Track sections

A plugin can add rows of its own to the track dialog (interface 1.3), under a heading, for the tracks it cares about: the NAM plugin adds its amp model and impulse response for guitar tracks. What the user sets there belongs to that track of that score.

Declare each section in the manifest:

"track_sections": [
  { "id": "amp", "title": "Amp", "plays": ["fretted", "fretless"] }
]

plays and does_not_play pick the tracks by instrument class, as instruments do; without them a section shows for every track. Then return it from Plugin::track_section(id), as a value implementing TrackSection:

• content(track, settings) returns the rows to show: the widgets of a tab, without a canvas. track is a TrackInfo (its index, name and class); settings is the track’s settings for this plugin, a JSON object, empty the first time.
• on(track, settings, widget, event) changes settings to match what the user did; the section is shown again from the new settings.

The plugin keeps nothing itself: OxiGuitar holds each track’s settings and sends them with every call. While the dialog is open they change with every use of a widget; OK applies them with the rest of the dialog as one change the user can undo, and Cancel drops them. An error from on is said in the footer, and the settings stay as they were.

No score format holds a plugin’s settings, so OxiGuitar saves them beside the score: song.gp3 keeps them in song.gp3.oxg, a small JSON file, one entry per track. Saving the score writes it, opening reads it, and oxiguitar-cli convert carries it to the new file. A track whose place changed (because another program moved tracks) finds its entry by name. A plugin gets a track’s settings again when the player prepares that track (with the instrument interface).

The SDK re-exports serde_json as oxiguitar_plugin::serde_json, so a plugin needs no dependency of its own for the settings.