/* vim: tabstop=4 shiftwidth=4 noexpandtab
 *
 * Graphics library
 */

#include <syscall.h>
#include <stdint.h>
#include "graphics.h"

DEFN_SYSCALL0(getgraphicsaddress, 11);
DEFN_SYSCALL1(kbd_mode, 12, int);
DEFN_SYSCALL0(kbd_get, 13);
DEFN_SYSCALL1(setgraphicsoffset, 16, int);

DEFN_SYSCALL0(getgraphicswidth,  18);
DEFN_SYSCALL0(getgraphicsheight, 19);
DEFN_SYSCALL0(getgraphicsdepth,  20);

uint16_t graphics_width  = 0;
uint16_t graphics_height = 0;
uint16_t graphics_depth  = 0;

/* Pointer to graphics memory */
uint8_t * gfx_mem = 0;

void init_graphics() {
	graphics_width  = syscall_getgraphicswidth();
	graphics_height = syscall_getgraphicsheight();
	graphics_depth  = syscall_getgraphicsdepth();
	gfx_mem = (void *)syscall_getgraphicsaddress();
}

uint32_t rgb(uint8_t r, uint8_t g, uint8_t b) {
	return 0xFF000000 + (r * 0x10000) + (g * 0x100) + (b * 0x1);
}

uint32_t alpha_blend(uint32_t bottom, uint32_t top, uint32_t mask) {
	float a = _RED(mask) / 256.0;
	uint8_t red = _RED(bottom) * (1.0 - a) + _RED(top) * a;
	uint8_t gre = _GRE(bottom) * (1.0 - a) + _GRE(top) * a;
	uint8_t blu = _BLU(bottom) * (1.0 - a) + _BLU(top) * a;
	return rgb(red,gre,blu);
}