feat: implement show

src/notification.rs

@@ -249,7 +249,29 @@ impl<'a> Notification {
 
     /// Tells the notification server to display the notification on the screen
     pub fn show(&self) -> Result<(), Box<dyn std::error::Error>> {
-        todo!();
+        let mut gerror = std::ptr::null_mut() as *mut GError;
+
+        if unsafe { notify_notification_show(self.inner, &mut gerror) } == 0 {
+            if gerror.is_null() {
+                return Err("Unknown error".into());
+            }
+
+            let err_msg = unsafe { *gerror }.message;
+
+            if err_msg.is_null() {
+                unsafe { g_error_free(gerror) };
+                return Err("Unknown error".into());
+            }
+
+            let err_msg_str = unsafe { std::ffi::CStr::from_ptr(err_msg) }
+                .to_string_lossy()
+                .to_string();
+
+            unsafe { g_error_free(gerror) };
+            return Err(err_msg_str.into());
+        }
+
+        Ok(())
     }
 
     /// Updates the notification text and icon.