Plugin API: expose playback order (RepeatList) for iteration

Your idea

Expose the playback order (RepeatList) to the Plugin API so that plugins can iterate through the score in the same order as the audio player.

Currently plugins can only iterate linearly:

var measure = curScore.firstMeasure;
while (measure) {
    // linear: 1, 2, 3, 4, 5
    // repeated sections visited only once
    measure = measure.nextMeasure;
}

With the proposed API, plugins could iterate in playback order:

var playback = curScore.repeatList();
for (var i = 0; i < playback.length; i++) {
    var measures = playback[i].measures;
    for (var m = 0; m < measures.length; m++) {
        // playback order: 1, 2, 3, 4, 1, 2, 3, 4, 5
        // handles repeats, voltas, DC, DS, Coda, Fine
    }
}

MuseScore already has a RepeatList class that does this expansion for the audio engine. The proposal is to expose it to plugins.

Problem to be solved

Plugins that need to process the score in playback order (lyrics extraction, chord sheet generation) must currently reimplement the entire repeat/jump/volta unwinding logic in JS. This logic covers:

• Simple repeats with configurable repeat count (2x, 3x, etc.)
• Volta brackets (1st, 2nd, 3rd endings and combined like "1-2", "3")
• DC (Da Capo), DS (Dal Segno) with optional playRepeats flag
• Coda, Fine, To Coda jumps
• Section breaks with independent repeat structures
• Nested repeats and jump loop prevention

Reimplementing this correctly in a plugin is error prone and would diverge from the actual playback behavior.

Prior art

Additional context

A concrete use case is a lyrics + chords export plugin that generates guitar songbook text. It needs playback order to correctly select verse lyrics during repeats and to expand DC/DS sections with the right lyrics and chord symbols.

Checklist

• This request follows the guidelines for reporting issues
• I have verified that this feature request has not been logged before, by searching the issue tracker for similar requests

Start by locating the existing RepeatList class used by the audio engine and the Plugin API entry points for score iteration. Compare the proposed repeatList() shape with current playback expansion, including repeats, voltas, jumps, codas, and section boundaries; the work is done when plugins can iterate the same playback order as the audio player.