[FEATURE] Bar relative context menus on systray

[ToxicMushroom]

Description of the requested feature

Example of a bar relative context menu.

Reasons:

• Looks nice and consistent
• The context menu then can't cover other systray items, allowing you to always access other systray items. Although I Just noticed that you can't directly switch to another item's context menu when you have one open so not sure how useful this is.

Proposed configuration syntax

:location ["bar" | "cursor"]
:spacing 8

Location would set the origin point for where to position the menu.
spacing would be applicable to :location "bar" to have it sticking to or spaced further from the bar

Additional context

Screenshot is from quickshell

[bbb651]

I tried Menu::popup_at_widget, this seems like a bug somewhere either in gtk3, gtk-layer-shell, compositors or all of the above, I tested many compositors and every single one has a different and undesired behavior:

diff --git a/crates/notifier_host/src/item.rs b/crates/notifier_host/src/item.rs
index a6cb2af..a314b95 100644
--- a/crates/notifier_host/src/item.rs
+++ b/crates/notifier_host/src/item.rs
@@ -90,7 +90,13 @@ impl Item {

     pub async fn popup_menu(&self, event: &gtk::gdk::EventButton, x: i32, y: i32) -> zbus::Result<()> {
         if let Some(menu) = &self.gtk_menu {
-            menu.popup_at_pointer(event.downcast_ref::<gtk::gdk::Event>());
+            menu.popup_at_widget(
+                &menu.attach_widget().expect("attach widget is set in `set_menu`"),
+                gtk::gdk::Gravity::South,
+                gtk::gdk::Gravity::North,
+                Some(event), // Also tested with `None`
+            );
             Ok(())
         } else {
             self.sni.context_menu(x, y).await

labwc (niri behaves the same, except the popup doesn't open/instantly closes sometimes)

sway

qtile (refuses to open any popoup at all)