From 59852ace856b5951f6b7ae56feae005a51696fa9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vladim=C3=ADr=20Vondru=C5=A1?= <mosra@centrum.cz>
Date: Mon, 13 Aug 2018 19:19:56 +0200
Subject: [PATCH] Math: ability to slice Range into lower dimensions.

---
 doc/changelog.dox                  |  3 +++
 src/Magnum/Math/Range.h            | 30 ++++++++++++++++++++++++++++
 src/Magnum/Math/Test/RangeTest.cpp | 32 ++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+)

diff --git a/doc/changelog.dox b/doc/changelog.dox
index 54cff986e..df1273c28 100644
--- a/doc/changelog.dox
+++ b/doc/changelog.dox
@@ -66,6 +66,9 @@ See also:
     @ref Math::Color4::fromSrgb(UnsignedInt, T), @ref Math::Color3::toSrgbInt(),
     and @ref Math::Color4::toSrgbAlphaInt() for easier conversion of packed
     24-/32-bit sRGB colors to and from @ref Math::Color3 / @ref Math::Color4
+-   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
 -   Added @ref Math::Constants::piQuarter()
 -   Added a convenience function @ref Math::select() as a constant
     interpolation counterpart to @ref Math::lerp()
diff --git a/src/Magnum/Math/Range.h b/src/Magnum/Math/Range.h
index c8a3e7758..8d1c95148 100644
--- a/src/Magnum/Math/Range.h
+++ b/src/Magnum/Math/Range.h
@@ -317,6 +317,16 @@ template<class T> class Range2D: public Range<2, T> {
         T& top() { return Range<2, T>::max().y(); }
         constexpr T top() const { return Range<2, T>::max().y(); } /**< @overload */
 
+        /** @brief Range in the X axis */
+        constexpr Range<1, T> x() const {
+            return {Range<2, T>::min().x(), Range<2, T>::max().x()};
+        }
+
+        /** @brief Range in the Y axis */
+        constexpr Range<1, T> y() const {
+            return {Range<2, T>::min().y(), Range<2, T>::max().y()};
+        }
+
         /**
          * @brief Range width
          *
@@ -470,6 +480,26 @@ template<class T> class Range3D: public Range<3, T> {
         T& front() { return Range<3, T>::max().z(); }
         constexpr T front() const { return Range<3, T>::max().z(); } /**< @overload */
 
+        /** @brief Range in the X axis */
+        constexpr Range<1, T> x() const {
+            return {Range<3, T>::min().x(), Range<3, T>::max().x()};
+        }
+
+        /** @brief Range in the Y axis */
+        constexpr Range<1, T> y() const {
+            return {Range<3, T>::min().y(), Range<3, T>::max().y()};
+        }
+
+        /** @brief Range in the Z axis */
+        constexpr Range<1, T> z() const {
+            return {Range<3, T>::min().z(), Range<3, T>::max().z()};
+        }
+
+        /** @brief Range in the XY plane */
+        constexpr Range<2, T> xy() const {
+            return {Range<3, T>::min().xy(), Range<3, T>::max().xy()};
+        }
+
         /**
          * @brief Range width
          *
diff --git a/src/Magnum/Math/Test/RangeTest.cpp b/src/Magnum/Math/Test/RangeTest.cpp
index 7ddc77f41..33d2c00f7 100644
--- a/src/Magnum/Math/Test/RangeTest.cpp
+++ b/src/Magnum/Math/Test/RangeTest.cpp
@@ -107,6 +107,7 @@ struct RangeTest: Corrade::TestSuite::Tester {
 
     void access();
     void compare();
+    void dimensionSlice();
     void size();
     void center();
 
@@ -144,6 +145,7 @@ RangeTest::RangeTest() {
 
               &RangeTest::access,
               &RangeTest::compare,
+              &RangeTest::dimensionSlice,
               &RangeTest::size,
               &RangeTest::center,
 
@@ -409,6 +411,36 @@ void RangeTest::compare() {
                                                   1.0f + TypeTraits<Float>::epsilon()/2.0f));
 }
 
+void RangeTest::dimensionSlice() {
+    constexpr Range1Di lineX{34, 47};
+    constexpr Range1Di lineY{23, 30};
+    constexpr Range1Di lineZ{-17, 12};
+    constexpr Range2Di rect{{34, 23}, {47, 30}};
+    constexpr Range3Di cube{{34, 23, -17}, {47, 30, 12}};
+
+    constexpr Range1Di x2 = rect.x();
+    constexpr Range1Di x3 = cube.x();
+    CORRADE_COMPARE(x2, lineX);
+    CORRADE_COMPARE(x3, lineX);
+    CORRADE_COMPARE(rect.x(), lineX);
+    CORRADE_COMPARE(cube.x(), lineX);
+
+    constexpr Range1Di y2 = rect.y();
+    constexpr Range1Di y3 = cube.y();
+    CORRADE_COMPARE(y2, lineY);
+    CORRADE_COMPARE(y3, lineY);
+    CORRADE_COMPARE(rect.y(), lineY);
+    CORRADE_COMPARE(cube.y(), lineY);
+
+    constexpr Range1Di z = cube.z();
+    CORRADE_COMPARE(z, lineZ);
+    CORRADE_COMPARE(cube.z(), lineZ);
+
+    constexpr Range2Di xy = cube.xy();
+    CORRADE_COMPARE(xy, rect);
+    CORRADE_COMPARE(cube.xy(), rect);
+}
+
 void RangeTest::size() {
     const Range1Di line(34, 47);
     const Range2Di rect({34, 23}, {47, 30});