// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef ASH_SHELF_SHELF_LAYOUT_MANAGER_H_
#define ASH_SHELF_SHELF_LAYOUT_MANAGER_H_

#include <memory>

#include "ash/ash_export.h"
#include "ash/drag_drop/scoped_drag_drop_observer.h"
#include "ash/public/cpp/app_list/app_list_controller_observer.h"
#include "ash/public/cpp/session/session_observer.h"
#include "ash/public/cpp/shelf_config.h"
#include "ash/public/cpp/shelf_types.h"
#include "ash/public/cpp/wallpaper/wallpaper_controller.h"
#include "ash/public/cpp/wallpaper/wallpaper_controller_observer.h"
#include "ash/shelf/drag_window_from_shelf_controller.h"
#include "ash/shelf/shelf.h"
#include "ash/shelf/shelf_metrics.h"
#include "ash/shelf/shelf_observer.h"
#include "ash/shelf/shelf_widget.h"
#include "ash/shell_observer.h"
#include "ash/system/locale/locale_update_controller_impl.h"
#include "ash/wm/desks/desks_controller.h"
#include "ash/wm/lock_state_observer.h"
#include "ash/wm/overview/overview_observer.h"
#include "ash/wm/splitview/split_view_controller.h"
#include "ash/wm/splitview/split_view_observer.h"
#include "ash/wm/wm_default_layout_manager.h"
#include "ash/wm/workspace/workspace_types.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/raw_ptr_exclusion.h"
#include "base/memory/weak_ptr.h"
#include "base/observer_list.h"
#include "base/scoped_observation.h"
#include "base/strings/string_number_conversions.h"
#include "base/timer/timer.h"
#include "third_party/abseil-cpp/absl/types/optional.h"
#include "ui/compositor/layer_animation_observer.h"
#include "ui/display/display.h"
#include "ui/display/display_observer.h"
#include "ui/gfx/geometry/insets.h"
#include "ui/gfx/geometry/rect.h"
#include "ui/wm/public/activation_change_observer.h"

namespace ui {
class EventHandler;
class LocatedEvent;
class MouseEvent;
class MouseWheelEvent;
class PresentationTimeRecorder;
}  // namespace ui

namespace ash {

enum class AnimationChangeType;
class DragWindowFromShelfController;
class HomeToOverviewNudgeController;
class InAppToHomeNudgeController;
class PanelLayoutManagerTest;
class Shelf;
class ShelfLayoutManagerObserver;
class ShelfLayoutManagerTestBase;
class ShelfWidget;
class SwipeHomeToOverviewController;

// ShelfLayoutManager is the layout manager responsible for the shelf and
// status widgets. The shelf is given the total available width and told the
// width of the status area. This allows the shelf to draw the background and
// layout to the status area.
// To respond to bounds changes in the status area StatusAreaLayoutManager works
// closely with ShelfLayoutManager.
class ASH_EXPORT ShelfLayoutManager : public AppListControllerObserver,
                                      public ShelfObserver,
                                      public ShellObserver,
                                      public SplitViewObserver,
                                      public OverviewObserver,
                                      public ::wm::ActivationChangeObserver,
                                      public LockStateObserver,
                                      public WmDefaultLayoutManager,
                                      public display::DisplayObserver,
                                      public SessionObserver,
                                      public WallpaperControllerObserver,
                                      public LocaleChangeObserver,
                                      public DesksController::Observer,
                                      public ShelfConfig::Observer {
 public:
  // See `drag_status_`. Visible for testing.
  enum DragStatus {
    kDragNone,
    kDragAttempt,
    kDragInProgress,
    kDragCancelInProgress,
    kDragCompleteInProgress,
    kDragHomeToOverviewInProgress,
    kFlingBubbleLauncherInProgress,
  };

  // Suspend work area updates within its scope. Note that relevant
  // ShelfLayoutManager must outlive this class.
  class ScopedSuspendWorkAreaUpdate {
   public:
    // |manager| is the ShelfLayoutManager whose visibility update is suspended.
    explicit ScopedSuspendWorkAreaUpdate(ShelfLayoutManager* manager);

