Module form 

One focus convention for every form and dialog.

A form is an ordered list of fields, each of a FieldKind. A modal says which fields it shows right now and which one has focus (Form); this module moves focus and decides what a key means, so every dialog answers the same keys the same way:

Key	Does
Tab / Shift+Tab, ↓ / ↑	next / previous field, wrapping
← / →	step a choice; move the cursor in a text field
Space	toggle a checkbox, next value of a choice, open a picker, press a button
Enter	submit, from any field (a multiline field types it; Ctrl+J submits)
Esc	cancel the form (an open picker closes first: picker_key)
Ctrl+P / Ctrl+N	history in a text field

h j k l are the arrows on a field that does not type. What a submit, a step or an action does stays with the modal: key says which happened, to which field.

Enums

FieldKind

How a field takes keys.

FormKey

What a key did to a form, for the modal to carry out.

ListMove

A move of a list’s cursor, from the keys every list answers: ↑ / k, ↓ / j, PageUp, PageDown, Home and End.

PickerKey

What a key did in an open picker.

Traits

Form

A form: its fields in order and the one with focus. The modal owns both; the default methods move focus the same way for every form.

Functions

key

What event does to form while no picker is open. Focus moves happen here; everything else is returned for the modal to do.

picker_form_key

event in a form with a picker open: the picker takes it (picker_key), choosing, toggling or closing through the form. Returns whether a picker was open.

picker_key

What event does in an open picker: type to narrow, ↑↓ move, Space chooses (or toggles in a list of several), Enter chooses, Esc closes the picker only. In a pick-one list Space chooses only while the filter is empty, and types a space once it narrows, so a name of several words can be typed; with nothing typed it would match nothing and blank the list under the key that opened it.

step_index

Index at stepped by delta through len values, wrapping.

step_value

current stepped by delta through all, wrapping; the first value when current is not among them.