It is time.

ui/views/controls/scrollbar/scroll_bar.h

-// Copyright (c) 2012 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 UI_VIEWS_CONTROLS_SCROLLBAR_SCROLL_BAR_H_
-#define UI_VIEWS_CONTROLS_SCROLLBAR_SCROLL_BAR_H_
-
-#include "base/basictypes.h"
-#include "base/compiler_specific.h"
-#include "ui/views/view.h"
-#include "ui/views/views_export.h"
-
-namespace views {
-
-class ScrollBar;
-
-/////////////////////////////////////////////////////////////////////////////
-//
-// ScrollBarController
-//
-// ScrollBarController defines the method that should be implemented to
-// receive notification from a scrollbar
-//
-/////////////////////////////////////////////////////////////////////////////
-class VIEWS_EXPORT ScrollBarController {
- public:
-  // Invoked by the scrollbar when the scrolling position changes
-  // This method typically implements the actual scrolling.
-  //
-  // The provided position is expressed in pixels. It is the new X or Y
-  // position which is in the GetMinPosition() / GetMaxPosition range.
-  virtual void ScrollToPosition(ScrollBar* source, int position) = 0;
-
-  // Returns the amount to scroll. The amount to scroll may be requested in
-  // two different amounts. If is_page is true the 'page scroll' amount is
-  // requested. The page scroll amount typically corresponds to the
-  // visual size of the view. If is_page is false, the 'line scroll' amount
-  // is being requested. The line scroll amount typically corresponds to the
-  // size of one row/column.
-  //
-  // The return value should always be positive. A value <= 0 results in
-  // scrolling by a fixed amount.
-  virtual int GetScrollIncrement(ScrollBar* source,
-                                 bool is_page,
-                                 bool is_positive) = 0;
-};
-
-/////////////////////////////////////////////////////////////////////////////
-//
-// ScrollBar
-//
-// A View subclass to wrap to implement a ScrollBar. Our current windows
-// version simply wraps a native windows scrollbar.
-//
-// A scrollbar is either horizontal or vertical
-//
-/////////////////////////////////////////////////////////////////////////////
-class VIEWS_EXPORT ScrollBar : public View {
- public:
-  virtual ~ScrollBar();
-
-  // Overridden from View:
-  virtual void GetAccessibleState(ui::AXViewState* state) override;
-
-  // Returns whether this scrollbar is horizontal.
-  bool IsHorizontal() const;
-
-  void set_controller(ScrollBarController* controller) {
-     controller_ = controller;
-  }
-  ScrollBarController* controller() const { return controller_; }
-
-  // Update the scrollbar appearance given a viewport size, content size and
-  // current position
-  virtual void Update(int viewport_size, int content_size, int current_pos);
-
-  // Returns the max and min positions.
-  int GetMaxPosition() const;
-  int GetMinPosition() const;
-
-  // Returns the position of the scrollbar.
-  virtual int GetPosition() const = 0;
-
-  // Get the width or height of this scrollbar, for use in layout calculations.
-  // For a vertical scrollbar, this is the width of the scrollbar, likewise it
-  // is the height for a horizontal scrollbar.
-  virtual int GetLayoutSize() const = 0;
-
-  // Get the width or height for this scrollbar which overlaps with the content.
-  // Default is 0.
-  virtual int GetContentOverlapSize() const;
-
-  virtual void OnMouseEnteredScrollView(const ui::MouseEvent& event);
-  virtual void OnMouseExitedScrollView(const ui::MouseEvent& event);
-
- protected:
-  // Create new scrollbar, either horizontal or vertical. These are protected
-  // since you need to be creating either a NativeScrollBar or a
-  // ImageScrollBar.
-  explicit ScrollBar(bool is_horiz);
-
- private:
-  const bool is_horiz_;
-
-  ScrollBarController* controller_;
-
-  int max_pos_;
-
-  DISALLOW_COPY_AND_ASSIGN(ScrollBar);
-};
-
-}  // namespace views
-
-#endif  // UI_VIEWS_CONTROLS_SCROLLBAR_SCROLL_BAR_H_