How to move vertical scrollbar to the viewport where found word occured - FlowDocument

Question

I have following FlowDocument with Paragraph in my XAML file:

<FlowDocumentScrollViewer ScrollViewer.HorizontalScrollBarVisibility="Auto" ScrollViewer.VerticalScrollBarVisibility="Auto">
    <FlowDocument Name="fDocument" PagePadding="10" FontFamily="Segoe UI" FontSize="22">
        <Paragraph Name="fdParagraph">
            Those who have denied the reality of moral distinctions, may be
            ranked among the disingenuous disputants; nor is it conceivable,
            that any human creature could ever seriously believe, that all
            characters and actions were alike entitled to the affection and
            regard of everyone. The difference, which nature has placed
            between one man and another, is so wide, and this difference is
            still so much farther widened, by education, example, and habit,
            that, where the opposite extremes come at once under our
            apprehension, there is no scepticism so scrupulous, and scarce
            any assurance so determined, as absolutely to deny all
            distinction between them. Let a man's insensibility be ever so
            great, he must often be touched with the images of Right and
            Wrong; and let his prejudices be ever so obstinate, he must
            observe, that others are susceptible of like impressions. The
            only way, therefore, of converting an antagonist of this kind, is
            to leave him to himself.
        </Paragraph>
    </FlowDocument>
</FlowDocumentScrollViewer>

Sometimes, I might have larger text content, which can not fit into current view port.

Is it possible and how to move vertical scrollbar to the viewport where found word occured?

Answer 1

In order to do this, you need to vertical position of TextPointer in FlowDocument, and call ScrollViewer method ScrollToVerticalOffset.

Briefly, this is how:

public static class FlowDocumentExtensions
    {
        public static void ScrollToWord(
            this FlowDocument flowDocument,
            ScrollViewer scrollViewer,
            string word)
        {
            var currentText = flowDocument.ContentStart;

            while (true)
            {
                TextPointer nextText = 
                       currentText.GetNextContextPosition(
                          LogicalDirection.Forward);
                if (nextText == null)
                    return;

                TextRange txt = new TextRange(currentText, nextText);

                int index = txt.Text.IndexOf(word, StringComparison.Ordinal);
                if (index > 0)
                {
                    TextPointer start = currentText.GetPositionAtOffset(index);

                    if (start != null)
                    {
                        var rect = start.GetCharacterRect(
                           LogicalDirection.Forward);
                        scrollViewer.ScrollToVerticalOffset(rect.Y);
                    }

                    return;
                }

                currentText = nextText;
            }
        }
    }

If you want to see how to get ScrollViewer from FlowDocument: Scroll a WPF FlowDocumentScrollViewer from code?