Add Rect intersection and union methods

SDL2pp/Rect.cc

@@ -19,6 +19,8 @@
   3. This notice may not be removed or altered from any source distribution.
 */
 
+#include <algorithm>
+
 #include <SDL2pp/Point.hh>
 
 #include <SDL2pp/Rect.hh>
@@ -150,6 +152,31 @@ bool Rect::Contains(const Rect& rect) const {
 	return rect.x >= x && rect.y >= y && rect.GetX2() <= GetX2() && rect.GetY2() <= GetY2();
 }
 
+bool Rect::Intersects(const Rect& rect) const {
+	return !(rect.GetX2() < x || rect.GetY2() < y || rect.x > GetX2() || rect.y > GetY2());
+}
+
+Rect Rect::GetUnion(const Rect& rect) const {
+	return Rect::FromCorners(
+			std::min(x, rect.x),
+			std::min(y, rect.y),
+			std::max(GetX2(), rect.GetX2()),
+			std::max(GetY2(), rect.GetY2())
+		);
+}
+
+Optional<Rect> Rect::GetIntersection(const Rect& rect) const {
+	if (!Intersects(rect))
+		return NullOpt;
+
+	return Rect::FromCorners(
+			std::max(x, rect.x),
+			std::max(y, rect.y),
+			std::min(GetX2(), rect.GetX2()),
+			std::min(GetY2(), rect.GetY2())
+		);
+}
+
 Rect Rect::operator+(const Point& offset) const {
 	return Rect(x + offset.x, y + offset.y, w, h);
 }

SDL2pp/Rect.hh

@@ -301,6 +301,36 @@ public:
 	////////////////////////////////////////////////////////////
 	bool Contains(const Rect& rect) const;
 
+	////////////////////////////////////////////////////////////
+	/// \brief Check whether the rect intersects another rect
+	///
+	/// \param rect Rect to check
+	///
+	/// \returns True if the rects intersect
+	///
+	////////////////////////////////////////////////////////////
+	bool Intersects(const Rect& rect) const;
+
+	////////////////////////////////////////////////////////////
+	/// \brief Calculate union with another rect
+	///
+	/// \param rect Rect to union with
+	///
+	/// \returns Rect representing intersection area or NullOpt if there was no intersection
+	///
+	////////////////////////////////////////////////////////////
+	Rect GetUnion(const Rect& rect) const;
+
+	////////////////////////////////////////////////////////////
+	/// \brief Calculate intersection with another rect
+	///
+	/// \param rect Rect to intersect with
+	///
+	/// \returns Rect representing intersection area or NullOpt if there was no intersection
+	///
+	////////////////////////////////////////////////////////////
+	Optional<Rect> GetIntersection(const Rect& rect) const;
+
 	////////////////////////////////////////////////////////////
 	/// \brief Get rectangle moved by a given offset
 	///