@houmingc You took that example straight from the documentation page for Rotation, which shows a picture of exactly what will happen. What more do you need? "Default angle" makes no sense. If you don't specify one there will be no rotation. It rotates around the origin along the axis. If you still don't understand, make a quick example and play around with it.

@Mike_Blackman said:

My application fails to load libqxcb.so plugin, because libqxcb.so plugin fails to locate Qt libraries. Prebuilt Qt solves this problem by using relative RUNPATH value within libqxcb.so.

Sorry, I don't know what the prebuilt libraries did to the RPATH/RUNPATH. You can ask the Qt engineers in the Interest mailing list: http://lists.qt-project.org/mailman/listinfo/interest (Subscribe to the list first, then post there)