diff -r 013afe9ee040 -r b465e2c34f23 graph_displayer_canvas-event.cc
--- a/graph_displayer_canvas-event.cc	Wed Jan 10 14:56:16 2007 +0000
+++ b/graph_displayer_canvas-event.cc	Fri Feb 02 10:13:33 2007 +0000
@@ -95,6 +95,45 @@
   return actual_tool;
 }
 
+bool GraphDisplayerCanvas::scrollEventHandler(GdkEvent* e)
+{
+  bool handled=false;
+  if(e->type==GDK_SCROLL)
+    {
+
+      //pointer shows this win point before zoom
+      XY win_coord(((GdkEventScroll*)e)->x, ((GdkEventScroll*)e)->y);
+
+      //the original scroll settings
+      int scroll_offset_x, scroll_offset_y;
+      get_scroll_offsets(scroll_offset_x, scroll_offset_y);
+
+      //pointer shows this canvas point before zoom
+      XY canvas_coord;
+      window_to_world(win_coord.x, win_coord.y, canvas_coord.x, canvas_coord.y);
+
+      if(((GdkEventScroll*)e)->direction) //IN
+	{
+	  zoomIn();
+	}
+      else
+	{
+	  zoomOut();
+	}
+
+      //pointer shows this window point after zoom
+      XY post_win_coord;
+      world_to_window(canvas_coord.x, canvas_coord.y, post_win_coord.x, post_win_coord.y);
+
+      //we have to add the difference between new and old window point to original scroll offset
+      scroll_to(scroll_offset_x+(int)(post_win_coord.x-win_coord.x),scroll_offset_y+(int)(post_win_coord.y-win_coord.y));
+      
+      //no other eventhandler is needed
+      handled=true;
+    }
+  return handled;
+}
+
 bool GraphDisplayerCanvas::moveEventHandler(GdkEvent* e)
 {
   static Gnome::Canvas::Text *coord_text = 0;