--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dialogs/CommentEditDialog.py	Wed Sep 26 18:08:57 2018 +0300
@@ -0,0 +1,86 @@
+#
+# This file is part of Beremiz, a Integrated Development Environment for
+# programming IEC 61131-3 automates supporting plcopen standard and CanFestival.
+#
+# Copyright (C) 2018: Andrey Skvortsov <andrej.skvortzov@gmail.com>
+#
+# See COPYING file for copyrights details.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+
+from __future__ import absolute_import
+
+import wx
+
+
+class CommentEditDialog(wx.Dialog):
+    """
+    This dialog behaves like wx.TextEntryDialog,
+    but additionaly it allows to set custom font and
+    exact size for wx.TextCtrl.
+    That allows to edit comment and immediately
+    see how it'll be shown on wiresheet.
+    """
+
+    def __init__(self, parent, font, value="", size=wx.Size(400, 200)):
+        """
+        Constructor
+
+        :param parent:
+            parent window (wx.Window)
+        :param font:
+            the font for text control
+        :param value:
+            the default value, which may be the empty string
+        :param size:
+            desired initial size for text control.
+            Minimal size of text control is limited
+            by (100,100)
+        """
+        wx.Dialog.__init__(self, parent, title=_("Please enter comment text"))
+        msg_label = wx.StaticText(self, label=_("Edit comment"))
+        input_size = wx.Size(max(size[0], 100), max(size[1], 100))
+        input = wx.TextCtrl(self, style=wx.TE_MULTILINE)
+        input.SetInitialSize(input_size)
+        input.SetFont(font)
+        input.SetValue(value)
+        buttons = self.CreateButtonSizer(wx.OK | wx.CANCEL)
+        sizer = wx.FlexGridSizer(cols=1, hgap=0, rows=3, vgap=10)
+        border = 20
+
+        sizer.Add(msg_label, 0,
+                  flag=wx.TOP | wx.LEFT | wx.RIGHT,
+                  border=border)
+        sizer.Add(input, 1,
+                  flag=wx.EXPAND | wx.LEFT | wx.RIGHT,
+                  border=border)
+        sizer.Add(buttons, 0,
+                  flag=wx.EXPAND | wx.LEFT | wx.RIGHT | wx.BOTTOM,
+                  border=border)
+
+        self.SetSizerAndFit(sizer)
+        self.input = input
+
+    def SetValue(self, value):
+        """Sets text value"""
+        self.input.SetValue(value)
+
+    def GetValue(self):
+        """
+        Returns the text that the user has entered
+        if the user has pressed wx.OK,
+        or the original value if the user has pressed Cancel.
+        """
+        return self.input.GetValue()

--- a/dialogs/__init__.py	Wed Sep 26 14:20:51 2018 +0300
+++ b/dialogs/__init__.py	Wed Sep 26 18:08:57 2018 +0300
@@ -27,6 +27,7 @@
 
 from __future__ import absolute_import
 
+from dialogs.CommentEditDialog import CommentEditDialog
 from dialogs.ConnectionDialog import ConnectionDialog
 from dialogs.ActionBlockDialog import ActionBlockDialog
 from dialogs.FBDBlockDialog import FBDBlockDialog

--- a/editors/Viewer.py	Wed Sep 26 14:20:51 2018 +0300
+++ b/editors/Viewer.py	Wed Sep 26 18:08:57 2018 +0300
@@ -2658,11 +2658,8 @@
             self.AddNewElement(connection, bbox, wire)
 
     def AddNewComment(self, bbox):
-        dialog = wx.TextEntryDialog(self.ParentWindow,
-                                    _("Edit comment"),
-                                    _("Please enter comment text"),
-                                    "", wx.OK | wx.CANCEL | wx.TE_MULTILINE)
-        dialog.SetClientSize(wx.Size(400, 200))
+        dialog = CommentEditDialog(self.ParentWindow,
+                                   self.GetFont())
         if dialog.ShowModal() == wx.ID_OK:
             value = dialog.GetValue()
             id = self.GetNewId()
@@ -3100,14 +3097,10 @@
         dialog.Destroy()
 
     def EditCommentContent(self, comment):
-        dialog = wx.TextEntryDialog(self.ParentWindow,
-                                    _("Edit comment"),
-                                    _("Please enter comment text"),
-                                    comment.GetContent(),
-                                    wx.OK | wx.CANCEL | wx.TE_MULTILINE)
-        width, height = comment.GetSize()
-        dialogSize = wx.Size(max(width + 30, 400), max(height + 60, 200))
-        dialog.SetClientSize(dialogSize)
+        dialog = CommentEditDialog(self.ParentWindow,
+                                   self.GetFont(),
+                                   comment.GetContent(),
+                                   comment.GetSize())
         if dialog.ShowModal() == wx.ID_OK:
             value = dialog.GetValue()
             rect = comment.GetRedrawRect(1, 1)