Win32::GUI Tutorial - Part 9 - Some peripheral issues

What about that console window?

One thing I have glossed over in all of the above is precisely how we run our Win32::GUI Perl program. There are a number of possibilities you might have used.

• Enter the command "perl MyApp.plx" from a Windows console window.

• Enter the command "perl MyApp.plx" in the Windows "Run" box.

• Double click on the file "MyApp.plx" (assuming you have .plx files associated with the perl.exe application).

In the first case, you will notice that the command prompt does not return until you close your GUI application's window. In the second and third case, it's worse - a console window opens and stays visible until the GUI application terminates.

This is ugly. Unfortunately, it's fairly inevitable, because of the way Windows works. Perl itself is a Windows "console" application, and so it behaves the way we see. You can't change this without changing Perl itself.

There is a fix for this, if you have Windows development tools available. Simply take a copy of perl.exe, call it perlw.exe, and change its "subsystem" setting from "console" to "windows". With Microsoft Visual Studio, the command to do this is

editbin /subsystem:windows perlw.exe

There is also an all-perl way to achieve the same result on Jenda's site: http://jenda.krynicky.cz/perl/GUIscripts.html

If you can't (or don't want to) create a perlw.exe, then a compromise is to hide the console window while your application is running. This is reasonable for the second and third cases above, but less so for the first (where the application is run from an existing console window).

The code to do this is

my ($DOS) = Win32::GUI::GetPerlWindow();
Win32::GUI::Hide($DOS);

Do this as early as possible. Obviously, if we hide the console, we must show it when we finish (otherwise, someone who runs your program from a command prompt will be very cross with you!)

To do this, we need to put

Win32::GUI::Show($DOS);

just before our program terminates. After the Win32::GUI::Dialog() call is usually the right place.