From c3fca8325f34ed240069db256ce9081e13c0b20a Mon Sep 17 00:00:00 2001
From: Rustam Sayfutdinov <rstm.sf@gmail.com>
Date: Thu, 11 Jun 2020 20:21:07 +0300
Subject: [PATCH] Add math utilities to compare single precision

---
 src/Avalonia.Base/Utilities/MathUtilities.cs | 85 ++++++++++++++++++++
 1 file changed, 85 insertions(+)

diff --git a/src/Avalonia.Base/Utilities/MathUtilities.cs b/src/Avalonia.Base/Utilities/MathUtilities.cs
index 3fb5f7a162..7949a62949 100644
--- a/src/Avalonia.Base/Utilities/MathUtilities.cs
+++ b/src/Avalonia.Base/Utilities/MathUtilities.cs
@@ -11,6 +11,8 @@ namespace Avalonia.Utilities
         // smallest such that 1.0+DoubleEpsilon != 1.0
         private const double DoubleEpsilon = 2.2204460492503131e-016;
 
+        private const float FloatEpsilon = 1.192092896e-07F;
+
         /// <summary>
         /// AreClose - Returns whether or not two doubles are "close".  That is, whether or 
         /// not they are within epsilon of each other.
@@ -26,6 +28,21 @@ namespace Avalonia.Utilities
             return (-eps < delta) && (eps > delta);
         }
 
+        /// <summary>
+        /// AreClose - Returns whether or not two floats are "close".  That is, whether or 
+        /// not they are within epsilon of each other.
+        /// </summary> 
+        /// <param name="value1"> The first float to compare. </param>
+        /// <param name="value2"> The second float to compare. </param>
+        public static bool AreClose(float value1, float value2)
+        {
+            //in case they are Infinities (then epsilon check does not work)
+            if (value1 == value2) return true;
+            float eps = (Math.Abs(value1) + Math.Abs(value2) + 10.0f) * FloatEpsilon;
+            float delta = value1 - value2;
+            return (-eps < delta) && (eps > delta);
+        }
+
         /// <summary>
         /// LessThan - Returns whether or not the first double is less than the second double.
         /// That is, whether or not the first is strictly less than *and* not within epsilon of
@@ -38,6 +55,18 @@ namespace Avalonia.Utilities
             return (value1 < value2) && !AreClose(value1, value2);
         }
 
+        /// <summary>
+        /// LessThan - Returns whether or not the first float is less than the second float.
+        /// That is, whether or not the first is strictly less than *and* not within epsilon of
+        /// the other number.
+        /// </summary>
+        /// <param name="value1"> The first single float to compare. </param>
+        /// <param name="value2"> The second single float to compare. </param>
+        public static bool LessThan(float value1, float value2)
+        {
+            return (value1 < value2) && !AreClose(value1, value2);
+        }
+
         /// <summary>
         /// GreaterThan - Returns whether or not the first double is greater than the second double.
         /// That is, whether or not the first is strictly greater than *and* not within epsilon of
@@ -50,6 +79,18 @@ namespace Avalonia.Utilities
             return (value1 > value2) && !AreClose(value1, value2);
         }
 
+        /// <summary>
+        /// GreaterThan - Returns whether or not the first float is greater than the second float.
+        /// That is, whether or not the first is strictly greater than *and* not within epsilon of
+        /// the other number.
+        /// </summary>
+        /// <param name="value1"> The first float to compare. </param>
+        /// <param name="value2"> The second float to compare. </param>
+        public static bool GreaterThan(float value1, float value2)
+        {
+            return (value1 > value2) && !AreClose(value1, value2);
+        }
+
         /// <summary>
         /// LessThanOrClose - Returns whether or not the first double is less than or close to
         /// the second double.  That is, whether or not the first is strictly less than or within
@@ -62,6 +103,18 @@ namespace Avalonia.Utilities
             return (value1 < value2) || AreClose(value1, value2);
         }
 
+        /// <summary>
+        /// LessThanOrClose - Returns whether or not the first float is less than or close to
+        /// the second float.  That is, whether or not the first is strictly less than or within
+        /// epsilon of the other number.
+        /// </summary>
+        /// <param name="value1"> The first float to compare. </param>
+        /// <param name="value2"> The second float to compare. </param>
+        public static bool LessThanOrClose(float value1, float value2)
+        {
+            return (value1 < value2) || AreClose(value1, value2);
+        }
+
         /// <summary>
         /// GreaterThanOrClose - Returns whether or not the first double is greater than or close to
         /// the second double.  That is, whether or not the first is strictly greater than or within
@@ -74,6 +127,18 @@ namespace Avalonia.Utilities
             return (value1 > value2) || AreClose(value1, value2);
         }
 
+        /// <summary>
+        /// GreaterThanOrClose - Returns whether or not the first float is greater than or close to
+        /// the second float.  That is, whether or not the first is strictly greater than or within
+        /// epsilon of the other number.
+        /// </summary>
+        /// <param name="value1"> The first float to compare. </param>
+        /// <param name="value2"> The second float to compare. </param>
+        public static bool GreaterThanOrClose(float value1, float value2)
+        {
+            return (value1 > value2) || AreClose(value1, value2);
+        }
+
         /// <summary>
         /// IsOne - Returns whether or not the double is "close" to 1.  Same as AreClose(double, 1),
         /// but this is faster.
@@ -84,6 +149,16 @@ namespace Avalonia.Utilities
             return Math.Abs(value - 1.0) < 10.0 * DoubleEpsilon;
         }
 
+        /// <summary>
+        /// IsOne - Returns whether or not the float is "close" to 1.  Same as AreClose(float, 1),
+        /// but this is faster.
+        /// </summary>
+        /// <param name="value"> The float to compare to 1. </param>
+        public static bool IsOne(float value)
+        {
+            return Math.Abs(value - 1.0f) < 10.0f * FloatEpsilon;
+        }
+
         /// <summary>
         /// IsZero - Returns whether or not the double is "close" to 0.  Same as AreClose(double, 0),
         /// but this is faster.
@@ -94,6 +169,16 @@ namespace Avalonia.Utilities
             return Math.Abs(value) < 10.0 * DoubleEpsilon;
         }
 
+        /// <summary>
+        /// IsZero - Returns whether or not the float is "close" to 0.  Same as AreClose(float, 0),
+        /// but this is faster.
+        /// </summary>
+        /// <param name="value"> The float to compare to 0. </param>
+        public static bool IsZero(float value)
+        {
+            return Math.Abs(value) < 10.0f * FloatEpsilon;
+        }
+
         /// <summary>
         /// Clamps a value between a minimum and maximum value.
         /// </summary>