Re: [Flightgear-devel] ISA conditions

[PlayeRom R. L. <rom...@pl...>]

Okay, I sent two merge requests with the update according to your 
instructions:

https://sourceforge.net/p/flightgear/fgdata/merge-requests/311/
https://sourceforge.net/p/flightgear/flightgear/merge-requests/320/

The only thing I couldn't eliminate was the use of fgGetBool in the 
constructor of FGEnvironment:

FGEnvironment::FGEnvironment() :
     is_isa(fgGetBool("/environment/atmosphere/is-isa", false))
{
     _init();
}

At first I thought it was enough to set is_isa = false; in the 
FGEnvironment::_init() method. But then, even though the setter set the 
is_isa flag to true, it was returned to false by the FGEnvironment copy 
constructor. From what I checked, the FGEnvironment copy constructor is 
run every frame of the animation. The normal FGEnvironment constructor 
only runs once, so I hope it won't be a big deal? Unless there is a 
better solution to initialize the is_isa flag?


W dniu 21.07.2023 o 12:02, James Turner pisze:
>
>> On 20 Jul 2023, at 16:03, PlayeRom Roman Ludwicki<rom...@pl...>  wrote:
>>
>> Nothing from me
>
> We need to do a bit of re-design on this: it’s going to cause issues to check specific non-C++ controlled properties inside _recalc_sl_temperature (check if local weather s on/off and the weather scenario name).
>
> We try to avoid using fgGetXYZ anywhere called more than once, and also we want to avoid making C++ code which breaks if Nasal is changed, which means we can’t read properties which are created by Nasal code to make simulation decision, usually.
>
> Instead I’d propose we add instead a flag property, something like ‘atmosphere/is-isa’, and Tie this in  FGEnvironment::Tie, and then map it to an internal bool (eg, bool _isISA in FGEnvironment.hxx), via new methods get_is_isa_atmosphere / set_is_isa_atmosphere in FGEnvironment. Then your if() test in _recalc_sl_temperature simply becomes a check of that bool value to decide which temperature calculation to use, no more use of fgGetBool / fgGetString.
>
> For this this to work, we would then adjust the listener callback in weather_scenarios.nas to check the local-weather / scenario-name values and update the value of /environment/atmosphere/is-isa accordingly.
>
> Hopefully that all makes sense : let me know if anything is unclear or if you need assistance with it.
>
> Kind regards,
> James
>
>
>
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-- 
Pozdrawiam
Roman Ludwicki