SDL3 windows crash when moving vertically

[A-Lamia]

Not exactly sure what’s causing it, SDL2 works fine.
With SDL3, moving the window vertically makes it crash.
Tested on KDE and couldn’t reproduce, so for now it looks like it’s only a Hyprland issue.

I found this bug when porting one of my odin projects over from SDL2 to SDL3
I've created a minimal reproduction bellow with C.

Video

output.mp4

Steps

1. Install SDL3
2. Compile and run bellow code with:
   • gcc main.c -o main -lSDL3; ./main
3. Move window vertically to crash.

#include <SDL3/SDL_events.h>
#include <SDL3/SDL_main.h>
#include <SDL3/SDL_render.h>
#include <SDL3/SDL_video.h>

int main(int argc, char **argv) {

  SDL_PropertiesID props = SDL_CreateProperties();

  SDL_SetStringProperty(props, SDL_PROP_WINDOW_CREATE_TITLE_STRING,
                        "Crashing Window");
  SDL_SetBooleanProperty(props, SDL_PROP_WINDOW_CREATE_RESIZABLE_BOOLEAN, true);
  SDL_SetNumberProperty(props, SDL_PROP_WINDOW_CREATE_WIDTH_NUMBER, 640);
  SDL_SetNumberProperty(props, SDL_PROP_WINDOW_CREATE_HEIGHT_NUMBER, 480);

  SDL_Window *window = SDL_CreateWindowWithProperties(props);
  SDL_Renderer *render = SDL_CreateRenderer(window, "");

  SDL_Event event;
  bool done = true;

  while (done) {
    bool poll = SDL_PollEvent(&event);

    if (poll) {
      if (event.type == SDL_EVENT_QUIT) {
        done = false;
      }
      if (event.key.scancode == SDL_SCANCODE_ESCAPE) {
        done = false;
      }
    }

    SDL_SetRenderDrawColor(render, 0, 0, 0, 255);
    SDL_RenderClear(render);
    SDL_RenderPresent(render);
  }

  SDL_DestroyWindow(window);
  SDL_DestroyProperties(props);

  return 0;
}

[vaxerski]

attach a WAYLAND_DEBUG=1 log please

[A-Lamia]

Yes it still happens on hyprland-git

[vaxerski]

@A-Lamia that does not look like the full output

[A-Lamia]

that's all i get in the terminal, does this write out a file ?

[DarkCreepy59]

SDL3 uses the X11 backend by default (because hyprland doesn't implement fifo-v1).
Try setting SDL_VIDEODRIVER=wayland and then attach a WAYLAND_DEBUG=1 log.

[A-Lamia]

It doesn't crash with SDL_VIDEODRIVER=wayland so it seems to be caused by x11 ?

[Zebra2711]

can’t reproduce

no_crash.mp4

[A-Lamia]

it's really strange im trying to figure out what the outlier is but i can't work it out

[A-Lamia]

So after some more testing i can move the window with out crashing with the keyboard using moveactive, it's only when i use the mouse.