    ScopedSuspendWorkAreaUpdate(const ScopedSuspendWorkAreaUpdate&) = delete;
    ScopedSuspendWorkAreaUpdate& operator=(const ScopedSuspendWorkAreaUpdate&) =
        delete;

    ~ScopedSuspendWorkAreaUpdate();

   private:
    // This field is not a raw_ptr<> because it was filtered by the rewriter
    // for: #union
    RAW_PTR_EXCLUSION ShelfLayoutManager* const manager_;
  };

  // Used to maintain a lock for the shelf visibility state. If locked, then we
  // should not update the state of the shelf visibility.
  class ScopedVisibilityLock {
   public:
    explicit ScopedVisibilityLock(ShelfLayoutManager* shelf);
    ~ScopedVisibilityLock();

   private:
    base::WeakPtr<ShelfLayoutManager> shelf_;
  };

  ShelfLayoutManager(ShelfWidget* shelf_widget, Shelf* shelf);

  ShelfLayoutManager(const ShelfLayoutManager&) = delete;
  ShelfLayoutManager& operator=(const ShelfLayoutManager&) = delete;

  ~ShelfLayoutManager() override;

  // Initializes observers.
  void InitObservers();

  // Clears internal data for shutdown process.
  void PrepareForShutdown();
  // Returns whether the shelf and its contents (shelf, status) are visible
  // on the screen.
  bool IsVisible() const;

  // Returns the ideal bounds of the shelf assuming it is visible.
  gfx::Rect GetIdealBounds() const;

  // Returns the ideal bounds of the shelf, but always returns in-app shelf
  // bounds in tablet mode.
  gfx::Rect GetIdealBoundsForWorkAreaCalculation() const;

  // Sets the bounds of the shelf and status widgets.
  void LayoutShelf(bool animate = false);

  // Sets display work area insets for the current shelf state, and target
  // bounds.
  void UpdateShelfWorkAreaInsets();

  // Updates display work area to account for the current shelf state and
  // bounds.
  void UpdateDisplayWorkArea();

  // Updates the visibility state. Relayouts the shelf if the visibility state
  // changes, or if `force_layout` is set.
  // `force_layout` should be used when state is set in response to events that
  // both affect the shelf bounds/layout and may change shelf visibility.
  void UpdateVisibilityState(bool force_layout);

  // Shows the shelf and hotseat for the back gesture.
  void UpdateVisibilityStateForBackGesture();

  // Invoked by the shelf when the auto-hide state may have changed.
  void UpdateAutoHideState();

  // Updates the auto-hide state for mouse events.
  void UpdateAutoHideForMouseEvent(ui::MouseEvent* event, aura::Window* target);

  // Shows or hides contextual nudges for shelf gestures, depending on the shelf
  // state.
  void UpdateContextualNudges();

  // Hides any visible contextual nudge for shelf gestures.
  void HideContextualNudges();

  // Called by AutoHideEventHandler to process the gesture events when shelf is
  // auto hidden.
  void ProcessGestureEventOfAutoHideShelf(ui::GestureEvent* event,
                                          aura::Window* target);

  // Handles events that are detected while the hotseat is kExtended in in-app
  // shelf.
  void ProcessGestureEventOfInAppHotseat(ui::GestureEvent* event,
                                         aura::Window* target);

  // Updates the auto-dim state. Returns true if successful.
  bool SetDimmed(bool dimmed);

  void AddObserver(ShelfLayoutManagerObserver* observer);
  void RemoveObserver(ShelfLayoutManagerObserver* observer);

  // Processes a gesture event and updates the status of the shelf when
  // appropriate. Returns true if the gesture has been handled and it should not
  // be processed any further, false otherwise.
  bool ProcessGestureEvent(const ui::GestureEvent& event_in_screen);

  // Handles mouse events from the shelf.
  void ProcessMouseEventFromShelf(const ui::MouseEvent& event_in_screen);

