WPF ScrollViewer更改TextBlock宽度

<ScrollViewer HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
    <TextBlock Text="这是一个文本块" />
</ScrollViewer>

<Window.Resources>
    <Style TargetType="ScrollViewer">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="ScrollViewer">
                    <Grid>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="Auto" />
                            <ColumnDefinition Width="*" />
                        </Grid.ColumnDefinitions>
                        <Grid.RowDefinitions>
                            <RowDefinition Height="Auto" />
                            <RowDefinition Height="*" />
                        </Grid.RowDefinitions>
                        <Border Grid.Column="1" Grid.Row="1" Background="{TemplateBinding Background}" />
                        <ScrollContentPresenter Grid.Column="1" Grid.Row="1" />
                        <ScrollBar x:Name="PART_VerticalScrollBar" Grid.Column="0" Grid.Row="1" Orientation="Vertical" />
                        <ScrollBar x:Name="PART_HorizontalScrollBar" Grid.Column="1" Grid.Row="0" Orientation="Horizontal" />
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</Window.Resources>

<ScrollViewer HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
    <TextBlock Text="这是一个文本块" Width="Auto" />
</ScrollViewer>