--- gimp-2.4.3-/app/display/gimpdisplayshell-coords.c	Mon Jan 21 06:22:00 2008
+++ gimp-painter--2.4.3/app/display/gimpdisplayshell-coords.c	Tue Jan 22 20:39:07 2008
@@ -277,16 +277,22 @@
           gdouble new_y;
 
           sin_new = coords->delta_x / coords->distance;
+          sin_old = shell->last_coords.delta_x / shell->last_coords.distance;
+          sin_avg = sin (asin (sin_old) * inertia_factor +
+                         asin (sin_new) * (1 - inertia_factor));
+
+          cos_new = coords->delta_y / coords->distance;
           cos_old = shell->last_coords.delta_y / shell->last_coords.distance;
           cos_avg = cos (acos (cos_old) * inertia_factor +
                          acos (cos_new) * (1 - inertia_factor));
+
           coords->delta_x = sin_avg * coords->distance;
           coords->delta_y = cos_avg * coords->distance;
 
           new_x = (shell->last_coords.x - coords->delta_x) * 0.5 + coords->x * 0.5;
           new_y = (shell->last_coords.y - coords->delta_y) * 0.5 + coords->y * 0.5;
 
-          cur_deviation = SQR (coords->x-new_x) + SQR (coords->y-new_y);
+          cur_deviation = SQR (coords->x - new_x) + SQR (coords->y - new_y);
 
           while (cur_deviation >= max_deviation)
           {