[api-minor] Use a local font or fallback on an embedded one (if it exists) for non-embedded fonts (bug 1766039)

- Replace FoxitSans with LiberationSans: LiberationSans is already there (for XFA) and we can use
it as a good replacement of FoxitSans.
- For now we just try to substitue standard fonts, the strategy is the following:
  * we try to find a font locally from a hardcoded list;
  * if it fails then we use Liberation as fallback (only for Helvetica for the moment);
  * else we just fallback on the system serif/sansserif/monospace font.

src/core/core_utils.js

@@ -423,6 +423,31 @@ function encodeToXmlString(str) {
   return buffer.join("");
 }
 
+function validateFontName(fontFamily, mustWarn = false) {
+  // See https://developer.mozilla.org/en-US/docs/Web/CSS/string.
+  const m = /^("|').*("|')$/.exec(fontFamily);
+  if (m && m[1] === m[2]) {
+    const re = new RegExp(`[^\\\\]${m[1]}`);
+    if (re.test(fontFamily.slice(1, -1))) {
+      if (mustWarn) {
+        warn(`FontFamily contains unescaped ${m[1]}: ${fontFamily}.`);
+      }
+      return false;
+    }
+  } else {
+    // See https://developer.mozilla.org/en-US/docs/Web/CSS/custom-ident.
+    for (const ident of fontFamily.split(/[ \t]+/)) {
+      if (/^(\d|(-(\d|-)))/.test(ident) || !/^[\w-\\]+$/.test(ident)) {
+        if (mustWarn) {
+          warn(`FontFamily contains invalid <custom-ident>: ${fontFamily}.`);
+        }
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
 function validateCSSFont(cssFontInfo) {
   // See https://developer.mozilla.org/en-US/docs/Web/CSS/font-style.
   const DEFAULT_CSS_FONT_OBLIQUE = "14";
@@ -447,25 +472,9 @@ function validateCSSFont(cssFontInfo) {
 
   const { fontFamily, fontWeight, italicAngle } = cssFontInfo;
 
-  // See https://developer.mozilla.org/en-US/docs/Web/CSS/string.
+  if (!validateFontName(fontFamily, true)) {
-  const m = /^("|').*("|')$/.exec(fontFamily);
-  if (m && m[1] === m[2]) {
-    const re = new RegExp(`[^\\\\]${m[1]}`);
-    if (re.test(fontFamily.slice(1, -1))) {
-      warn(`XFA - FontFamily contains unescaped ${m[1]}: ${fontFamily}.`);
     return false;
   }
-  } else {
-    // See https://developer.mozilla.org/en-US/docs/Web/CSS/custom-ident.
-    for (const ident of fontFamily.split(/[ \t]+/)) {
-      if (/^(\d|(-(\d|-)))/.test(ident) || !/^[\w-\\]+$/.test(ident)) {
-        warn(
-          `XFA - FontFamily contains invalid <custom-ident>: ${fontFamily}.`
-        );
-        return false;
-      }
-    }
-  }
 
   const weight = fontWeight ? fontWeight.toString() : "";
   cssFontInfo.fontWeight = CSS_FONT_WEIGHT_VALUES.has(weight)
@@ -617,6 +626,7 @@ export {
   stringToUTF16String,
   toRomanNumerals,
   validateCSSFont,
+  validateFontName,
   XRefEntryException,
   XRefParseException,
 };

