feat(tab): add H/P text labels on hammer-on / pull-off arcs by rafaelsales · Pull Request #2609 · CoderLine/alphaTab

rafaelsales · 2026-03-23T03:09:35Z

Summary

In the Tab (and TabMixed) renderer, hammer-on and pull-off connections are drawn as arcs between notes but the conventional H / P text labels were never rendered.

This PR adds H/P label rendering and correctly handles edge cases like H/P chains and multiple H/P on the same beat.

Changes

Commit 1 — feat(tab): add H/P text labels to hammer-on and pull-off arcs

TieGlyph.ts — adds a getSlurText() virtual method (returns undefined by default) and draws the label text at the arc midpoint in paint() when present.
TabSlurGlyph.ts — accepts an optional slurText?: string constructor parameter and overrides getSlurText() to return it.
TabBeatContainerGlyph.ts — passes 'H' or 'P' when creating effect slurs for hammer-pull origin notes.

Commit 2 — fix(tab): handle H/P chain and same-beat edge cases

TabSlurGlyph.ts — tryExpand() now accepts an optional slurText parameter and rejects merging slurs with different labels (prevents label loss when multiple H/P on same beat share beam direction).
TabBeatContainerGlyph.ts — creates individual arcs per H/P pair using hammerPullOrigin/hammerPullDestination links (instead of the collapsed effectSlurOrigin/effectSlurDestination). This renders chains like 5{h} 7{h} 5 as two separate arcs (H then P) instead of one collapsed arc. Non-H/P effect slurs (e.g. legato slides) continue to use the existing effectSlur path, guarded by !n.isHammerPullOrigin / !n.isHammerPullDestination.

How it looks

Test plan

Simple hammer-on (ascending fret) → "H" label
Simple pull-off (descending fret) → "P" label
H then P in same bar → separate arcs with correct labels
H and P on different strings → H above, P below
H/P chain (5{h} 7{h} 5) → individual H and P arcs
Long chain (5{h} 7{h} 5{h} 7) → alternating H/P/H arcs
Legato slide ({sl}) → arc without label (regression check)
Plain notes → no arcs, no labels (regression check)

Running the local test page

Step 1 — Save the HTML below as test-hp-labels.html in the repo root.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>AlphaTab – Hammer-on / Pull-off H/P Labels</title>
    <style>
        body { font-family: sans-serif; max-width: 900px; margin: 40px auto; padding: 0 20px; background: #fff; }
        h2 { margin-top: 32px; font-size: 1em; color: #333; }
        p { color: #555; font-size: 0.9em; }
        .at-wrap { border: 1px solid #ddd; border-radius: 4px; margin-top: 8px; }
        .at-footer { display: none; }
    </style>
</head>
<body>
    <h1>Hammer-on / Pull-off H/P Labels</h1>
    <p>
        Each section renders a different H/P scenario in the Tab stave profile.
        Each arc should display an <strong>H</strong> or <strong>P</strong> label above it.
    </p>

    <h2>1. Simple hammer-on (5→7 on string 3)</h2>
    <div id="at1" class="at-wrap"></div>

    <h2>2. Simple pull-off (7→5 on string 3)</h2>
    <div id="at2" class="at-wrap"></div>

    <h2>3. Hammer-on then pull-off (5→7, 7→5) in the same bar</h2>
    <div id="at3" class="at-wrap"></div>

    <h2>4. H and P on different strings (string 3 H, string 4 P)</h2>
    <div id="at4" class="at-wrap"></div>

    <h2>5. H/P chain (5→7→5) — individual H then P arcs</h2>
    <div id="at5" class="at-wrap"></div>

    <h2>6. Long chain (5→7→5→7) — alternating H/P arcs</h2>
    <div id="at6" class="at-wrap"></div>

    <h2>7. Legato slide — arc without H/P label</h2>
    <div id="at7" class="at-wrap"></div>

    <h2>8. Plain notes — no arc, no label</h2>
    <div id="at8" class="at-wrap"></div>

