In the previous section, we defined clWorkerThread and iTask classes that allow us to execute lengthy operations outside of the UI thread in C++ code. The final thing we need to organize a responsive interface is the ability to pass around events across different threads. To do this, we need a callable interface, which can encapsulate the parameters passed to a method, and a thread-safe mechanism to pass such capsules across the threads.
A nice candidate for such a capsule is std::packaged_task, which is not supported in the most recent MinGW toolchain. Therefore, we will define our own lightweight reference-counted abstract class iAsyncCapsule, which implements a single method, Invoke():
class iAsyncCapsule: public iIntrusiveCounter
{
public:
virtual void Invoke() = 0;
};We call a prioritized collection of iAsyncCapsule instances wrapped in clPtr an asynchronous queue. The clAsyncQueue class implements the DemultiplexEvents() method, which...