Container size scan, improvements

src/GuiApp/Avalonia/FileTime.GuiApp/Converters/ItemSizeToSizeConverter.cs

@@ -0,0 +1,19 @@
+using System.Globalization;
+using Avalonia.Data.Converters;
+using FileTime.App.ContainerSizeScanner;
+
+namespace FileTime.GuiApp.Converters;
+
+public class ItemSizeToSizeConverter : IMultiValueConverter
+{
+    public object? Convert(IList<object?> values, Type targetType, object? parameter, CultureInfo culture)
+    {
+        if (values is [ISizePreviewItem previewItem, ContainerPreview sizeContainerViewModel, double width and > 0])
+        {
+            var cumulativeSize = sizeContainerViewModel.TopItems.Select(i => i.Size.Value).Sum();
+            return width * previewItem.Size.Value / cumulativeSize;
+        }
+
+        return null;
+    }
+}