pdfjs-dist/src/display/font_loader.js

/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
/* Copyright 2012 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/* globals PDFJS, shadow, isWorker, assert, warn, FontRendererFactory,
           bytesToString, globalScope */

'use strict';

PDFJS.disableFontFace = false;

var FontLoader = {
  insertRule: function fontLoaderInsertRule(rule) {
    var styleElement = document.getElementById('PDFJS_FONT_STYLE_TAG');
    if (!styleElement) {
        styleElement = document.createElement('style');
        styleElement.id = 'PDFJS_FONT_STYLE_TAG';
        document.documentElement.getElementsByTagName('head')[0].appendChild(
          styleElement);
    }

    var styleSheet = styleElement.sheet;
    styleSheet.insertRule(rule, styleSheet.cssRules.length);
  },
//#if !(MOZCENTRAL)
  get loadTestFont() {
    // This is a CFF font with 1 glyph for '.' that fills its entire width and
    // height.
    return shadow(this, 'loadTestFont', atob(
      'T1RUTwALAIAAAwAwQ0ZGIDHtZg4AAAOYAAAAgUZGVE1lkzZwAAAEHAAAABxHREVGABQAFQ' +
      'AABDgAAAAeT1MvMlYNYwkAAAEgAAAAYGNtYXABDQLUAAACNAAAAUJoZWFk/xVFDQAAALwA' +
      'AAA2aGhlYQdkA+oAAAD0AAAAJGhtdHgD6AAAAAAEWAAAAAZtYXhwAAJQAAAAARgAAAAGbm' +
      'FtZVjmdH4AAAGAAAAAsXBvc3T/hgAzAAADeAAAACAAAQAAAAEAALZRFsRfDzz1AAsD6AAA' +
      'AADOBOTLAAAAAM4KHDwAAAAAA+gDIQAAAAgAAgAAAAAAAAABAAADIQAAAFoD6AAAAAAD6A' +
      'ABAAAAAAAAAAAAAAAAAAAAAQAAUAAAAgAAAAQD6AH0AAUAAAKKArwAAACMAooCvAAAAeAA' +
      'MQECAAACAAYJAAAAAAAAAAAAAQAAAAAAAAAAAAAAAFBmRWQAwAAuAC4DIP84AFoDIQAAAA' +
      'AAAQAAAAAAAAAAACAAIAABAAAADgCuAAEAAAAAAAAAAQAAAAEAAAAAAAEAAQAAAAEAAAAA' +
      'AAIAAQAAAAEAAAAAAAMAAQAAAAEAAAAAAAQAAQAAAAEAAAAAAAUAAQAAAAEAAAAAAAYAAQ' +
      'AAAAMAAQQJAAAAAgABAAMAAQQJAAEAAgABAAMAAQQJAAIAAgABAAMAAQQJAAMAAgABAAMA' +
      'AQQJAAQAAgABAAMAAQQJAAUAAgABAAMAAQQJAAYAAgABWABYAAAAAAAAAwAAAAMAAAAcAA' +
      'EAAAAAADwAAwABAAAAHAAEACAAAAAEAAQAAQAAAC7//wAAAC7////TAAEAAAAAAAABBgAA' +
      'AQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAEAAAAAAA' +
      'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA' +
      'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA' +
      'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA' +
      'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAMAAA' +
      'AAAAD/gwAyAAAAAQAAAAAAAAAAAAAAAAAAAAABAAQEAAEBAQJYAAEBASH4DwD4GwHEAvgc' +
      'A/gXBIwMAYuL+nz5tQXkD5j3CBLnEQACAQEBIVhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWF' +
      'hYWFhYWFhYAAABAQAADwACAQEEE/t3Dov6fAH6fAT+fPp8+nwHDosMCvm1Cvm1DAz6fBQA' +
      'AAAAAAABAAAAAMmJbzEAAAAAzgTjFQAAAADOBOQpAAEAAAAAAAAADAAUAAQAAAABAAAAAg' +
      'ABAAAAAAAAAAAD6AAAAAAAAA=='
    ));
  },

  loadTestFontId: 0,

  loadingContext: {
    requests: [],
    nextRequestId: 0
  },

  isSyncFontLoadingSupported: (function detectSyncFontLoadingSupport() {
    if (isWorker)
      return false;

