SDL_SetWindowResizable seemingly ignored

[XavierCS-dev]

OS: Fedora 39 Compositor: wl-roots (Hyprland) SDL version: 2.28.5 (from dnf package manager)

When setting SDL_SetWindowResizable(window, SDL_FALSE); The window should become no longer resizeable. This usually results in a floating window, as is the behaviour with winit. However this is not the case with SDL, the window can still be freely resized.

Here is the full code

#include <SDL2/SDL.h>
#include <SDL2/SDL_events.h>
#include <SDL2/SDL_video.h>

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

  SDL_Window *window = SDL_CreateWindow(
    "SDL2Test",
    SDL_WINDOWPOS_UNDEFINED,
    SDL_WINDOWPOS_UNDEFINED,
    640,
    480,
    0
  );

  SDL_SetWindowResizable(window, SDL_FALSE);

  SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_SOFTWARE);
  SDL_Event event;
  int game_state = 1;
  while (game_state) {
    while (SDL_PollEvent(&event)) {
      SDL_SetRenderDrawColor(renderer, 255, 0, 0, SDL_ALPHA_OPAQUE);
      SDL_RenderClear(renderer);
      SDL_RenderPresent(renderer);
      int width;
      int height;
      SDL_GetWindowSize(window, &width, &height);
      printf("%d %d\n", width, height);
      switch (event.type) {
        case SDL_QUIT:
          game_state = 0;
          break;
        default:
          break;
      }
    }
  }

  SDL_DestroyWindow(window);
  SDL_Quit();

  return 0;
}

[XavierCS-dev]

Setting the window as resizeable in the flags, then disabling resizing seems to fix the issue.

[XavierCS-dev]

It seems setting any other flags along with RESIZEABLE also breaks the resizing

SDL_SetWindowResizable works:

  SDL_Window *window = SDL_CreateWindow(
    "SDL2Test",
    SDL_WINDOWPOS_UNDEFINED,
    SDL_WINDOWPOS_UNDEFINED,
    640,
    480,
    SDL_WINDOW_RESIZABLE
  );

SDL_SetWindowResizable doesn't work:

  SDL_Window *window = SDL_CreateWindow(
    "SDL2Test",
    SDL_WINDOWPOS_UNDEFINED,
    SDL_WINDOWPOS_UNDEFINED,
    640,
    480,
    SDL_WINDOW_VULKAN | SDL_WINDOW_RESIZABLE
  );

[XavierCS-dev]

These functions seem to work as expected after creating the renderer...

[slouken]

I think this is fixed in the latest SDL2 code, can you try the latest release?

[Kontrabant]

I'm not seeing this on GNOME or KDE; the window in your sample is non-resizable in both X11 and Wayland.

Seems like Hyprland had a bug that allowed non-resizable windows to be resized that was fixed not too long ago: https://github.com/hyprwm/Hyprland/issues/4920

[Sackzement]

Not sure, if this helps with the issue, but I noticed that rendering in the code example is inside the event-polling loop:

while (game_state) { // game loop start
    while (SDL_PollEvent(&event)) { // event polling start

        // rendering is here <------------

        switch (event.type) {
            // event handling
        }
    } // event polling end
} // game loop end

Can reordering it maybe help?:

while (game_state) { // game loop start
    while (SDL_PollEvent(&event)) { // event polling start
        switch (event.type) {
            // event handling
        }
    } // event polling end

    // rendering is here now <----------

} // game loop end

I'm not that familiar with Wayland and Hyprland and how everything works there. Just wanted to give my 2 cents :)

Edit: Here is the reordered code for easy copy and pasting:

#include <SDL2/SDL.h>
#include <SDL2/SDL_events.h>
#include <SDL2/SDL_video.h>

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

  SDL_Window *window = SDL_CreateWindow(
    "SDL2Test",
    SDL_WINDOWPOS_UNDEFINED,
    SDL_WINDOWPOS_UNDEFINED,
    640,
    480,
    0
  );

  SDL_SetWindowResizable(window, SDL_FALSE);

  SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_SOFTWARE);
  
  SDL_Event event;
  int game_state = 1;
  while (game_state) {

    while (SDL_PollEvent(&event)) {
      switch (event.type) {
        case SDL_QUIT:
          game_state = 0;
          break;
        default:
          break;
      }
    }
    
    SDL_SetRenderDrawColor(renderer, 255, 0, 0, SDL_ALPHA_OPAQUE);
    SDL_RenderClear(renderer);
    SDL_RenderPresent(renderer);
    int width;
    int height;
    SDL_GetWindowSize(window, &width, &height);
    printf("%d %d\n", width, height);
  }

  SDL_DestroyWindow(window);
  SDL_Quit();

  return 0;
}

[XavierCS-dev]

I'm not seeing this on GNOME or KDE; the window in your sample is non-resizable in both X11 and Wayland.

Seems like Hyprland had a bug that allowed non-resizable windows to be resized that was fixed not too long ago: hyprwm/Hyprland#4920

It may be a combination of what you mentioned as well as what @slouken mentioned. I am not sure though, I guess I will have to wait for newer packages with Fedora, for now, locking the window size after the renderer is created seems to work, I am not sure how it will behave when using SDL with Vulkan though, will need to test it when I have time.

[XavierCS-dev]

Not sure, if this helps with the issue, but I noticed that rendering in the code example is inside the event-polling loop:

while (game_state) { // game loop start
    while (SDL_PollEvent(&event)) { // event polling start

        // rendering is here <------------

        switch (event.type) {
            // event handling
        }
    } // event polling end
} // game loop end

Can reordering it maybe help?:

while (game_state) { // game loop start
    while (SDL_PollEvent(&event)) { // event polling start
        switch (event.type) {
            // event handling
        }
    } // event polling end

    // rendering is here now <----------

} // game loop end

I'm not that familiar with Wayland and Hyprland and how everything works there. Just wanted to give my 2 cents :)

Edit: Here is the reordered code for easy copy and pasting:

#include <SDL2/SDL.h>
#include <SDL2/SDL_events.h>
#include <SDL2/SDL_video.h>

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

  SDL_Window *window = SDL_CreateWindow(
    "SDL2Test",
    SDL_WINDOWPOS_UNDEFINED,
    SDL_WINDOWPOS_UNDEFINED,
    640,
    480,
    0
  );

  SDL_SetWindowResizable(window, SDL_FALSE);

  SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_SOFTWARE);
  
  SDL_Event event;
  int game_state = 1;
  while (game_state) {

    while (SDL_PollEvent(&event)) {
      switch (event.type) {
        case SDL_QUIT:
          game_state = 0;
          break;
        default:
          break;
      }
    }
    
    SDL_SetRenderDrawColor(renderer, 255, 0, 0, SDL_ALPHA_OPAQUE);
    SDL_RenderClear(renderer);
    SDL_RenderPresent(renderer);
    int width;
    int height;
    SDL_GetWindowSize(window, &width, &height);
    printf("%d %d\n", width, height);
  }

  SDL_DestroyWindow(window);
  SDL_Quit();

  return 0;
}

Hi, It doesn't affect the window sizing, but thanks for pointing it out! I had realised what I had done when MangoHUD was reporting 0 FPS apart from when I moved my mouse. I appreciate the easy copy pasting for testing.

[jamesl-github]

do as XavierCS-dev said -- call it AFTER creating the renderer

[slouken]

Since we believe this bug is fixed upstream, I'm going to go ahead and close this for now. Please reopen if you find it's an issue with SDL.