Menu button

ui.MenuButton creates a button showing a label and an arrow, which opens a menu of the system's below it, as the system's pop-up buttons do: as the pointer goes down on it, or for Enter, Space or Down while it has the keyboard focus. The function builds the items when the menu opens, and runs again in the frame after one was chosen, where its Chosen reports it:

ui.MenuButton(c, "Sort by", func(m *ui.Menu) {
	for _, by := range []string{"Name", "Date", "Size"} {
		if m.Item(by).Checked(app.sort == by).Chosen() {
			app.sort = by
		}
	}
})

Items

Menus take the same items as context menus: Item, with Checked, Disabled and Shortcut, Separator and Submenu.

Any button

Element.Menu gives the same menu to any button, as one showing only an icon:

ui.Button(c, "").Label("More").Children(func() { ui.Icon(c, dots) }).Menu(func(m *ui.Menu) {
	if m.Item("Duplicate").Chosen() {
		app.duplicate()
	}
	if m.Item("Delete").Chosen() {
		app.delete()
	}
})

In a toolbar, a menu button takes no face of its own until hovered.

Accessibility

Assistive technology sees a menu button: AXMenuButton on macOS, a push button with a menu on Linux, and a button that expands on Windows.