sdl2_wayland_libdecor_bug.cpp

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

/* Compile with:
 *   g++ -g -o sdl2_wayland_libdecor_bug sdl2_wayland_libdecor_bug.cpp `sdl2-config --cflags --libs`
 */

const int disp_w = 400, disp_h = 300;
static SDL_Window *window = NULL;
static SDL_Renderer *renderer = NULL;
SDL_Rect rect = { 0, 0, 100, 100 };
#define FPS 60



static void update_screen() {
  if (++rect.x + rect.w >= disp_w) {
    rect.x = 0;
  }
  if (++rect.y + rect.h >= disp_h) {
    rect.y = 0;
  }
  SDL_RenderClear (renderer);
  SDL_SetRenderDrawColor(renderer, 255, 0, 0, 255);
  SDL_RenderFillRect(renderer, &rect);
  SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
  SDL_RenderPresent(renderer);
}

static uint32_t timer_handler(uint32_t interval, void *param) {
  SDL_Event event;
  event.type = SDL_USEREVENT;
  SDL_PushEvent(&event);
  return interval;
}

void wait_loop() {
  while (1) {
    SDL_Event event;
    SDL_WaitEvent(&event);
    switch (event.type) {
      case SDL_QUIT: exit(0); break;
      case SDL_USEREVENT: update_screen(); break;
    }
  }
}

void poll_loop() {
  while (1) {
    SDL_Event event;
    int ret = SDL_PollEvent(&event);
    if (ret == 1) 
    switch (event.type) {
      case SDL_QUIT: exit(0); break;
      case SDL_USEREVENT: update_screen(); break;
    }
    SDL_Delay(1000/FPS);
  }
}



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

  SDL_InitSubSystem(SDL_INIT_VIDEO | SDL_INIT_TIMER);
  SDL_CreateWindowAndRenderer(disp_w, disp_h, 0, &window, &renderer);
  SDL_SetWindowTitle(window, "Test app");

  int mode = (argc > 1) ?  (int)strtol(argv[1], (char **)NULL, 10) : 0;
  switch(mode) {
  case 0:
    printf("Scheduling SDL_USEREVENT with no window displayed. SDL_WaitEvent will hang\n");
    SDL_AddTimer(1000 / FPS, timer_handler, NULL);
    wait_loop();
    break;
  case 1:
    printf("Scheduling SDL_USEREVENT and force window display. SDL_WaitEvent will read events ~on window interactions\n");
    SDL_AddTimer(1000 / FPS, timer_handler, NULL);
    update_screen();
    wait_loop();
    break;
  case 2:
    printf("Displaying window and then scheduling SDL_USEREVENT. SDL_WaitEvent will read events ~on window interactions\n");
    update_screen();
    SDL_AddTimer(1000 / FPS, timer_handler, NULL);
    wait_loop();
    break;
  case 3:
    printf("Using SDL_PollEvent instead of SDL_WaitEvent. Should be fine\n");
    SDL_AddTimer(1000 / FPS, timer_handler, NULL);
    poll_loop();
    break;
  default:
    printf("Run as %s [0 | 1 | 2 | 3]\n", argv[0]);
    exit(1);
  }

  return 0;
}