From 2bb0fb39998a55b6843261d714d8067e6d12b40a Mon Sep 17 00:00:00 2001
From: EZForever <34133756+EZForever@users.noreply.github.com>
Date: Wed, 28 Oct 2020 17:26:53 +0800
Subject: [PATCH 1/3] Add test case for glm::angle() sign bug introduced by
 #946

---
 test/ext/ext_quaternion_trigonometric.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/test/ext/ext_quaternion_trigonometric.cpp b/test/ext/ext_quaternion_trigonometric.cpp
index 1c1d6084..d2371252 100644
--- a/test/ext/ext_quaternion_trigonometric.cpp
+++ b/test/ext/ext_quaternion_trigonometric.cpp
@@ -21,6 +21,12 @@ static int test_angle()
 		Error += glm::equal(A, 90.0f, Epsilon) ? 0 : 1;
 	}
 
+	{
+		glm::quat const Q = glm::angleAxis(glm::two_pi<float>() - 1.0f, glm::vec3(1, 0, 0));
+		float const A = glm::angle(Q);
+		Error += glm::equal(A, 1.0f, Epsilon) ? 1 : 0;
+	}
+
 	return Error;
 }
 

From a66b782134f9577f55fd890c56e33024ff700fd3 Mon Sep 17 00:00:00 2001
From: EZForever <34133756+EZForever@users.noreply.github.com>
Date: Thu, 29 Oct 2020 13:50:31 +0800
Subject: [PATCH 2/3] fix: glm::angle() discards the sign of result for angles
 in range (2*pi-1, 2*pi)

---
 glm/ext/quaternion_trigonometric.inl | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/glm/ext/quaternion_trigonometric.inl b/glm/ext/quaternion_trigonometric.inl
index 06b7c4c3..56880e22 100644
--- a/glm/ext/quaternion_trigonometric.inl
+++ b/glm/ext/quaternion_trigonometric.inl
@@ -7,7 +7,10 @@ namespace glm
 	{
 		if (abs(x.w) > cos_one_over_two<T>())
 		{
-			return asin(sqrt(x.x * x.x + x.y * x.y + x.z * x.z)) * static_cast<T>(2);
+			T const a = asin(sqrt(x.x * x.x + x.y * x.y + x.z * x.z)) * static_cast<T>(2);
+			if(x.w < static_cast<T>(0))
+				return two_pi<T>() - a;
+			return a;
 		}
 
 		return acos(x.w) * static_cast<T>(2);

From f109b9185f7fab0c9ca3c61b0dac18beeb201546 Mon Sep 17 00:00:00 2001
From: EZForever <34133756+EZForever@users.noreply.github.com>
Date: Thu, 29 Oct 2020 14:02:04 +0800
Subject: [PATCH 3/3] Make CI happy

---
 glm/ext/quaternion_trigonometric.inl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/glm/ext/quaternion_trigonometric.inl b/glm/ext/quaternion_trigonometric.inl
index 56880e22..896449aa 100644
--- a/glm/ext/quaternion_trigonometric.inl
+++ b/glm/ext/quaternion_trigonometric.inl
@@ -9,7 +9,7 @@ namespace glm
 		{
 			T const a = asin(sqrt(x.x * x.x + x.y * x.y + x.z * x.z)) * static_cast<T>(2);
 			if(x.w < static_cast<T>(0))
-				return two_pi<T>() - a;
+				return pi<T>() * static_cast<T>(2) - a;
 			return a;
 		}