Math: added Range::scaledFromCenter().

doc/changelog.dox

@@ -97,13 +97,15 @@ See also:
     shortest-path
 -   Added @ref Math::Range2D::x(), @ref Math::Range3D::x(),
     @ref Math::Range2D::y(), @ref Math::Range3D::y(), @ref Math::Range3D::z()
-    and @ref Math::Range3D::y() for slicing ranges into lower dimensions
+    and @ref Math::Range3D::xy() for slicing ranges into lower dimensions
 -   Added @ref Math::intersect() and @ref Math::intersects() as a counterpart
     to @ref Math::join() for operating with @ref Math::Range instances
 -   Added @ref Math::Range::contains() overloading taking a range, in addition
     to vector
 -   Added @ref Math::Range::fromCenter() and documented a hint how to create
     integral centered ranges
+-   Added @ref Math::Range::scaledFromCenter() as a counterpart to
+    @ref Math::Range::scaled()
 -   @ref Math::Range is now constructible from a @ref std::pair of values,
     making it usable in combination with @ref Math::minmax(), for example
 -   Added @ref Math::Constants::piQuarter(), @ref Math::Constants::sqrtHalf()

src/Magnum/Math/Range.h

@@ -223,12 +223,25 @@ template<UnsignedInt dimensions, class T> class Range {
          * @brief Scaled range
          *
          * Multiplies the minimal and maximal coordinates by given amount.
+         * Center *doesn't* remain the same, use @ref scaledFromCenter() for
+         * that operation.
          * @see @ref padded()
          */
         Range<dimensions, T> scaled(const VectorType& scaling) const {
             return {_min*scaling, _max*scaling};
         }
 
+        /**
+         * @brief Range scaled from the center
+         *
+         * Scales the size, while center remains the same.
+         * @see @ref scaled(), @ref padded(), @ref fromCenter()
+         */
+        Range<dimensions, T> scaledFromCenter(const VectorType& scaling) const {
+            /* Can't use *T(0.5) because that won't work for integers */
+            return fromCenter(center(), size()*scaling/T(2));
+        }
+
         /**
          * @brief Whether given point is contained inside the range
          *

src/Magnum/Math/Test/RangeTest.cpp

@@ -116,6 +116,7 @@ struct RangeTest: Corrade::TestSuite::Tester {
     void translated();
     void padded();
     void scaled();
+    void scaledFromCenter();
 
     void containsVector();
     void containsRange();
@@ -158,6 +159,7 @@ RangeTest::RangeTest() {
               &RangeTest::translated,
               &RangeTest::padded,
               &RangeTest::scaled,
+              &RangeTest::scaledFromCenter,
 
               &RangeTest::containsVector,
               &RangeTest::containsRange,
@@ -531,6 +533,16 @@ void RangeTest::scaled() {
     Range2Di b({68, -69}, {94, -90});
 
     CORRADE_COMPARE(a.scaled({2, -3}), b);
+    CORRADE_COMPARE((a.size()*Vector2i{2, -3}), b.size());
+}
+
+void RangeTest::scaledFromCenter() {
+    Range2Di a{{34, 22}, {48, 30}};
+    Range2Di b{{27, 38}, {55, 14}};
+
+    CORRADE_COMPARE(a.scaledFromCenter({2, -3}), b);
+    CORRADE_COMPARE(a.center(), b.center());
+    CORRADE_COMPARE((a.size()*Vector2i{2, -3}), b.size());
 }
 
 void RangeTest::containsVector() {