src/Pure/System/isabelle_system.scala

     new Font(family, if (bold) Font.BOLD else Font.PLAIN, size)
 
   def install_fonts()
   {
     val ge = GraphicsEnvironment.getLocalGraphicsEnvironment()
+    for (font <- Path.split(getenv_strict("ISABELLE_FONTS")))
+      ge.registerFont(Font.createFont(Font.TRUETYPE_FONT, font.file))
+  }
+
+  def install_fonts_jfx()
+  {
     for (font <- Path.split(getenv_strict("ISABELLE_FONTS"))) {
-      ge.registerFont(Font.createFont(Font.TRUETYPE_FONT, font.file))
-
       val stream = new BufferedInputStream(new FileInputStream(font.file))
       try { javafx.scene.text.Font.loadFont(stream, 1.0) }
       finally { stream.close }
     }
   }