[Bug-XBoard] [bug #8847] Moving backward while examining on FICS not reported to engine

[Tim Mann]

Follow-up Comment #2, bug #8847 (project xboard):

The bug submitter must have been examining a game on FICS while in zippy mode
(-zp).  Zippy mode is the only case where xboard is connected to both an ICS
and an engine at the same time.  (Or at least it was in 4.2.7... have we added
anything in 4.4.x that changes that?)

Testing the user's scenario on 4.2.7, it's true: if you connect to FICS in
zippy mode, examine an existing game, and hit the [>] button on xboard, it
sends "forward" to the ICS and the move that ICS sends back gets sent to the
engine.  And if you hit the [<] button, it sends "backward" to the ICS, but it
does not send "undo" (or anything else) to the engine, so the engine gets out
of sync with the board position being examined.  This is bad because if you
then hit [>] again to go forward, the engine rejects the move sent back from
ICS as illegal and causes xboard to display an error message.

It's not clear what the right fix is for this.  AFAICS, there is no reason
the engine should participate in examine mode, so ideally we would detect
you've gone into that mode and not send it anything.  I don't remember enough
about the ICS protocol to know if it's easy to detect that.

In the short term, the workaround is to log in separately (not in zippy mode)
if you want to examine games.


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