Improve missing font fallback families

Author: mrtcode

src/core/fonts.js

@@ -1125,15 +1125,18 @@ class Font {
 
     let isSerifFont = !!(properties.flags & FontFlags.Serif);
     // Fallback to checking the font name, in order to improve text-selection,
-    // since the /Flags-entry is often wrong (fixes issue13845.pdf).
-    if (!isSerifFont && !properties.isSimulatedFlags) {
+    // since the /Flags-entry is often wrong (fixes issue13845.pdf). When the
+    // font file is missing, the family also affects canvas fallback rendering.
+    if (!isSerifFont && (!properties.isSimulatedFlags || !file)) {
       const stdFontMap = getStdFontMap(),
         nonStdFontMap = getNonStdFontMap(),
         serifFonts = getSerifFonts();
       for (const namePart of name.split("+")) {
         let fontName = normalizeFontName(namePart);
         fontName = stdFontMap[fontName] || nonStdFontMap[fontName] || fontName;
         fontName = fontName.split("-", 1)[0];
+        // TeX fonts commonly append the design size, e.g. CMR8.
+        fontName = fontName.replace(/\d+$/, "");
         if (serifFonts[fontName]) {
           isSerifFont = true;
           break;

src/core/standard_fonts.js

@@ -218,6 +218,11 @@ const getSerifFonts = getLookupTableFactory(function (t) {
   t.Clearface = true;
   t.Cochin = true;
   t.Colonna = true;
+  t.CMBX = true;
+  t.CMMI = true;
+  t.CMR = true;
+  t.CMSL = true;
+  t.CMTI = true;
   t["Computer Modern"] = true;
   t["Concrete Roman"] = true;
   t.Constantia = true;
@@ -271,6 +276,7 @@ const getSerifFonts = getLookupTableFactory(function (t) {
   t["Museo Slab"] = true;
   t["New York"] = true;
   t["Nimbus Roman"] = true;
+  t.NimbusRomNo9L = true;
   t["NPS Rawlinson Roadway"] = true;
   t.NuptialScript = true;
   t.Palatino = true;