Summer of Code is ending (the official deadline for writing code is 20th August) and so my work on the icon cache is also coming to an end.
Yesterday I committed the last crucial piece of code. The cache now periodically checks for icon theme updates, so as soon as you install some new icons, they should be used and the obsolete cache be discarded.
This means that the cache is now fd.o icontheme spec-compliant and all the necessary features should be implemented :-)
Some smaller things remain to be done, such as further performance improvements and final benchmarking. I hope to complete the code part in the coming days and most of benchmarking will probably be done after the 20th.
Speaking of benchmarks, I did some a few days ago. As you have probably heard already, perhaps the most extreme case is kfind which starts up in about 4 secs without the cache and in a bit less than 1 sec (of which just 300ms is icon loading) with the cache. That's with hot caches (i.e. operating system has cached some of the data already). With cold caches it's 12secs vs 2.5secs.
Dolphin uses quite a few icons as well. With cold caches it takes 3.9 secs with iconcache and 5.2 secs without it to start. With hot caches it's 1.2 vs 1.5 secs.
I also noticed about one second improvement (12 vs 13 secs) in full KDE session startup time (with Dolphin, Konqueror, Konsole and KBounce autostarted). I have to admit it's a bit less than I had hoped for, but KDE's startup time will probably be improved prior to 4.0 anyway. Anyway I will make further benchmarks to find out more accurate numbers.
The times are measured from when KPixmapCache contructor is called (which should be at most 100ms after the program is started) until the last find() call (after which the application should be ready to be used).