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 * are met:
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#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_PAGE_AUTOSCROLL_CONTROLLER_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_PAGE_AUTOSCROLL_CONTROLLER_H_

#include "base/gtest_prod_util.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/layout/geometry/physical_offset.h"
#include "third_party/blink/renderer/platform/geometry/float_point.h"
#include "third_party/blink/renderer/platform/geometry/float_size.h"
#include "third_party/blink/renderer/platform/heap/handle.h"

namespace blink {

class LocalFrame;
class Node;
class Page;
class LayoutBox;
class LayoutObject;

enum AutoscrollType {
  kNoAutoscroll,
  kAutoscrollForDragAndDrop,
  kAutoscrollForSelection,
  kAutoscrollForMiddleClick,
};

enum MiddleClickMode {
  // Middle button was just pressed but was neither released nor moved out of
  // the deadzone yet.
  kMiddleClickInitial,
  // Mouse was moved out of the deadzone while still holding middle mouse
  // button.  In this mode, we'll stop autoscrolling when it's released.
  kMiddleClickHolding,
  // Middle button was released while still in the deadzone.  In this mode,
  // we'll stop autoscrolling when any button is clicked.
  kMiddleClickToggled,
};

// AutscrollController handels autoscroll and middle click autoscroll for
// EventHandler.
class CORE_EXPORT AutoscrollController final
    : public GarbageCollected<AutoscrollController> {
 public:
  explicit AutoscrollController(Page&);

  void Trace(Visitor*) const;

  // Selection and drag-and-drop autoscroll.
  void Animate();
  bool SelectionAutoscrollInProgress() const;
  bool AutoscrollInProgressFor(const LayoutBox*) const;
  bool AutoscrollInProgress() const;
  void StartAutoscrollForSelection(LayoutObject*);
  void StopAutoscroll();
  void StopAutoscrollIfNeeded(LayoutObject*);
  void UpdateAutoscrollLayoutObject();
  void UpdateDragAndDrop(Node* target_node,
                         const FloatPoint& event_position,
                         base::TimeTicks event_time);

  // Middle-click autoscroll.
  void StartMiddleClickAutoscroll(LocalFrame*,
                                  LayoutBox* scrollable,
                                  const FloatPoint& position,
                                  const FloatPoint& position_global);
  void HandleMouseMoveForMiddleClickAutoscroll(
      LocalFrame*,
      const FloatPoint& position_global,
      bool is_middle_button);
  void HandleMouseReleaseForMiddleClickAutoscroll(LocalFrame*,
                                                  bool is_middle_button);
  void StopMiddleClickAutoscroll(LocalFrame*);
  bool MiddleClickAutoscrollInProgress() const;

 private:
  // For test.
  bool IsAutoscrolling() const;

  Member<Page> page_;
  AutoscrollType autoscroll_type_ = kNoAutoscroll;

  // Selection and drag-and-drop autoscroll.
  void ScheduleMainThreadAnimation();
  LayoutBox* autoscroll_layout_object_ = nullptr;
  LayoutBox* pressed_layout_object_ = nullptr;
  PhysicalOffset drag_and_drop_autoscroll_reference_position_;
  base::TimeTicks drag_and_drop_autoscroll_start_time_;

  // Middle-click autoscroll.
  LayoutBox* horizontal_autoscroll_layout_box_ = nullptr;
  LayoutBox* vertical_autoscroll_layout_box_ = nullptr;
  FloatPoint middle_click_autoscroll_start_pos_global_;
  gfx::Vector2dF last_velocity_;
  MiddleClickMode middle_click_mode_ = kMiddleClickInitial;

  FRIEND_TEST_ALL_PREFIXES(AutoscrollControllerTest,
                           CrashWhenLayoutStopAnimationBeforeScheduleAnimation);
  FRIEND_TEST_ALL_PREFIXES(AutoscrollControllerTest,
                           ContinueAutoscrollAfterMouseLeaveEvent);
  FRIEND_TEST_ALL_PREFIXES(AutoscrollControllerTest, StopAutoscrollOnResize);
  FRIEND_TEST_ALL_PREFIXES(AutoscrollControllerTest, AutoscrollIsNotPropagated);
  FRIEND_TEST_ALL_PREFIXES(AutoscrollControllerTest,
                           AutoscrollIsPropagatedInYDirection);
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_PAGE_AUTOSCROLL_CONTROLLER_H_