Add TokenizingTextBox Workaround for IconSource FontSize Styling issue

Ref microsoft/microsoft-ui-xaml#2568
Also added WPF TryFindResource method to LogicalTree helpers - thanks for review/assist @rudyhuyn

Author: michael-hawker

Microsoft.Toolkit.Uwp.SampleApp/SamplePages/TabView/TabViewPage.xaml.cs

@@ -69,5 +69,5 @@ private void Tabs_TabDraggedOutside(object sender, TabDraggedOutsideEventArgs e)
             TabViewNotification.Show("Tore Tab '" + str + "' Outside of TabView.", 2000);
         }
         #pragma warning restore CS0618 // Type or member is obsolete
-    }    
+    }
 }

Microsoft.Toolkit.Uwp.SampleApp/SamplePages/TokenizingTextBox/TokenizingTextBoxXaml.bind

@@ -16,7 +16,7 @@
       <controls:TokenizingTextBox
           x:Name="TokenBox"
           PlaceholderText="Add Actions"
-          QueryIcon="{ex:SymbolIconSource Glyph=Setting, FontSize=16}"
+          QueryIcon="{ex:SymbolIconSource Glyph=Setting}"
           MaxHeight="104"
           HorizontalAlignment="Stretch"
           TextMemberPath="Text"
@@ -52,7 +52,7 @@
             PlaceholderText="Select Names"
             MaxHeight="104"
             HorizontalAlignment="Stretch"
-            QueryIcon="{ex:SymbolIconSource Glyph=Find, FontSize=16}"
+            QueryIcon="{ex:SymbolIconSource Glyph=Find}"
             TextMemberPath="Text"
             TokenDelimiter=","
             IsItemClickEnabled="True">

Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.xaml

@@ -12,6 +12,7 @@
     <Thickness x:Key="TokenizingTextBoxPresenterMargin">0,0,6,0</Thickness>
     <x:Double x:Key="TokenizingTextBoxTokenSpacing">2</x:Double>
     <Thickness x:Key="TextControlBorderThemeThicknessFocused">2</Thickness>
+    <x:Double x:Key="TokenizingTextBoxIconFontSize">16</x:Double>
 
     <controls:TokenizingTextBoxStyleSelector x:Key="TokenizingTextBoxStyleSelector"
                                              TextStyle="{StaticResource TokenizingTextBoxItemTextStyle}"

Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.cs

@@ -101,6 +101,15 @@ private void OnApplyTemplateAutoSuggestBox(AutoSuggestBox auto)
                 // Setup a binding to the QueryIcon of the Parent if we're the last box.
                 if (Content is PretokenStringContainer str && str.IsLast)
                 {
+                    // Workaround for https://github.com/microsoft/microsoft-ui-xaml/issues/2568
+                    if (Owner.QueryIcon is FontIconSource fis &&
+                        fis.ReadLocalValue(FontIconSource.FontSizeProperty) == DependencyProperty.UnsetValue)
+                    {
+                        // This can be expensive, could we optimize?
+                        // Also, this is changing the FontSize on the IconSource (which could be shared?)
+                        fis.FontSize = Owner.TryFindResource("TokenizingTextBoxIconFontSize") as double? ?? 16;
+                    }
+
                     var iconBinding = new Binding()
                     {
                         Source = Owner,

Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.xaml

@@ -15,12 +15,14 @@
                           Background="{ThemeResource TextControlButtonBackground}"
                           BorderBrush="{ThemeResource TextControlButtonBorderBrush}"
                           BorderThickness="{TemplateBinding BorderThickness}">
+                        <!-- FontSize is ignored here, see https://github.com/microsoft/microsoft-ui-xaml/issues/2568 -->
+                        <!-- Set in code-behind link:TokenizingTextBoxItem.AutoSuggestBox.cs#L104 -->
                         <TextBlock x:Name="GlyphElement"
                                    HorizontalAlignment="Center"
                                    VerticalAlignment="Center"
                                    AutomationProperties.AccessibilityView="Raw"
                                    FontFamily="{ThemeResource SymbolThemeFontFamily}"
-                                   FontSize="{ThemeResource AutoSuggestBoxIconFontSize}"
+                                   FontSize="{ThemeResource TokenizingTextBoxIconFontSize}"
                                    FontStyle="Normal"
                                    Foreground="{ThemeResource TextControlButtonForeground}"
                                    Text="&#xE10A;" />

Microsoft.Toolkit.Uwp.UI/Extensions/Tree/LogicalTree.cs

@@ -286,5 +286,37 @@ private static string ContentPropertySearch(Type type)
 
             return ContentPropertySearch(type.GetTypeInfo().BaseType);
         }
+
+        /// <summary>
+        /// Provides a WPF compatible version of TryFindResource to provide a static resource lookup.
+        /// If the key is not found in the current element's resources, the logical tree is then searched element-by-element to look for the resource in each element's resources.
+        /// If none of the elements contain the resource, the Application's resources are then searched.
+        /// <seealso href="https://docs.microsoft.com/en-us/dotnet/api/system.windows.frameworkelement.tryfindresource"/>
+        /// <seealso href="https://docs.microsoft.com/en-us/dotnet/desktop-wpf/fundamentals/xaml-resources-define#static-resource-lookup-behavior"/>
+        /// </summary>
+        /// <param name="start"><see cref="FrameworkElement"/> to start searching for Resource.</param>
+        /// <param name="resourceKey">Key to search for.</param>
+        /// <returns>Requested resource or null.</returns>
+        public static object TryFindResource(this FrameworkElement start, object resourceKey)
+        {
+            object value = null;
+            var current = start;
+
+            // Look in our dictionary and then walk-up parents
+            while (current != null)
+            {
+                if (current.Resources?.TryGetValue(resourceKey, out value) == true)
+                {
+                    return value;
+                }
+
+                current = current.Parent as FrameworkElement;
+            }
+
+            // Finally try application resources.
+            Application.Current?.Resources?.TryGetValue(resourceKey, out value);
+
+            return value;
+        }
     }
 }