Execution of signal handlers

[Grossert Alexander EXT <Alexander Grossert extern mchh siemens de>]

OS: Solaris 9
gtk: version 1.2

I have written a GUI using 2 message windows to show the progress of the program. Most of the functions connected to a signal from a button contain
some sleep() calls between the message outputs. But when pressing a button for a short period nothing happens and then suddenly all messages are printed out together.

It seems to me the main application window is updated only after the function called by the corresponding signal has finished execution.

Can anyone tell me how to force an update of the application window while executing the called function?

Thanks.