diff -r a375e31bf312 -r c1298e7ffe3a graphics/GraphicCommons.py
--- a/graphics/GraphicCommons.py	Sun Mar 05 00:38:25 2017 +0000
+++ b/graphics/GraphicCommons.py	Fri Mar 24 12:07:47 2017 +0000
@@ -1,26 +1,26 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
-#This file is part of PLCOpenEditor, a library implementing an IEC 61131-3 editor
-#based on the plcopen standard. 
+# This file is part of Beremiz, a Integrated Development Environment for
+# programming IEC 61131-3 automates supporting plcopen standard and CanFestival.
 #
-#Copyright (C) 2007: Edouard TISSERANT and Laurent BESSARD
+# Copyright (C) 2007: Edouard TISSERANT and Laurent BESSARD
 #
-#See COPYING file for copyrights details.
+# See COPYING file for copyrights details.
 #
-#This library 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 2.1 of the License, or (at your option) any later version.
+# 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 library 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.
+# 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 library; if not, write to the Free Software
-#Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+# 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.
 
 import wx
 from math import *
@@ -1351,19 +1351,35 @@
             self.Edge = edge    
             self.Negated = False
     
+    # assume that pointer is already inside of this connector
+    def ConnectionAvailable(self, direction=None, exclude=True):
+        wire_nums = len(self.Wires)
+        
+        connector_free = (wire_nums<= 0)
+        connector_max_used = ((wire_nums > 0) and self.OneConnected)
+        if (self.Parent.CurrentLanguage in ["SFC", "LD"]) and (self.Type == "BOOL"):
+            connector_max_used = False;
+
+        # connector is available for new connection
+        connect  = connector_free or not connector_max_used
+        return connect, connector_max_used
+                           
     # Tests if the point given is near from the end point of this connector
-    def TestPoint(self, pt, direction = None, exclude = True):
-        parent_pos = self.ParentBlock.GetPosition()
-        if (not (len(self.Wires) > 0 and self.OneConnected and exclude) or self.Type == "BOOL")\
-            and direction is None or self.Direction == direction:
+    def TestPoint(self, pt, direction=None, exclude=True):
+        inside = False;
+        check_point = (not exclude) and (direction is None or self.Direction == direction);
+
+        if check_point:
             # Calculate a square around the end point of this connector
+            parent_pos = self.ParentBlock.GetPosition()
             x = parent_pos[0] + self.Pos.x + self.Direction[0] * CONNECTOR_SIZE - ANCHOR_DISTANCE
             y = parent_pos[1] + self.Pos.y + self.Direction[1] * CONNECTOR_SIZE - ANCHOR_DISTANCE
             width = ANCHOR_DISTANCE * 2 + abs(self.Direction[0]) * CONNECTOR_SIZE
             height = ANCHOR_DISTANCE * 2 + abs(self.Direction[1]) * CONNECTOR_SIZE
             rect = wx.Rect(x, y, width, height)
-            return rect.InsideXY(pt.x, pt.y)
-        return False
+            inside = rect.InsideXY(pt.x, pt.y);
+                           
+        return inside
     
     # Draws the highlightment of this element if it is highlighted
     def DrawHighlightment(self, dc):
@@ -1551,6 +1567,7 @@
         self.OverEnd = False
         self.ComputingType = False
         self.Font = parent.GetMiniFont()
+        self.ErrHighlight = False
     
     def GetDefinition(self):
         if self.StartConnected is not None and self.EndConnected is not None:
@@ -2590,8 +2607,13 @@
     def DrawHighlightment(self, dc):
         scalex, scaley = dc.GetUserScale()
         dc.SetUserScale(1, 1)
-        dc.SetPen(MiterPen(HIGHLIGHTCOLOR, (2 * scalex + 5)))
-        dc.SetBrush(wx.Brush(HIGHLIGHTCOLOR))
+        # If user trying to connect wire with wrong input, highlight will become red.
+        if self.ErrHighlight == True and not (self.EndConnected):
+            highlightcolor = wx.RED
+        else:
+            highlightcolor = HIGHLIGHTCOLOR
+        dc.SetPen(MiterPen(highlightcolor, (2 * scalex + 5)))
+        dc.SetBrush(wx.Brush(highlightcolor))
         dc.SetLogicalFunction(wx.AND)
         # Draw the start and end points if they are not connected or the mouse is over them
         if len(self.Points) > 0 and (not self.StartConnected or self.OverStart):
@@ -2873,10 +2895,15 @@
                    wx.Point(self.Pos.x + self.Size[0], self.Pos.y + self.Size[1]),
                    wx.Point(self.Pos.x, self.Pos.y + self.Size[1])]
         dc.DrawPolygon(polygon)
+
+        # dc.SetBrush call is workaround for the issue with wx.PrinterDC
+        # with wxPython 3.0 on GNU/Linux (don't remove it)
+        dc.SetBrush(wx.WHITE_BRUSH)
         lines = [wx.Point(self.Pos.x + self.Size[0] - 10, self.Pos.y),
                  wx.Point(self.Pos.x + self.Size[0] - 10, self.Pos.y + 10),
                  wx.Point(self.Pos.x + self.Size[0], self.Pos.y + 10)]
         dc.DrawLines(lines)
+
         # Draws the comment content
         y = self.Pos.y + 10
         for idx, line in enumerate(self.Content.splitlines()):