How to switch order of selection rectangle and text for RichTextBox ('SelectionOpacity="1"', 'UseAdornerForTextboxSelectionRendering="false"')

Question

Hi,

I want to turn off the opacity of selection rectangle on text fields (such as: TextBox & RichTextBox), by setting SelectionOpacity="1". When doing so, the text becomes hidden, due to the default order of selection rectangle and the text itself. I've discovered this special flag: UseAdornerForTextboxSelectionRendering, that when set to false, switches the default order, and then the text becomes visible, even though the selection is set to opacity of 1.

This works wonderfully for System.Windows.Controls.TextBox, but unfortunately not for System.Windows.Controls.RichTextBox.

I've created a very small project that isolates the issue: Just create a new WPF project with the following code:

MainWindow.xaml:

<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="*" />
        <RowDefinition Height="*" />
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*" />
        <ColumnDefinition Width="*" />
    </Grid.ColumnDefinitions>
    <Label Content="TextBox" HorizontalAlignment="Center" VerticalAlignment="Center" FontSize="25"></Label>
    <TextBox Height="80" Width="500" Grid.Column="1" SelectionOpacity="1"></TextBox>

    <Label Content="RichTextBox" Grid.Row="1" HorizontalAlignment="Center" VerticalAlignment="Center" FontSize="25"></Label>
    <RichTextBox Height="80" Width="500" Grid.Row="1" Grid.Column="1" SelectionOpacity="1"></RichTextBox>
</Grid>

MainWindow.xaml.cs:

public MainWindow()
{
    AppContext.SetSwitch("Switch.System.Windows.Controls.Text.UseAdornerForTextboxSelectionRendering", false);
    InitializeComponent();
   
}

This results in the following result for System.Windows.Controls.TextBox:

But unfortunately, it looks as following for System.Windows.Controls.RichTextBox:

How do I achieve the same result for RichTextBox, as the one I got for the regular TextBox?

Thank you for the help!

Answer 1

Hi,@WPF-Learner.

When I set AppContext.SetSwitch("Switch.System.Windows.Controls.Text.UseAdornerForTextboxSelectionRendering", false); the TextBox behaves fine and the RichTextBox cannot display the text.

The fact that the switch only applies to TextBox and PasswordBox as stated in the docs. It doesn't work for RichTextBox.

At least not using this, or any other, switch. It is recommended that you Set the SelectionOpacity programmatically if you don't want to change the XAML markup.

    <RichTextBox Name="richTextBox" Height="80" Grid.Row="1"  Width="500" Grid.Column="1" SelectionOpacity="1"></RichTextBox>

codebehind:

  richTextBox.SelectionOpacity = 0.7;

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