TIP #153 Version 1.1: Adding a [winfo tophierarchy] Command

This is not necessarily the current version of this TIP.

Abstract

The [winfo toplevel] command returns the Tk toplevel window that encloses the window that's passed as an argument. However, Tk extensions may allow the creation of windows which reside at the top of a window hierarchy, but are not Tk toplevel widgets. If a subwindow of one of these top-of-hierarchy widgets is passed to [winfo toplevel], it returns an empty string, making it impossible to determine what hierarchy the window resides in. This TIP proposes adding a [winfo tophierarchy] command that will return the top window in the hierarchy regardless of what type of widget it is.

Rationale

Focus control does not work properly for top-of-hierarchy Tk windows other than toplevel widgets. This is an artifact of Tk's inability to determine the top of a window hierarchy for such windows. Prior to Tk 8.4, top-of-hierarchy windows other than toplevels were not possible, so the changes proposed in this TIP would be moot. However, they are now possible due to the incorporation into the Tk core of the changes proposed in TIP #47.

Command Syntax

The proposed syntax is essentially the same as for the [winfo toplevel] command:

 winfo tophierarchy "windowName"

should return the window at the top of the hierarchy containing "windowName".

Implementation

The implementation of the [winfo tophierarchy] command closely mirrors the implementation of [winfo toplevel]. It also requires changes to a few lines of code in the Tk library, where [winfo toplevel] really should be [winfo tophierarchy].

Patches

A patch (against Tk 8.4.4) that implements the changes described above may be found at http://www.eecs.umich.edu/~mckay/computer/tk.winfo.patch.gz

Copyright

This document is in the public domain.

This is not necessarily the current version of this TIP.