diff -r b6256ea3b7c5 -r 990ffb84489b src/Pure/GUI/gui_thread.scala
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Pure/GUI/gui_thread.scala	Wed Jul 23 11:19:24 2014 +0200
@@ -0,0 +1,57 @@
+/*  Title:      Pure/GUI/gui_thread.scala
+    Module:     PIDE-GUI
+    Author:     Makarius
+
+Evaluation within the GUI thread: implementation for AWT/Swing.
+*/
+
+package isabelle
+
+
+import javax.swing.SwingUtilities
+
+
+object GUI_Thread
+{
+  /* context check */
+
+  def assert[A](body: => A) =
+  {
+    Predef.assert(SwingUtilities.isEventDispatchThread())
+    body
+  }
+
+  def require[A](body: => A) =
+  {
+    Predef.require(SwingUtilities.isEventDispatchThread())
+    body
+  }
+
+
+  /* event dispatch queue */
+
+  def now[A](body: => A): A =
+  {
+    if (SwingUtilities.isEventDispatchThread()) body
+    else {
+      lazy val result = { assert { Exn.capture(body) } }
+      SwingUtilities.invokeAndWait(new Runnable { def run = result })
+      Exn.release(result)
+    }
+  }
+
+  def later(body: => Unit)
+  {
+    if (SwingUtilities.isEventDispatchThread()) body
+    else SwingUtilities.invokeLater(new Runnable { def run = body })
+  }
+
+
+  /* delayed events */
+
+  def delay_first(delay: => Time)(event: => Unit): Simple_Thread.Delay =
+    Simple_Thread.delay_first(delay) { later { event } }
+
+  def delay_last(delay: => Time)(event: => Unit): Simple_Thread.Delay =
+    Simple_Thread.delay_last(delay) { later { event } }
+}