Allow nullable trampolines with scope="call"

[EPashkin]

Part of gtk-rs/gdk#287

changes only in gdk:

--- a/src/auto/seat.rs
+++ b/src/auto/seat.rs
@@ -91,7 +91,7 @@ impl Seat {
                 panic!("cannot get closure...")
             };
         }
-        let prepare_func = Some(prepare_func_func::<P> as _);
+        let prepare_func = if prepare_func_data.is_some() { Some(prepare_func_func::<P> as _) } else { None };
         let super_callback0: &Option<&mut dyn (FnMut(&Seat, &Window))> = &prepare_func_data;
         unsafe {
             from_glib(gdk_sys::gdk_seat_grab(self.to_glib_none().0, window.as_ref().to_glib_none().0, capabilities.to_glib(), owner_events.to_glib(), cursor.to_glib_none().0, event.to_glib_none().0, prepare_func, super_callback0 as *const _ as usize as *mut _))

--- a/src/auto/window.rs
+++ b/src/auto/window.rs
@@ -908,7 +908,7 @@ impl<O: IsA<Window>> WindowExt for O {
             };
             res.to_glib()
         }
-        let child_func = Some(child_func_func as _);
+        let child_func = if child_func_data.is_some() { Some(child_func_func as _) } else { None };
         let super_callback0: &Option<&mut dyn (FnMut(&Window) -> bool)> = &child_func_data;
         unsafe {
             gdk_sys::gdk_window_invalidate_maybe_recurse(self.as_ref().to_glib_none().0, region.to_glib_none().0, child_func, super_callback0 as *const _ as usize as *mut _);

@jangernert can you test this change just in case?

cc @GuillaumeGomez

[jangernert]

@EPashkin how would I test this?

[EPashkin]

Clone gdk repo crate branch,
add changes to Seat::grab,
add Replace or Path to your local gdk copy to Cargo.toml in your project.

[GuillaumeGomez]

Thanks! 👍

[sdroege]

👍

Good that we didn't do a release yet, the callback fixes from before were apparently incomplete :)

[jangernert]

@EPashkin the patches only apply to master which then causes some dependency resolve problems when overwriting gdk with the patched master version.

edit:
adapted the first patch slightly for the crate branch. "Works for me"^TM

[EPashkin]

@jangernert Thanks for checking