Fix Encoding Mapping Mismatches in FontForge

Character encoding mapping mismatches in FontForge occur when the internal glyph slots, glyph names, or Unicode code points do not align with standard character maps, causing fonts to display incorrect characters or render as empty tofu boxes. This guide provides a straightforward method to diagnose encoding discrepancies, switch to standard Unicode vectors, correct misaligned individual glyphs, and validate character maps before generating production-ready font files.

1. Verify and Switch the Encoding Vector

FontForge allows fonts to be displayed and organized under different encoding standards, such as legacy platform encodings or standard Unicode. An incorrect view can make mappings appear misaligned.

  1. Navigate to the top menu and select Encoding.
  2. Check which encoding is active. If it is set to a legacy standard (such as ISO-8859 or Mac OS Roman), select Unicode (BMP) for standard character sets or Unicode (Full) for expanded sets including emojis or historical scripts.
  3. Choose Reencode rather than "Force Encoding" when prompted. Selecting Reencode moves glyphs to their designated Unicode slots based on their assigned Unicode values, preserving their correct identities.

2. Differentiate Between "Reencode" and "Force Encoding"

Misusing these two functions is the primary cause of mapping errors in FontForge:

  • Reencode: Rearranges the display order inside the FontForge font view so that every glyph appears at the slot defined by the active encoding table, matching its assigned Unicode value.
  • Force Encoding: Leaves the glyphs in their current sequential grid positions and overwrites their character assignments with the codepoints of the selected encoding. Do not use Force Encoding unless you are importing an unencoded raw glyph stream that you know matches an exact sequential layout.

3. Correct Individual Glyph Unicode Assignments

If a specific glyph types the wrong character, its internal Unicode assignment is incorrect.

  1. Locate and double-click the problematic glyph, or right-click it in the main font view.
  2. Select Element > Glyph Info (or press Ctrl + I / Cmd + I).
  3. In the Unicode tab:
    • Check the Unicode Value field (formatted in hexadecimal, such as U+0041 for "A").
    • Check the Glyph Name (standard names like A, adieresis, or uni0041).
  4. To fix a mismatch, enter the correct Unicode hexadecimal value or standard Adobe Glyph List (AGL) name.
  5. Click Set From Name if the name is correct, or update the Unicode value directly.
  6. Click OK to apply.

4. Resolve Name-to-Unicode Conflicts Automatically

When dealing with multiple imported glyphs containing correct names but incorrect Unicode codepoints, automate the repair:

  1. Select all affected glyphs or select the entire font using Ctrl + A / Cmd + A.
  2. Go to Element > Glyph Info.
  3. Alternatively, navigate to Encoding > Rename Glyphs > Adobe Glyph List to force standard glyph names.
  4. Go to Encoding > Assign Unicode to Named Glyphs to re-index all codepoints directly from their standard names.

5. Check for Duplicate Unicode Assignments

FontForge will fail to generate valid OpenType/TrueType tables properly if two distinct glyphs share the same Unicode slot.

  1. Go to Element > Validation > Find Problems.
  2. In the dialog, navigate to the General or Encoding section.
  3. Check the box for Duplicate Unicode values and Unencoded glyphs.
  4. Click OK. FontForge will highlight all conflicting glyphs.
  5. Manually edit or detach the duplicates via Encoding > Detach Glyphs.

6. Generate Clean Font Tables

Once mappings are corrected, ensure FontForge compiles the proper character map (cmap) tables:

  1. Go to File > Generate Fonts.
  2. Select your desired output format (OpenType (CFF) .otf or TrueType .ttf).
  3. Click the Options button in the file dialog.
  4. Ensure OpenType is selected, which compiles a modern Unicode cmap table, ensuring broad cross-platform compatibility across operating systems and web browsers.