[Gimp-developer] "Cancel" function and plugins

[Toby Speight]

(Delurk: I'm a sporadic developer of plugins, some of which are almost
good enough to shove in the registry, and I've watched this list for a
few months)

One of my current projects is a multifrequency blend tool (inspired
by, but not based on, the enblend program), and as part of its
operation, it invokes a couple of other plugins (I don't see the point
in reinventing wheels!).

One thing that's not covered in any of the "how to write a plugin"
guides is how to poll for cancel.  Of course, the plugin could have
its own cancel button, but then the user would have to know which
sub-plugin is running and find the correct cancel button!  (I'm happy
to deal with the call to the sub-plugin returning GIMP_PDB_CANCEL).

So - how does a plugin poll the Gimp's cancel button?  I couldn't find
any examples in the src/plug-ins directory...