xwayland: support sending clipboard change notification on focus (#9111)

src/xwayland/XWM.hpp

@@ -44,13 +44,16 @@ struct SXSelection {
     xcb_window_t     owner     = 0;
     xcb_timestamp_t  timestamp = 0;
     SP<CXDataSource> dataSource;
+    bool             notifyOnFocus = false;
 
     void             onSelection();
+    void             onKeyboardFocus();
     bool             sendData(xcb_selection_request_event_t* e, std::string mime);
     int              onRead(int fd, uint32_t mask);
 
     struct {
         CHyprSignalListener setSelection;
+        CHyprSignalListener keyboardFocusChange;
     } listeners;
 
     std::unique_ptr<SXTransfer> transfer;