diff -r 56cd8111b7f7 -r 41300fa6a67c src/gui/util/qsystemtrayicon.cpp
--- a/src/gui/util/qsystemtrayicon.cpp	Tue Jan 26 12:42:25 2010 +0200
+++ b/src/gui/util/qsystemtrayicon.cpp	Tue Feb 02 00:43:10 2010 +0200
@@ -380,6 +380,9 @@
     On Windows, the \a millisecondsTimeoutHint is usually ignored by the system
     when the application has focus.
 
+    On Mac OS X, the Growl notification system must be installed for this function to
+    display messages.
+ 
     \sa show() supportsMessages()
   */
 void QSystemTrayIcon::showMessage(const QString& title, const QString& msg,