Workload in a QThread blocks main application's event loop ?

[jacek]

Is there a way (1 liner) to trigger a slot of another thread?

You could try to send QMetaCall event, but it probably won't fit in one line. Maybe you could add a boolean flag and some method that sets it when thread should stop itself?

The threadProgressing() signal (Qt::QueuedConnection) is only received by the GUI thread when the worker thread returns to the event loop. Is emit effectively only happening in the event loop?

The docs say:

With queued connections, the slot is invoked when control returns to the event loop of the thread to which the object belongs. The slot is executed in the thread where the receiver object lives.

Unless something has changed in Qt 4.1.1, sender doesn't even need to live in a thread with a running event loop (see the Mandelbrot example --- there's no event loop running in RenderThread).