The prompt function. This is a function pointer (which is frequently given as an anonymous function) or nil; if it's nil, we won't show any prompt at all, otherwise we'll call the function pointer to display a prompt as needed.

Begin the input style. This should do anything required to set the font to the desired attributes for the input text. By default, we'll simply display <.inputline> to set up the default input style.

End the input style. By default, we'll close the <.inputline> that we opened in beginInputFont().