I am not sure about the nature of the signal/slot mechanism in Qt 4.5. When a signal is emitted, is it a blocking function call or a thread? Say this
emit GrabLatestData();
// proceed with latest data
Will all the signal/slot chain be resolved before proceeding to the next line?
It depends. From the documentation:
When a signal is emitted, the slots connected to it are usually executed immediately, just like a normal function call. When this happens, the signals and slots mechanism is totally independent of any GUI event loop. Execution of the code following the
emitstatement will occur once all slots have returned. The situation is slightly different when using queued connections; in such a case, the code following the emit keyword will continue immediately, and the slots will be executed later.
So in normal cases, it will be synchronous and blocking, and with queued connections it will be asynchronous and non-blocking.
laalto's answer above is correct. One further point though: if all of your QObjects belong to the same thread and you haven't manually specified queued connections, then the execution of slots connected to the signal occurs synchronously - all processing will be done before the next line after the 'emit' statement. Since this is the most common case, the answer to your question is normally 'yes'.
The documentation on signals and slots across multiple threads may be helpful to you.