feat: flow the TOC rail across visible sections#7
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Replace the single-active scrollspy with a continuous rail marker whose top and height track the projection of the visible document window onto the on-page TOC entries. The yellow highlight now spans (and slides across) exactly the sections currently on screen, sized by how much of each section is visible, instead of snapping to one heading. Link labels keep a binary highlight (thresholded) while only the rail flows. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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What
Makes the right-rail "On this page" indicator dynamic. Instead of a single yellow heading that snaps as you scroll, the rail highlight now flows to cover the sections currently on screen.
How
.toc-flow) is positioned along the TOC's left border. Each frame (rAF-throttled scroll/resize), we compute, per section, the portion visible in the viewport and project that slice onto the section's TOC entry. The marker'stop/heightspan from the first to the last visible entry — a continuous bar that slides and stretches across the entry boundary as sections share the screen.border-leftactive state is removed in favour of the flowing marker.Pure progressive enhancement, zero new dependencies. Falls back to no marker if JS is off.
Verification
pnpm buildpasses (13 pages).🤖 Generated with Claude Code