Combobox

ui.Combobox creates a combobox choosing a *string among options: a field showing the choice, whose text filters the options below it as the user types, those starting with it first, while a click or Down shows them all; a click showing them selects the choice, for typing to replace. Up and Down move among them and Enter chooses, as does a click; Escape closes them, and the text goes back to the choice when the field loses the focus. Changed reports a new choice.

ui.Combobox(c, &app.font, fonts).Label("Font")

The field keeps the keyboard focus while the user types and picks. Placeholder shows a text in it while its text is empty.

For a text that may be anything, with suggestions, use autocomplete; for a short list without typing, a select.

Without a look

ui.ComboboxBase is a combobox without a look: an Input whose text filters the Items of a Popup below it, which the arrows highlight and Enter or a click chooses (Chosen): see custom widgets. When the options are those matching what was typed, as here, tell assistive technology with cb.Input.AutoComplete(ui.AutoCompleteList).

A popup without options hides, unless it holds something else to read, as a row saying that nothing matches, which then shows in their place:

cb.Popup(func(panel ui.Element) {
	panel.Padding(4).Background(t.Background).Border(1, t.Border)
	matches := app.matching(app.query)
	for _, f := range matches {
		cb.Item(f).Padding(6, 10).Children(func() { ui.Text(c, f) })
	}
	if len(matches) == 0 {
		ui.Text(c, "No matches found").Padding(6, 10).TextColor(t.TextMuted)
	}
})

Accessibility

Assistive technology sees a combo box named by its Label, editable as a text field, which expands, and whose options complete what was typed (aria-autocomplete="list"); the option the arrows are on has the focus for it, and reads as which of how many it is. With no options, the focus stays in the field, and a popup showing a row in their place is read out as it appears.