zerozone.c

这个是延伸mame的在wince平台下的游戏模拟器的代码

/***************************************************************************

  vidhrdw/zerozone.c

***************************************************************************/

#include "driver.h"
#include "vidhrdw/generic.h"

unsigned char *zerozone_videoram;

extern int videoram_size;
static unsigned char *video_dirty;



int zerozone_videoram_r(int offset)
{
	return READ_WORD(&zerozone_videoram[offset]);
}

void zerozone_videoram_w(int offset,int data)
{
	int oldword = READ_WORD (&zerozone_videoram[offset]);
	int newword = COMBINE_WORD (oldword, data);

	if (oldword != newword)
	{
		WRITE_WORD (&zerozone_videoram[offset],newword);
		video_dirty[offset / 2] = 1;
	}
}



/* free the palette dirty array */
void zerozone_vh_stop(void)
{
	free (video_dirty);
}

/* claim a palette dirty array */
int zerozone_vh_start(void)
{
	video_dirty = malloc (videoram_size/2);

	if (!video_dirty)
	{
		zerozone_vh_stop();
		return 1;
	}

	memset(video_dirty,1,videoram_size/2);

	return 0;
}

void zerozone_update_palette (void)
{
	unsigned short palette_map[16]; /* range of color table is 0-15 */
	int i;

	memset (palette_map, 0, sizeof (palette_map));

	/* Find colors used in the background tile plane */
	for (i = 0; i < videoram_size; i += 2)
	{
		int tile, color;

		tile = READ_WORD (&zerozone_videoram[i]) & 0xfff;
		color = (READ_WORD (&zerozone_videoram[i]) & 0xf000) >> 12;

		palette_map[color] |= Machine->gfx[0]->pen_usage[tile];
	}

	/* Now tell the palette system about those colors */
	for (i = 0;i < 16;i++)
	{
		int usage = palette_map[i];
		int j;

		if (usage)
		{
			palette_used_colors[i * 16 + 0] = PALETTE_COLOR_TRANSPARENT;
			for (j = 1; j < 16; j++)
				if (palette_map[i] & (1 << j))
					palette_used_colors[i * 16 + j] = PALETTE_COLOR_USED;
				else
					palette_used_colors[i * 16 + j] = PALETTE_COLOR_UNUSED;
		}
		else
			memset(&palette_used_colors[i * 16],PALETTE_COLOR_UNUSED,16);
	}

	if (palette_recalc ())
		memset(video_dirty,1,videoram_size/2);

}

void zerozone_vh_screenrefresh(struct osd_bitmap *bitmap,int full_refresh)
{
	int offs;

	zerozone_update_palette ();

	if (full_refresh)
		memset(video_dirty,1,videoram_size/2);

	/* Do the background first */
	for (offs = 0;offs < videoram_size;offs += 2)
	{
		int tile, color;

		tile = READ_WORD (&zerozone_videoram[offs]) & 0xfff;
		color = (READ_WORD (&zerozone_videoram[offs]) & 0xf000) >> 12;

		if (video_dirty[offs/2])
		{
			int sx,sy;


			video_dirty[offs/2] = 0;

			sx = (offs/2) / 32;
			sy = (offs/2) % 32;

			drawgfx(bitmap,Machine->gfx[0],
				tile,
				color,
				0,0,
				8*sx,8*sy,
				0,TRANSPARENCY_NONE,0);
		}
	}
}