How to Auto Space a Whole Font in FontForge

Yes, you can automatically space an entire font using FontForge's built-in metric algorithms. This guide outlines how to use the automated spacing features in FontForge, explains how the underlying algorithm calculates side bearings, and highlights the necessary steps to refine the results for professional typography.

How to Auto-Space All Glyphs

To apply automatic spacing across your entire font, follow these steps in the FontForge font view window:

  1. Select All Glyphs: Press Ctrl + A (or Cmd + A on macOS) to select every character in the font database. Alternatively, use the menu bar: Edit > Select > Select All.
  2. Open Auto Space: Navigate to the top menu and click Metrics > Auto Space....
  3. Configure Spacing Parameters: A configuration window will appear. Here, you specify:
    • Spacing between glyphs: The target visual space (in font units) desired between standard vertical stems.
    • Reference Glyphs: FontForge typically uses typical lowercase characters like "n" and "o" as baseline references to determine overall density.
  4. Apply Changes: Click OK. FontForge will iterate through the selected glyphs and calculate new Left Side Bearings (LSB) and Right Side Bearings (RSB) based on your parameters.

How the Algorithm Works

FontForge’s auto-spacing algorithm evaluates the outer contours of each glyph. Instead of merely measuring bounding boxes, it analyzes the optical mass and negative space along the left and right perimeters. It attempts to equalize the visual area between adjacent characters so that straight stems, rounds, and open shapes appear uniformly separated.

Adding Auto-Kerning

Spacing alone controls the individual advance width and side bearings of each glyph. Irregular combinations (such as "AV", "To", or "L'") still require kerning pairs. You can automate this process immediately after auto-spacing:

  1. Keep all glyphs selected.
  2. Go to Metrics > Auto Kern....
  3. Choose the kerning subtable to write to (or create a new one).
  4. Specify the maximum number of pairs and the visual gap threshold.
  5. Click OK to generate kerning offsets for problematic letter combinations.

Limitations and Practical Tips

While the auto-space algorithm provides a solid foundation and saves substantial setup time, it is not a complete substitute for visual proofing:

  • Diagonal and Asymmetrical Shapes: Characters with pronounced angles (like A, V, W, k, and x) often receive disproportionate padding from purely mathematical algorithms.
  • Punctuation and Symbols: Quotation marks, hyphens, and periods frequently need custom spacing metrics relative to standard body letters.
  • Manual Review: Always test your font using a metrics window (Metrics > New Metrics Window) with sample text strings (such as "HOHONON" or "minimum") to verify optical rhythm and manually adjust side bearings where necessary.