How to get whether richtextbox last word is BringIntoView(shown) or not in WPF?

Question

i am working in wpf,i have a richtextbox with some contents.if the contents are exceeded to richtextbox i want to hide bottom border.if the content within the richtextbox i want to show the bottom border.Now i am using the below code to bring the exceeded content to view in richtextbox.

 FrameworkContentElement fce = (startPos.Parent as FrameworkContentElement);
            if (fce != null)
            {
                fce.BringIntoView();
            }

But i want to display the bottom border,once the last word shown in that richtextbox.How to achieve this?

Note: I already known how to show bottom border dynamically.but i want to know last word are displayed within the richtextbox or not?

Regards Arjun

Answer 1

I can provide you with a method to check whether the upper left corner of a character is visible or not. Create a class library Tools with the following content:

public class ToolsRtb
{
    public static bool PositionVisibleIs(RichTextBox rtb, TextPointer pos)
    {
        // Rectangle around the character to check
        Rect r = pos.GetCharacterRect(LogicalDirection.Forward);

        // Upper left corner of the rectangle ...
        Point upperLeftCorner = r.Location;

        HitTestResult result = VisualTreeHelper.HitTest(rtb, upperLeftCorner);

        // ... is visible?
        if (result != null)
            return true;
        else
            return false;
    }   
}

Note that PositionVisibleIs(...) is a static method and not dedicated to a specific object. In the code behind file of the window which contains your RichTextBox use the method like this:

// Is the last character of the current document visible?
if (ToolsRtb.PositionVisibleIs(rtb, rtb.Document.ContentEnd) == true)
{
    ...
}

Hope this helps.