[Danielku15]

Note

AI-authored disclosure (alphatab-ai-authored-v1)

Portions of this content were authored by an AI agent. The agent has read
AGENTS.md and the human submitter accepts responsibility for
compliance with the rules in that document.

Issues

Fixes #3010

Proposed changes

The scrubber always drew into a fixed 600-unit viewBox (400 when compact), stretched to its container with preserveAspectRatio="none". As a result:

• Bar numbers, tempo labels and the cursor knob were stretched horizontally on wide players and squeezed on narrow ones; the knob became an oval.
• Every bar got a tick, whatever the width. A long song on a narrow player turned its ticks into a solid band.
• The bar numbers were fixed at 16, 32 and 48, whatever the width or song length.

The issue's proposed patch measures the width and picks power-of-two steps. This PR builds on that and also handles label size, the edges of the scrubber and the tempo labels:

• True size. The scrubber measures its width and draws in CSS pixels, so text, lines and the knob keep their size at any width. Until the first measurement (e.g. on server-rendered website pages) it uses the previous 600/400 widths.
• Density follows the space. Bar numbers step in powers of two (1, 2, 4, 8, 16 … bars), at least 48 px apart. The spacing also grows with the digit count of long songs. Ticks are at least 4 px apart, with major and mid ticks derived from the label step. With a 96-bar score this gives a label every 2nd bar at 3440 px and every 16th at 900 px. A 1000-bar song at 600 px draws 126 ticks instead of 1001.
• 1-based bar numbers. Labels read 1, 9, 17 … at the start of their bar, matching the rendered score and the slider's "Bar N of M" value text. Before, "16" sat where the score's bar 17 begins.
• Labels stay inside. The first and last bar numbers are pulled in so they don't spill past the ends.
• Tempo labels. Near the right edge a label moves to the left of its marker. Colliding labels are dropped based on their actual width; before, the check used a fixed 60-unit gap that changed with the width.
• Playback cost. Ticks, labels and tempo markers are only rebuilt when the width, song or tempo markers change, not on every bar during playback.

The scrubber's height (38 px, 22 px compact) and its props are unchanged, so the transport, the compact player and the website's landing player keep their layout.

Checked in the playground control demo at 3440, 1400, 900 and 760 px (the 760 px window triggers the wrapped full-row transport).

Checklist

• I consent that this change becomes part of alphaTab under its current or any future open source license
• This PR is linked to an accepted issue (see above)
• Changes are implemented
• New tests were added
• I have read AGENTS.md if an AI helped draft any part of this PR

AI authorship disclosure

• No AI agent authored any part of this PR (description, code, tests, or commit messages)
• An AI agent contributed to this PR. The AI-authored disclosure block
  (alphatab-ai-authored-v1) is present at the top of this body, and I have
  personally reviewed every change and can explain each one

Further details

• This is a breaking change
• Docs / release notes updated in website/