  // Handles events from ShelfWidget.
  void ProcessGestureEventFromShelfWidget(ui::GestureEvent* event_in_screen);

  // Handles mouse wheel events from the shelf.
  void ProcessMouseWheelEventFromShelf(ui::MouseWheelEvent* event);

  // Handles scroll events from the shelf.
  void ProcessScrollEventFromShelf(ui::ScrollEvent* event);

  // Returns whether the current state of the shelf allows a gesture fling or
  // scroll to show the bubble launcher.
  bool IsBubbleLauncherShowOnGestureScrollAvailable();

  // Handles a fling event over the shelf. Returns whether the event was handled
  // by the manager or false if it was ignored.
  bool MaybeHandleShelfFling(const ui::GestureEvent& event_in_screen);

  // Cleans up after a fling event was successfully completed on the shelf.
  void CompleteShelfFling(const ui::LocatedEvent& event_in_screen);

  // Returns true if the location is within the bounds of the area designated to
  // receive the gesture fling or scroll over the shelf to show the bubble
  // launcher.
  bool IsLocationInBubbleLauncherShowBounds(
      const gfx::Point& location_in_screen);

  // Contains logic that is the same between mouse wheel and gesture scrolling.
  void ProcessScrollOffset(int offset, const ui::LocatedEvent& event);

  // Computes how the shelf background should be painted based on the current
  // state.
  ShelfBackgroundType ComputeShelfBackgroundType() const;

  // Updates the background of the shelf if it has changed.
  void MaybeUpdateShelfBackground(AnimationChangeType change_type);

  // Returns whether the shelf should show a blurred background. This may
  // return false even if background blur is enabled depending on the session
  // state.
  bool ShouldBlurShelfBackground();

  // Returns true if at least one window is visible.
  bool HasVisibleWindow() const;

  // Cancel the drag if the shelf is in drag progress.
  void CancelDragOnShelfIfInProgress();

  // Suspends shelf visibility updates, to be used during shutdown. Since there
  // is no balanced "resume" public API, the suspension will be indefinite.
  void SuspendVisibilityUpdateForShutdown();

  // Called when ShelfItems are interacted with in the shelf.
  void OnShelfItemSelected(ShelfAction action);

  // WmDefaultLayoutManager:
  void OnWindowResized() override;
  void SetChildBounds(aura::Window* child,
                      const gfx::Rect& requested_bounds) override;

  // ShelfObserver:
  void OnShelfAutoHideBehaviorChanged() override;

  // ShellObserver:
  void OnUserWorkAreaInsetsChanged(aura::Window* root_window) override;
  void OnPinnedStateChanged(aura::Window* pinned_window) override;
  void OnShellDestroying() override;

  // SplitViewObserver:
  void OnSplitViewStateChanged(SplitViewController::State previous_state,
                               SplitViewController::State state) override;

  // OverviewObserver:
  void OnOverviewModeWillStart() override;
  void OnOverviewModeStarting() override;
  void OnOverviewModeStartingAnimationComplete(bool canceled) override;
  void OnOverviewModeEnding(OverviewSession* overview_session) override;
  void OnOverviewModeEndingAnimationComplete(bool canceled) override;
  void OnOverviewModeEnded() override;

  // AppListControllerObserver:
  void OnAppListVisibilityWillChange(bool shown, int64_t display_id) override;
  void OnAppListVisibilityChanged(bool shown, int64_t display_id) override;

  // wm::ActivationChangeObserver:
  void OnWindowActivated(ActivationReason reason,
                         aura::Window* gained_active,
                         aura::Window* lost_active) override;

  // LockStateObserver:
  void OnLockStateEvent(LockStateObserver::EventType event) override;

  // SessionObserver:
  void OnSessionStateChanged(session_manager::SessionState state) override;
  void OnLoginStatusChanged(LoginStatus loing_status) override;

  // WallpaperControllerObserver:
  void OnWallpaperBlurChanged() override;
  void OnFirstWallpaperShown() override;

  // DisplayObserver:
  void OnDisplayMetricsChanged(const display::Display& display,
                               uint32_t changed_metrics) override;

