listeners disapper when cloneing Node or El

[MuhannadAlrusayni]

I'm trying to store nodes in structs and use them later in view.

use case:

    #[derive(Clone, Debug)]
    pub enum Msg {
        Home,
        AboutUs
    }

    #[derive(Debug)]
    pub struct Flexbox {
        items: Vec<Node<Msg>>,
    }

    fn view_flexbox(flexbox: &Flexbox) -> Node<Msg> {
        div![
            flexbox.items.clone()
        ]
    }

    #[test]
    fn test_listeners() {
        let items = vec![
            button![simple_ev(Ev::Click, Msg::Home), "Home"],
            button![simple_ev(Ev::Click, Msg::AboutUs), "About us"]
        ];

        let flexbox = Flexbox {items};
        // this panic show that flexbox items have listeners
        panic!("{:#?}", flexbox);
        let node = view_flexbox(&flexbox);
        // this panic show that node doesn't children doesn't have listeners
        panic!("{:#?}", node);
    }

It seems listeners are not cloned with the node/el:

seed/src/virtual_dom/node/el.rs

Lines 206 to 221 in 60d7de4

	/// Allow the user to clone their Els. Note that there's no easy way to clone the
	/// closures within listeners or lifestyle hooks, so we omit them.
	impl<Ms> Clone for El<Ms> {
	fn clone(&self) -> Self {
	Self {
	tag: self.tag.clone(),
	attrs: self.attrs.clone(),
	style: self.style.clone(),
	children: self.children.clone(),
	node_ws: self.node_ws.clone(),
	listeners: Vec::new(),
	namespace: self.namespace.clone(),
	hooks: LifecycleHooks::new(),
	}
	}
	}

Is there way to fix this ?

[MartinKavik]

I don't know, @David-OConnor ?
However I've added it to my todo-list - #293. I plan to do a bigger update for virtual DOM in January.
Or you can try to fix it.

[MuhannadAlrusayni]

I don't think I can do it, and if I try I need to understand the internal code for seed first and this would need non trivial time which I don't have right now.

[MuhannadAlrusayni]

Yew seems to have similar issue, and they already have draft PR yewstack/yew#786 , it might be helpful to get some inspiration from them.

[MartinKavik]

@MuhannadAlrusayni thanks. I'll be working on it in January.
Closing in favor of #293

[MuhannadAlrusayni]

I got time to solve this issue, but I need some assistance :D.

So the problem is that Listener<Ms> doesn't implement Clone, it also contains EventHandler<Ms> and Closure<_> both don't implement Clone too.

First let's talk about EventHandler<Ms> which contains a closure Box<dyn FnMut(web_sys::Event) -> Ms>, this closure will be used to create Closure<_> in attach function.

Then we have Closure<_> which get created in attach function, and passed to add_event_listener_with_callback which add event listener in js world, Listener<Ms> stores this closure so it can detach it later with detach function.

If I understood correctly, EventHandler<Ms> must be cloned when we clone Listener<Ms>, while Closure<_> shouldn't be cloned when we clone Listener<Ms>.

So we have to implement Clone for EventHandler<Ms>, one way to do that is by wrap type that contain Rc. Then implement Clone for Listener<Ms>.

Please correct me if I miss something, if I my understood is correct I can open PR for this.

[MuhannadAlrusayni]

cc @MartinKavik @David-OConnor ?

[MartinKavik]

@MuhannadAlrusayni sorry for the delay. I've written some comments to PR, but I don't know that code so well to answer you properly.
And see my todos with VirtualDOM - #293 (especially point 1.) - Listener patching has to be refactored to fix some issues and improve performance. I hope I can remove Ms: Clone restrictions as a side-effect.