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Debian – Window seems to be created twice

When I compile and run a simple application in C which uses the SDL library (version 2) the window seems to open twice; first I see a window which opens and closes really rapidly and then the window comes up and stays (for two seconds). Any ideas what may be causing this?

Here is the test program:

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

#define SCREEN_WIDTH 640
#define SCREEN_HEIGHT 480

int main(int argc, char* args[]) {
  SDL_Window* window = NULL;
  SDL_Surface* screenSurface = NULL;
  if (SDL_Init(SDL_INIT_VIDEO) < 0) {
    fprintf(stderr, "could not initialize sdl2: %sn", SDL_GetError());
    return 1;
  }
  window = SDL_CreateWindow(
                "hello_sdl2",
                SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
                SCREEN_WIDTH, SCREEN_HEIGHT,
                SDL_WINDOW_SHOWN
                );
  if (window == NULL) {
    fprintf(stderr, "could not create window: %sn", SDL_GetError());
    return 1;
  }
  screenSurface = SDL_GetWindowSurface(window);
  SDL_FillRect(screenSurface, NULL, SDL_MapRGB(screenSurface->format, 0xFF, 0xFF, 0xFF));
  SDL_UpdateWindowSurface(window);
  SDL_Delay(2000);
  SDL_DestroyWindow(window);
  SDL_Quit();
  return 0;
}

I compile the program with

gcc -o hello_sdl2 hello_sdl2.c -lSDL2

and the version is

$ gcc --version
gcc (Debian 12.2.0-14) 12.2.0
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ sdl2-config --version
2.26.5

Edit 2024-08-27:

$ cat /etc/debian_version 
12.6
$ wmctrl -m
Name: Blackbox
Class: N/A
PID: N/A
Window manager's "showing the desktop" mode: N/A
Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    As pointed out by Ted Lyngmo in the comments the solution is to use the flag SDL_WINDOW_HIDDEN in the call to SDL_CreateWindow and then call SDL_ShowWindow after the call to SDL_GetWindowSurface:

    ...
window = SDL_CreateWindow("hello_sdl2",
    SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
    SCREEN_WIDTH, SCREEN_HEIGHT,
    SDL_WINDOW_HIDDEN);
...
screenSurface = SDL_GetWindowSurface(window);
SDL_ShowWindow(window);
...

    Note: If SDL_ShowWindow is called before SDL_GetWindowSurface the "flickering" issue remains.


  2. 0

    try adding a check in case the program runs twice

    int main(int argc, char* args[]) {
    printf("Program started!n");
    //your code..
}
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