src/core/evaluator.js

@@ -68,6 +68,7 @@ import { bidi } from "./bidi.js";
 import { ColorSpace } from "./colorspace.js";
 import { DecodeStream } from "./decode_stream.js";
 import { FontFlags } from "./fonts_utils.js";
+import { getFontSubstitution } from "./font_substitutions.js";
 import { getGlyphsUnicode } from "./glyphlist.js";
 import { getLookupTableFactory } from "./core_utils.js";
 import { getMetrics } from "./metrics.js";
@@ -4174,6 +4175,7 @@ class PartialEvaluator {
           type,
           name: baseFontName,
           loadedName: baseDict.loadedName,
+          systemFontInfo: null,
           widths: metrics.widths,
           defaultWidth: metrics.defaultWidth,
           isSimulatedFlags: true,
@@ -4193,6 +4195,14 @@ class PartialEvaluator {
         if (standardFontName) {
           file = await this.fetchStandardFontData(standardFontName);
           properties.isInternalFont = !!file;
+          if (!properties.isInternalFont && this.options.useSystemFonts) {
+            properties.systemFontInfo = getFontSubstitution(
+              this.idFactory,
+              this.options.standardFontDataUrl,
+              baseFontName,
+              standardFontName
+            );
+          }
         }
         return this.extractDataStructures(dict, dict, properties).then(
           newProperties => {
@@ -4264,6 +4274,7 @@ class PartialEvaluator {
     }
     let isInternalFont = false;
     let glyphScaleFactors = null;
+    let systemFontInfo = null;
     if (fontFile) {
       if (fontFile.dict) {
         const subtypeEntry = fontFile.dict.get("Subtype");
@@ -4296,6 +4307,14 @@ class PartialEvaluator {
       if (standardFontName) {
         fontFile = await this.fetchStandardFontData(standardFontName);
         isInternalFont = !!fontFile;
+        if (!isInternalFont && this.options.useSystemFonts) {
+          systemFontInfo = getFontSubstitution(
+            this.idFactory,
+            this.options.standardFontDataUrl,
+            fontName.name,
+            standardFontName
+          );
+        }
       }
     }
 
@@ -4325,6 +4344,7 @@ class PartialEvaluator {
       isType3Font,
       cssFontInfo,
       scaleFactors: glyphScaleFactors,
+      systemFontInfo,
     };
 
