[dia/dia-0-97] Bug 728405 - back-port some bounding box calculation fixes from master

[Hans Breuer <hans src gnome org>]

commit 8b8ae09fcc16cc0522679099728f779e291d959c
Author: Hans Breuer <hans breuer org>
Date:   Fri Apr 18 13:28:45 2014 +0200

    Bug 728405 - back-port some bounding box calculation fixes from master
    
    ... so that the unit test works without complaints.

 lib/boundingbox.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/lib/boundingbox.c b/lib/boundingbox.c
index fd50da7..46adbfa 100644
--- a/lib/boundingbox.c
+++ b/lib/boundingbox.c
@@ -494,7 +494,7 @@ polybezier_bbox(const BezPoint *pts, int numpoints,
        account with the "pointy corners" X (and PS) add when LINEJOIN_MITER mode is 
        in force. */
 
-    if ((!start) && (!end)) { /* We have a non-extremity vertex. */
+    if (!end) { /* only the last segment might not produce overshoot. */
       Point vpx,vxn;
       real co,alpha;
 
@@ -515,7 +515,7 @@ polybezier_bbox(const BezPoint *pts, int numpoints,
         real overshoot;
         Point vovs,pto;
 
-       if (finite(alpha))
+       if (alpha > 0.0 && alpha < M_PI)
          overshoot = extra->middle_trans / sin(alpha/2.0);
        else /* prependicular? */
          overshoot = extra->middle_trans;