Advancing the Cursor for insertion

I thought I would attempt to re-create the plugin for HalfTime plugin for MuseScore 2.0. For each rest or note in a selection, I want to replace it by a note or rest half its length, with the entire replacement for the selection also being half the length.

I tried finding a way to remove or replace an existing Chord and I couldn't find one. Since most of the music I would apply this to is on Voice 1, I thought I would just add new Chords to Voice 2. I clone the Chord, set its duration to 1/2 of the current Chord, add it at a Cursor position and try to advance the Cursor.

I use one Cursor for Voice 1 and one Cursor for Voice 2. Both are rewound to the beginning of the selection. I add the new Chord to Voice 2 using the second Cursor. A Chord is added, but it appears to retain the original duration. I then advance both Cursors. The first Cursor advances to the next chord, the second Cursor does not advance—it appears not to understand that a note was added. The problem may be that the Cursor was created from a selection with an empty Voice 2.

Here's my entire plugin so far. I'm hoping there are some methods that I am not aware of that I can use to solve my problem. One awkward part of the plugin interface is that it appears that you read duration in ticks, but you set them with setDuration() as numerator, denominator. I am trying to use a numerator of 1 and a denominator of ticks / 120.

Thanks for any assistance.

// Halve the duration of every note in the selection

import QtQuick 2.0
import MuseScore 1.0

MuseScore {
      version:  "1.0"
      description: "TBD"
      menuPath: "Plugins.Notes.Halve Duration"

      // Halve note durations

      function halveDuration()
      {
            // Find out where to start making our changes. If a selection is present, we start from the
            // beginning of the selection. If not, we don't do anything

            var cursor = curScore.newCursor();
            cursor.rewind(1);

            if (!cursor.segment) Qt.quit(); 
            var startTrack = cursor.track;

            // Find the end of the region we will alter
      
            cursor.rewind(2);
            var endTrack = cursor.track;
            var endTick = cursor.tick;
            if (endTick == 0) endTick = curScore.lastSegment.tick + 1;
            console.log(startTrack + " - " + endTrack + " - " + endTick);

            var newCursor = curScore.newCursor();
            var newTrack;

            // Process one track at a time

            for (var track = startTrack; track <= endTrack; track += 4) {
                  console.log("\nChecking track " + track);
                  cursor.rewind(1);
                  newCursor.rewind(1);
                  newTrack = track + 1;
                  newCursor.track = newTrack;

                  // Process each segment

                  while (cursor.segment && cursor.tick < endTick) {
                        console.log("Cur Tick: " + cursor.tick);
                        console.log("New Tick: " + newCursor.tick);
                        var element = cursor.segment.elementAt(track);
                        var newTick = 0;

                        if (element) {
                              switch (element.type) {
                              case Element.CHORD:
                                    var newChord = element.clone();
                                    console.log("Found CHORD. Duration = " + element.duration);
                                    newChord.duration = element.duration / 2;
                                    newTick = element.duration;
                                    console.log("New chord duration = " + newChord.duration);
                                    newCursor.setDuration(1, cursor.tick / 240);
                                    newCursor.add(newChord);
                                    break;
                              case Element.CHORDREST:
                                    var newRest = element.clone();
                                    console.log("Found CHORDREST. Duration = " + element.duration);
                                    newRest.duration = element.duration / 2;
                                    newTick = element.duration;
                                    console.log("New rest duration = " + newChord.duration);
                                    newCursor.setDuration(1, cursor.tick / 240);
                                    newCursor.add(newRest);
                                    break;
                              default:
                                    console.log("Not Chord or Rest");
                                    break;
                              }
                        }
                        cursor.next();
                        newCursor.next();
                  }
            }
      }
          
      onRun: {
            console.log("hello halveDuration");

            if (typeof curScore !== 'undefined') {
                  halveDuration();
            }
            Qt.quit();
      }
}

Here's the debug output when I select four quarter notes from one measure:

Debug: hello halveDuration
Debug: 0 - 3 - 1920
Debug: 
Checking track 0
Debug: Cur Tick: 0
Debug: New Tick: 0
Debug: Found CHORD. Duration = 480
Debug: New chord duration = 240
Debug: Cur Tick: 480
Debug: New Tick: 0
Debug: Found CHORD. Duration = 480
Debug: New chord duration = 240
Debug: Cur Tick: 960
Debug: New Tick: 0
Debug: Found CHORD. Duration = 480
Debug: New chord duration = 240
Debug: Cur Tick: 1440
Debug: New Tick: 0
Debug: Found CHORD. Duration = 480
Debug: New chord duration = 240

Here's what the score looks like. Before running the plugin, only Voice 1 exists. Afterwards (this screen shot), you can still see Voice 1 and one quarter not for Voice 2 that was added by the plugin.