     if (composite) {

src/core/font_substitutions.js

@@ -0,0 +1,478 @@
+/* Copyright 2023 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.
+ */
+
+import { normalizeFontName } from "./fonts_utils.js";
+import { validateFontName } from "./core_utils.js";
+
+const NORMAL = {
+  style: "normal",
+  weight: "normal",
+};
+const BOLD = {
+  style: "normal",
+  weight: "bold",
+};
+const ITALIC = {
+  style: "italic",
+  weight: "normal",
+};
+const BOLDITALIC = {
+  style: "italic",
+  weight: "bold",
+};
+
+const substitutionMap = new Map([
+  [
+    "Times-Roman",
+    {
+      local: [
+        "Times New Roman",
+        "Times-Roman",
+        "Times",
+        "Liberation Serif",
+        "Nimbus Roman",
+        "Nimbus Roman L",
+        "Tinos",
+        "Thorndale",
+        "TeX Gyre Termes",
+        "FreeSerif",
+        "DejaVu Serif",
+        "Bitstream Vera Serif",
+        "Ubuntu",
+      ],
+      style: NORMAL,
+      ultimate: "serif",
+    },
+  ],
+  [
+    "Times-Bold",
+    {
+      local: {
+        alias: "Times-Roman",
+        append: "Bold",
+      },
+      style: BOLD,
+      ultimate: "serif",
+    },
+  ],
+  [
+    "Times-Italic",
+    {
+      local: {
+        alias: "Times-Roman",
+        append: "Italic",
+      },
+      style: ITALIC,
+      ultimate: "serif",
+    },
+  ],
+  [
+    "Times-BoldItalic",
+    {
+      local: {
+        alias: "Times-Roman",
+        append: "Bold Italic",
+      },
+      style: BOLDITALIC,
+      ultimate: "serif",
+    },
+  ],
+  [
+    "Helvetica",
+    {
+      local: [
+        "Helvetica",
+        "Helvetica Neue",
+        "Arial",
+        "Arial Nova",
+        "Liberation Sans",
+        "Arimo",
+        "Nimbus Sans",
+        "Nimbus Sans L",
+        "A030",
+        "TeX Gyre Heros",
+        "FreeSans",
+        "DejaVu Sans",
+        "Albany",
+        "Bitstream Vera Sans",
+        "Arial Unicode MS",
+        "Microsoft Sans Serif",
+        "Apple Symbols",
+        "Cantarell",
+      ],
+      path: "LiberationSans-Regular.ttf",
+      style: NORMAL,
+      ultimate: "sans-serif",
+    },
+  ],
+  [
+    "Helvetica-Bold",
+    {
+      local: {
+        alias: "Helvetica",
+        append: "Bold",
+      },
+      path: "LiberationSans-Bold.ttf",
+      style: BOLD,
+      ultimate: "sans-serif",
+    },
+  ],
+  [
+    "Helvetica-Oblique",
+    {
+      local: {
+        alias: "Helvetica",
+        append: "Italic",
+      },
+      path: "LiberationSans-Italic.ttf",
+      style: ITALIC,
+      ultimate: "sans-serif",
+    },
+  ],
+  [
+    "Helvetica-BoldOblique",
+    {
+      local: {
+        alias: "Helvetica",
+        append: "Bold Italic",
+      },
+      path: "LiberationSans-BoldItalic.ttf",
+      style: BOLDITALIC,
+      ultimate: "sans-serif",
+    },
+  ],
+  [
+    "Courier",
+    {
+      local: [
+        "Courier",
+        "Courier New",
+        "Liberation Mono",
+        "Nimbus Mono",
+        "Nimbus Mono L",
+        "Cousine",
+        "Cumberland",
+        "TeX Gyre Cursor",
+        "FreeMono",
+      ],
+      style: NORMAL,
+      ultimate: "monospace",
+    },
+  ],
+  [
+    "Courier-Bold",
+    {
+      local: {
+        alias: "Courier",
+        append: "Bold",
+      },
+      style: BOLD,
+      ultimate: "monospace",
+    },
+  ],
+  [
+    "Courier-Oblique",
+    {
+      local: {
+        alias: "Courier",
+        append: "Italic",
+      },
+      style: ITALIC,
+      ultimate: "monospace",
+    },
+  ],
+  [
+    "Courier-BoldOblique",
+    {
+      local: {
+        alias: "Courier",
+        append: "Bold Italic",
+      },
+      style: BOLDITALIC,
+      ultimate: "monospace",
+    },
+  ],
+  [
+    "ArialBlack",
+    {
+      prepend: ["Arial Black"],
+      style: {
+        style: "normal",
+        weight: "900",
+      },
+      fallback: "Helvetica-Bold",
+    },
+  ],
+  [
+    "ArialBlack-Bold",
+    {
+      alias: "ArialBlack",
+    },
+  ],
+  [
+    "ArialBlack-Italic",
+    {
+      prepend: ["Arial Black Italic"],
+      local: {
+        alias: "ArialBlack",
+        append: "Italic",
+      },
+      style: {
+        style: "italic",
+        weight: "900",
+      },
+      fallback: "Helvetica-BoldOblique",
+    },
+  ],
+  [
+    "ArialBlack-BoldItalic",
+    {
+      alias: "ArialBlack-Italic",
+    },
+  ],
+  [
+    "ArialNarrow",
+    {
+      prepend: [
+        "Arial Narrow",
+        "Liberation Sans Narrow",
+        "Helvetica Condensed",
+        "Nimbus Sans Narrow",
+        "TeX Gyre Heros Cn",
+      ],
+      style: NORMAL,
+      fallback: "Helvetica",
+    },
+  ],
+  [
+    "ArialNarrow-Bold",
+    {
+      local: {
+        alias: "ArialNarrow",
+        append: "Bold",
+      },
+      style: BOLD,
+      fallback: "Helvetica-Bold",
+    },
+  ],
+  [
+    "ArialNarrow-Italic",
+    {
+      local: {
+        alias: "ArialNarrow",
+        append: "Italic",
+      },
+      style: ITALIC,
+      fallback: "Helvetica-Oblique",
+    },
+  ],
+  [
+    "ArialNarrow-BoldItalic",
+    {
+      local: {
+        alias: "ArialNarrow",
+        append: "Bold Italic",
+      },
+      style: BOLDITALIC,
+      fallback: "Helvetica-BoldOblique",
+    },
+  ],
+  [
+    "Calibri",
+    {
+      prepend: ["Calibri", "Carlito"],
+      style: NORMAL,
+      fallback: "Helvetica",
+    },
+  ],
+  [
+    "Calibri-Bold",
+    {
+      local: {
