Duplicate points

Definition

Two consecutive on-curve points sit within 0.5fu of each other — the second adds no information and may cause hinting noise.

How Patens surfaces this

The Patens audit module checks for duplicate-points across five teaching surfaces: the edit-panel inline issue list, the project-wide audit page, the release pre-flight check, the family hub, and the home-page project tile. Every surface shows the same plain-English explanation and links back to this page. This rule has a one-click Fix button in the editor — the audit module both detects the issue and applies a deterministic correction with a labelled snapshot, so the ⌘Z path back is preserved.

Run this check yourself

Patens runs every audit rule live as you draw — including this one. The editor (in private alpha) shows duplicate-points firing on real glyphs, or check your own work from the CLI:

npx patens audit your-project.font.json

Canonical references

Primary literature where this rule is established or explained. Drawn from the open-licensed corpus — browse the full 42-source canonical library or read the research artifact.

• Unified Font Object 3 Specification ↗

  Tal Leming, Just van Rossum, Erik van Blokland · 2003 · unifiedfontobject.org· § Glyph — point definitions

  Two points at identical coordinates produce undefined Bézier curvature; remove the duplicate.

Related rules in Contour shape

• contour-winding-collision Contour winding collision
• empty Empty glyph
• near-collinear-points Near-collinear points
• off-grid-points Off-grid points
• open-contour Open contour
• self-intersecting Self-intersecting contour
• sharp-kink Sharp kink
• tiny-contour Tiny contour