= Description

This occurs when trying to reconfigure previously opened window to make it full-screen. Relevant code is listed below.

= Output 

QUAKE ERROR: Couldn't set fullscreen state mode: That operation is not supported

= Environment

Fedora 25 running Gnome Wayland session.

Name        : gnome-shell
Arch        : x86_64
Epoch       : 0
Version     : 3.22.2
Release     : 2.fc25

Name        : SDL2
Arch        : x86_64
Epoch       : 0
Version     : 2.0.5
Release     : 2.fc25

== Code 

draw_context variable contains existing SDL_Window* so first part which creates window is skipped.

if (!draw_context)
{
    flags = SDL_WINDOW_HIDDEN;

    if (vid_borderless.value)
        flags |= SDL_WINDOW_BORDERLESS;
    
    draw_context = SDL_CreateWindow (caption, SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, width, height, flags);
    if (!draw_context)
        Sys_Error ("Couldn't create window");

    SDL_VERSION(&sys_wm_info.version);
    if(!SDL_GetWindowWMInfo(draw_context,&sys_wm_info))
        Sys_Error ("Couldn't get window wm info");
}

/* Ensure the window is not fullscreen */
if (VID_GetFullscreen ())
{
    if (SDL_SetWindowFullscreen (draw_context, 0) != 0)
        Sys_Error("Couldn't set fullscreen state mode");
}

/* Set window size and display mode */
SDL_SetWindowSize (draw_context, width, height);
SDL_SetWindowPosition (draw_context, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED);
if (SDL_SetWindowDisplayMode (draw_context, VID_SDL2_GetDisplayMode(width, height, bpp)) != 0)
    Sys_Error ("Couldn't set display mode for fullscreen: %s", SDL_GetError());
SDL_SetWindowBordered (draw_context, vid_borderless.value ? SDL_FALSE : SDL_TRUE);

/* Make window fullscreen if needed, and show the window */
if (fullscreen) {
    if (SDL_SetWindowFullscreen (draw_context, SDL_WINDOW_FULLSCREEN) != 0)
        Sys_Error ("Couldn't set fullscreen state mode: %s", SDL_GetError());
}

SDL_ShowWindow (draw_context);