+        alias: "Calibri",
+        append: "Bold",
+      },
+      style: BOLD,
+      fallback: "Helvetica-Bold",
+    },
+  ],
+  [
+    "Calibri-Italic",
+    {
+      local: {
+        alias: "Calibri",
+        append: "Italic",
+      },
+      style: ITALIC,
+      fallback: "Helvetica-Oblique",
+    },
+  ],
+  [
+    "Calibri-BoldItalic",
+    {
+      local: {
+        alias: "Calibri",
+        append: "Bold Italic",
+      },
+      style: BOLDITALIC,
+      fallback: "Helvetica-BoldOblique",
+    },
+  ],
+]);
+
+const fontAliases = new Map([["Arial-Black", "ArialBlack"]]);
+
+/**
+ * Create the src path to use to load a font (see FontFace).
+ * @param {Array<String>} prepend A list of font names to search first.
+ * @param {Array<String>|Object} local A list of font names to search. If an
+ *   Object is passed, then local.alias is the name of an other substition font
+ *   and local.append is a String to append to the list of fonts in the alias.
+ *   For example if local.alias is "Foo" and local.append is "Bold" then the
+ *   list of fonts will be "FooSubst1 Bold", "FooSubst2 Bold", etc.
+ * @returns an String with the local fonts.
+ */
+function makeLocal(prepend, local) {
+  let append = "";
+  if (!Array.isArray(local)) {
+    // We are getting our list of fonts in the alias and we'll append Bold,
+    // Italic or both.
+    append = ` ${local.append}`;
+    local = substitutionMap.get(local.alias).local;
+  }
+  let prependedPaths = "";
+  if (prepend) {
+    prependedPaths = prepend.map(name => `local(${name})`).join(",") + ",";
+  }
+  return (
+    prependedPaths + local.map(name => `local(${name}${append})`).join(",")
+  );
+}
+
+/**
+ * Get a font substitution for a given font.
+ * The general idea is to have enough information to create a CSS rule like
+ * this:
+ *   @font-face {
+ *    font-family: 'Times';
+ *    src: local('Times New Roman'), local('Subst1'), local('Subst2'),
+ *         url(.../TimesNewRoman.ttf)
+ *    font-weight: normal;
+ *    font-style: normal;
+ *   }
+ * or use the FontFace API.
+ *
+ * @param {Object} idFactory The ids factory.
+ * @param {String} localFontPath Path to the fonts directory.
+ * @param {String} baseFontName The font name to be substituted.
+ * @param {String} standardFontName The standard font name to use if the base
+ *   font is not available.
+ * @returns an Object with the CSS, the loaded name, the src and the style.
+ */
+function getFontSubstitution(
+  idFactory,
+  localFontPath,
+  baseFontName,
+  standardFontName
+) {
+  let mustAddBaseFont = false;
+
+  // It's possible to have a font name with spaces, commas or dashes, hence we
+  // just replace them by a dash.
+  baseFontName = normalizeFontName(baseFontName);
+
+  // First, check if we've a substitution for the base font.
+  let substitution = substitutionMap.get(baseFontName);
+  if (!substitution) {
+    // Check if we've an alias for the base font, Arial-Black is the same as
+    // ArialBlack
+    for (const [alias, subst] of fontAliases) {
+      if (baseFontName.startsWith(alias)) {
+        baseFontName = `${subst}${baseFontName.substring(alias.length)}`;
+        substitution = substitutionMap.get(baseFontName);
+        break;
+      }
+    }
+  }
+
+  if (!substitution) {
+    // If not, check if we've a substitution for the standard font.
+    substitution = substitutionMap.get(standardFontName);
+    mustAddBaseFont = true;
+  }
+
+  const loadedName = `${idFactory.getDocId()}_sf_${idFactory.createFontId()}`;
+  if (!substitution) {
+    if (!validateFontName(baseFontName)) {
+      // If the baseFontName is not valid we don't want to use it.
+      return null;
+    }
+    // Maybe we'll be lucky and the OS will have the font.
+    const bold = /bold/gi.test(baseFontName);
+    const italic = /oblique|italic/gi.test(baseFontName);
+    const style =
+      (bold && italic && BOLDITALIC) ||
+      (bold && BOLD) ||
+      (italic && ITALIC) ||
+      NORMAL;
+    return {
+      css: `${loadedName},sans-serif`,
+      loadedName,
+      src: `local(${baseFontName})`,
+      style,
+    };
+  }
+
+  while (substitution.alias) {
+    // If we've an alias, use the substitution for the alias.
+    // For example, ArialBlack-Bold is an alias for ArialBlack because the bold
+    // version of Arial Black is not available.
+    substitution = substitutionMap.get(substitution.alias);
+  }
+
+  const { fallback, style } = substitution;
+
+  // Prepend the fonts to test before the fallback font.
+  let prepend = substitution.prepend;
+
+  if (fallback) {
+    // We've a fallback font: this one is a standard font we want to use in case
+    // nothing has been found from the prepend list.
+    prepend ||= substitutionMap.get(substitution.local.alias).prepend;
+    substitution = substitutionMap.get(fallback);
+  }
+
+  const { local, path, ultimate } = substitution;
+  let src = makeLocal(prepend, local);
+  if (path && localFontPath !== null) {
+    // PDF.js embeds some fonts we can use.
+    src += `,url(${localFontPath}${path})`;
+  }
+
+  // Maybe the OS will have the exact font we want so just prepend it to the
+  // list.
+  if (mustAddBaseFont && validateFontName(baseFontName)) {
+    src = `local(${baseFontName}),${src}`;
+  }
+
+  return {
+    css: `${loadedName},${ultimate}`,
+    loadedName,
+    src,
+    style,
+  };
+}
+
+export { getFontSubstitution };

