X-Git-Url: https://git.carlh.net/gitweb/?a=blobdiff_plain;f=src%2Flib%2Frect.h;h=d0daec43712ab4c5cd7a0bf88cf27c3c5fc69a74;hb=55861a0b4ad4270f80b8d1ae10230cf2ebb25735;hp=5758dd04e4496955af9b7cc994c492bf785c40b6;hpb=218ffe2c5f92ed19ec488cda5012b64fcabd5e3f;p=dcpomatic.git

diff --git a/src/lib/rect.h b/src/lib/rect.h
index 5758dd04e..d0daec437 100644
--- a/src/lib/rect.h
+++ b/src/lib/rect.h
@@ -1,19 +1,20 @@
 /*
     Copyright (C) 2013 Carl Hetherington <cth@carlh.net>
 
-    This program is free software; you can redistribute it and/or modify
+    This file is part of DCP-o-matic.
+
+    DCP-o-matic is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation; either version 2 of the License, or
     (at your option) any later version.
 
-    This program is distributed in the hope that it will be useful,
+    DCP-o-matic is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
 
     You should have received a copy of the GNU General Public License
-    along with this program; if not, write to the Free Software
-    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+    along with DCP-o-matic.  If not, see <http://www.gnu.org/licenses/>.
 
 */
 
@@ -21,6 +22,7 @@
 #define DCPOMATIC_RECT_H
 
 #include "position.h"
+#include <boost/optional.hpp>
 #include <algorithm>
 
 /* Put this inside a namespace as Apple put a Rect in the global namespace */
@@ -67,16 +69,24 @@ public:
 		return Position<T> (x, y);
 	}
 
-	Rect<T> intersection (Rect<T> const & other) const
+	boost::optional<Rect<T> > intersection (Rect<T> const & other) const
 	{
-		T const tx = max (x, other.x);
-		T const ty = max (y, other.y);
+		/* This isn't exactly the paragon of mathematical precision */
+
+		T const tx = std::max (x, other.x);
+		T const ty = std::max (y, other.y);
 
-		return Rect (
+		Rect r (
 			tx, ty,
-			min (x + width, other.x + other.width) - tx,
-			min (y + height, other.y + other.height) - ty
+			std::min (x + width, other.x + other.width) - tx,
+			std::min (y + height, other.y + other.height) - ty
 			);
+
+		if (r.width < 0 || r.height < 0) {
+			return boost::optional<Rect<T> > ();
+		}
+
+		return r;
 	}
 
 	void extend (Rect<T> const & other)