opentype.js

// opentype.js
// https://github.com/nodebox/opentype.js
// (c) 2015 Frederik De Bleser
// opentype.js may be freely distributed under the MIT license.

/* global DataView, Uint8Array, XMLHttpRequest  */

import inflate from 'tiny-inflate';
import Font from './font';
import Glyph from './glyph';
import { CmapEncoding, GlyphNames, addGlyphNames } from './encoding';
import parse from './parse';
import BoundingBox from './bbox';
import Path from './path';
import { nodeBufferToArrayBuffer } from './util';
import cmap from './tables/cmap';
import cff from './tables/cff';
import fvar from './tables/fvar';
import glyf from './tables/glyf';
import gpos from './tables/gpos';
import gsub from './tables/gsub';
import head from './tables/head';
import hhea from './tables/hhea';
import hmtx from './tables/hmtx';
import kern from './tables/kern';
import ltag from './tables/ltag';
import loca from './tables/loca';
import maxp from './tables/maxp';
import _name from './tables/name';
import os2 from './tables/os2';
import post from './tables/post';
import meta from './tables/meta';

/**
 * The opentype library.
 * @namespace opentype
 */

// File loaders /////////////////////////////////////////////////////////
/**
 * Loads a font from a file. The callback throws an error message as the first parameter if it fails
 * and the font as an ArrayBuffer in the second parameter if it succeeds.
 * @param  {string} path - The path of the file
 * @param  {Function} callback - The function to call when the font load completes
 */
function loadFromFile(path, callback) {
    var fs = require('fs');
    fs.readFile(path, function(err, buffer) {
        if (err) {
            return callback(err.message);
        }

        callback(null, nodeBufferToArrayBuffer(buffer));
    });
}
/**
 * Loads a font from a URL. The callback throws an error message as the first parameter if it fails
 * and the font as an ArrayBuffer in the second parameter if it succeeds.
 * @param  {string} url - The URL of the font file.
 * @param  {Function} callback - The function to call when the font load completes
 */
function loadFromUrl(url, callback) {
    var request = new XMLHttpRequest();
    request.open('get', url, true);
    request.responseType = 'arraybuffer';
    request.onload = function() {
        if (request.status !== 200) {
            return callback('Font could not be loaded: ' + request.statusText);
        }

        return callback(null, request.response);
    };

    request.onerror = function () {
        callback('Font could not be loaded');
    };

    request.send();
}

// Table Directory Entries //////////////////////////////////////////////
/**
 * Parses OpenType table entries.
 * @param  {DataView}
 * @param  {Number}
 * @return {Object[]}
 */
function parseOpenTypeTableEntries(data, numTables) {
    var tableEntries = [];
    var p = 12;
    for (var i = 0; i < numTables; i += 1) {
        var tag = parse.getTag(data, p);
        var checksum = parse.getULong(data, p + 4);
        var offset = parse.getULong(data, p + 8);
        var length = parse.getULong(data, p + 12);
        tableEntries.push({tag: tag, checksum: checksum, offset: offset, length: length, compression: false});
        p += 16;
    }

    return tableEntries;
}

/**
 * Parses WOFF table entries.
 * @param  {DataView}
 * @param  {Number}
 * @return {Object[]}
 */
function parseWOFFTableEntries(data, numTables) {
    var tableEntries = [];
    var p = 44; // offset to the first table directory entry.
    for (var i = 0; i < numTables; i += 1) {
        var tag = parse.getTag(data, p);
        var offset = parse.getULong(data, p + 4);
        var compLength = parse.getULong(data, p + 8);
        var origLength = parse.getULong(data, p + 12);
        var compression;
        if (compLength < origLength) {
            compression = 'WOFF';
        } else {
            compression = false;
        }

        tableEntries.push({tag: tag, offset: offset, compression: compression,
            compressedLength: compLength, originalLength: origLength});
        p += 20;
    }

    return tableEntries;
}

/**
 * @typedef TableData
 * @type Object
 * @property {DataView} data - The DataView
 * @property {number} offset - The data offset.
 */

/**
 * @param  {DataView}
 * @param  {Object}
 * @return {TableData}
 */
function uncompressTable(data, tableEntry) {
    if (tableEntry.compression === 'WOFF') {
        var inBuffer = new Uint8Array(data.buffer, tableEntry.offset + 2, tableEntry.compressedLength - 2);
        var outBuffer = new Uint8Array(tableEntry.originalLength);
        inflate(inBuffer, outBuffer);
        if (outBuffer.byteLength !== tableEntry.originalLength) {
            throw new Error('Decompression error: ' + tableEntry.tag + ' decompressed length doesn\'t match recorded length');
        }

        var view = new DataView(outBuffer.buffer, 0);
        return {data: view, offset: 0};
    } else {
        return {data: data, offset: tableEntry.offset};
    }
}

