QXmpp is a cross-platform C++ XMPP client library based on the Qt framework. It tries to use Qt's programming conventions in order to ease the learning curve for new programmers.
QXmpp based clients are built using QXmppClient instances which handle the establishment of the XMPP connection and provide a number of high-level "managers" to perform specific tasks. You can write your own managers to extend QXmpp by subclassing QXmppClientExtension.
Managers to perform specific tasks:
XMPP stanzas: If you are interested in a more low-level API, you can refer to these classes.