How to Fix Duplicate Points in FontForge Glyphs

Duplicate point errors occur when two or more nodes occupy the exact same coordinate on a glyph's outline, causing rendering glitches, export failures, and validation warnings. This guide provides a straightforward walkthrough on identifying and fixing duplicate points in FontForge using automated cleanup commands, the validation tool, and manual editing techniques.

Method 1: Use the Simplify Tool

The quickest way to eliminate duplicate or redundant points across one or more glyphs is FontForge’s automated simplification feature.

  1. Open your font project in FontForge.
  2. In the font view, select the glyphs containing the errors (or press Ctrl + A / Cmd + A to select all).
  3. Navigate to the top menu and select Element > Simplify > Simplify (Shortcut: Ctrl + Shift + M or Cmd + Shift + M).
  4. FontForge will evaluate the contours, merge points that share coordinates, and remove collinear redundant points without noticeably altering the shape.

Method 2: Detect and Fix with "Find Problems"

FontForge includes a dedicated tool to search for specific vector errors across your outlines.

  1. Select your target glyph(s) in the font view, or open the specific glyph in the Glyph Edit window.
  2. Go to Element > Find Problems...
  3. In the dialog box, navigate to the Points tab.
  4. Check the box labeled Points too close and set the distance threshold to 0 (or a very small value like 1 or 2 units to catch nearly identical coordinates).
  5. Ensure the action at the bottom is set to either highlight the problem or automatically fix it if prompted.
  6. Click OK. FontForge will step through each glyph and highlight the overlapping points for review or automatically merge them.

Method 3: Manual Removal in the Glyph Editor

If automated tools alter the curve tension or you need precise control over which control handles are preserved, resolve the issue manually.

  1. Double-click the affected glyph to open the Glyph Edit window.
  2. Press the Tab key repeatedly to cycle through the nodes sequentially. When the selection cursor fails to move visually between two steps, you have located the duplicate point.
  3. Alternatively, marquee-select the area around the suspected point. Check the point coordinate display in the info palette; if multiple points are selected within a zero-width bounding box, duplicates are present.
  4. Select one of the overlapping points and press Delete or Backspace. FontForge will remove the redundant node while preserving the contour continuity.

Verify the Fix

After applying any of the methods above, verify that the outline is valid:

  1. Go to Element > Validate > Validate.
  2. Review the report to confirm that the duplicate point warnings have cleared.
  3. Save your SFD file and proceed with font generation.