As I look into re-implementing the ability to choose combo colour for an
object (also known as "colourhax") from the editor UI, I stumble upon
these wretched ternary items again and sigh a deep sigh of annoyance.
The structure is overly rigid. `TernaryItem` does nothing that
`DrawableTernaryItem` couldn't, except make it more annoying to add
specific sub-variants of `DrawableTernaryItem` that could do more
things.
Yes you could sprinkle more levels of virtuals to
`CreateDrawableButton()` or something, but after all, as Saint Exupéry
says, "perfection is finally attained not when there is no longer
anything to add, but when there is no longer anything to take away."
So I'm leaning for taking one step towards perfection.
More specifically, this fixes placement blueprints not beginning placement when using touch input while the cursor was previously outside compose area, due to the placement blueprint not existing (removed from the scene by `ComposeBlueprintContainer`).
Touched on in https://github.com/ppy/osu/discussions/28581.
After a bit more usage of the editor I do agree with this and think that
making the fades a bit more gentle helps a lot.
This was reported in https://github.com/ppy/osu/pull/28474, albeit the
code changes proposed there did not fix the issue at all.
See 8b6385f7d0 for demonstration of the
crash scenario. Basically what is happening there is:
- The starting premise is that there is a spinner placement active.
- At this time, a drag selection is started via the timeline.
- Once the drag selection finds at least one suitable object to select,
it mutates `SelectedItems`.
- When selection changes for any reason, the `HitObjectComposer`
decides to switch to the "select" tool, regardless of why
the selection changed.
- Changing the active tool causes the current placement - if any -
to be committed, which mutates the beatmap.
- Back at the drag box selection code, this causes a "collection
modified when enumerating" exception.
The proposed fix here is to eagerly commit active placement - if any -
when drag selection is initiated via the timeline, which avoids this
issue. This also appears to vaguely match stable behaviour and is sort
of consistent with the logic of committing any outstanding changes upon
switching to the selection tool.