  // LocaleChangeObserver:
  void OnLocaleChanged() override;

  // DesksController::Observer:
  void OnDeskSwitchAnimationLaunching() override;
  void OnDeskSwitchAnimationFinished() override;

  ShelfVisibilityState visibility_state() const {
    return state_.visibility_state.value_or(SHELF_VISIBLE);
  }

  ShelfBackgroundType shelf_background_type() const {
    return shelf_background_type_;
  }

  bool is_active_session_state() const { return state_.IsActiveSessionState(); }

  bool is_shelf_auto_hidden() const { return state_.IsShelfAutoHidden(); }

  // Locks or unlocks the state of shelf auto-hide. On unlock, the auto-hide
  // state will be recomputed.
  void LockAutoHideState(bool lock_auto_hide_state);

  ShelfAutoHideBehavior auto_hide_behavior() const {
    return shelf_->auto_hide_behavior();
  }

  // ShelfConfig::Observer:
  void OnShelfConfigUpdated() override;

  float GetOpacity() const;

  bool updating_bounds() const { return phase_ == ShelfLayoutPhase::kMoving; }
  ShelfAutoHideState auto_hide_state() const { return state_.auto_hide_state; }
  HotseatState hotseat_state() const {
    return shelf_widget_->hotseat_widget()->state();
  }

  DragWindowFromShelfController* window_drag_controller_for_testing() {
    return window_drag_controller_.get();
  }

  SwipeHomeToOverviewController*
  swipe_home_to_overview_controller_for_testing() {
    return swipe_home_to_overview_controller_.get();
  }

  HomeToOverviewNudgeController*
  home_to_overview_nudge_controller_for_testing() {
    return home_to_overview_nudge_controller_.get();
  }

  DragStatus drag_status_for_test() const { return drag_status_; }

  // Gets the target HotseatState based on the current state of HomeLauncher,
  // Overview, Shelf, and any active gestures.
  // TODO(manucornet): Move this to the hotseat class.
  HotseatState CalculateHotseatState(ShelfVisibilityState visibility_state,
                                     ShelfAutoHideState auto_hide_state) const;

  // Called when the shelf alignment changes - updates shelf visibility state
  // and bounds to reflect the new shelf alignment.
  void HandleShelfAlignmentChange();

  // Called when the visibility for a tray bubble in the shelf's status area
  // changes.
  void OnShelfTrayBubbleVisibilityChanged(bool bubble_shown);

  void UpdateWorkAreaInsetsAndNotifyObservers(
      const gfx::Rect& shelf_bounds_for_workarea_calculation,
      const gfx::Insets& shelf_insets,
      const gfx::Insets& in_session_shelf_insets);

  // Called from the scrollable shelf container when it updates its bounds.
  void HandleScrollableShelfContainerBoundsChange() const;

 private:
  void UpdateWorkAreaInsetsAndNotifyObserversInternal(
      const gfx::Rect& shelf_bounds_for_workarea_calculation,
      const gfx::Insets& shelf_insets,
      const gfx::Insets& in_session_shelf_insets);

  class UpdateShelfObserver;
  friend class AshMessagePopupCollectionTest;
  friend class DimShelfLayoutManagerTestBase;
  friend class NotificationTrayTest;
  friend class PanelLayoutManagerTest;
  friend class Shelf;
  friend class ShelfLayoutManagerTestBase;
  friend class ShelfLayoutManagerWindowDraggingTest;
  friend class SystemNudgeTest;
  friend class TrayBackgroundViewTest;
  friend class UnifiedSystemTrayTest;

  struct State {
    State();

    // Returns true when a secondary user is being added to an existing session.
    bool IsAddingSecondaryUser() const;

    bool IsScreenLocked() const;

    // Returns whether the session is in an active state.
    bool IsActiveSessionState() const;

    // Returns whether shelf is in auto-hide mode and is currently hidden.
    bool IsShelfAutoHidden() const;

    // Returns whether shelf is currently visible.
    bool IsShelfVisible() const;

