# TIP 541: Add support for 'end' index in ttk::combobox current
	Author:         Francois Vogel <fvogelnew1@free.fr>
	State:          Final
	Type:           Project
	Vote:           Done
	Created:        8-May-2019
	Post-History:   
	Keywords:       Tcl
	Tcl-Version:    8.6
	Tcl-Branch:     bug-2858503fff
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# Abstract

This TIP proposes to add support for the <b>end</b> logical index in the <b>current</b> command of <b>ttk::combobox</b>.

# Rationale

<b>ttk::combobox current</b> <i>newIndex</i> sets the combobox value to the element at position <i>newIndex</i> in the list of the combobox <b>-values</b>. So far only integers were supported as <i>newIndex</i>.

It would be consistent with other uses of indices, and certainly useful, to be able to specify <i>newIndex</i> as the <b>end</b> index, that is the last element in the list of the combobox <b>-values</b>.

This was originally requested in a [RFE](https://core.tcl-lang.org/tk/tktview/2858503fffffffffffffffffffffffffffffffff).

# Specification

<b>ttk::combobox current <i>newIndex</i></b>

If <i>newIndex</i> is supplied, sets the combobox value to the element at position <i>newIndex</i> in the list of <b>-values</b> (in addition to integers, the <b>end</b> index is supported and indicates the last element of the list). Otherwise, returns the index of the current value in the list of <b>-values</b> or -1 if the current value does not appear in the list. 

# Implementation

See the [`bug-2858503fff`](https://core.tcl-lang.org/tk/timeline?r=bug-2858503fff&unhide) branch, aka [`tip-541`](https://core.tcl-lang.org/tk/timeline?r=tip-541&unhide). This branch includes implementation, updated documentation and new tests.

The branch targets 8.6 since there is no danger of incompatibility: the new feature was an error case so far.

# Copyright

This document has been placed in the public domain.
