src/Pure/GUI/gui.scala

   def isabelle_icons(): List[ImageIcon] =
     for (icon <- List("isabelle/isabelle_transparent-32.gif", "isabelle/isabelle_transparent.gif"))
       yield new ImageIcon(getClass.getClassLoader.getResource(icon))
 
   def isabelle_image(): Image = isabelle_icon().getImage
+
+  def isabelle_image_large(): Image =
+    Toolkit.getDefaultToolkit.getImage(
+      File.platform_path(Path.explode("~~/lib/logo/isabelle_transparent-128.png")))
+
+  def set_application_icon()
+  {
+    if (Platform.is_macos) {
+      val image = isabelle_image_large()
+      val app =
+        Class.forName("com.apple.eawt.Application")
+          .getDeclaredMethod("getApplication").invoke(null)
+      app.getClass.getDeclaredMethod("setDockIconImage", classOf[Image]).invoke(app, image)
+    }
+  }
 
 
   /* location within multi-screen environment */
 
   final case class Screen_Location(point: Point, bounds: Rectangle)