src/Pure/GUI/gui.scala

--- a/src/Pure/GUI/gui.scala	Wed Nov 28 13:59:29 2018 +0100
+++ b/src/Pure/GUI/gui.scala	Wed Nov 28 14:00:22 2018 +0100
@@ -246,8 +246,7 @@
   def install_fonts()
   {
     val ge = GraphicsEnvironment.getLocalGraphicsEnvironment()
-    for (path <- Isabelle_Fonts.files())
-      ge.registerFont(Font.createFont(Font.TRUETYPE_FONT, path.file))
+    Isabelle_Fonts.fonts().foreach(entry => ge.registerFont(entry.font))
   }
 }