X-Git-Url: https://main.carlh.net/gitweb/?a=blobdiff_plain;f=src%2Flib%2Frect.h;h=602acfc4b8bb5cd6fb691c21861e5a19a54a2248;hb=eb0bdad79aa8a8b32e7d23149cf0a0c8f1dfd380;hp=1feb8ad4fed460d19a9f83439e21bdd0abcc1ea0;hpb=854f2e5bbb7ffb9758b823af87034033033f3cb8;p=dcpomatic.git

diff --git a/src/lib/rect.h b/src/lib/rect.h
index 1feb8ad4f..602acfc4b 100644
--- a/src/lib/rect.h
+++ b/src/lib/rect.h
@@ -21,20 +21,22 @@
 #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)
@@ -66,16 +68,24 @@ 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);
-	
-		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)
@@ -86,6 +96,15 @@ public:
 		height = std::max (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
 	{
 		return (p.x >= x && p.x <= (x + width) && p.y >= y && p.y <= (y + height));