subframe7536/maple-font · error · ValueError

No hhea table found.

Error message

No hhea table found.

What it means

adjust_line_height rewrites line-height metrics and requires both the hhea and OS/2 tables to be present in the fontTools font object. This ValueError is raised when the 'hhea' table is missing, meaning the loaded font is malformed or of a type that lacks horizontal header metrics. It fails fast instead of silently writing partial metrics.

Source

Thrown at source/py/utils.py:415

    axisValRec = ot.AxisValue()  # type: ignore
    axisValRec.AxisIndex = axis.AxisOrdering
    axisValRec.Flags = 0
    axisValRec.Format = 1
    axisValRec.ValueNameID = id
    axisValRec.Value = 1.0
    stat_table.AxisValueArray.AxisValue.append(axisValRec)
    stat_table.AxisValueCount += 1


def adjust_line_height(
    font: TTFont, factor: float, metric: tuple[float, float]
) -> None:
    """
    Adjust the line height of the font by modifying the hhea and OS/2 table.
    """

    if "hhea" not in font:
        raise ValueError("No hhea table found.")
    if "OS/2" not in font:
        raise ValueError("No OS/2 table found.")

    head = font["head"]
    hhea = font["hhea"]
    os2 = font["OS/2"]

    asc, desc = metric
    # Maintain original ascender/descender ratio
    ascender_ratio = asc / (asc - desc)  # type: ignore
    # Calculate target total height
    target_total_height = int(round(factor * (asc - desc)))

    # Calculate new metrics
    new_ascender = int(round(target_total_height * ascender_ratio))
    new_descender = new_ascender - target_total_height

    print(f"Change vertical metric to [{new_ascender}, {new_descender}]")

View on GitHub (pinned to c08fda97fe)

Solutions

1. Load the font with fontTools TTFont and ensure the hhea table exists: check `"hhea" in font` before calling.
2. Re-export or repair the source font so it includes an hhea table (e.g. via fonttools ttLib or a font editor).
3. Verify the build input path points at the correct TTF source, not a subsetted/stripped artifact.
4. Upgrade fontTools if an old version failed to read the table from a valid font.

Example fix

// before
# adjust_line_height(font, metric)  # raises if hhea missing
// after
from fontTools.ttLib import TTFont
# font = TTFont(path)  # ensure proper load
# if "hhea" not in font: raise RuntimeError(f"{path} lacks hhea table")
# adjust_line_height(font, metric)

from fontTools.ttLib import TTFont

def require_tables(path, tables=("hhea", "OS/2")):
    font = TTFont(path)
    missing = [t for t in tables if t not in font]
    if missing:
        raise ValueError(f"{path} missing tables: {missing}")
    return font

def has_hhea(font) -> bool:
    return "hhea" in font  # fontTools TTFont supports __contains__

try:
    adjust_line_height(font, metric)
except ValueError as e:
    if str(e) == "No hhea table found.":
        raise RuntimeError("Input font is malformed: rebuild it with fontTools") from e
    raise

When it happens

Trigger: Calling adjust_line_height (via build_nf, build_cn, or build_variable_fonts) on a font object where "hhea" not in font — e.g. a CFF/OTF variant stripped of hhea, a corrupted font file, or passing a non-TTF/incorrectly converted font object.

Common situations: Supplying a source font that lost its hhea table during conversion; pointing the build at a non-font or heavily subsetted font; using a font produced by a tool that dropped hhea; passing the wrong object (not a TTFont with tables loaded).

Related errors

• No OS/2 table found.
• No hhea table found.
• No OS/2 table found.
• Glyph '{glyph_name}' not found in font.
• Font does not have an OS/2 table.

AI-assisted analysis of subframe7536/maple-font@c08fda97fe (2026-08-28). Data as JSON: /api/errors/beb7a0d46f0d4775. Report an issue: GitHub.