How can I see whether a scrollviewer child element is visible, and make it visible if it isn't?

Question

In a scrollviewer I have a textblock with 1000 inlines e.g.

XAML

<Grid>
    <ScrollViewer>
        <TextBlock Name="textBlock1" TextWrapping="Wrap" />
    </ScrollViewer>        
</Grid>

C#

public MainWindow()
    {
        InitializeComponent();

        for (int i = 0; i < 1000; i++)
        {
            textBlock1.Inlines.Add(new Run("Inline number " + i.ToString() + ". "));
        }
    }

How do I see if a particular inline element (e.g. number 850) is visible and, if it isn't, get the scrollviewer to scroll so that it is.

I'm fairly new to C# and wpf.

Thanks for your help.

Answer 1

Since the Run objects aren't Visuals you cannot use ScrollIntoView like you might be able to for some objects. I was able to accomplish it by locating the top offset of the desired Run and instructing the scrollviewer to scroll to that offset.

    <Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"></RowDefinition>
        <RowDefinition Height="*"></RowDefinition>
    </Grid.RowDefinitions>

    <Button Grid.Row="0" x:Name="findButton" Click="findButton_Click_1">Find It</Button>
    <ScrollViewer x:Name="scrollViewer1" Grid.Row="1">
        <TextBlock Name="textBlock1" TextWrapping="Wrap" />
    </ScrollViewer>
</Grid>

Here is the code-behind. It's hard-coded to find Run # 850...

        Run target;

    public MainWindow()
    {
        InitializeComponent();

        for (int i = 0; i < 1000; i++)
        {
            var run = new Run("Inline number " + i.ToString() + ". ");
            if (i==850)
                target = run;
            textBlock1.Inlines.Add(run);
        }
    }

    public void findButton_Click_1(object sender, RoutedEventArgs e)
    {
        var contentStart = target.ContentStart;
        var rect = contentStart.GetCharacterRect(LogicalDirection.Forward);
        scrollViewer1.ScrollToVerticalOffset(rect.Top);
    }