Why is the flow document printed word wrap?-CodePudding

WPF flow document code, as follows:

 
XMLNS="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
XMLNS: x="http://schemas.microsoft.com/winfx/2006/xaml" 
XMLNS: d="http://schemas.microsoft.com/expression/blend/2008" 
XMLNS: MC="http://schemas.openxmlformats.org/markup-compatibility/2006" 
XMLNS: local="CLR namespace: WpfApp3" 
MC: Ignorable="d" 
Title="MainWindow" Height="450" Width="800" & gt; 
 
 
 
 Journey to the west journey to the west journey to the west journey to the west journey to the west journey to the west journey to the west journey to the west journey to the west journey to the west journey to the west & lt;/Paragraph>

 
Private void Button_Click (object sender, RoutedEventArgs e) 
{
PrintDialog CurrentPrintDialog=new PrintDialog (); 
CurrentPrintDialog. PrintDocument (((IDocumentPaginatorSource) flowdocument). DocumentPaginator, "aa"); 
}

So point flow document, using the A4 format, print it out, why is the word wrap?