Closes https://github.com/ppy/osu/issues/30163.
If I'm to be blunt, the decoupled stuff in song select makes my head
spin. I spent a solid 20 minutes thinking how I was going to fix this
one but then finally realised that generally most of the cause there
was the fact that `AdvancedStats` was seeing the new rulesets *before*
the "ensure global selected mods are valid for current ruleset" logic,
and so decided to just _delay_ that until the decoupled transfer
thingamajig happens.
I was honestly considering combining `BeatmapInfo`, `Ruleset`, and
`Mods` into one property on `AdvancedStats`. I figured I'd rather not
push my luck and try the baseline version first, but I honestly think
that direction is going to be required at some point to properly corral
all of the decoupled madness taking place in song select.
Fixes issue described in the following comment:
https://github.com/ppy/osu/pull/25759#issuecomment-1855954637
That is just not how the tooltip system is supposed to be used.
To name the individual sins:
- Caching and returning a tooltip instance like the classes that used
tooltips is incorrect. The lifetime of tooltip instances is managed by
the tooltip container. `GetCustomTooltip()` is called by it
exclusively. It should return a fresh instance every time.
- Not putting actual data in `IHasCustomTooltip.TooltipContent` is
wrong.
- Having `Tooltip.SetContent()` be a no-op is *grossly and flagrantly*
wrong.
I'm not even sure which particular combination of the above
transgressions caused the issue as it presented itself, but at this time
I frankly do not care.
The recent changes related to adding support for working beatmap load
cancellation exposed a flaw in the beatmap difficulty cache. With the
way the difficulty computation logic was written, any error in the
calculation process (including beatmap load timeout, or cancellation)
would result in a 0.00 star rating being permanently cached in memory
for the given beatmap.
To resolve, change the difficulty cache's return type to nullable.
In failure scenarios, `null` is returned, rather than
`default(StarDifficulty)` as done previously.
`AdvancedStats` was locally assuming that the only changes in mods that
are relevant to it are if the mods are `IApplicableToDifficulty`. This
is not true, as other mods (such as `IApplicableToRate` mods, or more
recently, Flashlight) can also affect star difficulty, which is shown on
one of the bars in `AdvancedStats`.
