for helm of opposite alignment.
Discovered and described by vultur-cadens.
The #adjust command can be used to split an object stack and if the
shop price of the two halves are different, the new stack will have
its obj->o_id modified to make the prices the same. That could be
used to tip off the player as to what the low bits of the next o_id
will be. Since no time passes, no intervening activity such as
random creation of a new monster can take place, so the player could
wish for something that depends on o_id with some degree of control.
Matters mainly for helms of opposite alignment intended to be used
by neutral characters since the player isn't supposed to be able to
control that. (Other items like T-shirt slogan text and candy bar
wrapper text had a similar issue but controlling those wouldn't have
had any tangible difference on play.)
The issue writeup suggested allowing the player to specify a helm's
alignment during a wish. That would defeat the purpose of having
o_id affect the helm's behavior in an arbitrary but repeatable way
so is rejected.
I implemented this fix before seeing a followup comment that suggests
using a more sophisticated decision than 'obj->o_id % N' for the
arbitrary effect. This just increments context.ident for the next
obj->o_id or mon->m_id by 1 or 2 instead of always by 1 and should
be adequate. It also has the side-effect that two consecutive wishes
for helm of opposite alignment won't necessary give one for each of
the two possible 'polarities', even with no intervening activity by
monsters, reinforcing the lack of player control.
Minor bonus fix: it moves the incrementing check for wrap-to-0 into
a single place instead of replicating that half a dozen times. Ones
that should have been there for shop billing and for objects loaded
from bones files were missing.
Fixes#596
b1d76a772f