Writing an X notification process

[Conn Copas]

X gurus, I am invoking GRASS functions by making calls from a Prolog program.
Ideally, I would like my X server to send a message to that process
upon the occurrence of significant events, such as the creation of new graphics
windows. Can anyone give me an idea of whether this is a trivial or an
outrageously difficult thing to do?

-- 
Conn V Copas
Loughborough University of Technology          tel : +44 (0)509 222689
Computer-Human Interaction Research Centre     fax : +44 (0)509 610815      
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