    // Returns whether shelf is in auto-hide mode in session and suupposed to be
    // hidden.
    bool IsShelfAutoHiddenInSession() const;

    // Returns true if the two states are considered equal. As
    // |auto_hide_state| only matters if |visibility_state| is
    // |SHELF_AUTO_HIDE|, Equals() ignores the |auto_hide_state| as
    // appropriate.
    bool Equals(const State& other) const;

    absl::optional<ShelfVisibilityState> visibility_state;
    ShelfAutoHideState auto_hide_state = SHELF_AUTO_HIDE_HIDDEN;
    WorkspaceWindowState window_state = WorkspaceWindowState::kDefault;

    // In session state.
    ShelfVisibilityState in_session_visibility_state = SHELF_VISIBLE;
    ShelfAutoHideState in_session_auto_hide_state = SHELF_AUTO_HIDE_HIDDEN;

    // True when the system is in the cancelable, pre-lock screen animation.
    bool pre_lock_screen_animation_active = false;
    session_manager::SessionState session_state =
        session_manager::SessionState::UNKNOWN;
  };

  // An enumration describing the various phases in which the shelf can be when
  // managing the bounds and opacity of its components.
  enum class ShelfLayoutPhase {
    kAtRest,  // No activity
    kAiming,  // Calculating target bounds
    kMoving,  // Laying out and animating to target bounds
  };

  // Suspends/resumes work area updates.
  void SuspendWorkAreaUpdate();
  void ResumeWorkAreaUpdate();

  // Sets the visibility of the shelf to |state|.
  // Relayouts the shelf if the shelf state (visibility, or autohide state)
  // changes, or if `force_layout` is set.
  // `force_layout` should be used when state is set in response to events that
  // both affect the shelf bounds/layout and may change shelf visibility.
  void SetState(ShelfVisibilityState visibility_state, bool force_layout);

  // Returns shelf visibility state based on current value of auto-hide
  // behavior setting.
  ShelfVisibilityState CalculateShelfVisibility();

  // Updates the shelf dim state.
  void UpdateShelfIconOpacity();

  // Updates the bounds and opacity of the shelf and status widgets.
  void UpdateBoundsAndOpacity(bool animate);

  // Returns true if a maximized or fullscreen window is being dragged from the
  // top of the display or from the caption area. Note currently for this case
  // it's only allowed in tablet mode, not in laptop mode.
  bool IsDraggingWindowFromTopOrCaptionArea() const;

  // Calculates shelf target bounds assuming visibility of
  // `state.visibilty_state` and `hotseat_target_state`.
  void UpdateTargetBounds(const State& state,
                          HotseatState hotseat_target_state);

  // Calculates the target bounds using `state_`.
  void CalculateTargetBounds();

  // Updates the target bounds if a gesture-drag is in progress. This is only
  // used by |CalculateTargetBounds()|.
  void UpdateTargetBoundsForGesture(HotseatState target_hotseat_state);

  // Updates the auto-hide state for drag-drop actions.
  void UpdateAutoHideForDragDrop(ScopedDragDropObserver::EventType event_type,
                                 const ui::DropTargetEvent* event);

  // Updates the auto-hide state immediately.
  void UpdateAutoHideStateNow();

  // Starts the auto-hide timer, so that the shelf will be hidden after the
  // timeout (unless something else happens to interrupt / reset it).
  void StartAutoHideTimer();

  // Stops the auto-hide timer and clears
  // |mouse_over_shelf_when_auto_hide_timer_started_|.
  void StopAutoHideTimer();

  // Returns the bounds of an additional region which can trigger showing the
  // shelf. This region exists to make it easier to trigger showing the shelf
  // when the shelf is auto hidden and the shelf is on the boundary between
  // two displays.
  gfx::Rect GetAutoHideShowShelfRegionInScreen() const;

  // Returns the auto-hide state. This value is determined from the shelf and
  // tray.
  ShelfAutoHideState CalculateAutoHideState(
      ShelfVisibilityState visibility_state) const;

