[tomboy] Watchers.cs: fix URL highlighting with multibytes in the text

[Alex Tereschenko <alexter src gnome org>]

commit 1c745ebc71e3c540f4384e5097f337dd0d4a03f3
Author: Alex Tereschenko <frozen and blue gmail com>
Date:   Sat May 27 20:08:07 2017 +0200

    Watchers.cs: fix URL highlighting with multibytes in the text
    
    Closes #45.
    
    Signed-off-by: Alex Tereschenko <frozen and blue gmail com>

 Tomboy/Watchers.cs |   13 +++++++------
 1 files changed, 7 insertions(+), 6 deletions(-)
---
diff --git a/Tomboy/Watchers.cs b/Tomboy/Watchers.cs
index 2f79385..b5f2191 100644
--- a/Tomboy/Watchers.cs
+++ b/Tomboy/Watchers.cs
@@ -542,6 +542,7 @@ namespace Tomboy
 
                        Buffer.RemoveTag (Note.TagTable.UrlTag, start, end);
 
+                       Gtk.TextIter searchiter = start;
                        for (Match match = regex.Match (start.GetSlice (end));
                                        match.Success;
                                        match = match.NextMatch ()) {
@@ -553,13 +554,13 @@ namespace Tomboy
                                     group.Index);
                                */
 
-                               Gtk.TextIter start_cpy = start;
-                               start_cpy.ForwardChars (group.Index);
-
-                               end = start_cpy;
-                               end.ForwardChars (group.Length);
+                               // Use the ForwardSearch instead of group's Index to account for multibyte 
chars in the text.
+                               // We'll search using the exact match value within provided boundaries.
+                               Gtk.TextIter startiter, enditer;
+                               searchiter.ForwardSearch (group.Value, Gtk.TextSearchFlags.VisibleOnly, out 
startiter, out enditer, end);
+                               searchiter = enditer;
 
-                               Buffer.ApplyTag (Note.TagTable.UrlTag, start_cpy, end);
+                               Buffer.ApplyTag (Note.TagTable.UrlTag, startiter, enditer);
                        }
                }