From 7affd7960fa3e5af3c25e0e9ccfdda1f67e3a83d Mon Sep 17 00:00:00 2001
From: King_DuckZ <king_duckz@gmx.com>
Date: Sat, 25 Jul 2015 21:18:45 +0200
Subject: [PATCH] Allow casting to vectors of lower dimensions.

---
 include/vectorwrapper/vectorwrapper.hpp | 26 +++++++++++++++----------
 include/vectorwrapper/vectorwrapper.inl |  2 +-
 test/unit/example.cpp                   | 11 +++++++++++
 3 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/include/vectorwrapper/vectorwrapper.hpp b/include/vectorwrapper/vectorwrapper.hpp
index 437f917..5ecd234 100644
--- a/include/vectorwrapper/vectorwrapper.hpp
+++ b/include/vectorwrapper/vectorwrapper.hpp
@@ -71,22 +71,29 @@ namespace vwr {
 			enum { value = get_offset_enum_from_index<T, 0>::value };
 		};
 
-		template <typename T, typename U, std::size_t TS=VectorWrapperInfo<T>::dimensions, std::size_t US=VectorWrapperInfo<U>::dimensions> struct have_compat_offsets {
-			enum { value = false };
-		};
-		template <typename T, typename U> struct have_compat_offsets<T, U, 1, 1> {
+		template <
+			typename T,
+			typename U,
+			std::size_t S=(
+				static_cast<int>(VectorWrapperInfo<T>::dimensions) < static_cast<int>(VectorWrapperInfo<U>::dimensions) ?
+					static_cast<int>(VectorWrapperInfo<T>::dimensions)
+				:
+					static_cast<int>(VectorWrapperInfo<U>::dimensions)
+				)
+			> struct have_compat_offsets;
+		template <typename T, typename U> struct have_compat_offsets<T, U, 1> {
 			enum {
 				value = true
 			};
 		};
-		template <typename T, typename U> struct have_compat_offsets<T, U, 2, 2> {
+		template <typename T, typename U> struct have_compat_offsets<T, U, 2> {
 			enum {
 				value =
 					VectorWrapperInfo<T>::offset_x - min_offset<T>::value == VectorWrapperInfo<U>::offset_x - min_offset<U>::value and
 					VectorWrapperInfo<T>::offset_y - min_offset<T>::value == VectorWrapperInfo<U>::offset_y - min_offset<U>::value
 			};
 		};
-		template <typename T, typename U> struct have_compat_offsets<T, U, 3, 3> {
+		template <typename T, typename U> struct have_compat_offsets<T, U, 3> {
 			enum {
 				value =
 					VectorWrapperInfo<T>::offset_x - min_offset<T>::value == VectorWrapperInfo<U>::offset_x - min_offset<U>::value and
@@ -94,7 +101,7 @@ namespace vwr {
 					VectorWrapperInfo<T>::offset_z - min_offset<T>::value == VectorWrapperInfo<U>::offset_z - min_offset<U>::value
 			};
 		};
-		template <typename T, typename U> struct have_compat_offsets<T, U, 4, 4> {
+		template <typename T, typename U> struct have_compat_offsets<T, U, 4> {
 			enum {
 				value =
 					VectorWrapperInfo<T>::offset_x - min_offset<T>::value == VectorWrapperInfo<U>::offset_x - min_offset<U>::value and
@@ -108,9 +115,8 @@ namespace vwr {
 		struct have_compat_layout {
 			enum {
 				value =
-					HasOffsetXEnum<VectorWrapperInfo<T>>::value and HasOffsetXEnum<VectorWrapperInfo<U>>::value and
-					static_cast<int>(VectorWrapperInfo<T>::dimensions) ==
-						static_cast<int>(VectorWrapperInfo<U>::dimensions) and
+					HasOffsetXEnum<VectorWrapperInfo<T>>::value and
+					HasOffsetXEnum<VectorWrapperInfo<U>>::value and
 					have_compat_offsets<T, U>::value
 			};
 		};
diff --git a/include/vectorwrapper/vectorwrapper.inl b/include/vectorwrapper/vectorwrapper.inl
index 81b6363..a10ff5c 100644
--- a/include/vectorwrapper/vectorwrapper.inl
+++ b/include/vectorwrapper/vectorwrapper.inl
@@ -79,7 +79,7 @@ namespace vwr {
 
 			//Assert that V2 won't stomp on part of V's data, unless the user
 			//has explicitly said he doesn't care.
-			static_assert((sizeof(typename VectorWrapperInfo<typename is_vec<V2>::vector_type>::scalar_type) * dimensions == sizeof(V2)) or
+			static_assert((sizeof(typename VectorWrapperInfo<typename is_vec<V2>::vector_type>::scalar_type) * VectorWrapperInfo<typename is_vec<V2>::vector_type>::dimensions == sizeof(V2)) or
 				IsCastIgnoreTrailingPropertiesSet<typename is_vec<V2>::vector_type>::value,
 				"V2 must not have any properties past the last coordinate");
 			static_assert(alignof(typename VectorWrapperInfo<V>::scalar_type) == alignof(V2), "Casting to V2 would give you a misaligned variable");
diff --git a/test/unit/example.cpp b/test/unit/example.cpp
index faa7d13..0046d21 100644
--- a/test/unit/example.cpp
+++ b/test/unit/example.cpp
@@ -2,6 +2,11 @@
 #include <gtest/gtest.h>
 
 namespace {
+	void test_svec2 (const vwr::svec2& parVec, float parX, float parY) {
+		EXPECT_EQ(parVec.x(), parX);
+		EXPECT_EQ(parVec.y(), parY);
+	}
+
 	void simplevec_double (vwr::SimpleVector3& parVec, float parX, float parY, float parZ) {
 		EXPECT_EQ(parVec.x, parX);
 		EXPECT_EQ(parVec.y, parY);
@@ -74,4 +79,10 @@ TEST(vwr, example) {
 		svec3 vec_b(vec);
 		EXPECT_EQ(vec_b, vec);
 	}
+
+	{
+		//You can also cast a svec3 to svec2, if you need to.
+		const svec3 vec(9.5f, 1.2f, 0.9f);
+		test_svec2(vec.cast<svec2>(), vec.x(), vec.y());
+	}
 }