src/core/fonts.js

@@ -98,6 +98,7 @@ const EXPORT_DATA_PROPERTIES = [
   "name",
   "remeasure",
   "subtype",
+  "systemFontInfo",
   "type",
   "vertical",
 ];
@@ -998,6 +999,7 @@ class Font {
       this.fallbackName = "sans-serif";
     }
 
+    this.systemFontInfo = properties.systemFontInfo;
     this.differences = properties.differences;
     this.widths = properties.widths;
     this.defaultWidth = properties.defaultWidth;

src/core/standard_fonts.js

@@ -100,10 +100,10 @@ const getFontNameToFileMap = getLookupTableFactory(function (t) {
   t["Courier-Bold"] = "FoxitFixedBold.pfb";
   t["Courier-BoldOblique"] = "FoxitFixedBoldItalic.pfb";
   t["Courier-Oblique"] = "FoxitFixedItalic.pfb";
-  t.Helvetica = "FoxitSans.pfb";
+  t.Helvetica = "LiberationSans-Regular.ttf";
-  t["Helvetica-Bold"] = "FoxitSansBold.pfb";
+  t["Helvetica-Bold"] = "LiberationSans-Bold.ttf";
-  t["Helvetica-BoldOblique"] = "FoxitSansBoldItalic.pfb";
+  t["Helvetica-BoldOblique"] = "LiberationSans-BoldItalic.ttf";
-  t["Helvetica-Oblique"] = "FoxitSansItalic.pfb";
+  t["Helvetica-Oblique"] = "LiberationSans-Italic.ttf";
   t["Times-Roman"] = "FoxitSerif.pfb";
   t["Times-Bold"] = "FoxitSerifBold.pfb";
   t["Times-BoldItalic"] = "FoxitSerifBoldItalic.pfb";

src/display/canvas.js

@@ -1950,6 +1950,8 @@ class CanvasGraphics {
     }
 
     const name = fontObj.loadedName || "sans-serif";
+    const typeface =
+      fontObj.systemFontInfo?.css || `"${name}", ${fontObj.fallbackName}`;
 
     let bold = "normal";
     if (fontObj.black) {
@@ -1958,7 +1960,6 @@ class CanvasGraphics {
       bold = "bold";
     }
     const italic = fontObj.italic ? "italic" : "normal";
-    const typeface = `"${name}", ${fontObj.fallbackName}`;
 
