Windows default to fullscreen desktop mode if they don't pick an explicit video mode

Rather than iterating over display modes using an index, there is a new function SDL_GetFullscreenDisplayModes() to get the list of available fullscreen modes on a display.
{
    SDL_DisplayID display = SDL_GetPrimaryDisplay();
    int num_modes = 0;
    SDL_DisplayMode **modes = SDL_GetFullscreenDisplayModes(display, &num_modes);
    if (modes) {
        for (i = 0; i < num_modes; ++i) {
            SDL_DisplayMode *mode = modes[i];
            SDL_Log("Display %" SDL_PRIu32 " mode %d:  %dx%d@%gHz, %d%% scale\n",
                    display, i, mode->pixel_w, mode->pixel_h, mode->refresh_rate, (int)(mode->display_scale * 100.0f));
        }
        SDL_free(modes);
    }
}

SDL_GetDesktopDisplayMode() and SDL_GetCurrentDisplayMode() return pointers to display modes rather than filling in application memory.

Windows now have an explicit fullscreen mode that is set, using SDL_SetWindowFullscreenMode(). The fullscreen mode for a window can be queried with SDL_GetWindowFullscreenMode(), which returns a pointer to the mode, or NULL if the window will be fullscreen desktop. SDL_SetWindowFullscreen() just takes a boolean value, setting the correct fullscreen state based on the selected mode.

src/video/emscripten/SDL_emscriptenvideo.c

@@ -136,8 +136,6 @@ int Emscripten_VideoInit(_THIS)
         return -1;
     }
 
-    SDL_AddDisplayMode(&_this->displays[0], &mode);
-
     Emscripten_InitMouse();
 
     /* We're done! */