Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!zaphod.mps.ohio-state.edu!wuarchive!psuvax1!psuvm!auvm!univrel
From: UNIVREL@auvm.auvm.edu
Newsgroups: comp.lang.modula2
Subject: Re: Help with Mouse Function Please
Message-ID: <90205.100101UNIVREL@auvm.auvm.edu>
Date: 24 Jul 90 14:01:01 GMT
References: <9007241146.AA05051@ctc.contel.com>
Organization: The American University - University Computing Center
Lines: 21

I have not worked with FST's compiler, but I have guess as to what is
causing the trouble.

You write your custom handler the same way that you write an interrupt
service routine.  You save all used registers on entry and restore them
them on exit.  However, and this is not well documented, the mouse
driver calls your custom handler via a FAR CALL.  Consequently, your
handler CANNOT return via an IRET, but it must return via an FRET.

Many M2 compilers can generate the appropriate code for an interrupt
type function and they generate the appropriate standard exit code
and return via an IRET; something you do not want a mouse handler to do.

The solution, if your compiler supports it, is to use in-line machine
code and insert it at the end of your routine.  The compiler's exit
code comes after your in-line code and therefore will have no effect.
qquit
Hope this helps.
Sajjad Ahrabi

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