Math: ability to create Rectangle from other of arbitrary type.

src/Math/Geometry/Rectangle.h

@@ -42,6 +42,21 @@ template<class T> class Rectangle {
             return {bottomLeft, bottomLeft+size};
         }
 
+        /**
+         * @brief %Rectangle from another of different type
+         *
+         * Performs only default casting on the values, no rounding or
+         * anything else. Example usage:
+         * @code
+         * Rectangle<float> floatingPoint({1.3f, 2.7f}, {-15.0f, 7.0f});
+         * auto integral = Rectangle<std::int8_t>::from(floatingPoint);
+         * // integral == {{1, 2}, {-15, 7}}
+         * @endcode
+         */
+        template<class U> inline constexpr static Rectangle<T> from(const Rectangle<U>& other) {
+            return {Vector2<T>::from(other.bottomLeft()), Vector2<T>::from(other.topRight())};
+        }
+
         /**
          * @brief Default constructor
          *

src/Math/Geometry/Test/RectangleTest.cpp

@@ -23,7 +23,8 @@ CORRADE_TEST_MAIN(Magnum::Math::Geometry::Test::RectangleTest)
 
 namespace Magnum { namespace Math { namespace Geometry { namespace Test {
 
-typedef Rectangle<std::int32_t> Rectanglei;
+typedef Geometry::Rectangle<float> Rectangle;
+typedef Geometry::Rectangle<std::int32_t> Rectanglei;
 typedef Vector2<std::int32_t> Vector2i;
 
 RectangleTest::RectangleTest() {
@@ -61,6 +62,8 @@ void RectangleTest::compare() {
 void RectangleTest::construct() {
     CORRADE_COMPARE(Rectanglei(), Rectanglei({0, 0}, {0, 0}));
     CORRADE_COMPARE(Rectanglei::fromSize({3, 5}, {23, 78}), Rectanglei({3, 5}, {26, 83}));
+    CORRADE_COMPARE(Rectanglei::from(Rectangle({1.3f, 2.7f}, {-15.0f, 7.0f})),
+                    Rectanglei({1, 2}, {-15, 7}));
 }
 
 void RectangleTest::size() {