Main sections
CALLBACK
CALLBACK FUNCTION foo: args#$
The CALLBACK modifier allows you to create functions that are overridable. This way you can provide a default way of handling things, but allow an include file to call a different function if specified.
If the same function exists in the project without the CALLBACK modifier, the one without the CALLBACK modifier will be used everywhere you call it. If no override exists, the CALLBACK marked function will be run.
SuperPrint("Hello World")
CALLBACK FUNCTION SuperPrint: a$
PRINT a$, 0,0
ENDFUNCTION
// Comment this out if you want only callback
FUNCTION SuperPrint: a$
LOCAL tx,ty
GETFONTSIZE tx, ty
tx = tx * LEN(a$)
DRAWRECT 0,0,tx,ty, RGB(0,0,255)
PRINT a$, 0,0
ENDFUNCTION