  // Returns the auto-hide state based on the position of an ongoing drag-drop.
  ShelfAutoHideState CalculateAutoHideStateBasedOnDragLocation() const;

  // Returns the auto-hide state if the cursor's current position can be used to
  // make a decision, or no value if its position gives no useful information.
  absl::optional<ShelfAutoHideState>
  CalculateAutoHideStateBasedOnCursorLocation() const;

  // Returns true if |window| is a descendant of the shelf.
  bool IsShelfWindow(aura::Window* window);

  // Returns true if |window| is a descendant of the status area.
  bool IsStatusAreaWindow(aura::Window* window);

  // Called when the LoginUI changes from visible to invisible.
  void UpdateShelfVisibilityAfterLoginUIChange();

  // Compute |target_bounds| opacity based on gesture and shelf visibility.
  float ComputeTargetOpacity(const State& state) const;

  // Returns true if there is a fullscreen window open that causes the shelf
  // to be hidden.
  bool IsShelfHiddenForFullscreen() const;

  // Returns true if there is a fullscreen or maximized window open that causes
  // the shelf to be auto hidden.
  bool IsShelfAutoHideForFullscreenMaximized() const;

  // Returns whether the active window for the shelf is a defined stylus app
  // in `kStylusAppIds`.
  bool IsActiveWindowStylusApp() const;

  // Returns true if the home gesture handler should handle the event.
  bool ShouldHomeGestureHandleEvent(float scroll_y) const;

  // Gesture drag related functions:
  bool StartGestureDrag(const ui::GestureEvent& gesture_in_screen);
  void UpdateGestureDrag(const ui::GestureEvent& gesture_in_screen);

  // Mouse drag related functions:
  void AttemptToDragByMouse(const ui::MouseEvent& mouse_in_screen);
  void StartMouseDrag(const ui::MouseEvent& mouse_in_screen);
  void UpdateMouseDrag(const ui::MouseEvent& mouse_in_screen);
  void ReleaseMouseDrag(const ui::MouseEvent& mouse_in_screen);

  // Drag related functions, utilized by both gesture drag and mouse drag:
  bool IsDragAllowed() const;
  bool StartShelfDrag(const ui::LocatedEvent& event_in_screen,
                      const gfx::Vector2dF& scroll_hint);
  // Sets the Hotseat up to be dragged, if applicable.
  void MaybeSetupHotseatDrag(const ui::LocatedEvent& event_in_screen);
  void UpdateDrag(const ui::LocatedEvent& event_in_screen,
                  float scroll_x,
                  float scroll_y);
  void CompleteDrag(const ui::LocatedEvent& event_in_screen);
  void CompleteDragHomeToOverview(const ui::LocatedEvent& event_in_screen);
  void CancelDrag(absl::optional<ShelfWindowDragResult> window_drag_result);
  void CompleteDragWithChangedVisibility();

  // Returns true if the gesture is swiping up on a hidden shelf or swiping down
  // on a visible shelf; other gestures should not change shelf visibility.
  bool IsSwipingCorrectDirection();

  // Returns true if should change the visibility of the shelf after drag.
  bool ShouldChangeVisibilityAfterDrag(
      const ui::LocatedEvent& gesture_in_screen);

  // Updates the mask to limit the content to the non lock screen container.
  // The mask will be removed if the workspace state is either in fullscreen
  // or maximized.
  void UpdateWorkspaceMask(WorkspaceWindowState window_state);

  // Sends a11y alert for entering/exiting
  // WorkspaceWindowState::kFullscreen workspace state.
  void SendA11yAlertForFullscreenWorkspaceState(
      WorkspaceWindowState current_workspace_window_state);

