c# - How to follow the end of a text in a TextBox with no NoWrap?

Question

I have a TextBox in xaml:

<TextBox Name="Text" HorizontalAlignment="Left" Height="75"   VerticalContentAlignment="Center" TextWrapping="NoWrap" Text="TextBox" Width="336"  BorderBrush="Black" FontSize="40" />

I add text to it with this method:

private string words = "Initial text contents of the TextBox.";

public async void textRotation()
{
    for(int a =0; a < words.Length; a++)
    {
        Text.Text = words.Substring(0,a);
        await Task.Delay(500);
    }
}

Once the text goes of out of the wrap is there a way to focus the end so the old text disappears to the left and the new on the right, as opposed to just adding it to the right without seeing.

Answer 1

A quick method is to measure the string (words) that needs scrolling with TextRenderer.MeasureText, divide the width measure in parts equals to the number of chars in the string and use ScrollToHorizontalOffset() to perform the scroll:

public async void textRotation()
{
    float textPart = TextRenderer.MeasureText(words, new Font(Text.FontFamily.Source, (float)Text.FontSize)).Width / words.Length;
    for (int i = 0; i < words.Length; i++)
    {
        Text.Text = words.Substring(0, i);
        await Task.Delay(100);
        Text.ScrollToHorizontalOffset(textPart * i);
    }
}

Same, but using the FormattedText class to measure the string:

public async void textRotation()
{
    var textFormat = new FormattedText(
        words, CultureInfo.CurrentCulture, System.Windows.FlowDirection.LeftToRight,
        new Typeface(this.Text.FontFamily, this.Text.FontStyle, this.Text.FontWeight, this.Text.FontStretch),
        this.Text.FontSize, null, null, 1);

    float textPart = (float)textFormat.Width / words.Length;
    for (int i = 0; i < words.Length; i++)
    {
        Text.Text = words.Substring(0, i);
        await Task.Delay(200);
        Text.ScrollToHorizontalOffset(textPart * i);
    }
}