diff --git a/src/warning.cpp b/src/warning.cpp
new file mode 100644
--- /dev/null
+++ b/src/warning.cpp
@@ -0,0 +1,181 @@
+/*
+ *
+ *  This file is part of the Virtual Leaf.
+ *
+ *  The Virtual Leaf 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 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  The Virtual Leaf 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 the Virtual Leaf.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *  Copyright 2010 Roeland Merks.
+ *
+ */
+
+#include <string>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <iostream>
+#include "warning.h"
+#ifdef QTGRAPHICS
+#include <qapplication.h>
+#include "canvas.h"
+#endif
+#include <QMessageBox>
+
+static const std::string _module_id("$Id$");
+
+int Quiet=0;
+
+/*
+ * ERROR: scream and die quickly.
+ */
+
+#ifndef QTGRAPHICS
+void MyWarning::error(char * fmt, ...)
+{
+    va_list ap;
+
+    va_start(ap, fmt);
+    vfprintf(stderr, fmt, ap);		/* invoke interface to printf       */
+    fprintf(stderr,"\n");     /* automatic \n by Roeland */
+    fflush(stderr);			/* drain std error buffer 	    */
+    va_end(ap);
+    exit(1);				/* quit with error status	    */
+}
+#else
+//#include <qmessagebox.h>
+#include "UniqueMessage.h"
+void MyWarning::error(const char *fmt, ...)
+{
+  va_list ap;
+  if (Quiet) return;
+  char *message = new char[1000];
+ 
+  va_start(ap, fmt);
+  vsnprintf(message, 999, fmt, ap);		/* invoke interface to printf       */
+  va_end(ap);
+  
+  QString qmess(message);
+  
+  bool batch = false;
+  
+  if (batch) {
+    // batch mode: print the message to stderr
+    fprintf(stderr, "Fatal error: %s\n",qmess.toStdString().c_str());
+    exit(1);
+  } else { // issue a dialog box
+    /* Solve this with signal and slot...! */
+	  //extern MainBase *main_window;
+    //((Main *)main_window)->stopSimulation();
+    
+	QMessageBox::critical( 0 , "Fatal error", qmess, QMessageBox::Abort, QMessageBox::NoButton, QMessageBox::NoButton );
+    fprintf(stderr, "Error: %s\n",qmess.toStdString().c_str());
+    QCoreApplication::exit(1);
+    std::exit(1);
+  }
+  delete[] message;
+  
+}
+#endif
+
+
+/*
+ * EPRINTF: scream, but don't die yet.
+ * Roeland changed this to "warning" (21/10/1998)
+ * and added an automatic "\n"
+ */
+
+#ifndef QTGRAPHICS
+void MyWarning::warning(const char * fmt, ...)
+{
+  va_list ap;
+  if (Quiet) return;
+  
+  va_start(ap, fmt);
+  vfprintf(stderr, fmt, ap);		/* invoke interface to printf       */
+  fprintf(stderr,"\n");     /* automatic \n by Roeland */
+  fflush(stderr);			/* drain std error buffer 	    */
+  va_end(ap);
+}
+#else 
+
+#include <qmessagebox.h>
+
+
+void MyWarning::warning(const char *fmt, ...)
+{
+  va_list ap;
+  if (Quiet) return;
+  char *message = new char[1000];
+ 
+  va_start(ap, fmt);
+  vsnprintf(message, 999, fmt, ap);		/* invoke interface to printf       */
+  va_end(ap);
+  
+  QString qmess(message);
+  
+  bool batch = false;
+  
+  if (batch) {
+    // batch mode: print the message to stderr
+    fprintf(stderr, "Warning: %s\n",qmess.toStdString().c_str());
+  } else { // issue a dialog box
+	  UniqueMessageBox msgBox( QString("Warning"), qmess );
+	  msgBox.exec();
+  }
+  delete[] message;
+
+}
+#endif
+
+/*! Issues a warning only once,
+  by comparing it to a list of warnings issued previously. */
+void MyWarning::unique_warning(const char *fmt, ...) {
+  
+  va_list ap;
+  if (Quiet) return;
+  char *message = new char[1000];
+ 
+  va_start(ap, fmt);
+  vsnprintf(message, 999, fmt, ap);		/* invoke interface to printf       */
+  va_end(ap);
+
+  static vector<string> previous_warnings;
+  
+  // search warning in list
+  if (find(
+	   previous_warnings.begin(),previous_warnings.end(), 
+	   string(message)) 
+      ==previous_warnings.end()) {
+    
+    // new warning, store in list
+    previous_warnings.push_back(string(message));
+    
+    // issue warning
+    warning("%s", message);
+   
+  } else {
+    // don't issue warning
+    return;
+  }
+}
+
+
+#ifdef TESTBED
+
+main(int argc, char * argv[])
+{
+    eprintf("warning: foo=%f\tbar=%d\tfum=\"%s\"\n", 3.1415, 32768, "waldo");
+    error("error: foo=%f\tbar=%d\tfum=\"%s\"\n", 3.1415, 32768, "waldo");
+}
+
+#endif