fix system ship unstealthiness

[agrrr3]

lienrag found the fleet unstealthiness to misbehave if in transit. (e.g. screenshot in forum )

if a candidate is not in a system (has SystemID -1) it matches nothing. the -1 as target is used to signal "match any system" (i.e. an SystemID but -1).

not sure if the implementation of InSystem is a bug or if it is correct and simply not helpful/not intuitive. Not Not InSystem id = xxx probably has to be the same as InSystem id = xxx for all xxx .

so for fleet unstealthiness code. the ship the stealth effect applies to is the target. the ships which are counted are the candidates.
according to my code dive the stealth of a ship on a starlane would be decreased depending on the count of all ships which are not on a starlane - which is clearly a bug.

the scope condition needs an InSystem condition (without id).

this PR contains three commits; one fixes a typo; one fixes the unstealthiness ; one moves the effect to a more fitting focs file

[geoffthemedio]

Not Not InSystem id = xxx probably has to be the same as InSystem id = xxx for all xxx

Not sure what your point is...

[agrrr3]

Not Not InSystem id = xxx probably has to be the same as InSystem id = xxx for all xxx

Not sure what your point is...

probably my point was i am not sure that the InOrIsSystem::Eval works correctly for the both search domains. but probably it does. and changing it (see below) would also be fine.

@geoffthemedio the underlying question was if we should change the behaviour of the condition not to interpret -1 as "match any system"; probably by using a different int constant (e.g. ANY_SYSTEM_ID -2)

[geoffthemedio]

probably my point was i am not sure that the InOrIsSystem::Eval works correctly for the both search domains.

What are the two search domains you mean?

the underlying question was if we should change the behaviour of the condition not to interpret -1 as "match any system"; probably by using a different int constant (e.g. ANY_SYSTEM_ID -2)

This is how most / all conditions and valuerefs work. ID -1 means "no particular object", and may result in matching anything or nothing, depending on the situation. Specifying or using a valueref that evaluates to -1 is also often different from specifying nothing, and sometimes one needs to include a no parameter version of a condition or apply earlier filtering to be sure one is getting a valid object ID and not -1 before passing it on...

[agrrr3]

probably my point was i am not sure that the InOrIsSystem::Eval works correctly for the both search domains.

What are the two search domains you mean?

matches and non_matches

the underlying question was if we should change the behaviour of the condition not to interpret -1 as "match any system"; probably by using a different int constant (e.g. ANY_SYSTEM_ID -2)

This is how most / all conditions and valuerefs work. ID -1 means "no particular object", and may result in matching anything or nothing, depending on the situation. Specifying or using a valueref that evaluates to -1 is also often different from specifying nothing, and sometimes one needs to include a no parameter version of a condition or apply earlier filtering to be sure one is getting a valid object ID and not -1 before passing it on...

ok, so InSystem id = Target.SystemID matching any object on a starlane is expected behavior. I added documentation entries in the wiki. case closed.