Bug#1023847: Patch for SDL_VIDEO_X11_NO_SHM environment variable

[王昊然]

Further debugging shows this wasn't the root cause, instead the X BadShmSeg
error is happening inside libGLX.so.0 function glXSwapBuffers, which is
called from src/video/x11/SDL_x11opengl.c, function X11_GL_SwapWindow. As
such I guess the bug may actually be in GLX.

2022-11-11 19:37 GMT+08:00, 王昊然 <msl0000023508 at gmail.com>:
> --- src/video/x11/SDL_x11framebuffer.c.orig2022-01-08 10:29:52.000000000
> +0800
> +++ src/video/x11/SDL_x11framebuffer.c2022-11-11 19:27:12.527050231 +0800
> @@ -42,6 +42,10 @@
>
>  static SDL_bool have_mitshm(Display *dpy)
>  {
> +    const char *no_shm = SDL_getenv("SDL_VIDEO_X11_NO_SHM");
> +    if(no_shm && *no_shm) {
> +        return SDL_FALSE;
> +    }
>      /* Only use shared memory on local X servers */
>      return X11_XShmQueryExtension(dpy) ? SDL_X11_HAVE_SHM : SDL_FALSE;
>  }
>