Approximate aspect ratio calculation on VideoMode (#982)

Note: Ratios that can be simplified like 16:10 will be reported as 8:5, blame monitor manufacturers

Author: aquagoose

.nuke/build.schema.json

@@ -29,6 +29,7 @@
             "AppVeyor",
             "AzurePipelines",
             "Bamboo",
+            "Bitbucket",
             "Bitrise",
             "GitHubActions",
             "GitLab",

src/Windowing/Silk.NET.Windowing.Common/PublicAPI/netstandard2.0/PublicAPI.Unshipped.txt

@@ -1 +1,2 @@
 #nullable enable
+Silk.NET.Windowing.VideoMode.AspectRatioEstimate.get -> Silk.NET.Maths.Vector2D<int>?

src/Windowing/Silk.NET.Windowing.Common/PublicAPI/netstandard2.1/PublicAPI.Unshipped.txt

@@ -1 +1,2 @@
 #nullable enable
+Silk.NET.Windowing.VideoMode.AspectRatioEstimate.get -> Silk.NET.Maths.Vector2D<int>?

src/Windowing/Silk.NET.Windowing.Common/Structs/VideoMode.cs

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System;
 using Silk.NET.Maths;
 
 namespace Silk.NET.Windowing
@@ -11,12 +12,11 @@ public VideoMode(Vector2D<int>? resolution = null, int? refreshRate = null)
         {
             Resolution = resolution;
             RefreshRate = refreshRate;
+            AspectRatioEstimate = resolution != null ? CalculateAspectRatio(resolution.Value) : null;
         }
 
         public VideoMode(int refreshRate)
-            : this(null, refreshRate)
-        {
-        }
+            : this(null, refreshRate) { }
 
         /// <summary>
         /// Resolution of the full screen window.
@@ -28,9 +28,35 @@ public VideoMode(int refreshRate)
         /// </summary>
         public int? RefreshRate { get; }
 
+        /// <summary>
+        /// Aspect ratio of the full screen window. This value will not be 100% accurate to the actual value, however
+        /// is more accurate to what a user may expect the ratio to be (for example a resolution of 1366x768 will appear
+        /// as 16:9, even though it is not quite 16:9 in reality).
+        /// </summary>
+        public Vector2D<int>? AspectRatioEstimate { get; }
+
         /// <summary>
         /// The default video mode. This uses the window size for resolution and doesn't care about other values.
         /// </summary>
         public static VideoMode Default => new VideoMode();
+
+        private static Vector2D<int> CalculateAspectRatio(Vector2D<int> res)
+        {
+            // Calculate the width-height ratio.
+            float ratio = res.X / (float) res.Y;
+
+            // Count up until the lowest value as the aspect ratio cannot be higher than the lowest value.
+            int lowestValue = res.X < res.Y ? res.X : res.Y;
+            for (int i = 1; i < lowestValue; i++)
+            {
+                // Multiply both together and calculate a good enough value, a bias of 0.1 seems to work well.
+                float multiplied = ratio * i;
+                if (multiplied - (int) multiplied < 0.1f)
+                    return new Vector2D<int>((int) multiplied, i);
+            }
+
+            return res;
+        }
+
     }
-}
+}