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hhea table ​

Provides horizontal layout metrics — ascender, descender, line gap, and caret slope for horizontal text.

Scope ​

  • Format family: Shared SFNT
  • Table tag in JSON: hhea

Specs ​

JSON Skeleton ​

This skeleton reflects fields currently parsed/written by Font Flux JS for this table.

json
{
  "tables": {
    "hhea": {
      "majorVersion": 0,
      "minorVersion": 0,
      "ascender": 0,
      "descender": 0,
      "lineGap": 0,
      "advanceWidthMax": 0,
      "minLeftSideBearing": 0,
      "minRightSideBearing": 0,
      "xMaxExtent": 0,
      "caretSlopeRise": 0,
      "caretSlopeRun": 0,
      "caretOffset": 0,
      "reserved1": 0,
      "reserved2": 0,
      "reserved3": 0,
      "reserved4": 0,
      "metricDataFormat": 0,
      "numberOfHMetrics": 0,
      "_checksum": 0
    }
  }
}

Top-level Fields ​

  • majorVersion - number (0..65535) [spec type: uint16] (must be 1)
  • minorVersion - number (0..65535) [spec type: uint16] (must be 0)
  • ascender - number [spec type: FWORD]
  • descender - number [spec type: FWORD]
  • lineGap - number [spec type: FWORD]
  • advanceWidthMax - number [spec type: UFWORD]
  • minLeftSideBearing - number [spec type: FWORD]
  • minRightSideBearing - number [spec type: FWORD]
  • xMaxExtent - number [spec type: FWORD]
  • caretSlopeRise - number (-32768..32767) [spec type: int16]
  • caretSlopeRun - number (-32768..32767) [spec type: int16]
  • caretOffset - number (-32768..32767) [spec type: int16]
  • reserved1 - number (-32768..32767)
  • reserved2 - number (-32768..32767)
  • reserved3 - number (-32768..32767)
  • reserved4 - number (-32768..32767)
  • metricDataFormat - number (-32768..32767) [spec type: int16] (0 for current format)
  • numberOfHMetrics - number (0..65535) [spec type: uint16]

Additional Nested Keys Seen In Implementation ​

  • majorVersion
  • minorVersion
  • ascender
  • descender
  • lineGap
  • advanceWidthMax
  • minLeftSideBearing
  • minRightSideBearing
  • xMaxExtent
  • caretSlopeRise
  • caretSlopeRun
  • caretOffset
  • reserved1
  • reserved2
  • reserved3
  • reserved4
  • metricDataFormat
  • numberOfHMetrics

Notes ​

  • Preserve _checksum for stable round-tripping.
  • If a table is only partially understood, prefer keeping unknown bytes in _raw instead of dropping data.
  • Validate with .validate() after edits.