Adding initial playback bar logic.

Harmonia.UI/Converters/SecondsToStringConverter.cs

@@ -0,0 +1,37 @@
+using Avalonia.Data.Converters;
+using System;
+using System.Globalization;
+
+namespace Harmonia.UI.Converters;
+
+public sealed class SecondsToStringConverter : IValueConverter
+{
+    public SecondsToStringConverter()
+    {
+
+    }
+
+    public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        if (value is not double doubleValue)
+            return null;
+
+        TimeSpan timeSpan = TimeSpan.FromSeconds(doubleValue);
+
+        if (timeSpan.Hours >= 1)
+            return timeSpan.ToString(@"%h\:mm\:ss");
+
+        return timeSpan.ToString(@"%m\:ss");
+    }
+
+    public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+    {
+        if (value == null)
+            return null;
+
+        if (value is not string stringValue)
+            return null;
+
+        return TimeSpan.Parse(stringValue);
+    }
+}