[ImageResizer] Fix issues with blank Width and Height controls (#37373)

* Allow custom preset's dimensions to be blank in the UI while still persisted as 0.

* XAML formatting - reorder namespaces.

* Add "(auto)" text to zero-value Width/Height in Settings. Ensure Width and Height fields in flyout are formatted to empty when their value is 0.

src/modules/imageresizer/ui/App.xaml

@@ -21,6 +21,8 @@
             <v:VisibilityBoolConverter x:Key="VisibilityBoolConverter" />
             <v:EnumToIntConverter x:Key="EnumToIntConverter" />
             <v:AccessTextToTextConverter x:Key="AccessTextToTextConverter" />
+            <v:NumberBoxValueConverter x:Key="NumberBoxValueConverter" />
+            <v:ZeroToEmptyStringNumberFormatter x:Key="ZeroToEmptyStringNumberFormatter" />
         </ResourceDictionary>
     </Application.Resources>
 </Application>

src/modules/imageresizer/ui/Views/AutoDoubleConverter.cs

@@ -10,29 +10,55 @@ using System.Windows.Data;
 
 using ImageResizer.Properties;
 
-namespace ImageResizer.Views
+namespace ImageResizer.Views;
+
+/// <summary>
+/// Converts between double and string for text-based controls bound to Width or Height fields.
+/// Optionally returns localized "Auto" text when the underlying value is 0, letting the UI show,
+/// for example "(auto) x 1024 pixels".
+/// </summary>
+[ValueConversion(typeof(double), typeof(string))]
+internal class AutoDoubleConverter : IValueConverter
 {
-    [ValueConversion(typeof(double), typeof(string))]
-    internal class AutoDoubleConverter : IValueConverter
-    {
-        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+    /// <summary>
+    /// Converts a double to a string, optionally showing "Auto" for 0 values. NaN values are
+    /// converted to empty strings.
+    /// </summary>
+    /// <param name="value">The value to convert from <see cref="double"/> to
+    /// <see cref="string"/>.</param>
+    /// <param name="targetType">The conversion target type. <see cref="string"/> here.</param>
+    /// <param name="parameter">Set to "Auto" to return the localized "Auto" string if the
+    /// value is 0.</param>
+    /// <param name="culture">The <see cref="CultureInfo"/> to use for the number formatting.
+    /// </param>
+    /// <returns>The string representation of the passed-in value.</returns>
+    public object Convert(object value, Type targetType, object parameter, CultureInfo culture) =>
+        value switch
         {
-            var d = (double)value;
+            double d => d switch
+            {
+                double.NaN => "0",
+                0 => (string)parameter == "Auto" ? Resources.Input_Auto : "0",
+                _ => d.ToString(culture),
+            },
 
-            return d != 0
-                ? d.ToString(culture)
-                : (string)parameter == "Auto"
-                    ? Resources.Input_Auto
-                    : string.Empty;
-        }
+            _ => "0",
+        };
 
-        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+    /// <summary>
+    /// Converts the string representation back to a double, returning 0 if the string is empty,
+    /// null or not a valid number in the specified culture.
+    /// </summary>
+    /// <param name="value">The string value to convert.</param>
+    /// <param name="targetType">The conversion target type. <see cref="double"/> here.</param>
+    /// <param name="parameter">Converter parameter. Unused.</param>
+    /// <param name="culture">The <see cref="CultureInfo"/> to use for the text parsing.</param>
+    /// <returns>The corresponding double value.</returns>
+    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) =>
+        value switch
         {
-            var text = (string)value;
-
-            return !string.IsNullOrEmpty(text)
-                ? double.Parse(text, culture)
-                : 0;
-        }
-    }
+            null or "" => 0,
+            string text when double.TryParse(text, NumberStyles.Any, culture, out double result) => result,
+            _ => 0,
+        };
 }

src/modules/imageresizer/ui/Views/InputPage.xaml

@@ -4,7 +4,8 @@
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:m="clr-namespace:ImageResizer.Models"
     xmlns:p="clr-namespace:ImageResizer.Properties"
-    xmlns:ui="http://schemas.lepo.co/wpfui/2022/xaml">
+    xmlns:ui="http://schemas.lepo.co/wpfui/2022/xaml"
+    xmlns:v="clr-namespace:ImageResizer.Views">
 
     <Grid>
         <Grid.RowDefinitions>
@@ -114,8 +115,12 @@
                     KeyDown="Button_KeyDown"
                     Minimum="0"
                     SpinButtonPlacementMode="Inline">
+                    <ui:NumberBox.NumberFormatter>
+                        <v:ZeroToEmptyStringNumberFormatter />
+                    </ui:NumberBox.NumberFormatter>
                     <ui:NumberBox.Value>
                         <Binding
+                            Converter="{StaticResource NumberBoxValueConverter}"
                             ElementName="SizeComboBox"
                             Mode="TwoWay"
                             Path="SelectedValue.Width"
@@ -143,8 +148,12 @@
                     Minimum="0"
                     SpinButtonPlacementMode="Inline"
                     Visibility="{Binding ElementName=SizeComboBox, Path=SelectedValue.ShowHeight, Converter={StaticResource BoolValueConverter}}">
+                    <ui:NumberBox.NumberFormatter>
+                        <v:ZeroToEmptyStringNumberFormatter />
+                    </ui:NumberBox.NumberFormatter>
                     <ui:NumberBox.Value>
                         <Binding
+                            Converter="{StaticResource NumberBoxValueConverter}"
                             ElementName="SizeComboBox"
                             Mode="TwoWay"
                             Path="SelectedValue.Height"

src/modules/imageresizer/ui/Views/NumberBoxValueConverter.cs

@@ -0,0 +1,32 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Globalization;
+using System.Windows.Data;
+
+namespace ImageResizer.Views;
+
+public class NumberBoxValueConverter : IValueConverter
+{
+    /// <summary>
+    /// Converts the underlying double value to a display-friendly format. Ensures that NaN values
+    /// are not propagated to the UI.
+    /// </summary>
+    public object Convert(object value, Type targetType, object parameter, CultureInfo culture) =>
+        value is double d && double.IsNaN(d) ? 0 : value;
+
+    /// <summary>
+    /// Converts the user input back to the underlying double value. If the input is not a valid
+    /// number, 0 is returned.
+    /// </summary>
+    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) =>
+        value switch
+        {
+            null => 0,
+            double d when double.IsNaN(d) => 0,
+            string str when !double.TryParse(str, out _) => 0,
+            _ => value,
+        };
+}

src/modules/imageresizer/ui/Views/ZeroToEmptyStringNumberFormatter.cs

@@ -0,0 +1,37 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Globalization;
+using Wpf.Ui.Controls;
+
+namespace ImageResizer.Views;
+
+public class ZeroToEmptyStringNumberFormatter : INumberFormatter, INumberParser
+{
+    public string FormatDouble(double? value) => value switch
+    {
+        null => string.Empty,
+        0 => string.Empty,
+        _ => value.Value.ToString(CultureInfo.CurrentCulture),
+    };
+
+    public double? ParseDouble(string value)
+    {
+        if (string.IsNullOrWhiteSpace(value))
+        {
+            return 0;
+        }
+
+        return double.TryParse(value, NumberStyles.Any, CultureInfo.CurrentCulture, out double result) ? result : 0;
+    }
+
+    public string FormatInt(int? value) => throw new NotImplementedException();
+
+    public string FormatUInt(uint? value) => throw new NotImplementedException();
+
+    public int? ParseInt(string value) => throw new NotImplementedException();
+
+    public uint? ParseUInt(string value) => throw new NotImplementedException();
+}