I don't know about QT3, but for Kdevelop:
"How can I enable code completion for external libraries?
When you have any C/C++ project opened, go to menu Project->Project Settings, in Project Options dialog choose C++ Specific tab, then Code Completion tab. Push Add Persistant Class Store button and complete the New Persistant Class Store wizard. After completing the wizard, make sure that the newly created class store is checked in the list of persistant class stores at Code Completion tab."
http://www.kdevelop.org/mediawiki/in...ompletion_FAQs