Cursor flickering on triplet feel

[Danielku15]

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

In the given example the playback cursor behaves very strange. The cursor does not follow exactly the beats as played. Refer to the reproduction steps for details on the scenarios.

Expected Behavior

The cursor should respect triplet-feel/swing durations correctly and always align with the beats as played.

Steps To Reproduce

Case 1: With grace note the cursor flicks quickly from the grace note forward and then back to the main note.

\track { instrument overdrivenguitar}
  \staff {score tabs}
    \tuning (Eb4 Bb3 Gb3 Db3 Ab2 Eb2) {
      label "Guitar Tune down ½ step"
    }
    \clef g2
    \tf triplet8th
    \ks c
      // Bar 1 / Voice 1 contents
      r.8
      3.2{sl}.8{gr onbeat}
      (0.1 5.2).4
      (0.1 5.2).8
      (0.1 5.2).8
      (0.1 5.2).8
      (0.1 5.2).8
      (0.4{hac} 0.5{hac} 0.6{hac}).8

Case 2: same song but without grace note. It seems second beat is advertised too long. the third beat is not highlighted. and from the second beat on the cursor is not really matching the beats.

\track { instrument overdrivenguitar}
  \staff {score tabs}
    \tuning (Eb4 Bb3 Gb3 Db3 Ab2 Eb2) {
      label "Guitar Tune down ½ step"
    }
    \clef g2
    \tf triplet8th
    \ks c
      // Bar 1 / Voice 1 contents
      r.8
    //   3.2{sl}.8{gr onbeat}
      (0.1 5.2).4
      (0.1 5.2).8
      (0.1 5.2).8
      (0.1 5.2).8
      (0.1 5.2).8
      (0.4{hac} 0.5{hac} 0.6{hac}).8

Link to jsFiddle, CodePen, Project

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Version and Environment

[AlphaTab][VersionInfo] alphaTab 1.9.0
Logger.ts:24 [AlphaTab][VersionInfo] commit: 0886cd46de429915e48e6743ecffd0171d5c0d6b
Logger.ts:24 [AlphaTab][VersionInfo] build date: 2026-07-03T14:54:38.406Z
Logger.ts:24 [AlphaTab][VersionInfo] High DPI: 2.1500000953674316
Logger.ts:24 [AlphaTab][VersionInfo] Platform: BrowserModule
Logger.ts:24 [AlphaTab][VersionInfo] WebPack: false
Logger.ts:24 [AlphaTab][VersionInfo] Vite: false
Logger.ts:24 [AlphaTab][VersionInfo] Browser: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/149.0.0.0 Safari/537.36
Logger.ts:24 [AlphaTab][VersionInfo] Window Size: 1778x952
Logger.ts:24 [AlphaTab][VersionInfo] Screen Size: 1920x1080

Platform

Web

Anything else?

This is a focused bug extracted from #2757