Support for external functions with long running time

After copying files it might be in the step ssPostInstall mandatory to call external helper functions to make several adjustments to the installation like initializing databases. You can run a separate exe, but then it is hard beam status information into the installer view (to see a separate progress window is not appreciated). So you have more control when you call an external function to execute these actions. But when this function has a longer running time, the installer seemingly freezes. You have to implement an own

PeekMessage-Loop and other more complicated things to keep a TOutputMarqueeProgressWizardPage alive.

A build in mechanism for async calls would help to keep more logic out of the installer.