seat: ignore duplicate set_selection request

This works around [1] and [2].

[1]: https://gitlab.gnome.org/GNOME/gtk/-/issues/5097
[2]: https://github.com/mahkoh/jay/issues/47

src/ifs/ipc.rs

@@ -63,6 +63,7 @@ pub trait IpcVtable: Sized {
     fn send_send(src: &Rc<Self::Source>, mime_type: &str, fd: Rc<OwnedFd>);
     fn remove_from_seat(device: &Self::Device);
     fn get_offer_seat(offer: &Self::Offer) -> Rc<WlSeatGlobal>;
+    fn source_eq(left: &Self::Source, right: &Self::Source) -> bool;
 }
 
 pub struct DeviceData<T: IpcVtable> {

src/ifs/ipc/wl_data_device.rs

@@ -280,6 +280,10 @@ impl IpcVtable for ClipboardIpc {
     fn get_offer_seat(offer: &Self::Offer) -> Rc<WlSeatGlobal> {
         offer.device.seat.clone()
     }
+
+    fn source_eq(left: &Self::Source, right: &Self::Source) -> bool {
+        left as *const _ == right as *const _
+    }
 }
 
 object_base! {

src/ifs/ipc/zwp_primary_selection_device_v1.rs

@@ -224,6 +224,10 @@ impl IpcVtable for PrimarySelectionIpc {
     fn get_offer_seat(offer: &Self::Offer) -> Rc<WlSeatGlobal> {
         offer.seat.clone()
     }
+
+    fn source_eq(left: &Self::Source, right: &Self::Source) -> bool {
+        left as *const _ == right as *const _
+    }
 }
 
 object_base! {

src/ifs/wl_seat.rs

@@ -673,6 +673,11 @@ impl WlSeatGlobal {
         field: &CloneCell<Option<Rc<T::Source>>>,
         src: Option<Rc<T::Source>>,
     ) -> Result<(), WlSeatError> {
+        if let (Some(new), Some(old)) = (&src, &field.get()) {
+            if T::source_eq(old, new) {
+                return Ok(());
+            }
+        }
         if let Some(new) = &src {
             ipc::attach_seat::<T>(new, self, ipc::Role::Selection)?;
         }