Adapt "Split Part at Playhead" to support multiple selected parts

[4dTailor]

Summary

Select multiple parts, and if they are under the playhead, it will split them one by one.
Also modifies the Split Part warning to take the part name.

[stakira]

Thanks! This looks correct and low-risk. Using the selection matches the other part actions, since right-clicking an unselected part selects it first, and the translations without {0} still work (string.Format just ignores the name).

One change I'd ask for before merging:

Make splitting several parts one undo step. Each SplitPart opens its own undo group, so splitting 5 parts takes 5 undos. Also, answering "No" in the "notes in the way" dialog for a later part leaves the earlier ones already split. Suggestion: first go through the selected parts, asking the question where needed and working out each split tick. Then do all the remove/add commands inside a single StartUndoGroup()/EndUndoGroup(). That also keeps the undo group from staying open while a dialog is waiting.

Nits:

• The command lambda no longer uses its argument, so ReactiveCommand.Create<UPart>(async _ => await SplitParts()) would make that clear.
• There's a whitespace-only blank line after SplitParts().
• The other languages won't show the part name until their captions get a {0}. Not a blocker, just worth mentioning to translators.

[4dTailor]

Asking a clarifying question regarding the "notes in the way" dialog, Is intended behaviour to abort the split if the user responds no, or to continue with the split, skipping the split for the part the user responded no to?

[stakira]

Asking a clarifying question regarding the "notes in the way" dialog, Is intended behaviour to abort the split if the user responds no, or to continue with the split, skipping the split for the part the user responded no to?

Either is fine for me. But again, no undo should be pushed if no part is splitted.

[4dTailor]

Changes have been made.
I've chosen the second option in terms of "notes in the way" behaviour - changing to the first option can be done by replacing Line 1859 and 1860 in MainWindow.axaml.cs with return;.

Extra changes:

• Changed context.part.split to Split part/s at playhead to indicate this new behaviour
• Sorted the selected parts by track number, so that splitting is done from top part to bottom part

[stakira]

Thanks for this! The undo grouping looks right: all dialogs finish before StartUndoGroup, "No" for every part returns before opening a group, and splits that end up doing nothing leave an empty group, which EndUndoGroup discards.

One bug though: when the selection includes a wave part, the first loop continues before partSplitTick.Add(...), so partSplitTick only has entries for voice parts while the second loop indexes selectedParts[i], which still contains the wave parts. For example, selecting a wave part plus voice parts A and B gives ticks [tA, tB], so the wave part is "split" at tA (no-op), A is split at B's tick, and B isn't split at all.

Simplest fix is to filter to voice parts up front, then every remaining part adds exactly one entry and the indices line up:

UVoicePart[] selectedParts = viewModel.TracksViewModel.Parts
    .Where(viewModel.TracksViewModel.SelectedParts.Contains)
    .OfType<UVoicePart>()
    .OrderBy(part => part.trackNo)
    .ToArray();

(and drop the is not UVoicePart check in the loop).

Smaller things:

• DocManager.Inst.playPosTick is read per part after each dialog; if playback is running, later parts split at later ticks. Reading it once before the loop avoids that.
• Optional: wrapping the split loop in try/finally { EndUndoGroup(); } so an exception can't leave the undo group open.
• The dialog title uses part.name while the log uses part.DisplayName; the latter is probably what the title should show.
• "Split part/s at playhead" might read better as "Split parts at playhead". The new {0} in dialogs.splitpart.caption also means the translated strings need updating, or they won't show the part name.

[4dTailor]

I've done the fixes above.

Notes

Regarding the translation string
I've avoided that issue by appending the display name outside of the translation string.
I want to note that a language with RTL text could make this change look wrong.

I've also added some part selection that visually highlights the targeted part.
Original selection behaviour is restored at the split part loop.

Regarding the Split part/s at playhead
I chose to rename this string that to indicate that splitting one part/many parts is possible, without adding a translation string for plurals and writing code for it. I've done the change as requested, but would like to note some minor confusion is possible regarding if the split part command still splits one part. An alternative candidate would be Split part(s) at playhead, shared by other commands with similar behaviour.