How can I make the Silverlight ScrollViewer scroll to show a child control with focus?

Question

I have a ScrollViewer which contains a Grid with multiple controls in it. The user can tab through the controls, but eventually they tab to a control that isn\'t in view - so th

Answer 1

I got this to work, with help of Kiril's answer above. The general context of this is that I have user-defineable forms in my application, and this code is used for rendering the controls on a form.

My general strategy was to add my controls to a Grid, then find all the children of the ScrollViewer using VisualTreeHelper, and add a GotFocus event handler to each control.

When the control gets focus, again using VisualTreeHelper, I search up the visual tree to find the control whose parent is the Grid that is being scrolled by the ScrollViewer. Then I scroll the ScrollViewer to make the control visible.

Here's the code (gridRender is the Grid that the controls are added to):

private void AfterFormRendered()
{
    var controls = VisualTreeHelperUtil.FindChildren(gridRender);
    foreach (var ctrl in controls)
    {
        ctrl.GotFocus += CtrlGotFocus;
    }
}

private void CtrlGotFocus(object sender, RoutedEventArgs e)
{
    var ctrl = sender as Control;
    var gridChildControl = VisualTreeHelperUtil.FindParentWithParent(ctrl, gridRender) as FrameworkElement;

    if (gridChildControl != null)
    {
        // Ensure the control is scrolled into view in the ScrollViewer.
        GeneralTransform focusedVisualTransform = gridChildControl.TransformToVisual(scrollViewer);
        Point topLeft = focusedVisualTransform.Transform(new Point(gridChildControl.Margin.Left, gridChildControl.Margin.Top));
        Rect rectangle = new Rect(topLeft, gridChildControl.RenderSize);
        double newOffset = scrollViewer.VerticalOffset + (rectangle.Bottom - scrollViewer.ViewportHeight);    

        scrollViewer.ScrollToVerticalOffset(newOffset);
    }
}

Note: the VisualTreeHelperUtil class is my own class that adds some useful searching functionality to the VisualTreeHelper class.