Centralize tree-filter class?

[Frans Englich]

Here and there, people need to sort & filter hierarchial item models, and 
currently the wheel is reinvented for this. Known cases:

* Recent thread "How to make QSortFilterProxyModel search through children in 
a treeWidget?" on kde-devel
* kdebase/workspace/ksysguard(as mentioned by Tapsell)
* kdenonbeta/kdom/patternist/
* It often creeps up on qt-interest
* Others?

This makes me consider if such functionality should be centralized. The code 
is small, but can be tricky to write(due to the complex contracts Qt's 
classes have in this area). The documentation for one such class is here:

http://patternist.sourceforge.net/documentation/API/classKXQTS_1_1TreeSortFilter.html

Should something like this be put centrally? Alternatives:

A: Nope, it should not.
B: One flirts with the trolls to get such functionality included in Qt 4.3
C: One puts KTreeSortFilter in kdegui

Currently, my preference is B. I have no particularly strong opinion about 
this, but perhaps others can give direction.


Cheers,

		Frans