +
+                       2 * kTabSliderButtonHorizontalInsets,
+                   kTabSliderButtonHeight);
+}
+
+BEGIN_METADATA(WindowCycleTabSliderButton, views::LabelButton)
+END_METADATA
+
+}  // namespace ash

ash/wm/window_cycle_tab_slider_button.h

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ASH_WM_WINDOW_CYCLE_TAB_SLIDER_BUTTON_H_
+#define ASH_WM_WINDOW_CYCLE_TAB_SLIDER_BUTTON_H_
+
+#include "ash/ash_export.h"
+#include "ui/views/controls/button/label_button.h"
+#include "ui/views/metadata/metadata_header_macros.h"
+
+namespace ash {
+
+// A button used in the WindowCycleTabSlider to choose between
+// all desks and current desks mode.
+class ASH_EXPORT WindowCycleTabSliderButton : public views::LabelButton {
+ public:
+  METADATA_HEADER(WindowCycleTabSliderButton);
+
+  WindowCycleTabSliderButton(views::Button::PressedCallback callback,
+                             const base::string16& label);
+  WindowCycleTabSliderButton(const WindowCycleTabSliderButton&) = delete;
+  WindowCycleTabSliderButton& operator=(const WindowCycleTabSliderButton&) =
+      delete;
+  ~WindowCycleTabSliderButton() override = default;
+
+  // views::View:
+  void OnPaintBackground(gfx::Canvas* canvas) override;
+  gfx::Size CalculatePreferredSize() const override;
+
+  void SetToggled(bool is_toggled);
+
+ private:
+  bool toggled_ = false;
+};
+
+}  // namespace ash
+
+#endif  // ASH_WM_WINDOW_CYCLE_TAB_SLIDER_BUTTON_H_

ui/chromeos/events/event_rewriter_chromeos.cc

@@ -965,7 +965,8 @@ bool EventRewriterChromeOS::ShouldRemapToRightClick(
       *matched_mask = kSearchLeftButton;
     }
   } else {
-    if (AreFlagsSet(flags, kAltLeftButton)) {
+    if (AreFlagsSet(flags, kAltLeftButton) &&
+        is_alt_left_click_remapping_enabled_) {
       *matched_mask = kAltLeftButton;
     }
   }

ui/chromeos/events/event_rewriter_chromeos.h

@@ -150,6 +150,13 @@ class EventRewriterChromeOS : public EventRewriter {
     privacy_screen_supported_ = supported;
   }
 
+  // Enable/disable alt + left click mapping to a right click. This only
+  // applies if the feature `chromeos::features::kUseSearchClickForRightClick`
+  // is not enabled.
+  void set_alt_left_click_remapping_enabled(bool enabled) {
+    is_alt_left_click_remapping_enabled_ = enabled;
+  }
+
   // EventRewriter overrides:
   EventDispatchDetails RewriteEvent(const Event& event,
                                     const Continuation continuation) override;
@@ -215,7 +222,8 @@ class EventRewriterChromeOS : public EventRewriter {
   // Returns true if this event should be remapped to a right-click.
   // |matched_mask| will be set to the variant (Alt+Click or Search+Click)
   // that was used to match based on flag/feature settings. |matched_mask|
-  // only has a valid value when returning true.
+  // only has a valid value when returning true. However, Alt+Click will not
+  // be remapped if |is_alt_left_click_remapping_enabled_| is false.
   bool ShouldRemapToRightClick(const MouseEvent& mouse_event,
                                int flags,
                                int* matched_mask) const;
@@ -325,6 +333,11 @@ class EventRewriterChromeOS : public EventRewriter {
   int latched_modifier_latches_;
   int used_modifier_latches_;
 
+  // Alt + left click maps to a right click by default. In some scenario, such
+  // as clicking a button in the Alt-Tab UI, this remapping undesirably prevents
+  // button clicking.
+  bool is_alt_left_click_remapping_enabled_ = true;
+
   DISALLOW_COPY_AND_ASSIGN(EventRewriterChromeOS);
 };