X-Git-Url: https://main.carlh.net/gitweb/?p=dcpomatic.git;a=blobdiff_plain;f=src%2Flib%2Frect.h;h=4851ad007fe11c6ce7b7469c2cb6f7367dd2eccd;hp=1feb8ad4fed460d19a9f83439e21bdd0abcc1ea0;hb=6ef1fc5f40567650ca9ef2b7644e4fdd97640ae6;hpb=f4030653da8f5a0b3daebe640f485b3daf9ef091

diff --git a/src/lib/rect.h b/src/lib/rect.h
index 1feb8ad4f..4851ad007 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/>.
 
 */
 
@@ -21,20 +22,22 @@
 #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 */
 
 namespace dcpomatic
 {
-	
+
 /** @struct Rect
  *  @brief A rectangle.
  */
-template <class T>	
+template <class T>
 class Rect
 {
 public:
-	
+
 	Rect ()
 		: x (0)
 		, y (0)
@@ -66,24 +69,43 @@ 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);
-	
-		return Rect (
+		/* 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);
+
+		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)
 	{
+		T old_x = x;
+		T old_y = y;
 		x = std::min (x, other.x);
 		y = std::min (y, other.y);
-		width = std::max (x + width, other.x + other.width) - x;
-		height = std::max (y + height, other.y + other.height) - y;
+		width = std::max (old_x + width, other.x + other.width) - x;
+		height = std::max (old_y + height, other.y + other.height) - y;
+	}
+
+	Rect<T> extended (T amount) const {
+		Rect<T> c = *this;
+		c.x -= amount;
+		c.y -= amount;
+		c.width += amount * 2;
+		c.height += amount * 2;
+		return c;
 	}
 
 	bool contains (Position<T> p) const