Detecting if web fonts are disable in Firefox.

extensions/firefox/components/PdfStreamConverter.js

@@ -71,6 +71,14 @@ function getBoolPref(pref, def) {
   }
 }
 
+function getIntPref(pref, def) {
+  try {
+    return Services.prefs.getIntPref(pref);
+  } catch (ex) {
+    return def;
+  }
+}
+
 function setStringPref(pref, value) {
   let str = Cc['@mozilla.org/supports-string;1']
               .createInstance(Ci.nsISupportsString);
@@ -351,6 +359,10 @@ ChromeActions.prototype = {
            getChromeWindow(this.domWindow).gFindBar &&
            'updateControlState' in getChromeWindow(this.domWindow).gFindBar;
   },
+  supportsDocumentFonts: function() {
+    var pref = getIntPref('browser.display.use_document_fonts', 1);
+    return !!pref;
+  },
   fallback: function(url, sendResponse) {
     var self = this;
     var domWindow = this.domWindow;

l10n/en-US/viewer.properties

@@ -120,3 +120,4 @@ text_annotation_type=[{{type}} Annotation]
 request_password=PDF is protected by a password:
 
 printing_not_supported=Warning: Printing is not fully supported by this browser.
+web_fonts_disabled=Web fonts are disabled: unable to use embedded PDF fonts.

src/api.js

@@ -90,6 +90,13 @@ var PDFDocumentProxy = (function PDFDocumentProxyClosure() {
     get fingerprint() {
       return this.pdfInfo.fingerprint;
     },
+    /**
+     * @return {boolean} true if embedded document fonts are in use. Will be
+     * set during rendering of the pages.
+     */
+    get embeddedFontsUsed() {
+      return this.transport.embeddedFontsUsed;
+    },
     /**
      * @param {number} The page number to get. The first page is 1.
      * @return {Promise} A promise that is resolved with a {PDFPageProxy}
@@ -340,6 +347,9 @@ var PDFPageProxy = (function PDFPageProxyClosure() {
         fontObjs.push(obj);
       }
 
+      this.transport.embeddedFontsUsed = this.transport.embeddedFontsUsed ||
+                                         fontObjs.length > 0;
+
       // Load all the fonts
       FontLoader.bind(
         fontObjs,
@@ -443,6 +453,7 @@ var WorkerTransport = (function WorkerTransportClosure() {
     this.pageCache = [];
     this.pagePromises = [];
     this.fontsLoading = {};
+    this.embeddedFontsUsed = false;
 
     // If worker support isn't disabled explicit and the browser has worker
     // support, create a new web worker and test if it/the browser fullfills

web/viewer.js

@@ -882,6 +882,19 @@ var PDFView = {
     return support;
   },
 
+  get supportsDocumentFonts() {
+    var support = true;
+//#if !(FIREFOX || MOZCENTRAL)
+//#else
+//  support = FirefoxCom.requestSync('supportsDocumentFonts');
+//#endif
+    Object.defineProperty(this, 'supportsDocumentFonts', { value: support,
+                                                           enumerable: true,
+                                                           configurable: true,
+                                                           writable: false });
+    return support;
+  },
+
   initPassiveLoading: function pdfViewInitPassiveLoading() {
     if (!PDFView.loadingBar) {
       PDFView.loadingBar = new ProgressBar('#loadingBar', {});
@@ -2035,6 +2048,10 @@ var PageView = function pageView(container, pdfPage, id, scale,
     if (outputScale.scaled) {
       ctx.scale(outputScale.sx, outputScale.sy);
     }
+//#if (FIREFOX || MOZCENTRAL)
+//  // Checking if document fonts are used only once
+//  var checkIfDocumentFontsUsed = !PDFView.pdfDocument.embeddedFontsUsed;
+//#endif
 
     // Rendering area
 
@@ -2047,6 +2064,14 @@ var PageView = function pageView(container, pdfPage, id, scale,
         delete self.loadingIconDiv;
       }
 
+//#if (FIREFOX || MOZCENTRAL)
+//    if (checkIfDocumentFontsUsed && PDFView.pdfDocument.embeddedFontsUsed &&
+//        !PDFView.supportsDocumentFonts) {
+//      console.error(mozL10n.get('web_fonts_disabled', null,
+//        'Web fonts are disabled: unable to use embedded PDF fonts.'));
+//      PDFView.fallback();
+//    }
+//#endif
       if (error) {
         PDFView.error(mozL10n.get('rendering_error', null,
           'An error occurred while rendering the page.'), error);