Allow unsetting target technology

[exyi]

AFAIK, target technology option could not be set to null from GUI - to all researches.

[veger]

Thank you for your PR!

I have no idea what target technology does ( 😊 ), but I tried this PR and can confirm this change allows to unset it.

[shpaass]

Hi @exyi! Thank you for the contribution!
Could you please explain what happens with cost analysis if the target is set to null? It would be awesome if you added your understanding as a message to your commit and as documentation to the CostAnalysis class.

[exyi]

Sure! The setting sets the resource objectives for the linear programming solver. Most importantly, YAFC then shows the estimated required resource amounts to something I'll actually need soon-ish, rather than in 1000 hours 😅. But it also affects the costs slightly, in this case it's probably that more aluminium processing byproducts will be needed after logi, making aluminium itself cheaper. EDIT: it's the other way

[shpaass]

Could you please describe the behavior before and after the change?
On my side, I always get Estimated amount for all researches no matter if I select nothing or not.

[exyi]

You have to save project and restart YAFC (or also change mining productivity...). That's another glitch that YAFC doesn't update the cost analysis when preferences change, only when settings change (same thing as Dorus encountered with the pollution cost flag Dorus#1). Now, the option is to also enable change event for preferences (see the linked commit), or move this into settings. Do you know the difference between the two?