TIP #94 Version 1.1: add listbox -underline option

This is not necessarily the current version of this TIP.

Abstract

This TIP proposes to add a [-underline] option to the [listbox] widget that would control whether the active item gets underlined when the widget has focus (currently hard-coded to show the underline).

Rationale

Tk has always had an underline on the active item in listboxes, which is shown when the listbox has focus. However this in incompatible with the style of listboxes on Windows, especially as used in dropdown boxes. Adding this would allow improved native look and feel.

Specification

    $listbox configure -underline $bool

The default would be on, which stays consistent with the current behavior. [-underline] may be confusing since [button] has a [-underline] option that takes an index to underline one character. Perhaps [-underlineactive] would be better, but I didn't see the need for another long option name.

Reference Implementation

This implementation is simple and would only extend one check in DisplayListbox for whether the underline should be drawn.

File: tcl/generix/tkListbox.c

Function: DisplayListbox

Copyright

This document has been placed in the public domain.

This is not necessarily the current version of this TIP.