libakgl/src/draw.c

/**
 * @file draw.c
 * @brief Implements the draw subsystem.
 */

#include <SDL3/SDL.h>
#include <SDL3_image/SDL_image.h>
#include <SDL3_mixer/SDL_mixer.h>
#include <akgl/game.h>

/* Draw a Gimpish background pattern to show transparency in the image */
void akgl_draw_background(int w, int h)
{
    SDL_Color col[2] = {
	{ 0x66, 0x66, 0x66, 0xff },
	{ 0x99, 0x99, 0x99, 0xff },
    };
    int i, x, y;
    SDL_FRect rect;
    const int dx = 8, dy = 8;

    rect.w = (float)dx;
    rect.h = (float)dy;
    for (y = 0; y < h; y += dy) {
	for (x = 0; x < w; x += dx) {
	    /* use an 8x8 checkerboard pattern */
	    i = (((x ^ y) >> 3) & 1);
	    SDL_SetRenderDrawColor(renderer->sdl_renderer, col[i].r, col[i].g, col[i].b, col[i].a);

	    rect.x = (float)x;
	    rect.y = (float)y;
	    SDL_RenderFillRect(renderer->sdl_renderer, &rect);
	}
    }
}