// Public API ///////////////////////////////////////////////////////////

/**
 * Parse the OpenType file data (as an ArrayBuffer) and return a Font object.
 * Throws an error if the font could not be parsed.
 * @param  {ArrayBuffer}
 * @return {opentype.Font}
 */
function parseBuffer(buffer) {
    var indexToLocFormat;
    var ltagTable;

    // Since the constructor can also be called to create new fonts from scratch, we indicate this
    // should be an empty font that we'll fill with our own data.
    var font = new Font({empty: true});

    // OpenType fonts use big endian byte ordering.
    // We can't rely on typed array view types, because they operate with the endianness of the host computer.
    // Instead we use DataViews where we can specify endianness.
    var data = new DataView(buffer, 0);
    var numTables;
    var tableEntries = [];
    var signature = parse.getTag(data, 0);
    if (signature === String.fromCharCode(0, 1, 0, 0) || signature === 'true' || signature === 'typ1') {
        font.outlinesFormat = 'truetype';
        numTables = parse.getUShort(data, 4);
        tableEntries = parseOpenTypeTableEntries(data, numTables);
    } else if (signature === 'OTTO') {
        font.outlinesFormat = 'cff';
        numTables = parse.getUShort(data, 4);
        tableEntries = parseOpenTypeTableEntries(data, numTables);
    } else if (signature === 'wOFF') {
        var flavor = parse.getTag(data, 4);
        if (flavor === String.fromCharCode(0, 1, 0, 0)) {
            font.outlinesFormat = 'truetype';
        } else if (flavor === 'OTTO') {
            font.outlinesFormat = 'cff';
        } else {
            throw new Error('Unsupported OpenType flavor ' + signature);
        }

        numTables = parse.getUShort(data, 12);
        tableEntries = parseWOFFTableEntries(data, numTables);
    } else {
        throw new Error('Unsupported OpenType signature ' + signature);
    }

    var cffTableEntry;
    var fvarTableEntry;
    var glyfTableEntry;
    var gposTableEntry;
    var gsubTableEntry;
    var hmtxTableEntry;
    var kernTableEntry;
    var locaTableEntry;
    var nameTableEntry;
    var metaTableEntry;
    var p;

    for (var i = 0; i < numTables; i += 1) {
        var tableEntry = tableEntries[i];
        var table;
        switch (tableEntry.tag) {
            case 'cmap':
                table = uncompressTable(data, tableEntry);
                font.tables.cmap = cmap.parse(table.data, table.offset);
                font.encoding = new CmapEncoding(font.tables.cmap);
                break;
            case 'cvt ' :
                table = uncompressTable(data, tableEntry);
                p = new parse.Parser(table.data, table.offset);
                font.tables.cvt = p.parseShortList(tableEntry.length / 2);
                break;
            case 'fvar':
                fvarTableEntry = tableEntry;
                break;
            case 'fpgm' :
                table = uncompressTable(data, tableEntry);
                p = new parse.Parser(table.data, table.offset);
                font.tables.fpgm = p.parseByteList(tableEntry.length);
                break;
            case 'head':
                table = uncompressTable(data, tableEntry);
                font.tables.head = head.parse(table.data, table.offset);
                font.unitsPerEm = font.tables.head.unitsPerEm;
                indexToLocFormat = font.tables.head.indexToLocFormat;
                break;
            case 'hhea':
                table = uncompressTable(data, tableEntry);
                font.tables.hhea = hhea.parse(table.data, table.offset);
                font.ascender = font.tables.hhea.ascender;
                font.descender = font.tables.hhea.descender;
                font.numberOfHMetrics = font.tables.hhea.numberOfHMetrics;
                break;
            case 'hmtx':
                hmtxTableEntry = tableEntry;
                break;
            case 'ltag':
                table = uncompressTable(data, tableEntry);
                ltagTable = ltag.parse(table.data, table.offset);
                break;
            case 'maxp':
                table = uncompressTable(data, tableEntry);
                font.tables.maxp = maxp.parse(table.data, table.offset);
                font.numGlyphs = font.tables.maxp.numGlyphs;
                break;
            case 'name':
                nameTableEntry = tableEntry;
                break;
            case 'OS/2':
                table = uncompressTable(data, tableEntry);
                font.tables.os2 = os2.parse(table.data, table.offset);
                break;
            case 'post':
                table = uncompressTable(data, tableEntry);
                font.tables.post = post.parse(table.data, table.offset);
                font.glyphNames = new GlyphNames(font.tables.post);
                break;
            case 'prep' :
                table = uncompressTable(data, tableEntry);
                p = new parse.Parser(table.data, table.offset);
                font.tables.prep = p.parseByteList(tableEntry.length);
                break;
            case 'glyf':
                glyfTableEntry = tableEntry;
                break;
            case 'loca':
                locaTableEntry = tableEntry;
                break;
            case 'CFF ':
                cffTableEntry = tableEntry;
                break;
            case 'kern':
                kernTableEntry = tableEntry;
                break;
            case 'GPOS':
                gposTableEntry = tableEntry;
                break;
            case 'GSUB':
                gsubTableEntry = tableEntry;
                break;
            case 'meta':
                metaTableEntry = tableEntry;
                break;
        }
    }

