With the new SLEG_STRUCT it is much easier to embed a struct
in a struct, where the sub-struct has limitations on when it is
being used.
This makes both the code easier to read (less magic) and avoids
the SaveLoad needing to know all these things about Stations
and Vehicles.
The commits following this will use this new functionality.
Currently, a few places do this manually. This has as drawback that
the Save() and Load() code need to be in sync, and that any change
can result in (old) savegames no longer loading. In general, it is
annoying code to maintain.
By putting everything in a description table, and use that for
both Save() and Load(), it becomes easier to see what is going on,
and hopefully less likely for people to make mistakes.
You can easily mistake SlList / SL_LST to be a list of SL_VAR, but
it is a list of SL_REF. With this rename, it hopefully saves a few
people from "wtf?" moments.
Prepare the full description and send it to SlObject. This does
require some code to be able to read to a SLE_VAR_NULL, like strings
etc, as there is no way to know their length beforehand.
It was rather confusing which one was for what, especially as some
SaveLoad flags were settings-only. Clean up this mess a bit by
having only Setting flags.
Basically, this changes "SaveLoad *" to either:
1) "SaveLoadTable" if a list of SaveLoads was meant
2) "SaveLoad &" if a single entry was meant
As added bonus, this removes SL_END / SLE_END / SLEG_END. This
also adds core/span.hpp, a "std::span"-lite.
This includes:
* CBID_VEHICLE_32DAY_CALLBACK
* CBID_VEHICLE_REFIT_COST
* CBID_VEHICLE_MODIFY_PROPERTY
This is on a per-property basis
The main benefit of this is to avoid callbacks not handled by the
vehicle's current sprite group from using the full graphics chain as
the "default" branch in the callback switch.
In the case where the graphics chain is long/expensive, a lot of work
had to be done before a callback failure result was eventually returned.
It now follows very simple rules:
0 - Fatal, user should know about this
1 - Error, but we are recovering
2 - Warning, wrong but okay if you don't know
3 - Info, information you might care about
4 -
5 - Debug #1 - High level debug messages
6 - Debug #2 - Low level debug messages
7 - Trace information
