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.
`SelectionHandler` is receiving input from anywhere out of necessity:
19f892687a/osu.Game/Screens/Edit/Compose/Components/SelectionHandler.cs (L119-L125)
Also important is that `BlueprintContainer` will selectively not block
right clicks to make sure they fall through to the
`ContextMenuContainer`:
19f892687a/osu.Game/Screens/Edit/Compose/Components/BlueprintContainer.cs (L122-L126)
But because the whole editor is sharing a `ContextMenuContainer` and
it's at a higher level than both components, we observe here the
playfield's `SelectionHandler` intercepting the right click before it
can reach the `ContextMenuContainer`.
The fix here is similar to what we're already doing in
`TimelineBlueprintContaienr`.
Seems to have had no consequence due to the way
`AutomaticBankAssignment` works (that flag is checked in
`PlacementBlueprint.UpdateTimeAndPosition()`, which runs essentially
every frame), but let's avoid putting it there at all ever.
`AllowDeselectionDuringDrag` is remove.
Instead, selected hit objects are not automatically deselected
when clock is seeked to a later time (the hit object is dead).
Update drag box selection even if mouse is not moved
(in case clock is running or scroll wheel is used).
Until now, the implementation of the overrides in `SelectionBlueprint`
have been confusing to the point where I would just implement by
trial-and-error (or copying from an existing implementation). This was
due to a combination of using "object" space coordinates
(ie. the thing the `Blueprint` is operating on) and screen-space coordinates.
This change switches all event related coordinates to screen-space,
which is how we already handle rotation/scale operations. With the
introduction of other editor types where the related objects are
drawables, this also makes a lot more sense.
