Add rect::shifted_by

Companion of rect::shift for const objects

src/sdl/rect.cpp

@@ -107,6 +107,19 @@ void rect::shift(const point& other)
 	this->y += other.y;
 }
 
+rect rect::shifted_by(int x, int y) const
+{
+	rect res = *this;
+	res.x += x;
+	res.y += y;
+	return res;
+}
+
+rect rect::shifted_by(const point& other) const
+{
+	return shifted_by(other.x, other.y);
+}
+
 std::ostream& operator<<(std::ostream& s, const rect& r)
 {
 	s << '[' << r.x << ',' << r.y << '|' << r.w << ',' << r.h << ']';

src/sdl/rect.hpp

@@ -147,6 +147,10 @@ public:
 	 * The point's X and Y coordinates will be added to the rectangle's.
 	 */
 	void shift(const point& p);
+
+	/** Returns a new rectangle shifted by the given relative position. */
+	rect shifted_by(int x, int y) const;
+	rect shifted_by(const point& p) const;
 };
 
 std::ostream& operator<<(std::ostream&, const rect&);