/* Copyright (C) 1994-2003 Revolution Software Ltd
 *
 * 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; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * $Header: /cvsroot/scummvm/scummvm/bs2/scroll.cpp,v 1.2 2003/07/28 03:12:49 kirben Exp $
 */

//------------------------------------------------------------------------------------
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>

#include "stdafx.h"
//#include "src\driver96.h"
#include "build_display.h"
#include "debug.h"
#include "defs.h"
#include "header.h"
#include "interpreter.h"
#include "layers.h"
#include "memory.h"
#include "object.h"
#include "protocol.h"
#include "resman.h"
#include "scroll.h"

//------------------------------------------------------------------------------------
#define MAX_SCROLL_DISTANCE 8	// max no of pixel allowed to scroll per cycle

//------------------------------------------------------------------------------------
uint8 scroll_fraction=16;	// used to be a define, but now it's flexible (see new functions below)
//------------------------------------------------------------------------------------
void	Set_scrolling(void)		//S2.1(2Mar94jel) refurnished Tony25Sept96 :-)
{
	// feet_x = 128+320	// normally we aim to get George's feet at (320,250) from top left of screen window
	// feet_y = 128+250

	// set scroll offsets according to the player's coords

	int16	offset_x;
	int16	offset_y;
	int16	dx, dy;
	uint16	scroll_distance_x;	// how much we want to scroll
	uint16	scroll_distance_y;


	if (SCROLL_X || SCROLL_Y)	// if the scroll offsets are being forced in script (05feb97 JAMES)
	{
		// ensure not too far right
		if (SCROLL_X < this_screen.max_scroll_offset_x)
			this_screen.scroll_offset_x = SCROLL_X;
		else
 			this_screen.scroll_offset_x = this_screen.max_scroll_offset_x;

		// ensure not too far down
		if (SCROLL_Y < this_screen.max_scroll_offset_y)
			this_screen.scroll_offset_y = SCROLL_Y;
		else
 			this_screen.scroll_offset_y = this_screen.max_scroll_offset_y;
	}
	else
	{
		offset_x = this_screen.player_feet_x-this_screen.feet_x;	// George's offset from the centre - the desired position for him
		offset_y = this_screen.player_feet_y-this_screen.feet_y;


		// prevent scrolling too far left/right/up/down
		offset_x = offset_x < 0 ? 0 : ( (uint32)offset_x > this_screen.max_scroll_offset_x ? this_screen.max_scroll_offset_x : offset_x );
		offset_y = offset_y < 0 ? 0 : ( (uint32)offset_y > this_screen.max_scroll_offset_y ? this_screen.max_scroll_offset_y : offset_y );

		if (this_screen.scroll_flag==2)	// first time on this screen - need absolute scroll immediately!
		{
			//Zdebug(42,"init scroll");
			this_screen.scroll_offset_x = offset_x;
			this_screen.scroll_offset_y = offset_y;
			this_screen.scroll_flag=1;
		}
		else	// catch up with required scroll offsets - speed depending on distance to catch up (dx and dy) & 'SCROLL_FRACTION' used
		{		// but limit to certain number of pixels per cycle (MAX_SCROLL_DISTANCE)

			dx = this_screen.scroll_offset_x - offset_x;
			dy = this_screen.scroll_offset_y - offset_y;

			if (dx < 0)				// current scroll_offset_x is less than the required value
			{
				scroll_distance_x = (1+(-dx)/scroll_fraction);	// => inc by (fraction of the differnce) NB. dx is -ve, so we subtract dx/SCROLL_FRACTION
				this_screen.scroll_offset_x += scroll_distance_x < MAX_SCROLL_DISTANCE ? scroll_distance_x : MAX_SCROLL_DISTANCE;
			}
			else if (dx > 0)	// current scroll_offset_x is greater than the required value
			{
				scroll_distance_x = (1+dx/scroll_fraction);		// => dec by (fraction of the differnce)
				this_screen.scroll_offset_x -= scroll_distance_x < MAX_SCROLL_DISTANCE ? scroll_distance_x : MAX_SCROLL_DISTANCE;
			}											// NB. I'm adding 1 to the result of dx/SCROLL_FRACTION, because it would otherwise
													//			not scroll at all when dx < SCROLL_FRACTION
			if (dy < 0)
			{
				scroll_distance_y = (1+(-dy)/scroll_fraction);
				this_screen.scroll_offset_y += scroll_distance_y < MAX_SCROLL_DISTANCE ? scroll_distance_y : MAX_SCROLL_DISTANCE;
			}
			else if (dy > 0)
			{
				scroll_distance_y = (1+dy/scroll_fraction);
				this_screen.scroll_offset_y -= scroll_distance_y < MAX_SCROLL_DISTANCE ? scroll_distance_y : MAX_SCROLL_DISTANCE;
			}
		}
	}
}
//------------------------------------------------------------------------------------
int32 FN_set_scroll_coordinate(int32 *params)	//Tony25Sept96
{
	// set the special scroll offset variables
	// call when starting screens and to change the camera within screens
	// call AFTER FN_init_background() to override the defaults
	// called feet_x and feet_y to retain intelectual compatibility with Sword1 !
	// feet_x & feet_y refer to the physical screen coords where the system will try to maintain George's feet

	// param	0 feet_x value
	// param	1 feet_y value


	this_screen.feet_x = params[0];
	this_screen.feet_y = params[1];


	return(IR_CONT);
}
//------------------------------------------------------------------------------------
//------------------------------------------------------------------------------------
int32 FN_set_scroll_speed_normal(int32 *params)		// James08aug97
{
	scroll_fraction=16;

	return(IR_CONT);
}
//------------------------------------------------------------------------------------
int32 FN_set_scroll_speed_slow(int32 *params)		// James08aug97
{
	scroll_fraction=32;

	return(IR_CONT);
}
//------------------------------------------------------------------------------------