    // User agent string sniffing is bad, but there is no reliable way to tell
    // if font is fully loaded and ready to be used with canvas.
    var userAgent = window.navigator.userAgent;
    var m = /Mozilla\/5.0.*?rv:(\d+).*? Gecko/.exec(userAgent);
    if (m && m[1] >= 14)
      return true;
    // TODO other browsers
    return false;
  })(),

  bind: function fontLoaderBind(fonts, callback) {
    assert(!isWorker, 'bind() shall be called from main thread');

    var rules = [], fontsToLoad = [];
    for (var i = 0, ii = fonts.length; i < ii; i++) {
      var font = fonts[i];

      // Add the font to the DOM only once or skip if the font
      // is already loaded.
      if (font.attached || font.loading === false) {
        continue;
      }
      font.attached = true;

      var rule = font.bindDOM();
      if (rule) {
        rules.push(rule);
        fontsToLoad.push(font);
      }
    }

    var request = FontLoader.queueLoadingCallback(callback);
    if (rules.length > 0 && !this.isSyncFontLoadingSupported) {
      FontLoader.prepareFontLoadEvent(rules, fontsToLoad, request);
    } else {
      request.complete();
    }
  },

  queueLoadingCallback: function FontLoader_queueLoadingCallback(callback) {
    function LoadLoader_completeRequest() {
      assert(!request.end, 'completeRequest() cannot be called twice');
      request.end = Date.now();

      // sending all completed requests in order how they were queued
      while (context.requests.length > 0 && context.requests[0].end) {
        var otherRequest = context.requests.shift();
        setTimeout(otherRequest.callback, 0);
      }
    }

    var context = FontLoader.loadingContext;
    var requestId = 'pdfjs-font-loading-' + (context.nextRequestId++);
    var request = {
      id: requestId,
      complete: LoadLoader_completeRequest,
      callback: callback,
      started: Date.now()
    };
    context.requests.push(request);
    return request;
  },

  prepareFontLoadEvent: function fontLoaderPrepareFontLoadEvent(rules,
                                                                fonts,
                                                                request) {
      /** Hack begin */
      // There's currently no event when a font has finished downloading so the
      // following code is a dirty hack to 'guess' when a font is
      // ready. It's assumed fonts are loaded in order, so add a known test
      // font after the desired fonts and then test for the loading of that
      // test font.

      function int32(data, offset) {
        return (data.charCodeAt(offset) << 24) |
               (data.charCodeAt(offset + 1) << 16) |
               (data.charCodeAt(offset + 2) << 8) |
               (data.charCodeAt(offset + 3) & 0xff);
      }

      function string32(value) {
        return String.fromCharCode((value >> 24) & 0xff) +
               String.fromCharCode((value >> 16) & 0xff) +
               String.fromCharCode((value >> 8) & 0xff) +
               String.fromCharCode(value & 0xff);
      }

      function spliceString(s, offset, remove, insert) {
        var chunk1 = data.substr(0, offset);
        var chunk2 = data.substr(offset + remove);
        return chunk1 + insert + chunk2;
      }

      var i, ii;

      var canvas = document.createElement('canvas');
      canvas.width = 1;
      canvas.height = 1;
      var ctx = canvas.getContext('2d');

      var called = 0;
      function isFontReady(name, callback) {
        called++;
        // With setTimeout clamping this gives the font ~100ms to load.
        if(called > 30) {
          warn('Load test font never loaded.');
          callback();
          return;
        }
        ctx.font = '30px ' + name;
        ctx.fillText('.', 0, 20);
        var imageData = ctx.getImageData(0, 0, 1, 1);
        if (imageData.data[3] > 0) {
          callback();
          return;
        }
        setTimeout(isFontReady.bind(null, name, callback));
      }

