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AmigActive 10
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AACD 10.iso
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vidhrdw
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centiped.c
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C/C++ Source or Header
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2000-04-04
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5KB
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213 lines
/***************************************************************************
vidhrdw.c
Functions to emulate the video hardware of the machine.
***************************************************************************/
#include "driver.h"
#include "vidhrdw/generic.h"
static int flipscreen;
static struct rectangle spritevisiblearea =
{
1*8, 31*8-1,
0*8, 30*8-1
};
/***************************************************************************
Centipede doesn't have a color PROM. Eight RAM locations control
the color of characters and sprites. The meanings of the four bits are
(all bits are inverted):
bit 3 alternate
blue
green
bit 0 red
The alternate bit affects blue and green, not red. The way I weighted its
effect might not be perfectly accurate, but is reasonably close.
***************************************************************************/
static void setcolor(int pen,int data)
{
int r,g,b;
r = 0xff * ((~data >> 0) & 1);
g = 0xff * ((~data >> 1) & 1);
b = 0xff * ((~data >> 2) & 1);
if (~data & 0x08) /* alternate = 1 */
{
/* when blue component is not 0, decrease it. When blue component is 0, */
/* decrease green component. */
if (b) b = 0xc0;
else if (g) g = 0xc0;
}
palette_change_color(pen,r,g,b);
}
WRITE_HANDLER( centiped_paletteram_w )
{
paletteram[offset] = data;
/* the char palette will be effectively updated by the next interrupt handler */
if (offset >= 12 && offset < 16) /* sprites palette */
{
int start = Machine->drv->gfxdecodeinfo[1].color_codes_start;
setcolor(start + (offset - 12),data);
}
}
static int powerup_counter;
void centiped_init_machine(void)
{
powerup_counter = 10;
}
int centiped_interrupt(void)
{
int offset;
int slice = 3 - cpu_getiloops();
int start = Machine->drv->gfxdecodeinfo[0].color_codes_start;
/* set the palette for the previous screen slice to properly support */
/* midframe palette changes in test mode */
for (offset = 4;offset < 8;offset++)
setcolor(4 * slice + start + (offset - 4),paletteram[offset]);
/* Centipede doesn't like to receive interrupts just after a reset. */
/* The only workaround I've found is to wait a little before starting */
/* to generate them. */
if (powerup_counter == 0)
return interrupt();
else
{
powerup_counter--;
return ignore_interrupt();
}
}
WRITE_HANDLER( centiped_vh_flipscreen_w )
{
if (flipscreen != (data & 0x80))
{
flipscreen = data & 0x80;
memset(dirtybuffer,1,videoram_size);
}
}
/***************************************************************************
Draw the game screen in the given osd_bitmap.
Do NOT call osd_update_display() from this function, it will be called by
the main emulation engine.
***************************************************************************/
void centiped_vh_screenrefresh(struct osd_bitmap *bitmap,int full_refresh)
{
int offs;
if (palette_recalc() || full_refresh)
memset (dirtybuffer, 1, videoram_size);
for (offs = videoram_size - 1;offs >= 0;offs--)
{
if (dirtybuffer[offs])
{
int sx,sy;
dirtybuffer[offs] = 0;
sx = offs % 32;
sy = offs / 32;
drawgfx(bitmap,Machine->gfx[0],
(videoram[offs] & 0x3f) + 0x40,
(sy + 1) / 8, /* support midframe palette changes in test mode */
flipscreen,flipscreen,
8*sx,8*sy,
&Machine->drv->visible_area,TRANSPARENCY_NONE,0);
}
}
/* Draw the sprites */
for (offs = 0;offs < 0x10;offs++)
{
int spritenum,color;
int flipx;
int x, y;
int sx, sy;
spritenum = spriteram[offs] & 0x3f;
if (spritenum & 1) spritenum = spritenum / 2 + 64;
else spritenum = spritenum / 2;
flipx = (spriteram[offs] & 0x80) ^ flipscreen;
x = spriteram[offs + 0x20];
y = 240 - spriteram[offs + 0x10];
/* Centipede is unusual because the sprite color code specifies the */
/* colors to use one by one, instead of a combination code. */
/* bit 5-4 = color to use for pen 11 */
/* bit 3-2 = color to use for pen 10 */
/* bit 1-0 = color to use for pen 01 */
/* pen 00 is transparent */
color = spriteram[offs+0x30];
Machine->gfx[1]->colortable[3] =
Machine->pens[Machine->drv->gfxdecodeinfo[1].color_codes_start + ((color >> 4) & 3)];
Machine->gfx[1]->colortable[2] =
Machine->pens[Machine->drv->gfxdecodeinfo[1].color_codes_start + ((color >> 2) & 3)];
Machine->gfx[1]->colortable[1] =
Machine->pens[Machine->drv->gfxdecodeinfo[1].color_codes_start + ((color >> 0) & 3)];
drawgfx(bitmap,Machine->gfx[1],
spritenum,0,
flipscreen,flipx,
x,y,
&spritevisiblearea,TRANSPARENCY_PEN,0);
/* mark tiles underneath as dirty */
sx = x >> 3;
sy = y >> 3;
{
int max_x = 1;
int max_y = 2;
int x2, y2;
if (x & 0x07) max_x ++;
if (y & 0x0f) max_y ++;
for (y2 = sy; y2 < sy + max_y; y2 ++)
{
for (x2 = sx; x2 < sx + max_x; x2 ++)
{
if ((x2 < 32) && (y2 < 30) && (x2 >= 0) && (y2 >= 0))
dirtybuffer[x2 + 32*y2] = 1;
}
}
}
}
}