diff --git a/Unix/CbOptions.cpp b/Unix/CbOptions.cpp
index c80a12bd526daa1747b6f68830d6f2bbeee3934d..c8026d5f695e3696897d355eca2d600b544f96ed 100644
--- a/Unix/CbOptions.cpp
+++ b/Unix/CbOptions.cpp
@@ -1,4 +1,4 @@
-/* $Id: CbOptions.cpp,v 1.10 2000-12-05 18:38:11 geuzaine Exp $ */
+/* $Id: CbOptions.cpp,v 1.11 2000-12-05 19:03:21 geuzaine Exp $ */
 
 #include "Gmsh.h"
 #include "GmshUI.h"
@@ -59,6 +59,7 @@ void OptionsCb (Widget w, XtPointer client_data, XtPointer call_data){
   case OPTIONS_FAST_REDRAW   : CTX.fast = !CTX.fast ; break ;
   case OPTIONS_DISPLAY_LISTS : CTX.display_lists = !CTX.display_lists ; break ;
   case OPTIONS_ALPHA_BLENDING: CTX.alpha = !CTX.alpha; break;
+  case OPTIONS_TRACKBALL     : CTX.useTrackball = !CTX.useTrackball; break;
   case OPTIONS_COLOR_SCHEME_SCALE: 
     XmScaleGetValue(WID.OD.miscColorSchemeScale, &e); Init_Colors(e);
     Init(); Draw();
diff --git a/Unix/CbOptions.h b/Unix/CbOptions.h
index b2cdca4e622e679e3a6c3ff2735264b1cce47919..141993e258a30e786cabb65b8b22029670392f12 100644
--- a/Unix/CbOptions.h
+++ b/Unix/CbOptions.h
@@ -1,4 +1,4 @@
-/* $Id: CbOptions.h,v 1.7 2000-11-26 15:43:48 geuzaine Exp $ */
+/* $Id: CbOptions.h,v 1.8 2000-12-05 19:03:21 geuzaine Exp $ */
 #ifndef _CB_OPTIONS_H_
 #define _CB_OPTIONS_H_
 
@@ -40,6 +40,7 @@
 #define  OPTIONS_DISPLAY_LISTS                  34
 #define  OPTIONS_FAST_REDRAW                    35
 #define  OPTIONS_COLOR_SCHEME_SCALE             36
+#define  OPTIONS_TRACKBALL                      37
 
 /* options geometrie */
 
diff --git a/Unix/Register.cpp b/Unix/Register.cpp
index 466cab389a439c5b960a22cafac5703caf66a9c9..c44e41bd0f62ca7b51caa65bb5f2b0ba94779381 100644
--- a/Unix/Register.cpp
+++ b/Unix/Register.cpp
@@ -1,4 +1,4 @@
-/* $Id: Register.cpp,v 1.9 2000-11-26 15:43:48 geuzaine Exp $ */
+/* $Id: Register.cpp,v 1.10 2000-12-05 19:03:21 geuzaine Exp $ */
 
 #include "Gmsh.h"
 #include "GmshUI.h"
@@ -216,6 +216,7 @@ void RegisterCallbacks_OD(Widgets_T *w){
   register_valchg_cb  (w->OD.miscMiscButt[2],    OptionsCb,  OPTIONS_FAST_REDRAW);
   register_valchg_cb  (w->OD.miscMiscButt[3],    OptionsCb,  OPTIONS_DISPLAY_LISTS);
   register_valchg_cb  (w->OD.miscMiscButt[4],    OptionsCb,  OPTIONS_ALPHA_BLENDING);
+  register_valchg_cb  (w->OD.miscMiscButt[5],    OptionsCb,  OPTIONS_TRACKBALL);
   register_valchg_cb  (w->OD.miscColorSchemeScale, OptionsCb, OPTIONS_COLOR_SCHEME_SCALE);
   register_drag_cb    (w->OD.miscColorSchemeScale, OptionsCb, OPTIONS_COLOR_SCHEME_SCALE);
   register_valchg_cb  (w->OD.miscProjButt[0],    OptionsCb,  OPTIONS_ORTHOGRAPHIC);