Swing Grid Support

[maiko3tattun]

New Feature:

• Added support for swing as a grid size option.
• Swing amount can be selected in 10% increments from 10% to 100%.

Changes:

• Changed triplet notation from "1/6" to "1/4 T" to make it more familiar and conventional.
• Swing is not only a visual change; it affects the overall rhythm of the song, so it is saved as part of the project. However, to avoid polluting the undo history, changes to grid size and swing amount are not recorded in the undo history.
• Consolidated snap-related calculations into MusicMath.cs.
• Fixed an issue where the numeric text in the slider dialog could be cut off.

Notes:

• At the most precise swing grid setting (1/16 Sw), 10% corresponds to 4 ticks, so the tick value never becomes fractional.
• The following snap-related operations were tested:
  • Note creation, resizing, moving, and splitting
  • Playhead movement
  • Curve selection
  • Quantization
  • Keyboard shortcuts for note movement and resizing, playhead movement
  • Note pasting

[Copilot]

Copilot review overview

🟡 Changes recommended

Swing snapping currently has persisted-state, coordinate-space, split-boundary, keyboard, and zoomed-rendering correctness issues.

Review effort: Balanced
Findings: 11

Open (11)

• Convert playhead to part-relative coordinates · New
• Use the original grid unit for swing phase · New
• Mark snap division changes as dirty for save tracking · New
• Initialize swing dialog from saved project swing · New
• Derive note duration from the snapped tick · New
• Preserve unsnapped keyboard movement step · New
• Clamp keyboard movement at the part start · New
• Preserve unsnapped keyboard resize step · New
• Avoid double-applying part position when snapping · New
• Find the last valid swing grid split point · New
• Clamp split bounds to the swing grid · New

What changed in this PR

Adds persisted swing-grid support across piano-roll rendering and editing.

Changes:

• Adds straight, triplet, and swing grid options with configurable swing amount.
• Centralizes snapping calculations in MusicMath.
• Applies swing snapping to editing, quantization, paste, and playhead operations.

File	Description
OpenUtau/​Views/​SliderDialog.axaml	Widens numeric value display.
OpenUtau/​Views/​NoteEditStates.cs	Uses swing-aware snapping in edit states.
OpenUtau/​ViewModels/​NotesViewModel.cs	Manages swing settings and snapping operations.
OpenUtau/​Strings/​Strings.axaml	Adds swing menu text.
OpenUtau/​Controls/​TickBackground.cs	Renders swing grid lines.
OpenUtau/​Controls/​PianoRoll.axaml.cs	Updates quantization and keyboard controls.
OpenUtau/​Controls/​PianoRoll.axaml	Binds swing to grid controls.
OpenUtau.Core/​Util/​MusicMath.cs	Implements centralized swing calculations.
OpenUtau.Core/​Ustx/​UProject.cs	Persists grid and swing settings.
OpenUtau.Core/​Editing/​NoteBatchEdits.cs	Adds swing-aware quantization.

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[maiko3tattun]

All issues have been resolved.