Add mania key count grouping to song select

[adminLAla]

Summary

I found the key count grouping in osu!stable's mania song select very useful.
While playing osu!lazer, I noticed that this grouping option was missing, so I implemented it here.

Changes

• Adds a ManiaKeyCount grouping mode in song select.
• Makes ManiaKeyCount available only when mania is the active ruleset.
• Keeps the UI label as Key Count.
• Keeps beatmap sets grouped together in this mode to avoid expanding all beatmap entries at once.
• Adds key count result caching for grouping calculations.
• Adds a cache size cap with auto-clear at 100,000 entries to prevent unbounded growth in very long sessions.

Testing

• dotnet build osu.Game.Tests -p:GenerateFullPaths=true -m -verbosity:m

  • Succeeded, 0 warnings, 0 errors.

• dotnet test osu.Game.Tests --filter "FullyQualifiedName~BeatmapCarouselFilterGroupingTest" -v minimal

  • Passed: 18, Failed: 0, Skipped: 0.

• InspectCode.ps1

  • Exits with code 1 in my local environment because dotnet-nvika is not available as a local tool.

• Equivalent static analysis steps were run manually:

  • dotnet jb inspectcode "osu.Desktop.slnf" --no-build --format=Xml --output="inspectcodereport.xml" --caches-home="inspectcode" --verbosity=WARN --jobs=1 --no-updates
  • nvika parsereport "inspectcodereport.xml" --treatwarningsaserrors
  • Result: 0 issues.

[bdach]

What is this? Why does it exist? Why is there any "caching" here at all? What's with the "mods signature", whatever it is?

[adminLAla]

Thanks for calling this out. You are right to question it.

I originally added the cache because I first assumed the lag came from repeatedly computing key counts during regrouping. After further testing, that assumption was wrong. The actual slowdown was caused by all groups being expanded, which increased the number of visible entries and rendering work while dragging the range slider.

Since the expansion behaviour has now been fixed, this cache (and the converter-mod signature key) does not provide meaningful value and only adds complexity. I will remove the caching/signature code and keep the grouping path straightforward.

I’ll push an update shortly.