From 8d38de825e9721be0a324ae4774ee75b7523ee02 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Wed, 7 Sep 2016 12:55:05 +0530
Subject: [PATCH] Fix undo not working with sort css

---
 src/calibre/gui2/tweak_book/editor/text.py | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/calibre/gui2/tweak_book/editor/text.py b/src/calibre/gui2/tweak_book/editor/text.py
index e101858247..eb26b02243 100644
--- a/src/calibre/gui2/tweak_book/editor/text.py
+++ b/src/calibre/gui2/tweak_book/editor/text.py
@@ -336,9 +336,16 @@ class TextEdit(PlainTextEdit):
         from calibre.gui2.dialogs.confirm_delete import confirm
         if confirm(_('Sorting CSS rules can in rare cases change the effective styles applied to the book.'
                      ' Are you sure you want to proceed?'), 'edit-book-confirm-sort-css', parent=self, config_set=tprefs):
+            c = self.textCursor()
+            c.beginEditBlock()
+            c.movePosition(c.Start), c.movePosition(c.End, c.KeepAnchor)
+            text = unicode(c.selectedText()).replace(PARAGRAPH_SEPARATOR, '\n').rstrip('\0')
             from calibre.ebooks.oeb.polish.css import sort_sheet
-            text = sort_sheet(current_container(), self.toPlainText()).cssText
-            self.setPlainText(text)
+            text = sort_sheet(current_container(), text).cssText
+            c.insertText(text)
+            c.movePosition(c.Start)
+            c.endEditBlock()
+            self.setTextCursor(c)
 
     def find(self, pat, wrap=False, marked=False, complete=False, save_match=None):
         if marked: