Fixed paused actor physics resuming after switching to another actor

[ohlidalp]

Fixes https://github.com/RigsOfRods/rigs-of-rods/issues/3105.

This was quite an endeavor - it turned out there's no single spot to correctly reset the physics pausd state (or skeletonview state - related). While researching how to add it, I realized scripts may want to know when (un)linking of actors happens, so I added a script event SE_GENERIC_TRUCK_LINKING_CHANGED for it.

What changed: code changed signifficantly; all data remained the same - code handling hooks/ties/ropes/slidenodes got only cosmetic edits. There are many new sanity/integrity checks in the (un)linking logic which will trigger Asserts on Debug and just prevent damage on Release.

What to test: Operation of ties/hooks/ropes/slidenodes, including savegame and abrupt deleting of one of the actors.

[CuriousMike56]

Almost perfect. Found one crash scenario:

• Spawn Liebherr LTM 1050-3.1 and any load, such as the Rock pack
• Press O to attach ties to the load
• Delete the load, disconnecting ties first doesn't matter.
• Spawn a copy of the load with CTRL+PERIOD, or spawn a different load
• Try to attach ties to other load -> crash

Under Debug I get infinite asserts when trying to backspace with the crane:

https://github.com/RigsOfRods/rigs-of-rods/assets/46073351/73e0e22a-964d-4381-bb63-7e68dab1718a

And clicking retry gives:

[ohlidalp]

I fixed the asserts on backspacing the Liebherr crane, and added many more asserts in the process, because those that triggered were completely legit, SyncReset() was actually forcing hooks/ropes/ties to inconsistent state.

[ohlidalp]

I pressed L to attach the hook, then tried to delete via top menu. EDIT: turned out to be faulty assert. EDIT2: fixed the actual problem.

[CuriousMike56]

Attached loads now move faster than the crane when using live repair mode (soft reset enabled):

https://github.com/RigsOfRods/rigs-of-rods/assets/46073351/327db4e2-d41e-4417-878e-b908cdcee454

vs master:

https://github.com/RigsOfRods/rigs-of-rods/assets/46073351/b1d91fb8-4a5f-4f88-b8a6-e1ded1b2b831

[ohlidalp]

@CuriousMike56 Ready for another test.

Turns out there was another bug in forced unlinking of inter-actor beams (both when deleting actor and hard-resetting) which left the actor data in inconsistent state. It's actually a very old bug in code written by Ulteq in ~2016/17 to fix multithreading problems related to inter-linking. It passed unnoticed until I introduced the RefCountingObjectPtr<> mechanic, which triggered the need for MSG_SIM_ACTOR_LINKING_REQUESTED and a bunch of asserts() to finaly kick the data into consistency.

[CuriousMike56]

https://github.com/RigsOfRods/rigs-of-rods/pull/3146#issuecomment-2140796036 still happens

[ohlidalp]

@CuriousMike56 Mystery solved: why did this only manifest when using ties (your scenario) and not hook (my initial scenario)? The reason is - by accident, the movement sync between the crane and the load was done once for each interconnecting beam, instead of once per actor pair. And because there's always just one hook beam, it worked OK with a hooked load, but there may be multiple ties (in this case 4), the load moved faster (4x in this case).

Fixed by adding a cache of unique actor pairs, and updating it each time linking changes.

[CuriousMike56]

Crane won't follow if you switch to the crate:

https://github.com/RigsOfRods/rigs-of-rods/assets/46073351/6aaebd10-d93b-475a-a983-a226552494b6

Also happens with a truck+trailer+load:

[ohlidalp]

@CuriousMike56 I apologize for all the trouble - it's all because I tried to automagically sync all state toggles in one place.

I'm rebooting this PR by reverting the offending commit. The paused physics problem is gone, as well as all the LiveRepair glitches, also the crash in https://github.com/RigsOfRods/rigs-of-rods/pull/3146#issuecomment-2071115449 is gone. However, now I'm observing these glitches:

• when you release a load from a hook (be it by pressing L or Hard-resetting), the skeletonview and physics paused states don't get reset. In 2022.12 it's the same except physicspause does get reset when unhooking by L (not by hardreset tho.).
• when you release a load from ties using O key, skeleton view gets reset, but physics-pause does not. Also when you hard reset, everything remains dirty. 2022.12 behaves the same.

[ohlidalp]

@CuriousMike56 I've refurbrished the prior commits without all the parts that touch LiveRepair (aka interactive reset). I tested all these cases:

• Switching from a physics-paused actor to another one -> stays paused.
• Unhooking/untying the load with sekeletonview or physics paused -> both are turned off on the load
• Removing the crane (with hooked/tied load) with sekeletonview or physics paused -> both are turned off on the load
• Hard-resetting the crane with sekeletonview or physics paused -> both are turned off on the load
• movement in soft reset when driving the crane -> works OK, one follows the other
• movement in soft reset when sitting in the load -> works OK, one follows the other

[CuriousMike56]

Seems the only remaining issue is the truck+trailer+load combo: Master (Viper N/B is visible, soft reset works as expected):

[ohlidalp]

@CuriousMike56 Ready for another test. I had to revert most of my new code, including the asserts. I re-tested all the above scenarios, including the crash scenario you found originally, including the truck/trailer/car combo.