Should I add option to convert trains within depot

[ttv86]

One of major pains in game is to convert from electric to monorail and from monorail to maglev. Is there any technical reason that convert tool can not convert trains within depots? If there isn't any, should I make the change in code and add a PR in GitHub for the game? I've tried to find anything relate to it, but only thing I've found is that people ask is it possible to do in current game, nothing about changing the game code.

[jfs]

It would probably be somewhat similar to this idea: Template-Based Train Replacement

The major challenge is that there isn't necessarily any direct match between the units available for each railtype, so fully automatic conversion would probably be out.

[ttv86]

Most of time people would be using this when first monorail or maglev trains become available. Then there is only one engine type available and train cars can be matched by their cargo type.
If tool would be used either to downgrade or used when there are more than 1 engine available, tool would choose best version first by according to is engine 1 or 2 headed and after it according by either fastest or cheapest (maybe an option for this? Open for conversation)

[Transportman]

I think there is an universal track/depot NewGRF that already supports this via autoreplace, and if not, changing autoreplace to make it possible would be the way forward. Then you could also change the converter tool, to execute such an autoreplace when upgrading a depot, if all train parts have a matching replacement set, execute the replaces and convert the depot, else return an error and don't convert anything.

[ttv86]

How it would sound if there is only 1 available option for any type of engine/car converter could convert it automatically. For example if there is only 1 monorail coal car, there isn't need for auto-replace to add from target car. Also same when only first monorail or maglev engine is available, converter tool could auto-match any engines with only available engine and cars by cargo type. If there are multiple options for any item type, player must map them in auto-replace window.

[jfs]

You're speaking from a vanilla-only viewpoint. Remember that playing with different vehicle sets is very common and needs to be supported just as well as vanilla for any new features.

My own solution is to send all trains to depot, convert the network but not the depots, build new depots next to the old, build a new train, set its orders to shared with the old ones still in the old depots, then clone the new train as many times as needed. At the end, sell the old trains and remove the depots.

[Alberth]

Another option is to play with a train set that does not force you to mass-replace everything. I use NUTS for that, but other train sets exist.

[ttv86]

I don't know every NewGRF set that exists, but at least I think that following auto convert logic should work: If there is one possible engine and only one match for each car by their cargo type, auto convert to it. Otherwise use auto replace tool. I can even live with only replace window mappings, but current way to convert all rails as jfs described is a LOT of work on any extensive rail network. If there is any change it will ever get to the actual game I can even code it myself, but if anyone else doesn't want that I don't even try.