[fpc-devel] GoToXY, Clrscr, Clreol, Write, and Writeln Cause Bad Side Affects

David Finkelstein dfinkelstein at comcast.net
Tue Nov 25 11:52:24 CET 2008

Since nobody responded to my entry "Distracting Scan Lines or Slow Display in Full Screen Mode" that I posted on November 11th, let me put it a different and very blunt way: 

GoToXY, Clrscr, Clreol, Write, and Writeln that worked fine in Turbo Pascal, just doesn't work properly in Free Pascal.  I successfully ported a large Turbo Pascal application to Free Pascal.  Everything works great EXCEPT for the User Interface.

The User Interface is based on a 25 X 80 window.  The application runs on Windows 98, Windows XP and Windows Vista clients.  On all  clients, the User Interface is horrible.

Full screen mode is not supported for DOS bat file windows under Vista unless you reinstall the video driver and fake out Vista by installing the driver in XP compatibility mode.  I successfully did this on 2 Vista clients that are running on computers made by different manufacturers.  The bat file windows in full screen mode run fine EXCEPT for the Free Pascal application.

The Windows 98 and Windows XP clients can run in a small window or full screen.  The Free Pascal application functions differently based on the size of the window... in that the output to the monitor is absolutley horrible.

On Windows 98, XP and Vista clients:

1. The screen randomly clears for 1 to 2 seconds, then redisplays its contents.  When the screen clears, I think I hear a clicking noise.

2. The screen randomly blinks for a fraction of a second.  That is, the screen goes dark, then redisplays its contents.  No clicking noise is heard.

3. Random horizontal lines appear and disappear on the screen as Clreol's and Write's are performed.

Question 1:

Of all the thousands of Free Pascal applications running, hasn't anyone seen this? Or do the laws of physics act diffently on the 8 client computers that are running my application?

Question 2:

Since GoToXY, Clrscr, Clreol, Write, and Writeln cause bad side affects, what functions should I use to create a full screen 80 X 25 window, position the cursor, clear the window, clear to end of line, change the cursor size, turn the cursor on and off, and display text?


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