  // Maybe start/update/end the window drag when swiping up from the shelf.
  bool MaybeStartDragWindowFromShelf(const ui::LocatedEvent& event_in_screen,
                                     const gfx::Vector2dF& scroll);
  void MaybeUpdateWindowDrag(const ui::LocatedEvent& event_in_screen,
                             const gfx::Vector2dF& scroll);
  absl::optional<ShelfWindowDragResult> MaybeEndWindowDrag(
      const ui::LocatedEvent& event_in_screen);
  // If overview session is active, goes to home screen if the gesture should
  // initiate transition to home. It handles the gesture only if the
  // |window_drag_controller_| is not handling a window drag (for example, in
  // split view mode).
  bool MaybeEndDragFromOverviewToHome(const ui::LocatedEvent& event_in_screen);
  void MaybeCancelWindowDrag();
  bool IsWindowDragInProgress() const;

  // Updates the visibility state because of the change on a status area tray.
  void UpdateVisibilityStateForTrayBubbleChange(bool bubble_shown);

  bool IsShelfContainerAnimating() const;

  bool in_shutdown_ = false;

  // True if the last mouse event was a mouse drag.
  bool in_mouse_drag_ = false;

  // True if a mouse or gesture drag is in progress.
  bool in_drag_drop_ = false;

  // Current state.
  State state_;

  ShelfLayoutPhase phase_ = ShelfLayoutPhase::kAtRest;

  bool updating_work_area_ = false;

  float target_opacity_ = 0.0f;

  const raw_ptr<ShelfWidget, ExperimentalAsh> shelf_widget_;
  const raw_ptr<Shelf, ExperimentalAsh> shelf_;

  // Count of pending visibility update suspensions. Skip updating the shelf
  // visibility state if it is greater than 0.
  int suspend_visibility_update_ = 0;

  // Count of pending work area update suspensions. Skip updating the work
  // area if it is greater than 0.
  int suspend_work_area_update_ = 0;

  base::OneShotTimer auto_hide_timer_;

  // Whether the mouse was over the shelf when the auto-hide timer started.
  // False when neither the auto-hide timer nor the timer task are running.
  bool mouse_over_shelf_when_auto_hide_timer_started_ = false;

  // Whether a drag was over the shelf when the auto-hide timer started.
  // False when neither the auto-hide timer nor the timer task are running.
  bool drag_over_shelf_when_auto_hide_timer_started_ = false;

  // Whether the mouse pointer (not the touch pointer) was over the shelf last
  // time we saw it. This is used to differentiate between mouse and touch in
  // the shelf auto-hide behavior.
  bool last_seen_mouse_position_was_over_shelf_ = false;

  // Whether the last location update from a drag-drop was over the shelf.
  bool last_seen_drag_position_was_over_shelf_ = false;

  base::ObserverList<ShelfLayoutManagerObserver>::Unchecked observers_;

  // The enum keeps track of the present status of the drag (from gesture or
  // mouse). The shelf reacts to drags, and can be set to auto hide for certain
  // events. For example, swiping up from the shelf in tablet mode can open the
  // fullscreen app list. Some shelf behaviour (e.g. visibility state,
  // background color etc.) are affected by various stages of the drag.
  DragStatus drag_status_ = kDragNone;

  // Whether the hotseat is being dragged.
  bool hotseat_is_in_drag_ = false;

  // Whether the EXTENDED hotseat should be hidden. Set when HotseatEventHandler
  // detects that the background has been interacted with.
  bool should_hide_hotseat_ = false;

  // Whether the overview mode is about to start. This becomes false again
  // once the overview mode has actually started.
  bool overview_mode_will_start_ = false;

  // Tracks the amount of the drag. The value is only valid when
  // |drag_status_| is set to kDragInProgress.
  float drag_amount_ = 0.f;

  // The velocity of the last drag event. Used to determine final state of the
  // hotseat.
  int last_drag_velocity_ = 0;

  // Manage the auto-hide state during drag.
  ShelfAutoHideState drag_auto_hide_state_ = SHELF_AUTO_HIDE_SHOWN;

  // Whether background blur is enabled.
  const bool is_background_blur_enabled_;

  // Pretarget handler responsible for hiding the hotseat.
  std::unique_ptr<ui::EventHandler> hotseat_event_handler_;

