GUI ScreenIO for Windows

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Basic Rules for using GUI ScreenIO

While GUI ScreenIO is extremely easy to use, there are a few rules you should observe when developing a GUI ScreenIO application:

Always use the 88-level items for testing and setting values

First, the 88-level items make your program more readable.

Second, the panel editor may assign different values to the 88-level items when the panel is modified.  If you refer to the value instead of to the 88-level name, your program may not work correctly after you re-edit the panel. 

Do NOT CLOSE your application panels; let GUI ScreenIO do it

You should not close your application panels manually; you don't need to.  It just makes your program more complicated, and it's completely unnecessary.  Don't do it.

GUI ScreenIO will determine when panels should be closed, and will close them automatically when it is appropriate. 

Really, it's true.  It works correctly all by itself.  Keep your life simple and forget about closing your application panels manually. 

How does GUI ScreenIO know when to close a panel?

OK, here's our secret.  When you redisplay a panel, GUI ScreenIO automatically closes all of the panels that you displayed after it.

For example, if you display base panel A, followed by popup B and property sheet C...

• If you call GUI ScreenIO to redisplay popup B, it will automatically close property sheet C;
• If you call GUI ScreenIO to redisplay base panel A, it will automatically close BOTH panels B and C.

That's all there is to it, and it works beautifully for any number of panels.

CLOSE the MAIN panel before you STOP RUN

The Main panel is a special case, since it only provides a container and startup information for your application.  Generally, you only display it when you start your application, and CLOSE it just before you terminate your application.

Always CLOSE your MAIN panel before you STOP RUN

GUI ScreenIO, like all Windows applications, must allocate memory when it is run.  In order to release this memory, you must notify GUI ScreenIO that you are finished with your application.

When you CLOSE your main panel, GUI ScreenIO will release the memory used by your application, save your settings, and perform various cleanup operations for you.

After you've CLOSEd the main, you can STOP RUN.

Do NOT CANCEL programs while panels used by the program are active

Although GUI ScreenIO will detect and handle this condition in most cases, it's poor programming practice to cancel active programs.  It's best to wait until your panel is closed before you CANCEL the program that handles it.

If you CANCEL a program while a panel it owns is active, GUI ScreenIO will detect that the program's memory is invalid, and will close the panel automatically.  (Most of the time.  Some compilers delay the actual release of memory in response to a CANCEL verb and this can fool GUI ScreenIO into believing the storage is still available.

CANCELing the MAIN panel's owner program

If you CANCEL a program that owns the MAIN panel of your application, your application will terminate abnormally and will fail to release the memory it was using.  Always close your MAIN panel before you CANCEL the program that owns it, and before you STOP RUN.

Finally, there is no point in CANCELing GS either, because it is tiny and no savings will result.