Other in KDE Base
Don't do the filtering ourselves, thats why kdelibs has widgets for that.
Also port to use QTreeWidget instead of QListWidget, the latter has a bug which breaks scrolling when some items are hidden (bugreport to TT is on its way).
So far I didn't notice any speed issues with the amount of debug area's kde currently has (about 600), but QTreeWidget is in general slower with a lot of items (quite noticeable with 10000) so as soon as QListWidget is fixed QTreeWidget should be replaced again by it.
I'll add the issue number from TT as soon as I receive it as a comment to this code