/*
   Copyright (C) 2003 by David White <dave@whitevine.net>
                 2004 - 2015 by Guillaume Melquiond <guillaume.melquiond@gmail.com>
   Part of the Battle for Wesnoth Project http://www.wesnoth.org/

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY.

   See the COPYING file for more details.
*/

/** @file */

#ifndef SCROLLBAR_HPP_INCLUDED
#define SCROLLBAR_HPP_INCLUDED

#include "button.hpp"

namespace gui {

class scrollarea;

/** Scrollbar */
class scrollbar : public widget
{
public:
	/**
	 * Create a scrollbar.
	 * @todo FIXME: parameterlist ??
	 */
	//- @param d         the display object
	//- @param pane      the widget where wheel events take place
	//- @param callback  a callback interface for warning that the grip has been moved
	scrollbar(CVideo &video);

	virtual void hide(bool value = true);

	/**
	 * Determine where the scrollbar is.
	 *
	 * @return  the position.
	 * @retval  returns 0 if the scrollbar is at the top,
	 * @retval  returns (full_size - shown_size) if it is at the bottom.
	 */
	unsigned get_position() const;

	unsigned get_max_position() const;

	/** Manually update the scrollbar. */
	void set_position(unsigned pos);

	/** Ensure the viewport contains the position. */
	void adjust_position(unsigned pos);

	/** Move the scrollbar. */
	void move_position(int dep);

	/** Set the relative size of the grip. */
	void set_shown_size(unsigned h);

	/** Set the relative size of the scrollbar. */
	void set_full_size(unsigned h);

	/** Set scroll rate. */
	void set_scroll_rate(unsigned r);

	/** Return true if the scrollbar has a valid size. */
	bool is_valid_height(int height) const;

	/** Scrolls down one step */
	void scroll_down();

	/** Scrolls up one step */
	void scroll_up();

protected:
	virtual handler_vector handler_members();
	virtual void update_location(SDL_Rect const &rect);
	virtual void handle_event(const SDL_Event& event);
	virtual void process_event();
	virtual void draw_contents();

private:
	SDL_Rect grip_area() const;
	SDL_Rect groove_area() const;
	surface mid_scaled_, groove_scaled_;

	button uparrow_, downarrow_;

	enum STATE { UNINIT, NORMAL, ACTIVE, DRAGGED };
	STATE state_;

	int minimum_grip_height_, mousey_on_grip_;
	// Relative data
	unsigned int grip_position_, grip_height_, full_height_;
	int scroll_rate_;

};

} // end namespace gui

#endif