src/vga.c


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#include <stdlib.h>
#include <stdint.h>
#include <dpmi.h>
#include <sys/nearptr.h>
#include <pc.h>

uint8_t *open_framebuffer()
{
    if (__djgpp_nearptr_enable() == 0)
        return NULL;

    return (uint8_t *)(0xa0000 + __djgpp_conventional_base);
}

void close_framebuffer()
{
    __djgpp_nearptr_disable();
}

void set_mode(uint8_t mode)
{
    __dpmi_regs regs = { 0 };
    regs.x.ax = mode;
    __dpmi_int(0x10, &regs);
}

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);
}