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AmigActive 10
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vidhrdw
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snowbros.c
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C/C++ Source or Header
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2000-05-04
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2KB
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103 lines
/***************************************************************************
vidhrdw.c
Functions to emulate the video hardware of the machine.
***************************************************************************/
#include "driver.h"
#include "vidhrdw/generic.h"
unsigned char *snowbros_spriteram;
size_t snowbros_spriteram_size;
/* Put in case screen can be optimised later */
WRITE_HANDLER( snowbros_spriteram_w )
{
COMBINE_WORD_MEM(&snowbros_spriteram[offset], data);
}
READ_HANDLER( snowbros_spriteram_r )
{
return READ_WORD(&snowbros_spriteram[offset]);
}
void snowbros_vh_screenrefresh(struct osd_bitmap *bitmap,int full_refresh)
{
int x=0,y=0,offs;
palette_recalc ();
/* no need to check the return code since we redraw everything each frame */
/*
* Sprite Tile Format
* ------------------
*
* Byte(s) | Bit(s) | Use
* --------+-76543210-+----------------
* 0-5 | -------- | ?
* 6 | -------- | ?
* 7 | xxxx.... | Palette Bank
* 7 | .......x | XPos - Sign Bit
* 9 | xxxxxxxx | XPos
* 7 | ......x. | YPos - Sign Bit
* B | xxxxxxxx | YPos
* 7 | .....x.. | Use Relative offsets
* C | -------- | ?
* D | xxxxxxxx | Sprite Number (low 8 bits)
* E | -------- | ?
* F | ....xxxx | Sprite Number (high 4 bits)
* F | x....... | Flip Sprite Y-Axis
* F | .x...... | Flip Sprite X-Axis
*/
/* This clears & redraws the entire screen each pass */
fillbitmap(bitmap,Machine->gfx[0]->colortable[0],&Machine->drv->visible_area);
for (offs = 0;offs < 0x1e00; offs += 16)
{
int sx = READ_WORD(&snowbros_spriteram[8+offs]) & 0xff;
int sy = READ_WORD(&snowbros_spriteram[0x0a+offs]) & 0xff;
int tilecolour = READ_WORD(&snowbros_spriteram[6+offs]);
if (tilecolour & 1) sx = -1 - (sx ^ 0xff);
if (tilecolour & 2) sy = -1 - (sy ^ 0xff);
if (tilecolour & 4)
{
x += sx;
y += sy;
}
else
{
x = sx;
y = sy;
}
if (x > 511) x &= 0x1ff;
if (y > 511) y &= 0x1ff;
if ((x>-16) && (y>0) && (x<256) && (y<240))
{
int attr = READ_WORD(&snowbros_spriteram[0x0e + offs]);
int tile = ((attr & 0x0f) << 8) + (READ_WORD(&snowbros_spriteram[0x0c+offs]) & 0xff);
drawgfx(bitmap,Machine->gfx[0],
tile,
(tilecolour & 0xf0) >> 4,
attr & 0x80, attr & 0x40,
x,y,
&Machine->drv->visible_area,TRANSPARENCY_PEN,0);
}
}
}