TIP 204: Virtual Events for Keyboard Traversal

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by Aug 21.
Author:		Joe English <jenglish@users.sourceforge.net>
State:		Final
Type:		Project
Tcl-Version:	8.5
Vote:		Done
Created:	21-Jun-2004
Post-History:	

Abstract

Proposes using two new virtual events, <> and <>, to notify widgets of keyboard navigation events.

Rationale

Certain widgets need to perform some action when they receive and/or lose keyboard focus because of keyboard traversal. For example, tabbing into an Entry or Spinbox widget selects the widget contents.

This cannot be done with a binding, since widgets may receive events for reasons other than keyboard traversal.

Tk currently implements this feature with special-case logic that checks the target window's widget class in the tk::TabToWindow procedure. The drawback to this approach is that it only works for the built-in widgets; third party widget sets like BWidgethttp://tcllib.sf.net/ , IWidgetshttp://sf.net/projects/incrtcl/ , and Tilehttp://tktable.sf.net/tile/ must implement their own workarounds.

Proposal

Change the standard Tk bindings for and to do the following:

Additionally, move the current code to handle traversal to Entry and Spinbox widgets from tk::TabToWindow to class bindings.

Implementation

See Tk Patch #976928http://sourceforge.net/support/tracker.php?aid=976928 .

The BWidget package has used an identical scheme since version 1.7; see Tcllib bug #720032http://sourceforge.net/support/tracker.php?aid=720032 for details.

Copyright

This document has been placed in the public domain.

History