Prevent floats from being represented in scientific notation in expression animation strings

Microsoft.Toolkit.Uwp.UI.Animations/Expressions/ExpressionNodes/Matrix3x2Node.cs

@@ -332,7 +332,7 @@ public Matrix4x4Node GetSubchannels(Subchannel s1, Subchannel s2, Subchannel s3,
         /// <returns>System.String.</returns>
         protected internal override string GetValue()
         {
-            return $"Matrix3x2({_value.M11},{_value.M12},{_value.M21},{_value.M22},{_value.M31},{_value.M32})";
+            return $"Matrix3x2({_value.M11.ToCompositionString()},{_value.M12.ToCompositionString()},{_value.M21.ToCompositionString()},{_value.M22.ToCompositionString()},{_value.M31.ToCompositionString()},{_value.M32.ToCompositionString()})";
         }
 
         private Matrix3x2 _value;

Microsoft.Toolkit.Uwp.UI.Animations/Expressions/ExpressionNodes/Matrix4x4Node.cs

@@ -403,10 +403,10 @@ public Matrix4x4Node GetSubchannels(Subchannel s1, Subchannel s2, Subchannel s3,
         /// <returns>System.String.</returns>
         protected internal override string GetValue()
         {
-            return $"Matrix4x4({_value.M11},{_value.M12},{_value.M13},{_value.M14}," +
-                             $"{_value.M21},{_value.M22},{_value.M23},{_value.M24}," +
-                             $"{_value.M31},{_value.M32},{_value.M33},{_value.M34}," +
-                             $"{_value.M41},{_value.M42},{_value.M43},{_value.M44})";
+            return $"Matrix4x4({_value.M11.ToCompositionString()},{_value.M12.ToCompositionString()},{_value.M13.ToCompositionString()},{_value.M14.ToCompositionString()}," +
+                             $"{_value.M21.ToCompositionString()},{_value.M22.ToCompositionString()},{_value.M23.ToCompositionString()},{_value.M24.ToCompositionString()}," +
+                             $"{_value.M31.ToCompositionString()},{_value.M32.ToCompositionString()},{_value.M33.ToCompositionString()},{_value.M34.ToCompositionString()}," +
+                             $"{_value.M41.ToCompositionString()},{_value.M42.ToCompositionString()},{_value.M43.ToCompositionString()},{_value.M44.ToCompositionString()})";
         }
 
         private Matrix4x4 _value;

Microsoft.Toolkit.Uwp.UI.Animations/Expressions/ExpressionNodes/QuaternionNode.cs

@@ -126,7 +126,7 @@ public static implicit operator QuaternionNode(Quaternion value)
         /// <returns>System.String.</returns>
         protected internal override string GetValue()
         {
-            return $"Quaternion({_value.X},{_value.Y},{_value.Z},{_value.W})";
+            return $"Quaternion({_value.X.ToCompositionString()},{_value.Y.ToCompositionString()},{_value.Z.ToCompositionString()},{_value.W.ToCompositionString()})";
         }
 
         private Quaternion _value;

Microsoft.Toolkit.Uwp.UI.Animations/Expressions/ExpressionNodes/ScalarNode.cs

@@ -254,8 +254,7 @@ public static implicit operator ScalarNode(int value)
         /// <returns>System.String.</returns>
         protected internal override string GetValue()
         {
-            // Important to use invariant culture to make sure that floats are written using a .
-            return _value.ToString(System.Globalization.CultureInfo.InvariantCulture);
+            return _value.ToCompositionString();
         }
 
         private float _value;

Microsoft.Toolkit.Uwp.UI.Animations/Expressions/ExpressionNodes/Vector2Node.cs

@@ -297,7 +297,7 @@ public Matrix4x4Node GetSubchannels(Subchannel s1, Subchannel s2, Subchannel s3,
         /// <returns>System.String.</returns>
         protected internal override string GetValue()
         {
-            return $"Vector2({_value.X},{_value.Y})";
+            return $"Vector2({_value.X.ToCompositionString()},{_value.Y.ToCompositionString()})";
         }
 
         private Vector2 _value;

Microsoft.Toolkit.Uwp.UI.Animations/Expressions/ExpressionNodes/Vector3Node.cs

@@ -320,7 +320,7 @@ public Matrix4x4Node GetSubchannels(Subchannel s1, Subchannel s2, Subchannel s3,
         /// <returns>System.String.</returns>
         protected internal override string GetValue()
         {
-            return $"Vector3({_value.X},{_value.Y},{_value.Z})";
+            return $"Vector3({_value.X.ToCompositionString()},{_value.Y.ToCompositionString()},{_value.Z.ToCompositionString()})";
         }
 
         private Vector3 _value;

Microsoft.Toolkit.Uwp.UI.Animations/Expressions/ExpressionNodes/Vector4Node.cs

@@ -343,7 +343,7 @@ public Matrix4x4Node GetSubchannels(Subchannel s1, Subchannel s2, Subchannel s3,
         /// <returns>System.String.</returns>
         protected internal override string GetValue()
         {
-            return $"Vector4({_value.X},{_value.Y},{_value.Z},{_value.W})";
+            return $"Vector4({_value.X.ToCompositionString()},{_value.Y.ToCompositionString()},{_value.Z.ToCompositionString()},{_value.W.ToCompositionString()})";
         }
 
         private Vector4 _value;

Microsoft.Toolkit.Uwp.UI.Animations/Extensions/System/FloatExtensions.cs

@@ -0,0 +1,48 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics.Contracts;
+
+namespace Microsoft.Toolkit.Uwp.UI.Animations
+{
+    /// <summary>
+    /// An extension <see langword="class"/> for the <see cref="float"/> type
+    /// </summary>
+    internal static class FloatExtensions
+    {
+        /// <summary>
+        /// Returns a <see cref="string"/> representation of a <see cref="float"/> that avoids scientific notation, which is not compatible with the composition expression animations API
+        /// </summary>
+        /// <param name="number">The input <see cref="float"/> to process</param>
+        /// <returns>A <see cref="string"/> representation of <paramref name="number"/> that can be used in a expression animation</returns>
+        [Pure]
+        public static string ToCompositionString(this float number)
+        {
+            var defaultString = number.ToString(System.Globalization.CultureInfo.InvariantCulture);
+            var eIndex = defaultString.IndexOf('E');
+
+            // If the default string representation is not in scientific notation, we can use it
+            if (eIndex == -1)
+            {
+                return defaultString;
+            }
+
+            // If the number uses scientific notation because it is too large, we can print it without the decimal places
+            var exponent = int.Parse(defaultString.Substring(eIndex + 1));
+            if (exponent >= 0)
+            {
+                return number.ToString($"F0", System.Globalization.CultureInfo.InvariantCulture);
+            }
+
+            // Otherwise, we need to print it with the right number of decimals
+            var decimalPlaces = -exponent // The number of decimal places is the exponent of 10
+                + eIndex // Plus each character in the mantissa
+                + (number < 0 ?
+                    -3 : // Minus the sign, dot and first number of the mantissa if negative
+                    -2); // Minus the dot and first number of the mantissa otherwise
+
+            return number.ToString($"F{decimalPlaces}", System.Globalization.CultureInfo.InvariantCulture);
+        }
+    }
+}