Gamma Init

app/WindowsDisplayAPI/Native/DisplayConfig/Structures/DisplayConfigRational.cs

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+using System;
+using System.Diagnostics.Contracts;
+using System.Runtime.InteropServices;
+
+namespace WindowsDisplayAPI.Native.DisplayConfig.Structures
+{
+    // https://msdn.microsoft.com/en-us/library/windows/hardware/ff553968(v=vs.85).aspx
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct DisplayConfigRational : IEquatable<DisplayConfigRational>
+    {
+        [MarshalAs(UnmanagedType.U4)] public readonly uint Numerator;
+        [MarshalAs(UnmanagedType.U4)] public readonly uint Denominator;
+
+        public DisplayConfigRational(uint numerator, uint denominator, bool simplify)
+            : this((ulong) numerator, denominator, simplify)
+        {
+        }
+
+        public DisplayConfigRational(ulong numerator, ulong denominator, bool simplify)
+        {
+            var gcm = simplify & (numerator != 0) ? Euclidean(numerator, denominator) : 1;
+            Numerator = (uint) (numerator / gcm);
+            Denominator = (uint) (denominator / gcm);
+        }
+
+        private static ulong Euclidean(ulong a, ulong b)
+        {
+            while (a != 0 && b != 0)
+            {
+                if (a > b)
+                {
+                    a %= b;
+                }
+                else
+                {
+                    b %= a;
+                }
+            }
+
+            return a == 0 ? b : a;
+        }
+
+        [Pure]
+        public ulong ToValue(ulong multiplier = 1)
+        {
+            if (Numerator == 0)
+            {
+                return 0;
+            }
+
+            return Numerator * multiplier / Denominator;
+        }
+
+        public bool Equals(DisplayConfigRational other)
+        {
+            if (Numerator == other.Numerator && Denominator == other.Denominator)
+            {
+                return true;
+            }
+
+            var left = Numerator / (double) Denominator;
+            var right = other.Numerator / (double) other.Denominator;
+
+            return Math.Abs(left - right) <= Math.Max(Math.Abs(left), Math.Abs(right)) * 1E-15;
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (ReferenceEquals(null, obj))
+            {
+                return false;
+            }
+
+            return obj is DisplayConfigRational rational && Equals(rational);
+        }
+
+        public override int GetHashCode()
+        {
+            unchecked
+            {
+                return ((int) Numerator * 397) ^ (int) Denominator;
+            }
+        }
+
+        public static bool operator ==(DisplayConfigRational left, DisplayConfigRational right)
+        {
+            return Equals(left, right) || left.Equals(right);
+        }
+
+        public static bool operator !=(DisplayConfigRational left, DisplayConfigRational right)
+        {
+            return !(left == right);
+        }
+    }
+}