    var nameTable = uncompressTable(data, nameTableEntry);
    font.tables.name = _name.parse(nameTable.data, nameTable.offset, ltagTable);
    font.names = font.tables.name;

    if (glyfTableEntry && locaTableEntry) {
        var shortVersion = indexToLocFormat === 0;
        var locaTable = uncompressTable(data, locaTableEntry);
        var locaOffsets = loca.parse(locaTable.data, locaTable.offset, font.numGlyphs, shortVersion);
        var glyfTable = uncompressTable(data, glyfTableEntry);
        font.glyphs = glyf.parse(glyfTable.data, glyfTable.offset, locaOffsets, font);
    } else if (cffTableEntry) {
        var cffTable = uncompressTable(data, cffTableEntry);
        cff.parse(cffTable.data, cffTable.offset, font);
    } else {
        throw new Error('Font doesn\'t contain TrueType or CFF outlines.');
    }

    var hmtxTable = uncompressTable(data, hmtxTableEntry);
    hmtx.parse(hmtxTable.data, hmtxTable.offset, font.numberOfHMetrics, font.numGlyphs, font.glyphs);
    addGlyphNames(font);

    if (kernTableEntry) {
        var kernTable = uncompressTable(data, kernTableEntry);
        font.kerningPairs = kern.parse(kernTable.data, kernTable.offset);
    } else {
        font.kerningPairs = {};
    }

    if (gposTableEntry) {
        var gposTable = uncompressTable(data, gposTableEntry);
        gpos.parse(gposTable.data, gposTable.offset, font);
    }

    if (gsubTableEntry) {
        var gsubTable = uncompressTable(data, gsubTableEntry);
        font.tables.gsub = gsub.parse(gsubTable.data, gsubTable.offset);
    }

    if (fvarTableEntry) {
        var fvarTable = uncompressTable(data, fvarTableEntry);
        font.tables.fvar = fvar.parse(fvarTable.data, fvarTable.offset, font.names);
    }

    if (metaTableEntry) {
        var metaTable = uncompressTable(data, metaTableEntry);
        font.tables.meta = meta.parse(metaTable.data, metaTable.offset);
        font.metas = font.tables.meta;
    }

    return font;
}

/**
 * Asynchronously load the font from a URL or a filesystem. When done, call the callback
 * with two arguments `(err, font)`. The `err` will be null on success,
 * the `font` is a Font object.
 * We use the node.js callback convention so that
 * opentype.js can integrate with frameworks like async.js.
 * @alias opentype.load
 * @param  {string} url - The URL of the font to load.
 * @param  {Function} callback - The callback.
 */
function load(url, callback) {
    var isNode = typeof window === 'undefined';
    var loadFn = isNode ? loadFromFile : loadFromUrl;
    loadFn(url, function(err, arrayBuffer) {
        if (err) {
            return callback(err);
        }
        var font;
        try {
            font = parseBuffer(arrayBuffer);
        } catch (e) {
            return callback(e, null);
        }
        return callback(null, font);
    });
}

/**
 * Synchronously load the font from a URL or file.
 * When done, returns the font object or throws an error.
 * @alias opentype.loadSync
 * @param  {string} url - The URL of the font to load.
 * @return {opentype.Font}
 */
function loadSync(url) {
    var fs = require('fs');
    var buffer = fs.readFileSync(url);
    return parseBuffer(nodeBufferToArrayBuffer(buffer));
}

export {
    Font,
    Glyph,
    Path,
    BoundingBox,
    parse as _parse,
    parseBuffer as parse,
    load,
    loadSync
};