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#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <dpmi.h>
#include <sys/nearptr.h>
#include <pc.h>
#include <dos.h>
#include "vga.h"
static uint8_t buffer[320 * 200];
static uint8_t *screen = NULL;
uint8_t open_framebuffer()
{
if (__djgpp_nearptr_enable() == 0)
return 0;
screen = (uint8_t *)(0xa0000 + __djgpp_conventional_base);
return 1;
}
void close_framebuffer()
{
__djgpp_nearptr_disable();
}
uint8_t set_mode(uint8_t mode)
{
__dpmi_regs regs = { 0 };
/* detect VGA card */
regs.x.ax = 0x1a00;
__dpmi_int(0x10, ®s);
if (regs.h.al != 0x1a)
return 0;
memset(®s, 0, sizeof(regs));
regs.x.ax = mode;
__dpmi_int(0x10, ®s);
if (mode == 0x13)
{
/* setup the VGA: 320x200 @ 60Hz */
/* from: https://gist.github.com/juj/34306e6da02a8a7043e393f01e013f24 */
disable();
/* XXX: probably not neeed */
wait_vsync();
outportw(0x3d4, 0x0011); /* Turn off write protect to CRTC registers */
outportw(0x3d4, 0x0b06); /* New vertical total=525 lines, bits 0-7 */
outportw(0x3d4, 0x3e07); /* New vertical total=525 lines, bits 8-9 */
outportw(0x3d4, 0xb910); /* Vsync start=scanline 185 */
outportw(0x3d4, 0x8f12); /* Vertical display end=scanline 399, bits 0-7 */
outportw(0x3d4, 0xb815); /* Vertical blanking start=scanline 440, bits 0-7 */
outportw(0x3d4, 0xe216); /* Adjust vblank end position */
outportw(0x3d4, 0x8511); /* Vsync length=2 lines + turn write protect back on */
/* XXX: probably not neeed */
wait_vsync();
outportw(0x3d4, 0x2813); /* 8 pixel chars */
outportw(0x3d4, 0x8e11); /* restore retrace */
enable();
}
return 1;
}
void wait_vsync()
{
while (inportb(0x3da) & 8);
while (!(inportb(0x3da) & 8));
}
void set_palette(const uint8_t *palette)
{
outportb(0x3c8, 0);
for (int i = 0; i < 768; i++)
outportb(0x3c9, palette[i] >> 2);
}
void blit(const uint8_t *sprite, const Rect *dst)
{
for (int32_t j = dst->y * 320; j < (dst->y + dst->h) * 320; j += 320)
for (int16_t i = dst->x; i < dst->x + dst->w; i++)
{
uint8_t b = *sprite++;
/* transparent */
if (b == TRANSPARENT)
continue;
/* clipping */
if (i < 0 || i >= 320 || j < 0 || j >= 200 * 320)
continue;
buffer[i + j] = b;
}
}
void blit_erase(uint8_t c)
{
memset(buffer, c, 320 * 200);
}
void blit_update()
{
memcpy(screen, buffer, 320 * 200);
}
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