Re: gEDA-user: geda-user Digest, Vol 46, Issue 27

[Stephen Ecob <silicon.on.inspiration@xxxxxxxxx>]

On Mon, Mar 8, 2010 at 10:13 PM, Harry Eaton <bumpelo@xxxxxxxxx> wrote:

[...]

>   It looks to me like the SQ() macro risks integer overflow when squaring
>   the lengths.

Thank you, good point.

Here's an updated patch that uses Manhattan distance instead - for the
tiny lengths involved it should be fine.

Peer review saves the day :)

diff --git a/src/djopt.c b/src/djopt.c
index 68b3641..230b3c7 100644
--- a/src/djopt.c
+++ b/src/djopt.c
@@ -75,6 +75,9 @@ RCSID ("$Id$");
 #define ORIENT(x) ((x) & 0xf0)
 #define DIRECT(x) ((x) & 0x0f)

+/* Manhattan length of the longest "freckle" */
+#define LONGEST_FRECKLE	2
+
 struct line_s;

 typedef struct corner_s
@@ -1230,6 +1233,33 @@ simple_optimize_corner (corner_s * c)
 	}
     }
   check (c, 0);
+  if (c->n_lines == 1 && !c->via)
+    {
+      corner_s *c0 = other_corner (c->lines[0], c);
+      if (abs(c->x - c0->x) + abs(c->y - c0->y) <= LONGEST_FRECKLE)
+	{
+          /*
+           * Remove this line, as it is a "freckle".  A freckle is an extremely
+           * short line (around 0.01 thou) that is unconnected at one end.
+           * Freckles are almost insignificantly small, but are annoying as
+           * they prevent the mitering optimiser from working.
+           * Freckles sometimes arise because of a bug in the autorouter that
+           * causes it to create small overshoots (typically 0.01 thou) at the
+           * intersections of vertical and horizontal lines. These overshoots
+           * are converted to freckles as a side effect of canonicalize_line().
+           * Note that canonicalize_line() is not at fault, the bug is in the
+           * autorouter creating overshoots.
+           * The autorouter bug arose some time between the 20080202
and 20091103
+           * releases.
+           * This code is probably worth keeping even when the
autorouter bug is
+           * fixed, as "freckles" could conceivably arise in other ways.
+           */
+	  dprintf ("freckle %d,%d to %d,%d\n",
+		   c->x, c->y, c0->x, c0->y);
+	  move_corner (c, c0->x, c0->y);
+	}
+    }
+  check (c, 0);
   return rv;
 }


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