Padding the content of a RichEditBox in a C# WinRT app

Question

I'm trying to apply padding to the top and bottom of a RichEditBox in a XAML/C# WinRT app, but it isn't producing the desired effect.

Basically, when I set the padding to these edges, the padding produces empty space that remains even when I scroll the content of the control. However, I would like it to pad the content of the RichEditBox, so that there is no visible empty space when the content is scrolled away from the top and bottom edges.

How can I do this?

Answer 1

What you're looking for is a Margin in the content being drawn, as you want the content being drawn to actually enlarge as opposed to the content being drawn a certain distance away from the edge.

In order to add this Margin , you'll need to edit the Template, which is set in the Style. The default style and template for the rich edit box is this :

<!-- Default style for System.Windows.Controls.RichEditBox -->
<Style TargetType="RichEditBox">
    <Setter Property="MinWidth" Value="{ThemeResource TextControlThemeMinWidth}" />
    <Setter Property="MinHeight" Value="{ThemeResource TextControlThemeMinHeight}" />
    <Setter Property="Foreground" Value="{ThemeResource TextBoxForegroundThemeBrush}" />
    <Setter Property="Background" Value="{ThemeResource TextBoxBackgroundThemeBrush}" />
    <Setter Property="SelectionHighlightColor" Value="{ThemeResource TextSelectionHighlightColorThemeBrush}" />
    <Setter Property="BorderBrush" Value="{ThemeResource TextBoxBorderThemeBrush}" />
    <Setter Property="BorderThickness" Value="{ThemeResource TextControlBorderThemeThickness}" />
    <Setter Property="FontFamily" Value="{ThemeResource ContentControlThemeFontFamily}" />
    <Setter Property="FontSize" Value="{ThemeResource ControlContentThemeFontSize}" />
    <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto" />
    <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto" />
    <Setter Property="ScrollViewer.IsDeferredScrollingEnabled" Value="False" />
    <Setter Property="TextWrapping" Value="Wrap" />
    <Setter Property="Padding" Value="{ThemeResource TextControlThemePadding}"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="RichEditBox">
                <Grid>
                    <VisualStateManager.VisualStateGroups>
                        <VisualStateGroup x:Name="CommonStates">
                            <VisualState x:Name="Disabled">
                                <Storyboard>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetName="BackgroundElement"
                                                                   Storyboard.TargetProperty="Background">
                                        <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextBoxDisabledBackgroundThemeBrush}" />
                                    </ObjectAnimationUsingKeyFrames>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetName="BorderElement"
                                                                   Storyboard.TargetProperty="BorderBrush">
                                        <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextBoxDisabledBorderThemeBrush}" />
                                    </ObjectAnimationUsingKeyFrames>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentElement"
                                                                   Storyboard.TargetProperty="Foreground">
                                        <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextBoxDisabledForegroundThemeBrush}" />
                                    </ObjectAnimationUsingKeyFrames>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetName="PlaceholderTextContentPresenter"
                                                                   Storyboard.TargetProperty="Foreground">
                                        <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextBoxDisabledForegroundThemeBrush}" />
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="Normal">
                                <Storyboard>
                                    <DoubleAnimation Storyboard.TargetName="BackgroundElement"
                                                     Storyboard.TargetProperty="Opacity"
                                                     Duration="0"
                                                     To="{ThemeResource TextControlBackgroundThemeOpacity}" />
                                    <DoubleAnimation Storyboard.TargetName="BorderElement"
                                                     Storyboard.TargetProperty="Opacity"
                                                     Duration="0"
                                                     To="{ThemeResource TextControlBorderThemeOpacity}" />
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="PointerOver">
                                <Storyboard>
                                    <DoubleAnimation Storyboard.TargetName="BackgroundElement"
                                                     Storyboard.TargetProperty="Opacity"
                                                     Duration="0"
                                                     To="{ThemeResource TextControlPointerOverBackgroundThemeOpacity}" />
                                    <DoubleAnimation Storyboard.TargetName="BorderElement"
                                                     Storyboard.TargetProperty="Opacity"
                                                     Duration="0"
                                                     To="{ThemeResource TextControlPointerOverBorderThemeOpacity}" />
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="Focused" />
                        </VisualStateGroup>
                    </VisualStateManager.VisualStateGroups>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto"/>
                        <RowDefinition Height="*"/>
                    </Grid.RowDefinitions>
                    <Border x:Name="BackgroundElement"
                            Grid.Row="1"
                            Background="{TemplateBinding Background}"
                            Margin="{TemplateBinding BorderThickness}"
                            Grid.ColumnSpan="2"
                            Grid.RowSpan="2"/>
                    <Border x:Name="BorderElement"
                            Grid.Row="1"
                            BorderBrush="{TemplateBinding BorderBrush}"
                            BorderThickness="{TemplateBinding BorderThickness}"
                            Grid.ColumnSpan="2"
                            Grid.RowSpan="1"/>
                    <ContentPresenter x:Name="HeaderContentPresenter"
                                      Grid.Row="0"
                                      Foreground="{ThemeResource TextBoxForegroundHeaderThemeBrush}"
                                      Margin="0,4,0,4"
                                      Grid.ColumnSpan="2"
                                      Content="{TemplateBinding Header}"
                                      ContentTemplate="{TemplateBinding HeaderTemplate}"
                                      FontWeight="Semilight" />
                    <ScrollViewer x:Name="ContentElement"
                                  Grid.Row="1"
                                  HorizontalScrollMode="{TemplateBinding ScrollViewer.HorizontalScrollMode}"
                                  HorizontalScrollBarVisibility="{TemplateBinding ScrollViewer.HorizontalScrollBarVisibility}"
                                  VerticalScrollMode="{TemplateBinding ScrollViewer.VerticalScrollMode}"
                                  VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}"
                                  IsHorizontalRailEnabled="{TemplateBinding ScrollViewer.IsHorizontalRailEnabled}"
                                  IsVerticalRailEnabled="{TemplateBinding ScrollViewer.IsVerticalRailEnabled}"
                                  IsDeferredScrollingEnabled="{TemplateBinding ScrollViewer.IsDeferredScrollingEnabled}"
                                  Margin="{TemplateBinding BorderThickness}"
                                  Padding="{TemplateBinding Padding}"
                                  IsTabStop="False"
                                  ZoomMode="Disabled" 
                                  AutomationProperties.AccessibilityView="Raw"/>
                    <ContentControl x:Name="PlaceholderTextContentPresenter"
                                  Grid.Row="1"
                                  Foreground="{ThemeResource TextBoxPlaceholderTextThemeBrush}"
                                  Margin="{TemplateBinding BorderThickness}"
                                  Padding="{TemplateBinding Padding}"
                                  IsTabStop="False"
                                  Grid.ColumnSpan="2"
                                  Content="{TemplateBinding PlaceholderText}" 
                                  IsHitTestVisible="False"/>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

