xormod/picture.c

#include <stdio.h>
#include <stdlib.h>

#include "picture.h"

Picture *Picture_new(SDL_Renderer *rend,
    int x, int y, int w, int h, uint32_t color) {
    
    Picture *p = calloc(1, sizeof(Picture));

    p->x1 = x;
    p->x2 = x + w;
    p->y1 = y;
    p->y2 = y + h;
    p->w = w;
    p->h = h;
    p->color = color;
    p->s = (w * sizeof(uint32_t) + 7) / 8 * 8;

    p->pixels = malloc(p->s * h);
    p->surface = SDL_CreateSurfaceFrom(w, h, SDL_PIXELFORMAT_RGBA32, p->pixels, p->s);
    if (p->surface == NULL) {
        fprintf(stderr, "Can't create surface: %s\n", SDL_GetError());
        exit(-1);
    }
    Picture_render(p, rend);
    return p;
}

typedef uint32_t uint32_4 __attribute__ ((vector_size (4 * sizeof(uint32_t))));

void Picture_render(Picture *p, SDL_Renderer *rend) {
    int w = p->w, h = p->h;
    uint32_4 c = {p->color, p->color, p->color, p->color};
    const uint32_4 y0 = { 0, 0, 0, 0 };
    const uint32_4 x0 = { 0, 1, 2, 3 };
    uint32_4 y = y0 + p->y1;
    for (int j = 0, r = 0; j < h; j++, y += 1) {
        uint32_4 x = x0 + p->x1;
        for (int i = 0; i < w; i += 4, r += 4, x += 4) {
            uint32_4 z = (x ^ y) % 9;
            uint32_4 f = (z==0) & c;
            memcpy(&p->pixels[r], (uint32_t*)&f, sizeof(f));
        }
    }
    if (p->texture) SDL_DestroyTexture(p->texture);
    p->texture = SDL_CreateTextureFromSurface(rend, p->surface);
    if (p->texture == NULL) {
        fprintf(stderr, "Can't create texture: %s\n", SDL_GetError());
        exit(-1);
    }
    SDL_SetTextureBlendMode(p->texture, SDL_BLENDMODE_NONE);
}

void Picture_move(Picture *p, int x, int y) {
    p->x1 += x;
    p->x2 += x;
    p->y1 += y;
    p->y2 += y;
}