  // Stores the previous workspace state. Used by
  // SendA11yAlertForFullscreenWorkspaceState to compare with current workspace
  // state to determite whether need to send an a11y alert.
  WorkspaceWindowState previous_workspace_window_state_ =
      WorkspaceWindowState::kDefault;

  // The display on which this shelf is shown.
  display::Display display_;

  // The current shelf background. Should not be assigned to directly, use
  // MaybeUpdateShelfBackground() instead.
  ShelfBackgroundType shelf_background_type_ = ShelfBackgroundType::kDefaultBg;

  ScopedSessionObserver scoped_session_observer_{this};
  base::ScopedObservation<WallpaperController, WallpaperControllerObserver>
      wallpaper_controller_observation_{this};

  display::ScopedDisplayObserver display_observer_{this};

  // Observer that allows drag events to un-hide an auto-hidden shelf.
  std::unique_ptr<ScopedDragDropObserver> drag_drop_observer_;

  // Location of the most recent mouse drag event in screen coordinates.
  gfx::Point last_mouse_drag_position_in_screen_;

  // Location of the most recent drag-drop event in screen coordinates.
  gfx::Point last_drag_drop_position_in_screen_;

  // Location of the beginning of a drag in screen coordinates.
  gfx::Point drag_start_point_in_screen_;

  // When it is true, |CalculateAutoHideState| returns the current auto-hide
  // state.
  bool is_auto_hide_state_locked_ = false;

  // An optional ScopedSuspendWorkAreaUpdate that gets created when suspend
  // visibility update is requested for overview and resets when overview no
  // longer needs it. It is used because OnOverviewModeStarting() and
  // OnOverviewModeStartingAnimationComplete() calls are not balanced.
  absl::optional<ScopedSuspendWorkAreaUpdate>
      overview_suspend_work_area_update_;

  // The window drag controller that will be used when a window can be dragged
  // up from shelf to homescreen, overview or splitview.
  std::unique_ptr<DragWindowFromShelfController> window_drag_controller_;

  // The gesture controller that switches from home screen to overview when it
  // detects an upward swipe from the home launcher shelf area.
  std::unique_ptr<SwipeHomeToOverviewController>
      swipe_home_to_overview_controller_;

  std::unique_ptr<HomeToOverviewNudgeController>
      home_to_overview_nudge_controller_;

  // Controller for the visibility of the InAppToHome gesture contextual nudge.
  std::unique_ptr<InAppToHomeNudgeController> in_app_to_home_nudge_controller_;

  // Whether upward fling from shelf should be handled as potential gesture from
  // overview to home. This is set to false when the swipe is handled by
  // |window_drag_controller_|, when the swipe is associated with a window
  // to drag. Note that the gesture will be handled only when the overview
  // session is active.
  bool allow_fling_from_overview_to_home_ = true;

  // Indicates whether shelf drag gesture can start window drag from shelf to
  // overview or home when hotseat is in extended state (the window drag will
  // only be allowed if drag started within shelf bounds).
  bool allow_window_drag_on_extended_hotseat_ = false;

  // Tracks whether the shelf is currently dimmed for inactivity.
  bool dimmed_for_inactivity_ = false;

  // Tracks whether the shelf and hotseat have been asked to be shown and
  // extended by the back gesture.
  bool state_forced_by_back_gesture_ = false;

  // Indicates whether shelf layout during shelf state update (in `SetState()`)
  // should be animated. If the shelf bounds and layout should be updated
  // without animation, `state_change_animation_disabled_` should be set before
  // calling `SetState()` or `UpdateVisibility()`.
  bool state_change_animation_disabled_ = false;

  // Callback to update the shelf's state when the visibility of system tray
  // changes.
  base::CancelableOnceClosure visibility_update_for_tray_callback_;

  // Records the presentation time for hotseat dragging.
  std::unique_ptr<ui::PresentationTimeRecorder>
      hotseat_presentation_time_recorder_;

  base::WeakPtrFactory<ShelfLayoutManager> weak_factory_{this};
};

}  // namespace ash

#endif  // ASH_SHELF_SHELF_LAYOUT_MANAGER_H_