svg2ttf/lib/ttf/tables/post.js

Converts SVG font to TTF font

'use strict'

// See documentation here: http://www.microsoft.com/typography/otspec/post.htm

var _ = require('lodash')
var ByteBuffer = require('microbuffer')

function tableSize (font, names) {
  var result = 36 // table header

  result += font.glyphs.length * 2 // name declarations
  _.forEach(names, function (name) {
    result += name.length
  })
  return result
}

function pascalString (str) {
  var bytes = []
  var len = str ? (str.length < 256 ? str.length : 255) : 0 // length in Pascal string is limited with 255

  bytes.push(len)
  for (var i = 0; i < len; i++) {
    var char = str.charCodeAt(i)

    bytes.push(char < 128 ? char : 95) // non-ASCII characters are substituted with '_'
  }
  return bytes
}

function createPostTable (font) {
  var names = []

  _.forEach(font.glyphs, function (glyph) {
    if (glyph.unicode !== 0) {
      names.push(pascalString(glyph.name))
    }
  })

  var buf = new ByteBuffer(tableSize(font, names))

  buf.writeInt32(0x20000) // formatType,  version 2.0
  buf.writeInt32(font.italicAngle) // italicAngle
  buf.writeInt16(font.underlinePosition) // underlinePosition
  buf.writeInt16(font.underlineThickness) // underlineThickness
  buf.writeUint32(font.isFixedPitch) // isFixedPitch
  buf.writeUint32(0) // minMemType42
  buf.writeUint32(0) // maxMemType42
  buf.writeUint32(0) // minMemType1
  buf.writeUint32(0) // maxMemType1
  buf.writeUint16(font.glyphs.length) // numberOfGlyphs

  // Array of glyph name indexes
  var index = 258 // first index of custom glyph name, it is calculated as glyph name index + 258

  _.forEach(font.glyphs, function (glyph) {
    if (glyph.unicode === 0) {
      buf.writeUint16(0)// missed element should have .notDef name in the Macintosh standard order.
    } else {
      buf.writeUint16(index++)
    }
  })

  // Array of glyph name indexes
  _.forEach(names, function (name) {
    buf.writeBytes(name)
  })

  return buf
}

module.exports = createPostTable