(filing this on boxes. Maybe it should be gtk instead)

When testing boxes under wayland/weston it crashes right after start. I get the error:
gdkwindow-wayland.c: mmap'ping temporary file failed: Invalid argument

It happens as a mmap-backed shm_pool is created. The requested size for it happens to be 0 and creating a mmap of size 0 is what causes this error.

The calls that lead to this happen in this order:
gdk_window_create_similar_surface
gdk_window_ref_impl_surface
gdk_wayland_window_ref_cairo_surface
gdk_wayland_window_ensure_cairo_surface
gdk_wayland_create_cairo_surface
_create_shm_pool
mmap (where it fails)

The problem is that the GdkWindow that gdk_window_create_similar_surface
is called on has 0 width and 0 height. The window size determines how much is mmap'ed for the shm_pool and this is of course 0.

I wonder if it is a bug to call this on a GdkWindow of size 0? or if the wayland backend of gtk should be fixed to handle it.

In case it helps with further debugging: The call to gdk_window_create_similar_surface requested a surface with width/height of 811/45.