Standardise time display formats across the editor

osu.Game/Extensions/EditorDisplayExtensions.cs

@@ -0,0 +1,26 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+
+namespace osu.Game.Extensions
+{
+    public static class EditorDisplayExtensions
+    {
+        /// <summary>
+        /// Get an editor formatted string (mm:ss:mss)
+        /// </summary>
+        /// <param name="milliseconds">A time value in milliseconds.</param>
+        /// <returns>An editor formatted display string.</returns>
+        public static string ToEditorFormattedString(this double milliseconds) =>
+            ToEditorFormattedString(TimeSpan.FromMilliseconds(milliseconds));
+
+        /// <summary>
+        /// Get an editor formatted string (mm:ss:mss)
+        /// </summary>
+        /// <param name="timeSpan">A time value.</param>
+        /// <returns>An editor formatted display string.</returns>
+        public static string ToEditorFormattedString(this TimeSpan timeSpan) =>
+            $"{(timeSpan < TimeSpan.Zero ? "-" : string.Empty)}{timeSpan:mm\\:ss\\:fff}";
+    }
+}