There seems to be some odd behaviour when GTK is asked to draw an

outline polygon with a clipping rectangle active. I don't know or
care whether this is GTK or my X server or what, but I'm working
around it by drawing the lines myself, which seems to sort it out.

[originally from svn r6227]

gtk.c

@@ -373,7 +373,17 @@ void gtk_draw_poly(void *handle, int *coords, int npoints,
     }
     assert(outlinecolour >= 0);
     gdk_gc_set_foreground(fe->gc, &fe->colours[outlinecolour]);
-    gdk_draw_polygon(fe->pixmap, fe->gc, FALSE, points, npoints);
+
+    /*
+     * In principle we ought to be able to use gdk_draw_polygon for
+     * the outline as well. In fact, it turns out to interact badly
+     * with a clipping region, for no terribly obvious reason, so I
+     * draw the outline as a sequence of lines instead.
+     */
+    for (i = 0; i < npoints; i++)
+	gdk_draw_line(fe->pixmap, fe->gc,
+		      points[i].x, points[i].y,
+		      points[(i+1)%npoints].x, points[(i+1)%npoints].y);
 
     sfree(points);
 }