Update menu.ts

[thebluepotato]

• Adds an optional event handler to determine whether the item, while shown, is disabled
• Adds support for registering an element when the popup has no children (for instance, was created with ztoolkit.UI.createElement() just before);

Fixes #70

[windingwind]

Thanks for the contribution. Actually the disabled or any attribute could be modified in the hook getVisibility. As we are adding an isDisabled, we'd better:

1. Unify their names. To me, the name isDisabled sounds like more of a static attribute getter, instead of a source of data.
2. Or, merge them into one onPopupShowing and let the user decide what to do
3. Or, add hooks for other possible attributes, e.g. checked.

[thebluepotato]

To the extent that these are callbacks, isDisabled and isVisible sound like a React state to me. Like the item asking "am I visible?". The alternative being to align with the existing getVisibility would be getDisability (!) or getDisabledStatus. If they're unified, they should probably align with each other, meaning that it should be "isHidden" and "isDisabled" or "isVisible" and "isEnabled" IMO.

A more general onPopupShowing might be nice too. However, what's nice about these specific handlers is that they avoid lots of boilerplate, whereas a general onPopupShowing would force us to call setAttribute every time. I think a mix of 1 and 2 would be best:

• Unify the names for those two rather common use cases (hidden or not, disabled or not)
• Add a more general onPopupShowing option

[windingwind]

I think a mix of 1 and 2 would be best

That sounds nice, let's do it this way.

You can just update the PR if you want :)

[windingwind]

btw, we also need an isChecked in that case, but only for type=check/radio menuitems. The type is immutable once the element is created and attached to the DOM.

[thebluepotato]

If you're up to it, feel free to introduce isChecked

[thebluepotato]

Also, should we rename onPopupShowing to onParentPopupShowing or something?

[windingwind]

Also, should we rename onPopupShowing to onParentPopupShowing or something?

Good point. Maybe onShowing would be enough?