[wp-hackers] prevent plugin activation if conditions are not met

[David Barbakadze]

hello, people!

I'm new to this list and to wordpress. nice to meet you therefore :)
wordpress code really does look as a poetry.

I'm working on a little add-on for NextGEN library. I'm writing it in
the form of plugin, but I want to prevent it's activation if some
confitions (installed NextGEN library) are not met. I'm able to throw
an error message with admin_notices hook, but cannot stop activation
process. Plugin does activate anyway. Then if I just do exit; it does
prevent it, but throws rather non-informative message: Plugin could
not be activated because it triggered a fatal error.

Is there a trick to combine both of them. I mean to throw beautiful
error and cancel plugin activation process?

Regards,
Dave