libart patch

[Alex Larsson <alexl redhat com>]

art_drect_svp() and art_drect_svp_union() are broken for svps that only 
contain segments that are "empty" accoding to art_drect_empty(). This is 
true for i.e. rectangles. Since the bboxes of the segments either have 
zero width or zero height the resultant union bbox is empty.

I will commit the attached patch to cvs that sort of fixes this for some 
cases, but in general the way libart handles empty rects is pretty 
broken. If your're using libart, please review your usage of 
art_drect_svp(),  art_drect_svp_union(), art_drect_empty() and
art_drect_union().

/ Alex

Index: art_rect_svp.c
===================================================================
RCS file: /cvs/gnome/libart_lgpl/art_rect_svp.c,v
retrieving revision 1.3
diff -u -p -r1.3 art_rect_svp.c
--- art_rect_svp.c	1999/09/01 07:04:21	1.3
+++ art_rect_svp.c	2001/11/16 17:03:49
@@ -22,6 +22,14 @@
 #include "art_rect.h"
 #include "art_rect_svp.h"
 
+#ifndef MAX
+#define MAX(a, b)  (((a) > (b)) ? (a) : (b))
+#endif /* MAX */
+
+#ifndef MIN
+#define MIN(a, b)  (((a) < (b)) ? (a) : (b))
+#endif /* MIN */
+
 /**
  * art_drect_svp: Find the bounding box of a sorted vector path.
  * @bbox: Where to store the bounding box.
@@ -34,14 +42,23 @@ art_drect_svp (ArtDRect *bbox, const Art
 {
   int i;
 
-  bbox->x0 = 0;
-  bbox->y0 = 0;
-  bbox->x1 = 0;
-  bbox->y1 = 0;
+  if (svp->n_segs == 0)
+    {
+      bbox->x0 = 0;
+      bbox->y0 = 0;
+      bbox->x1 = 0;
+      bbox->y1 = 0;
+      return;
+    }
 
-  for (i = 0; i < svp->n_segs; i++)
+  art_drect_copy (bbox, &svp->segs[0].bbox);
+  
+  for (i = 1; i < svp->n_segs; i++)
     {
-      art_drect_union (bbox, bbox, &svp->segs[i].bbox);
+      bbox->x0 = MIN (bbox->x0, svp->segs[i].bbox.x0);
+      bbox->y0 = MIN (bbox->y0, svp->segs[i].bbox.y0);
+      bbox->x1 = MAX (bbox->x1, svp->segs[i].bbox.x1);
+      bbox->y1 = MAX (bbox->y1, svp->segs[i].bbox.y1);
     }
 }
 
@@ -56,10 +73,8 @@ art_drect_svp (ArtDRect *bbox, const Art
 void
 art_drect_svp_union (ArtDRect *bbox, const ArtSVP *svp)
 {
-  int i;
+  ArtDRect svp_bbox;
 
-  for (i = 0; i < svp->n_segs; i++)
-    {
-      art_drect_union (bbox, bbox, &svp->segs[i].bbox);
-    }
+  art_drect_svp (&svp_bbox, svp);
+  art_drect_union (bbox, bbox, &svp_bbox);
 }