Thanks for explaining.
It rises some questions, but if there is a detailed documentation for this, please give me the link, but I am unsure if I was able to find it.
To understand it properly, let's have the following example:
We have a bone A, animations1-3 and 3 tracks.
Track 0 - empty or unset (in our case, several empty tracks waiting for specific animations)
Track 1 - animation1 that animates bone A (has keys for A) which is interrupted in the middle, mixed to other animation2 which has no keys for A
Track 2 - another third animation3 that has no keys for A
What is the correct and expected behavior? After the mixing, should bone A have keys from setup or from interrupted animation1 (depending on when we started mixing)?
And please note that from my observation, this behavior changed with the previous code change in the first post. And that what I see in Spine Preview (trying to simulate something very similar) is different from the Unity runtime. There is still a small chance that something is bad in my code, but as I said it was working ok before runtime update. Also I need to be sure what is the correct behavior before diving deeper.
Another edge case might be what happens when on track 1 or 2 happens mixing during mixing, or calling update or anything special like that (there are some cases like this, difficult to simulate in Spine editor preview). May I ask if you have any test projects for testing these layering cases? Maybe I can try it on them?
Didn't know about the Layered tick box! That sounds very useful, can you please share a more detailed info or docs link on it?