Mahapps Metro Richtextbox削减了g字母的底部

Question

My problem with the RichTextBox control is that it cuts off the bottom part of 'g', 'q', and 'j' letters of the last Paragraph added to it. My application is a chat, so it adds one paragraph per message to the FlowDocument of this RichTextBox and it scrolls down.

I think this is not the problem of Paragraph because this happens only with the last Paragraph. When a new one is added and the old is scrolled upper then it doesn't have this problem.

The XAML code looks like this:

<Border Grid.Row="0" BorderThickness="0,1" BorderBrush="Gray">
    <ScrollViewer Margin="0,5">
        <RichTextBox IsUndoEnabled="False" IsReadOnly="True" BorderThickness="0" IsDocumentEnabled="True" Background="Transparent">
            <FlowDocument />
        </RichTextBox>
    </ScrollViewer>
</Border>

And I add a new Paragraph with this C# code:

Paragraph p = new Paragraph();
p.Margin = new Thickness(0, 2, 0, 2);
p.Inlines.Add(new Run(msg.Text));
rtbDocument.Blocks.Add(p);

I hope that somebody knows a clever solution for this problem, thanks in advance!

Ps.: I don't know the exact name of this problem, so I would be happy if somebody would modify the title of this question to a proper one :)

Answer 1

I think it is related to line stacking. Line stacking strategy on MSDN .

I used following approach without problems :

    <Border Grid.Row="1" BorderThickness="0,1" BorderBrush="Gray" Grid.RowSpan="2">                
          <RichTextBox x:Name="rtbDocument" ScrollViewer.VerticalScrollBarVisibility="Auto" IsUndoEnabled="False" IsReadOnly="True" BorderThickness="5" IsDocumentEnabled="True" Background="Transparent" Margin="0,34,0,69">
             <FlowDocument/>
          </RichTextBox>                
     </Border>

Paragraph p = new Paragraph();            
p.FontSize = 20;
p.Margin = new Thickness(0, 5, 0, 5);
p.Inlines.Add(new Run("some gqgb qqj"));
rtbDocument.Document.Blocks.Add(p);

//

Your problem is reproduced if I do following changes to FlowDocument in your RichTextBox :

<FlowDocument LineHeight="20" LineStackingStrategy="BlockLineHeight" />

or, to your code like :

Paragraph p = new Paragraph();
p.LineHeight = 20;
p.LineStackingStrategy = LineStackingStrategy.BlockLineHeight;

or,

<FlowDocument LineStackingStrategy="BlockLineHeight" />

p.LineHeight = 20;

See figure below :

Removing LineStackingStrategy altogether will work as it will use default value of MaxHeight. Or, you can set it explicitly :

<FlowDocument LineStackingStrategy="MaxHeight" />