[XBoard-devel] overruling engine features

[h.g. muller]

I just added 3 new options on which I have somewhat mixed fealings;
their only purpose is basically to wreck proper (documented) operation
of XBoard. They can be needed, however to prrovide work-arounds for
non-compliant engines. In particular, that silly stuff with SIGINT causes
problems running Windows binaries of engines under wine: normally
SIGINT would kill the engine process, of course, and the protocol specs
recomend either to let the engine suppress sending of it by announcing
"feature sigint=0" at startup, or ignore SIGINT. Problem is that under
wine, engines that ignore sigint die anyway when they receive it. This
should be considered a wine bug, but it is very damaging to the usefulness
of XBoard, as most engines are only availableasWindows binaries.

So I needed an option for the user to turn off sigint even when the engine
does not do it, and I figured it was more versatile to then allow
the user to specify or overrule any engine feature. But of course
that offers the user a powerful tool to completely wreck the protocol.

This is especially dangerous since the option changing the feature
defaults is now implemented as persistent; perhaps we should configure
XBoard such that the /etc/xboard.conf resets the option to an empty
string _after_ having read the user settings file, so that people can
only enable the persistence by first removing that line from the master
settings file.