    <script src="packages/alphatab/dist/alphaTab.js"></script>
    <script>
        const apis = [];
        const settings = {
            core: {
                engine: 'html5',
                fontDirectory: 'packages/alphatab/dist/font/',
                logLevel: 0,
            },
            display: {
                staveProfile: 'Tab',
                scale: 1.5,
            },
            notation: {
                elements: {
                    guitarTuning: false,
                    trackNames: false,
                }
            },
            player: { enablePlayer: false },
        };

        function renderTex(containerId, tex) {
            const api = new alphaTab.AlphaTabApi(
                document.getElementById(containerId),
                settings
            );
            api.tex(tex, [0]);
            apis.push(api);
        }

        const queue = [
            ['at1', ':4 5.3{h} 7.3 r r'],
            ['at2', ':4 7.3{h} 5.3 r r'],
            ['at3', ':4 5.3{h} 7.3 7.3{h} 5.3'],
            ['at4', ':4 5.3{h} 7.3 8.4{h} 5.4'],
            ['at5', ':4 5.3{h} 7.3{h} 5.3 r'],
            ['at6', ':8 5.3{h} 7.3{h} 5.3{h} 7.3 r r r r'],
            ['at7', ':4 5.3{sl} 7.3 r r'],
            ['at8', ':4 5.3 7.3 5.3 7.3'],
        ];

        queue.forEach(([id, tex]) => {
            renderTex(id, tex);
        });
    </script>
</body>
</html>

Step 2 — Build the web bundle and start a local server from the repo root:

npm install
npm run build-web
python3 -m http.server 8765

Step 3 — Open http://localhost:8765/test-hp-labels.html in your browser.

In the Tab renderer, the arc connecting hammer-on and pull-off notes is now annotated with an "H" (ascending fret = hammer-on) or "P" (descending fret = pull-off) label above the arc midpoint. The label is drawn via an overridden paint() in TabSlurGlyph, reusing the same canvas.fillText path already used for whammy/bend slurText. TieGlyph's coordinate fields (_startX/Y, _endX/Y, _tieHeight, _shouldPaint) are widened from private to protected to allow the subclass to read them during paint. Fixes CoderLine#2608

Danielku15 · 2026-03-27T09:23:58Z

Great addition, thanks for the change. We might need to check some additional edge cases like:

Having multiple hammer-on/pull-offs on the same beat.
Having Direct hammer-on/pull-off chains

- Individual arcs per H/P pair in chains (e.g. 5{h} 7{h} 5 now renders separate H and P arcs instead of one collapsed arc) - Prevent tryExpand from merging slurs with different H/P labels (fixes label loss when multiple H/P on same beat share beam direction) - Guard existing effectSlur blocks to skip H/P notes, keeping legato slide rendering unaffected

rafaelsales · 2026-04-02T14:41:48Z

Thanks for the review! I've pushed a follow-up commit addressing both edge cases:

1. Direct H/P chains

The model (Note.finish()) collapses effect slur chains into a single arc from first to last note. For 5{h} 7{h} 5, this produced one arc labeled "H" instead of two separate arcs.

Fix: The renderer now uses hammerPullOrigin/hammerPullDestination links directly (instead of the collapsed effectSlurOrigin/effectSlurDestination) to create individual arcs per H/P pair, each with the correct label. Non-H/P effect slurs (legato slides) continue using the existing effectSlur path.

2. Multiple H/P on the same beat

When two notes on the same beat pair had H/P effects with the same beam direction, tryExpand() merged them into one slur, silently discarding the second label.

Fix: tryExpand() now accepts an optional slurText parameter and rejects merging when the labels differ.

Both are covered by new test cases in the test page (sections 5 and 6).

rafaelsales force-pushed the feature/issue-2608 branch 2 times, most recently from ee5fd63 to f23e3bd Compare March 23, 2026 03:39

rafaelsales force-pushed the feature/issue-2608 branch from f23e3bd to 6901cd3 Compare March 23, 2026 03:41

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

feat(tab): add H/P text labels on hammer-on / pull-off arcs#2609

feat(tab): add H/P text labels on hammer-on / pull-off arcs#2609
rafaelsales wants to merge 2 commits intoCoderLine:developfrom
rafaelsales:feature/issue-2608

rafaelsales commented Mar 23, 2026 •

edited

Loading

Uh oh!

Danielku15 commented Mar 27, 2026

Uh oh!

rafaelsales commented Apr 2, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Conversation

rafaelsales commented Mar 23, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Summary

Changes

How it looks

Test plan

Uh oh!

Danielku15 commented Mar 27, 2026

Uh oh!

rafaelsales commented Apr 2, 2026

1. Direct H/P chains

2. Multiple H/P on the same beat

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

rafaelsales commented Mar 23, 2026 •

edited

Loading