delegate macros as attributes

[l4l]

For now for implementing a certain feature, one need to implement trait, then call a delegate_<feat>! on the structure which seems a little bit redundant, so instead of this:

impl<T: Xyz + 'static> ShmHandler for SimpleWindow<T> {
    fn shm_state(&mut self) -> &mut Shm {
        &mut self.shm
    }
}

delegate_shm!(@<T: Xyz + 'static> SimpleWindow<T>);

it would be nice to have this instead:

#[sctk::delegate]
impl<T: Xyz + 'static> ShmHandler for SimpleWindow<T> {
    fn shm_state(&mut self) -> &mut Shm {
        &mut self.shm
    }
}

[wash2]

While this would be nice, currently the Handler traits don't always map 1:1 to delegate_<feat>! macros. Maybe things could be refactored a bit to make this work though. Also, how it's currently done matches the smithay crate.

[l4l]

currently the Handler traits don't always map 1:1 to delegate_! macros

You mean using supertraits for delegate macros bound? I didn't find any relative example, perhaps you have any related code to share?

[wash2]

https://github.com/Smithay/client-toolkit/blob/master/examples/data_device.rs has an example of what I mean. PrimarySelectionDeviceHandler and PrimarySelectionSourceHandler both need to be implemented and used with delegate_primary_selection. Data device is similar. I guess I mean, #[sctk::delegate] would be used with just one of the trait implementations in these cases?

[l4l]

Oh, I see what you mean. Perhaps this could be solved with an additional trait specifically for delegation? E.g given the following defintions:

trait PrimarySelection {
  fn selection(..);
  fn send_request(..);
  fn cancelled(..);
}

impl<T: PrimarySelection> PrimarySelectionDeviceHandler for T {
  fn selection(self, args) { PrimarySelection::selection(self, args) }
}

impl<T: PrimarySelection> PrimarySelectionSourceHandler for T {
  fn send_request(self, args) { PrimarySelection::send_request(self, args) }
  fn cancelled(self, args) { PrimarySelection::cancelled(self, args) }
}

Then in user code impl only PrimarySelection:

#[sctk::delegate]
impl PrimarySelection for MySelection {
 ...
}

I'm not sure yet about this being breaking change though. That might be a problem