Index: trunk/src_plugins/hid_gtk/gtkhid-gdk.c
===================================================================
--- trunk/src_plugins/hid_gtk/gtkhid-gdk.c	(revision 6909)
+++ trunk/src_plugins/hid_gtk/gtkhid-gdk.c	(revision 6910)
@@ -614,7 +614,7 @@
 
 void ghid_draw_arc(pcb_hid_gc_t gc, pcb_coord_t cx, pcb_coord_t cy, pcb_coord_t xradius, pcb_coord_t yradius, pcb_angle_t start_angle, pcb_angle_t delta_angle)
 {
-	gint vrx, vry, vrx2, vry2, tune_x, tune_y;
+	gint vrx2, vry2;
 	double w, h, radius;
 	render_priv *priv = gport->render_priv;
 
@@ -627,8 +627,6 @@
 		return;
 
 	USE_GC(gc);
-	vrx = Vz(xradius);
-	vry = Vz(yradius);
 	vrx2 = Vz(xradius*2.0);
 	vry2 = Vz(yradius*2.0);
 
@@ -650,15 +648,8 @@
 	if (start_angle >= 180)
 		start_angle -= 360;
 
-
-	/* we calculated with doubles but the API needs ints; there might be
-	   an error of +-1 in the rounding that may add up when gdk calculates
-	   the endpoint. This hack will fix that error. */
-	tune_x = Vx(cx+xradius) - (Vx(cx - xradius) + vrx2);
-	tune_y = Vy(cy+yradius) - (Vy(cy - yradius) + vry2);
-
 	gdk_draw_arc(gport->drawable, priv->u_gc, 0,
-							 Vx(cx - xradius) + tune_x, Vy(cy - yradius) + tune_y,
+							 pcb_round(Vxd(cx) - Vzd(xradius) + 0.5), pcb_round(Vyd(cy) - Vzd(yradius) + 0.5),
 							 pcb_round(vrx2), pcb_round(vry2),
 							 (start_angle + 180) * 64, delta_angle * 64);
 }
Index: trunk/src_plugins/hid_gtk/gui.h
===================================================================
--- trunk/src_plugins/hid_gtk/gui.h	(revision 6909)
+++ trunk/src_plugins/hid_gtk/gui.h	(revision 6910)
@@ -323,6 +323,31 @@
 	return pcb_round((double)z / gport->view.coord_per_px + 0.5);
 }
 
+static inline double Vxd(pcb_coord_t x)
+{
+	double rv;
+	if (conf_core.editor.view.flip_x)
+		rv = (PCB->MaxWidth - x - gport->view.x0) / gport->view.coord_per_px;
+	else
+		rv = (x - gport->view.x0) / gport->view.coord_per_px;
+	return rv;
+}
+
+static inline double Vyd(pcb_coord_t y)
+{
+	double rv;
+	if (conf_core.editor.view.flip_y)
+		rv = (PCB->MaxHeight - y - gport->view.y0) / gport->view.coord_per_px;
+	else
+		rv = (y - gport->view.y0) / gport->view.coord_per_px;
+	return rv;
+}
+
+static inline double Vzd(pcb_coord_t z)
+{
+	return (double)z / gport->view.coord_per_px;
+}
+
 static inline pcb_coord_t Px(int x)
 {
 	pcb_coord_t rv = x * gport->view.coord_per_px + gport->view.x0;