unoplatform/uno · error · Exception

No supported cmap subtable found (Platform 3/Encoding 1 or 1

Error message

No supported cmap subtable found (Platform 3/Encoding 1 or 10, or Platform 0)

What it means

The cmap table exists but none of its encoding records matched the selector: Platform 3 (Windows) Encoding 1 (Unicode BMP) or 10 (Unicode full), or Platform 0 (Unicode). If selectedSubtableOffset stays 0 after scanning all subtable records, the tool throws. Fonts with only legacy platform encodings (e.g. Platform 1 Macintosh only) or malformed encoding records hit this.

Source

Thrown at src/FontFallbackPreprocessor/Program.cs:317

			if (platformId == 3 && (encodingId == 1 || encodingId == 10))
			{
				if (selectedPlatformId != 3 || (encodingId == 10 && selectedEncodingId == 1))
				{
					selectedSubtableOffset = offset;
					selectedPlatformId = platformId;
					selectedEncodingId = encodingId;
				}
			}
			else if (platformId == 0 && selectedPlatformId != 3)
			{
				selectedSubtableOffset = offset;
				selectedPlatformId = platformId;
				selectedEncodingId = encodingId;
			}
		}

		if (selectedSubtableOffset == 0)
			throw new Exception("No supported cmap subtable found (Platform 3/Encoding 1 or 10, or Platform 0)");

		// 4. Parse subtable
		// The offset in the encoding record is relative to the beginning of the cmap table.
		long subtablePosition = cmapOffset + selectedSubtableOffset;
		fs.Seek(subtablePosition, SeekOrigin.Begin);
		ushort format = ReadUInt16Be(reader);

		if (format == 4)
		{
			return ReadFormat4(reader);
		}
		else if (format == 12)
		{
			return ReadFormat12(reader);
		}
		else
		{
			throw new Exception($"cmap format {format} not supported (only 4 and 12)");

View on GitHub (pinned to 0418340488)

Solutions

1. Replace the font with a Unicode-encoded version (Noto fonts ship Platform 3/Encoding 1 subtables).
2. Extend the selector to accept Macintosh Platform 1 as a last-resort fallback if Unicode coverage is acceptable.
3. Skip fonts with no usable Unicode cmap when generating fallback maps.

// After scanning subtables, fall back to Macintosh Platform 1 if no Unicode subtable
if (selectedSubtableOffset == 0 && macSubtableOffset != 0) { selectedSubtableOffset = macSubtableOffset; }

try { ReadCmap(path); }
catch (Exception ex) when (ex.Message.Contains("No supported cmap subtable")) { Log.Warn($"{path} has no Unicode cmap; skipping."); }

When it happens

Trigger: A cmap table whose encoding records are exclusively legacy (Macintosh/Platform 1, or custom platform IDs), or whose Platform-3/0 records have offsets of 0, leaving no selectable Unicode subtable.

Common situations: Parsing older legacy fonts (early Mac TTFs, symbol fonts) that predate Unicode cmap subtables; an OTF with only format-0/2 subtables on Macintosh platform; a font whose Windows Unicode subtable was stripped.

Related errors

• cmap table not found
• cmap format {format} not supported (only 4 and 12)

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/f1bb474470be2324. Report an issue: GitHub.