From 96b44de9b64cf658d34980e8fb04c909fc72ff6d Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sat, 21 May 2016 08:44:55 +0530
Subject: [PATCH] Add a note about the bug the previous workaround was for

---
 src/calibre/gui2/main_window.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/calibre/gui2/main_window.py b/src/calibre/gui2/main_window.py
index 5a4a3f6c61..eccc0be6d4 100644
--- a/src/calibre/gui2/main_window.py
+++ b/src/calibre/gui2/main_window.py
@@ -164,6 +164,9 @@ class MainWindow(QMainWindow):
         return QMainWindow.event(self, ev)
 
 def clone_menu(menu):
+    # This is needed to workaround a bug in Qt 5.5+ and Unity. When the same
+    # QAction object is used in both a QMenuBar and a QMenu, sub-menus of the
+    # QMenu flicker when rendered under Unity.
     def clone_action(ac, parent):
         if ac.isSeparator():
             ans = QAction(parent)