JavaFX is inactive by default;

--- a/src/Pure/System/isabelle_system.scala	Wed Sep 19 21:06:35 2012 +0200
+++ b/src/Pure/System/isabelle_system.scala	Wed Sep 19 21:07:09 2012 +0200
@@ -297,9 +297,13 @@
   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))
+  }
 
+  def install_fonts_jfx()
+  {
+    for (font <- Path.split(getenv_strict("ISABELLE_FONTS"))) {
       val stream = new BufferedInputStream(new FileInputStream(font.file))
       try { javafx.scene.text.Font.loadFont(stream, 1.0) }
       finally { stream.close }

--- a/src/Pure/build-jars	Wed Sep 19 21:06:35 2012 +0200
+++ b/src/Pure/build-jars	Wed Sep 19 21:07:09 2012 +0200
@@ -206,8 +206,7 @@
   isabelle_jdk jar cfe "$(jvmpath "$TARGET")" isabelle.GUI_Setup META-INF isabelle || \
     fail "Failed to produce $TARGET"
 
-  cp "$JFXRT" \
-    "$SCALA_HOME/lib/scala-compiler.jar" \
+  cp "$SCALA_HOME/lib/scala-compiler.jar" \
     "$SCALA_HOME/lib/scala-library.jar" \
     "$SCALA_HOME/lib/scala-swing.jar" "$TARGET_DIR/ext"