Author:        Vince Darley <vince.darley@eurobios.com>
State:         Final
Type:          Project
Tcl-Version:   8.4.0
Vote:          Done
Created:       06-Nov-2000
Post-History:

Abstract

Add to wm the ability to do the windows-titlebar-icon manipulation that the Winico extension currently provides, without the bugs noted in that extension.

Proposal

Modify wm on Windows only to allow an optional -default argument.

wm iconbitmap .winpath ?-default? filename

And to allow a file which is of valid windows-icon format to be interpreted as such. Any file which is not correctly interpreted as an icon will be handled as before, by the bitmap code (which will generally either do nothing, or throw an error, thus maintaining backwards compatibility).

The -default argument, if given, will change not the icon of the .winpath given, but rather the default icon for all windows in the current application for which no specific icon as been set.

An implementation already exists, which fixes the basic "wrapper window" problems and which has the above syntax. The issues surrounding reference counting of icons in use has also been addressed in this patch so that icons no longer in use are released (the Winico patch required manual deletion of icons). This reference implementation is available from ftp://ftp.ucsd.edu/pub/alpha/tcl/tkWinWm.diff (documentation has been separately patched, and can also be made available).

Rationale

There have been many requests on news:comp.lang.tcl for this ability in the Tk core, and several bug reports filed against Winico, and this ability has been placed on the Tk 8.4 roadmap. http://purl.org/tcl/home/software/tcltk/roadmap.tml

The choice of wm iconbitmap is suggested, because wm iconbitmap currently doesn't appear to do anything on Windows, yet is the obvious choice for the user trying to set the window's icon (e.g. many posts on news:comp.lang.tcl are actually asking why wm iconbitmap doesn't do anything).

In the future we may wish to extend wm iconbitmap on all platforms so that other image types can be accepted (e.g. .gif, .png). This proposal extends naturally to allow such future work. The primary changes required will be icon<->image conversion routines.

Alternatives

Fix the core so that Winico can work properly as an extension.

My implementation as shown that this would require a couple of patches, and also the exporting of an additional obscure function into Tk's stub table (a function which would ensure that Tk's window manager is completely initialised). It would also not help the users posting to news:comp.lang.tcl asking "why doesn't wm iconbitmap do anything?"

Objections

This is platform specific and should go in an extension

See Alternatives above, also see the future suggestion above in which this kind of code can be usefully extended in a cross-platform way.

The -default flag is weird, and it means we ignore the window name

I agree, but please suggest a better alternative rather than just moaning. The command with the -default flag is in my opinion more useful than the command without (for example it makes sure that Tk's built-in dialogs have the icon of your application). An alternative might be to use wm iconbitmap -default filename, but that involves more significant modifications of the semantics of wm. It might, however, be a good idea.

wm iconbitmap will still do nothing when given a bitmap

Yes, but there's that backwards compatibility issue. This should be properly documented with pointers to the use of valid icon file formats. When or if proper support is added to Tk for .gif, .png or even Tk images as icons, this bug can be fixed. The purpose of this TIP is not to fix that bug, but to provide a better solution.

Copyright