On Windows, a screensaver is just an .EXE file renamed to .SCR, and Xojo should be able to make them, but you’ll likely need to write your own graphics routines. The command line switches you’ll need to accommodate are: /s to launch the screensaver, /c to configure the screensaver, /p to preview the screensaver.
The application title also needs to begin with “SCRNSAVE:” followed by the name of the screensaver, this is for the windows control panel to recognize it.
I could be wrong but wasn’t there a “hack-ish” way to this? I could of swore I seen something online about making a screen saver with XOJO… but its been quite a while.