src/Pure/System/isabelle_system.scala

 
 import java.lang.System
 import java.util.regex.Pattern
 import java.util.Locale
 import java.io.{InputStream, OutputStream, File => JFile, BufferedReader, InputStreamReader,
-  BufferedWriter, OutputStreamWriter, IOException}
+  BufferedWriter, OutputStreamWriter, IOException, FileInputStream, BufferedInputStream}
 import java.awt.{GraphicsEnvironment, Font}
 import java.awt.font.TextAttribute
 
 import scala.io.Source
 import scala.util.matching.Regex

     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")))
+    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 }
+    }
   }
 }