tweak

Fltk/openglWindow.cpp

@@ -160,6 +160,7 @@ void openglWindow::draw()
     glDisable(GL_BLEND);
     glDisable(GL_LINE_STIPPLE);
     glEnable(GL_DEPTH_TEST);
+    glDrawBuffer(GL_BACK);
   }
   else if(addPointMode) { 
     // draw the whole scene and the point to add