Fixing so the hack is no longer needed

Author: Keboo

src/MainDemo.Wpf/SmartHint.xaml.cs

@@ -17,24 +17,10 @@ public partial class SmartHint : UserControl
     internal static void SetRichTextBoxText(DependencyObject element, object value) => element.SetValue(RichTextBoxTextProperty, value);
     internal static object GetRichTextBoxText(DependencyObject element) => element.GetValue(RichTextBoxTextProperty);
 
-    private SmartHintViewModel ViewModel { get; }
-
     public SmartHint()
     {
-        DataContext = ViewModel = new SmartHintViewModel();
+        DataContext = new SmartHintViewModel();
         InitializeComponent();
-
-        Loaded += SmartHint_Loaded;
-    }
-
-    private void SmartHint_Loaded(object sender, RoutedEventArgs e)
-    {
-        // HACK! For some strange reason, the calculation of the left margin for the hint is initially wrong if these values are set as default in the view model directly.
-        // Setting them here is a bit hacky, but it makes the demo page work, and I don't think this would be an issue in a real world application so I can live the hack.
-        // To see the issue in action: Simply comment out the 2 lines below, open the "Smart Hint" page and toggle the "IsReadOnly" checkbox in the "TextBox styles" section;
-        // that will place the hint on top of the prefix text for unknown reasons.
-        ViewModel.PrefixText = "Pre";
-        ViewModel.SuffixText = "Suf";
     }
 
     private void HasErrors_OnToggled(object sender, RoutedEventArgs e)

src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.TextBox.xaml

@@ -151,24 +151,6 @@
                                 Opacity="{TemplateBinding wpf:HintAssist.HintOpacity}"
                                 Visibility="{TemplateBinding wpf:TextFieldAssist.HasLeadingIcon, Converter={x:Static converters:BooleanToVisibilityConverter.CollapsedInstance}}" />
 
-                  <TextBlock x:Name="PrefixTextBlock"
-                             Grid.Column="1"
-                             Margin="0,0,2,0"
-                             VerticalAlignment="Center"
-                             FontSize="{TemplateBinding FontSize}"
-                             Opacity="{TemplateBinding wpf:HintAssist.HintOpacity}"
-                             Text="{TemplateBinding wpf:TextFieldAssist.PrefixText}">
-                    <TextBlock.Visibility>
-                      <MultiBinding Converter="{StaticResource PrefixSuffixTextVisibilityConverter}">
-                        <Binding ElementName="Hint" Path="IsHintInFloatingPosition" />
-                        <Binding Path="(wpf:TextFieldAssist.PrefixText)" RelativeSource="{RelativeSource TemplatedParent}" />
-                        <Binding Path="(wpf:TextFieldAssist.PrefixTextVisibility)" RelativeSource="{RelativeSource TemplatedParent}" />
-                        <Binding Path="IsKeyboardFocusWithin" RelativeSource="{RelativeSource TemplatedParent}" />
-                        <Binding Path="IsReadOnly" RelativeSource="{RelativeSource TemplatedParent}" Converter="{x:Static converters:InvertBooleanConverter.Instance}" />
-                      </MultiBinding>
-                    </TextBlock.Visibility>
-                  </TextBlock>
-
                   <ScrollViewer x:Name="PART_ContentHost"
                                 Grid.Column="2"
                                 HorizontalAlignment="Stretch"
@@ -237,6 +219,24 @@
                     </wpf:SmartHint.Hint>
                   </wpf:SmartHint>
 
+                  <TextBlock x:Name="PrefixTextBlock"
+                             Grid.Column="1"
+                             Margin="0,0,2,0"
+                             VerticalAlignment="Center"
+                             FontSize="{TemplateBinding FontSize}"
+                             Opacity="{TemplateBinding wpf:HintAssist.HintOpacity}"
+                             Text="{TemplateBinding wpf:TextFieldAssist.PrefixText}">
+                    <TextBlock.Visibility>
+                      <MultiBinding Converter="{StaticResource PrefixSuffixTextVisibilityConverter}">
+                        <Binding ElementName="Hint" Path="IsHintInFloatingPosition" />
+                        <Binding Path="(wpf:TextFieldAssist.PrefixText)" RelativeSource="{RelativeSource TemplatedParent}" />
+                        <Binding Path="(wpf:TextFieldAssist.PrefixTextVisibility)" RelativeSource="{RelativeSource TemplatedParent}" />
+                        <Binding Path="IsKeyboardFocusWithin" RelativeSource="{RelativeSource TemplatedParent}" />
+                        <Binding Path="IsReadOnly" RelativeSource="{RelativeSource TemplatedParent}" Converter="{x:Static converters:InvertBooleanConverter.Instance}" />
+                      </MultiBinding>
+                    </TextBlock.Visibility>
+                  </TextBlock>
+                  
                   <TextBlock x:Name="SuffixTextBlock"
                              Grid.Column="3"
                              Margin="2,0,0,0"