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#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_SCROLL_SCROLL_ANIMATOR_BASE_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_SCROLL_SCROLL_ANIMATOR_BASE_H_

#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/scroll/scroll_animator_compositor_coordinator.h"
#include "third_party/blink/renderer/core/scroll/scroll_types.h"
#include "third_party/blink/renderer/core/scroll/scrollable_area.h"
#include "third_party/blink/renderer/platform/heap/handle.h"
#include "third_party/blink/renderer/platform/wtf/forward.h"

namespace blink {

class CompositorAnimationTimeline;
class ScrollableArea;
class Scrollbar;

// ScrollAnimatorBase is the common base class for all user scroll animators.
// Every scrollable area has a lazily-created animator for user-input scrolls
// (ScrollableArea::scroll_animator_).
//
// ScrollAnimatorBase is directly instantiated when scroll animations are
// disabled.  In this case, all scrolls are instantaneous.

class CORE_EXPORT ScrollAnimatorBase
    : public ScrollAnimatorCompositorCoordinator {
 public:
  static ScrollAnimatorBase* Create(ScrollableArea*);

  explicit ScrollAnimatorBase(ScrollableArea*);
  ~ScrollAnimatorBase() override;

  virtual void Dispose() {}

  // A possibly animated scroll. The base class implementation always scrolls
  // immediately, never animates. If the scroll is animated and currently the
  // animator has an in-progress animation, the ScrollResult will always return
  // no unusedDelta and didScroll=true, i.e. fully consuming the scroll request.
  // This makes animations latch to a single scroller. Note, the semantics are
  // currently somewhat different on Mac - see ScrollAnimatorMac.mm.
  virtual ScrollResult UserScroll(ScrollGranularity,
                                  const ScrollOffset& delta,
                                  ScrollableArea::ScrollCallback on_finish);

  virtual void ScrollToOffsetWithoutAnimation(const ScrollOffset&);

  void SetCurrentOffset(const ScrollOffset&);
  ScrollOffset CurrentOffset() const;
  virtual ScrollOffset DesiredTargetOffset() const { return CurrentOffset(); }

  // Returns how much of pixelDelta will be used by the underlying scrollable
  // area.
  virtual ScrollOffset ComputeDeltaToConsume(const ScrollOffset& delta) const;

  // ScrollAnimatorCompositorCoordinator implementation.
  ScrollableArea* GetScrollableArea() const override {
    return scrollable_area_;
  }
  void TickAnimation(double monotonic_time) override {}
  void CancelAnimation() override {}
  void TakeOverCompositorAnimation() override {}
  void UpdateCompositorAnimations() override {}
  void NotifyCompositorAnimationFinished(int group_id) override {}
  void NotifyCompositorAnimationAborted(int group_id) override {}
  void LayerForCompositedScrollingDidChange(
      CompositorAnimationTimeline*) override {}

  virtual void ContentAreaWillPaint() const {}
  virtual void MouseEnteredContentArea() const {}
  virtual void MouseExitedContentArea() const {}
  virtual void MouseMovedInContentArea() const {}
  virtual void MouseEnteredScrollbar(Scrollbar&) const {}
  virtual void MouseExitedScrollbar(Scrollbar&) const {}
  virtual void ContentsResized() const {}
  virtual void ContentAreaDidShow() const {}
  virtual void ContentAreaDidHide() const {}

  virtual void FinishCurrentScrollAnimations() {}

  virtual void DidAddVerticalScrollbar(Scrollbar&) {}
  virtual void WillRemoveVerticalScrollbar(Scrollbar&) {}
  virtual void DidAddHorizontalScrollbar(Scrollbar&) {}
  virtual void WillRemoveHorizontalScrollbar(Scrollbar&) {}

  virtual void NotifyContentAreaScrolled(const ScrollOffset&,
                                         mojom::blink::ScrollType) {}

  virtual bool SetScrollbarsVisibleForTesting(bool) { return false; }

  void Trace(Visitor*) override;

 protected:
  virtual void NotifyOffsetChanged();

  Member<ScrollableArea> scrollable_area_;

  ScrollOffset current_offset_;
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_SCROLL_SCROLL_ANIMATOR_BASE_H_