sdlbug.c

#include <stdio.h>
#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>

#define WIDTH 800
#define HEIGHT 600
#define IMG_PATH "blinky.png"

int main (int argc, char *argv[]) {

	// variable declarations
	SDL_Window *win = NULL;
	SDL_Renderer *renderer = NULL;
	SDL_Surface *img = NULL;
        SDL_Rect src;
        SDL_Rect dst;
	
	// Initialize SDL.
	if (SDL_Init(SDL_INIT_VIDEO) < 0)
			return 1;

        int imgFlags = IMG_INIT_PNG;
        if( !( IMG_Init( imgFlags ) & imgFlags ) ) {
          printf( "SDL_image could not initialize! SDL_image Error: %s\n", IMG_GetError() );
          exit(1);
        }
	
	// create the window
	win = SDL_CreateWindow("Image Loading", 0, 0, WIDTH, HEIGHT, 0);
	
	// load our image
	img = IMG_Load(IMG_PATH);
        if (!img) {
          printf("failed to load image\n");
          exit(1);
        }

        /* set up the basic pattern */
        for (int i = 0; i < 4; i++) {
          for (int j = 0; i < 4; i++) {
            dst.x = 172*i;
            dst.y = 176*j;
            dst.w = 172;
            dst.h = 176;
            SDL_BlitSurface(img, NULL, SDL_GetWindowSurface(win), &dst);
          }
        }

        /* this is where things fail */
        src.x = 0;
        src.y = 50;
        src.w = WIDTH;
        src.h = HEIGHT;

        dst = src;
        dst.y = 100;

        int r = SDL_BlitSurface(SDL_GetWindowSurface(win), &src, SDL_GetWindowSurface(win), &dst);
        if (r) {
          printf("Blitting failed!\n");
        }

        /* verify that dst has been altered as expected */
        printf("x,y,w,h: %d,%d,%d,%d\n",dst.x, dst.y, dst.w, dst.h);
        
	// main loop
	while (1) {
		
		// event handling
		SDL_Event e;
		if ( SDL_PollEvent(&e) ) {
			if (e.type == SDL_QUIT)
				break;
			else if (e.type == SDL_KEYUP && e.key.keysym.sym == SDLK_ESCAPE)
				break;
		} 
                //                SDL_BlitSurface(img, NULL, SDL_GetWindowSurface(win), NULL);
                SDL_UpdateWindowSurface(win);
                SDL_Delay(10);
	}
        SDL_FreeSurface(img);
	SDL_DestroyWindow(win);
	
	return 0;
}