Notice the ScrollViewer is applying the Padding directly. Unfortunately, this is not what you want. If you replace it with a ContentPresenter which applies the Padding as a TemplateBinding to its Margin , it should present as you desire.

<ScrollViewer 
  Grid.Row="1"
  HorizontalScrollMode="{TemplateBinding ScrollViewer.HorizontalScrollMode}"
  HorizontalScrollBarVisibility="{TemplateBinding ScrollViewer.HorizontalScrollBarVisibility}"
  VerticalScrollMode="{TemplateBinding ScrollViewer.VerticalScrollMode}"
  VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}"
  IsHorizontalRailEnabled="{TemplateBinding ScrollViewer.IsHorizontalRailEnabled}"
  IsVerticalRailEnabled="{TemplateBinding ScrollViewer.IsVerticalRailEnabled}"
  IsDeferredScrollingEnabled="{TemplateBinding ScrollViewer.IsDeferredScrollingEnabled}"
  Margin="{TemplateBinding BorderThickness}"
  IsTabStop="False"
  ZoomMode="Disabled" 
  AutomationProperties.AccessibilityView="Raw">
      <ContentPresenter x:Name="ContentElement" Margin="{TemplateBinding Padding}"/>
</ScrollViewer>

Notice that you have to set the Name of the ContentPresenter to ContentElement so that the control logic knows about it.

Hope this helps and happy coding!