Add onOpen, onClose and onTouch callbacks

[JesusTheHun]

When using a combobox in a form, there is a concept of touched fields : if a field is required to not be empty for example, we don't want to show an error message right away when the form loads, it wouldn't make any sense, but once he touches the field (focus the input) and leave the focus with an invalid value (empty input), the field is considered "touched" and therefore, now, we want to show the error message.

Right now we have to use workarounds to make this work, and mark the field as touched :

Combobox : onBlur of the input
Listbox : onBlur of the options
Switch : onChange of the switch
RadioGroup : not possible. onChange is only triggered when the value actually changes, so if the user clicks on the selected option, it doesn't work. Using onClick on any element below the RadioGroup element doesn't work, I assume you stopped the propagation of the click event during the capture phase.

Using those hackround to make this work is pretty annoying and requires research on how the headlessui components actually work in term of focus management, to get it right. I'm not even sure I got it right yet.

onTouch has a strong semantic but is applicable to all components.
onOpen & onClose are more general purpose callbacks so they could be used for the touched state, but they are not applicable in the case of a Switch or a RadioGroup.

How do you feel about this ?

[peteruithoven]

I'd like to add another use case for a Combobox onOpen event.
The Combobox, when I open it by using the Combobox.Button it puts it in an open mode and clears the ComboBox.Input. If I use the ComboBox.Input to query an server for options based on the input I don't have an event to send a query to get all the options when the input is emptied on open.
I can control the value of ComboBox.Input, but then there is no event to do something with the moment of opening the Combobox.

[kwojcik]

We are using Listbox as a multi-select input to filter the contents of a table, whenever the filters are updated we re-request data from the backend. Without an onClose, we have to re-request data on every change instead of when the user is done choosing options which is a perf issue.