chrome/browser/ui/views/tabs/vertical/tab_drag_scroll_handler.h

// Copyright 2026 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CHROME_BROWSER_UI_VIEWS_TABS_VERTICAL_TAB_DRAG_SCROLL_HANDLER_H_
#define CHROME_BROWSER_UI_VIEWS_TABS_VERTICAL_TAB_DRAG_SCROLL_HANDLER_H_

#include "base/callback_list.h"
#include "base/timer/timer.h"
#include "ui/gfx/geometry/rect.h"

namespace views {
class ScrollView;
}  // namespace views

// `TabDragScrollHandler` is responsible for managing scrolling as tabs
// are dragged near the edge of a scroll view.
class TabDragScrollHandler {
 public:
  TabDragScrollHandler() = default;
  ~TabDragScrollHandler() = default;
  TabDragScrollHandler(const TabDragScrollHandler& other) = delete;
  TabDragScrollHandler& operator=(const TabDragScrollHandler&) = delete;

  // Updates scrolling according to the new drag bounds. This may either stop
  // or start scrolling, or update the rate.
  void OnDraggedTabPositionUpdated(
      views::ScrollView& scroll_view,
      const gfx::Rect& dragged_view_bounds_in_scroll_view);

  // Stops scrolling, or does nothing if scrolling is not in progress.
  void StopScrolling();

 private:
  void StartOrContinueScrolling(views::ScrollView& scroll_view,
                                float vertical_increments);
  void UpdateScrollOffset(views::ScrollView& scroll_view);

  // Timer used to update scroll offsets at a constant rate.
  base::RepeatingTimer scroll_timer_;

  // The offset to apply on each scroll event. Negative values scroll upwards.
  float vertical_scroll_increment_;
};

#endif  // CHROME_BROWSER_UI_VIEWS_TABS_VERTICAL_TAB_DRAG_SCROLL_HANDLER_H_