feat: round-trip a redundant staves element in mx::api - #421
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MusicXML lets a <note> carry its own playback velocity in the dynamics and end-dynamics attributes, the MIDI Note On and Note Off velocities expressed as percentages of the default forte level. The api had no home for either, so the reader dropped them and an author could not state them. NoteData gains velocityStart and velocityStop. Both are optional doubles that default to empty, so a note that says nothing about playback still writes no attribute. The names avoid "dynamics", which in the api already means the printed marking (a MarkData in noteAttachmentData) rather than how hard the note is played. Pins the thirteen foundsuite Inventions in the api round-trip baseline. Each one carried a per-note velocity that was the only thing it lost on write.
MusicXML's <identification>/<source> names the edition, manuscript, or other publication a score was made from. The api had nowhere to keep it, so the reader discarded it and every write dropped the element. ScoreData gains an optional source string. Optional rather than a plain string because <source></source> is legal and means something different from saying nothing at all. Pins five more files in the api round-trip baseline whose only divergence was the dropped element.
<direction directive="yes"> aligns a direction with the measure's time signature instead of with the note it is anchored to, which is how a tempo or style marking at the head of a movement is usually placed. The api had no field for it, so the attribute was dropped on write. DirectionData gains a tri-state directive following the api's Bool convention: unspecified does not write an attribute, yes and no are written verbatim. <harmony> does not carry the attribute, so only <direction> reads and writes it. Pins three more files in the api round-trip baseline.
MusicXML states a part's staff count in <staves>, and a part that omits the element has one staff. mx wrote the element only when the part had more than one staff, so a source that spelled out the redundant <staves>1</staves> lost it. PartData gains writeStaffCount, defaulting to false. It only affects a single-staff part; a part with more than one staff writes its count either way, since without it every note would land on staff one. The reader sets it when the source spelled the element out. Pins three more files in the api round-trip baseline.
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Claude
This was referenced Aug 23, 2026
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August 23, 2026 18:58
…ff-count Signed-off-by: Matthew James Briggs <matthew.james.briggs@gmail.com>
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Human Summary
TODO: human writes here
Summary
MusicXML states a part's staff count in
<attributes>/<staves>, and a part that omits the element has one staff. mx wrote the element only when the part had more than one staff, so a source that spelled out the redundant<staves>1</staves>lost it.PartDatagainsbool writeStaffCount, defaulting to false. It only affects a single-staff part: a part with more than one staff writes its count either way, since without it every note would land on staff one. The reader sets it when the source spelled the element out and the count is one, so the common case stays at the default.PartReader::calculateNumStavesnow also reports whether a<staves>element was seen. The count alone cannot tell you, since one is both "the source said one" and "the source said nothing".Non-breaking: one new field defaulting to the behavior mx had before.
Round-trip corpus
Adds 3 files to
roundtrip-baseline.txt(402 -> 405).drop:staveswas the fourth entry on the classifier worklist.Testing
StaffCountApiTestcovers the single-staff default, the single-staff override, and a two-staff part that writes its count regardless (*StaffCount*: 8 assertions in 3 test cases)make api-test(6314 assertions in 582 test cases)make api-roundtrip(405 passed, 0 failed of 405 pinned)make api-roundtrip-discoverreports exactly the 3 new passes and no regressionsmake fmtReferences
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