      var loadTestFontId = 'lt' + Date.now() + this.loadTestFontId++;
      // Chromium seems to cache fonts based on a hash of the actual font data,
      // so the font must be modified for each load test else it will appear to
      // be loaded already.
      // TODO: This could maybe be made faster by avoiding the btoa of the full
      // font by splitting it in chunks before hand and padding the font id.
      var data = this.loadTestFont;
      var COMMENT_OFFSET = 976; // has to be on 4 byte boundary (for checksum)
      data = spliceString(data, COMMENT_OFFSET, loadTestFontId.length,
                          loadTestFontId);
      // CFF checksum is important for IE, adjusting it
      var CFF_CHECKSUM_OFFSET = 16;
      var XXXX_VALUE = 0x58585858; // the "comment" filled with 'X'
      var checksum = int32(data, CFF_CHECKSUM_OFFSET);
      for (i = 0, ii = loadTestFontId.length - 3; i < ii; i += 4) {
        checksum = (checksum - XXXX_VALUE + int32(loadTestFontId, i)) | 0;
      }
      if (i < loadTestFontId.length) { // align to 4 bytes boundary
        checksum = (checksum - XXXX_VALUE +
                    int32(loadTestFontId + 'XXX', i)) | 0;
      }
      data = spliceString(data, CFF_CHECKSUM_OFFSET, 4, string32(checksum));

      var url = 'url(data:font/opentype;base64,' + btoa(data) + ');';
      var rule = '@font-face { font-family:"' + loadTestFontId + '";src:' +
                 url + '}';
      FontLoader.insertRule(rule);

      var names = [];
      for (i = 0, ii = fonts.length; i < ii; i++) {
        names.push(fonts[i].loadedName);
      }
      names.push(loadTestFontId);

      var div = document.createElement('div');
      div.setAttribute('style',
                       'visibility: hidden;' +
                       'width: 10px; height: 10px;' +
                       'position: absolute; top: 0px; left: 0px;');
      for (i = 0, ii = names.length; i < ii; ++i) {
        var span = document.createElement('span');
        span.textContent = 'Hi';
        span.style.fontFamily = names[i];
        div.appendChild(span);
      }
      document.body.appendChild(div);

      isFontReady(loadTestFontId, function() {
        document.body.removeChild(div);
        request.complete();
      });
      /** Hack end */
  }
//#else
//bind: function fontLoaderBind(fonts, callback) {
//  assert(!isWorker, 'bind() shall be called from main thread');
//
//  for (var i = 0, ii = fonts.length; i < ii; i++) {
//    var font = fonts[i];
//    if (font.attached)
//      continue;
//
//    font.attached = true;
//    font.bindDOM()
//  }
//
//  setTimeout(callback);
//}
//#endif
};

var FontFace = (function FontFaceClosure() {
  function FontFace(name, file, properties) {
    if (arguments.length === 1) {
      // importing translated data
      var data = arguments[0];
      for (var i in data) {
        this[i] = data[i];
      }
      return;
    }
  }
  FontFace.prototype = {
    get renderer() {
      var renderer = FontRendererFactory.create(this);
      return shadow(this, 'renderer', renderer);
    },
    bindDOM: function FontFace_bindDOM() {
      if (!this.data)
        return null;

      if (PDFJS.disableFontFace) {
        this.disableFontFace = true;
        return null;
      }

      var data = bytesToString(this.data);
      var fontName = this.loadedName;

      // Add the font-face rule to the document
      var url = ('url(data:' + this.mimetype + ';base64,' +
                 window.btoa(data) + ');');
      var rule = '@font-face { font-family:"' + fontName + '";src:' + url + '}';

      FontLoader.insertRule(rule);

      if (PDFJS.pdfBug && 'FontInspector' in globalScope &&
          globalScope['FontInspector'].enabled)
        globalScope['FontInspector'].fontAdded(this, url);

      return rule;
    }
  };
  return FontFace;
})();