Qt

Qt is a relatively high-level framework, which also reflects in its multithreading API. Another defining feature of Qt is that it wraps its own code (QApplication and QMainWindow) along with the use of a meta-compiler (qmake) to implement its signal-slot architecture and other defining features of the framework.

As a result, Qt's threading support cannot be added into existing code as-is, but requires one to adapt one's code to fit the framework.