Fix assertion failure on opening content properties (#816).

[dcpomatic.git] / src / lib / rect.h

diff --git a/src/lib/rect.h b/src/lib/rect.h
index 1feb8ad4fed460d19a9f83439e21bdd0abcc1ea0..602acfc4b8bb5cd6fb691c21861e5a19a54a2248 100644 (file)
--- 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));