Why is this a thing at all? How has it survived this long? I don't know.
As far as I can tell this only manifests on selected beatmaps with "slow
swells" that spend the entire beatmap moving in the background. On other
beatmaps the tick is faded out, probably due to the initial transform
application that normally "works" but fails hard on these slow swells.
Can be seen on https://osu.ppy.sh/beatmapsets/1432454#taiko/2948222.
This commit removes ISkinnableSwell for taiko swell animations. In place
of it, an event named UpdateHitProgress is added to DrawableSwell, and
the skin swells are converted to listen to said event and
ApplyCustomUpdateState, like how spinner skinning is implemented for
std.
I don't know how to reproduce this issue in a test, so no tests for now.
Nonetheless, this fixes the issue for me at least on one map:
https://osu.ppy.sh/beatmapsets/1899665#taiko/3915653
This workaround is similar to #16475 (the test from that commit got
eventually removed for some reason).
4a7b011a53773d547b60401f609d7e394482a3ab inadvertently unearthed that
nested strong hits could play samples of their own accord, rather than
delegating to `DrumSampleTriggerSource` as they were supposed to. This
was an unfortunate omission due to how the inheritance structure of
`TaikoHitObject` looks like (some irrelevant classes omitted for
brevity):
DrawableTaikoHitObject
DrawableTaikoHitObject<TObject> <-- `GetSamples()` was overridden to empty here
DrawableTaikoStrongableHitObject
DrawableHit
DrawableDrumRoll
DrawableDrumRollTick
DrawableSwell
DrawableSwellTick
DrawableStrongNestedHit <-- all strong nested hits are here => didn't receive `GetSamples()` override
DrawableHit.StrongNestedHit
DrawableDrumRoll.StrongNestedHit
DrawableDrumRollTick.StrongNestedHit
To fix, move the `GetSamples()` override one level higher, to the
non-generic `DrawableTaikoHitObject`, to suppress the spurious sample
playbacks.
The stale reference in the comment was also updated to match current
code.