     // Some font backends cannot handle fonts below certain size.
     // Keeping the font at minimal size and using the fontSizeScale to change

src/display/font_loader.js

@@ -19,6 +19,7 @@ import {
   FeatureTest,
   shadow,
   string32,
+  unreachable,
   warn,
 } from "../shared/util.js";
 import { isNodeJS } from "../shared/is_node.js";
@@ -30,7 +31,7 @@ class FontLoader {
   }) {
     this._document = ownerDocument;
 
-    this.nativeFontFaces = [];
+    this.nativeFontFaces = new Set();
     this.styleElement =
       typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")
         ? styleElement
@@ -43,10 +44,15 @@ class FontLoader {
   }
 
   addNativeFontFace(nativeFontFace) {
-    this.nativeFontFaces.push(nativeFontFace);
+    this.nativeFontFaces.add(nativeFontFace);
     this._document.fonts.add(nativeFontFace);
   }
 
+  removeNativeFontFace(nativeFontFace) {
+    this.nativeFontFaces.delete(nativeFontFace);
+    this._document.fonts.delete(nativeFontFace);
+  }
+
   insertRule(rule) {
     if (!this.styleElement) {
       this.styleElement = this._document.createElement("style");
@@ -62,7 +68,7 @@ class FontLoader {
     for (const nativeFontFace of this.nativeFontFaces) {
       this._document.fonts.delete(nativeFontFace);
     }
-    this.nativeFontFaces.length = 0;
+    this.nativeFontFaces.clear();
 
     if (this.styleElement) {
       // Note: ChildNode.remove doesn't throw if the parentNode is undefined.
@@ -71,13 +77,44 @@ class FontLoader {
     }
   }
 
+  async loadSystemFont(info) {
+    assert(
+      !this.disableFontFace,
+      "loadSystemFont shouldn't be called when `disableFontFace` is set."
+    );
+
+    if (this.isFontLoadingAPISupported) {
+      const { loadedName, src, style } = info;
+      const fontFace = new FontFace(loadedName, src, style);
+      this.addNativeFontFace(fontFace);
+      try {
+        await fontFace.load();
+      } catch {
+        warn(
+          `Cannot load system font: ${loadedName} for style ${style.style} and weight ${style.weight}.`
+        );
+        this.removeNativeFontFace(fontFace);
+      }
+      return;
+    }
+
+    unreachable(
+      "Not implemented: loadSystemFont without the Font Loading API."
+    );
+  }
+
   async bind(font) {
     // Add the font to the DOM only once; skip if the font is already loaded.
-    if (font.attached || font.missingFile) {
+    if (font.attached || (font.missingFile && !font.systemFontInfo)) {
       return;
     }
     font.attached = true;
 
+    if (font.systemFontInfo) {
+      await this.loadSystemFont(font.systemFontInfo);
+      return;
+    }
+
     if (this.isFontLoadingAPISupported) {
       const nativeFontFace = font.createNativeFontFace();
       if (nativeFontFace) {

web/app_options.js

@@ -210,7 +210,12 @@ const defaultOptions = {
   cMapUrl: {
     /** @type {string} */
     value:
-      typeof PDFJSDev === "undefined" ? "../external/bcmaps/" : "../web/cmaps/",
+      // eslint-disable-next-line no-nested-ternary
+      typeof PDFJSDev === "undefined"
+        ? "../external/bcmaps/"
+        : PDFJSDev.test("MOZCENTRAL")
+        ? "resource://pdf.js/web/cmaps/"
+        : "../web/cmaps/",
     kind: OptionKind.API,
   },
   disableAutoFetch: {
@@ -271,8 +276,11 @@ const defaultOptions = {
   standardFontDataUrl: {
     /** @type {string} */
     value:
+      // eslint-disable-next-line no-nested-ternary
       typeof PDFJSDev === "undefined"
         ? "../external/standard_fonts/"
+        : PDFJSDev.test("MOZCENTRAL")
+        ? "resource://pdf.js/web/standard_fonts/"
         : "../web/standard_fonts/",
     kind: OptionKind.API,
   },