Commits on Apr 26, 2024

1. Truncate start time of juice stream nested objects …

   Intended as at least a partial solution to
   ppy#26436. In testing, two of the three
   replays from the issue are FCs with this change, and the third is
   improved (and not fully fixed).
   
   As it turns out, stable truncates the end time of sliders to integers:
   
       https://github.com/peppy/osu-stable-reference/blob/79addff0f5d2a328059d2842d6d2968cfb740956/osu!/GameplayElements/HitObjects/Osu/SliderOsu.cs#L1037
   
   and the start time of all juice stream parts is also truncated to
   integers:
   
       https://github.com/peppy/osu-stable-reference/blob/79addff0f5d2a328059d2842d6d2968cfb740956/osu!/GameplayElements/HitObjects/Fruits/SliderFruits.cs#L86-L166
   
   This matters for replay playback when mappers push limits. For instance,
   let's take one case from the issue. In one of the maps involved, there
   was a juice-stream-ending fruit at time 7093.9655 according to lazer,
   which was also a hyperfruit.
   
   The broken replay on this map included one frame at time 7093, with the
   catcher position before the hyperdash, and one frame at time 7097,
   with the catcher position *after* the hyperdash. Which meant that
   the replay handler moved *out of the way* of the hyperfruit at time
   7093.9655, deciding that it is *after* the replay frame that was
   supposed to be catching it.
   
   (For reference, the relevant replay playback code is here:
   
       https://github.com/ppy/osu/blob/3da5831075b187e967ca300dcba0a6761f07d1dd/osu.Game.Rulesets.Catch/Replays/CatchFramedReplayInputHandler.cs#L20-L31
   
   Note the handling of `position`. Any frame with an action is important,
   which means that as long as any key is held, interpolation will not
   take place.)
   
   On stable this is not a thing, because the fruit's end time was being
   truncated to `int`, therefore moving it back to time 7093 and restoring
   temporal integrity.
   
   This probably doesn't matter in other rulesets that much because
   the input tolerances in something like osu! or taiko are much higher.
   catch is rather knife-edge, what with mappers doing the "edge dash" /
   "pixel jump" stuff (tl;dr: placing a circle just barely outside of
   hyperdash range, so that a perfect normal dash is required to catch it).
   Thus, this is applied locally to catch for now until proven necessary
   to put it elsewhere too.

   

   bdach committed Apr 26, 2024
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