SilverLight 2.0 mouse wheel scrolling work-around

I'm new to the Silverlight experience and the potential is clear (the WPF similarity is a winning concept). I've encountered the scrolling issue and i can't say i get it. I want to share a straight forward and naive solution I've scribbled.

Accepting the Mouse wheel events

The first step is to register to the HtmlPage.Window events for all browser types.

HtmlPage.Window.AttachEvent("DOMMouseScroll", OnMouseScroll); // firefox HtmlPage.Window.AttachEvent("onmousewheel", OnMouseScroll); HtmlPage.Document.AttachEvent("onmousewheel", OnMouseScroll); // ie

Create the mouse scroll event handler

This method is invoked when the events registered above. It expects a m_scroller (ScrollViewer instance) to be set correctly (we will set it in the next part) and invokes the ScrollToVerticalOffset method.

/// Mouse scroll handler private void OnMouseScroll(object sender, HtmlEventArgs args) { double delta = 0; ScriptObject e = args.EventObject; // safari & firefox if (e.GetProperty("detail") != null) { delta = ((double)e.GetProperty("detail"))* -100; } else if (e.GetProperty("wheelDelta") != null) // ie && Opera { delta = ((double)e.GetProperty("wheelDelta")); } //if scroller is recognized update it if (m_scroller != null) { m_scroller.ScrollToVerticalOffset(m_scroller.VerticalOffset + delta * -1 * 0.1); } }

Register a control to enable mouse wheel scrolling

We need to register to the only the GotFocus event of the Page.xaml control to enable the scrolling. The Register method encapsulates the action.

/// Register the top most control (page.xaml) only to activate scrolling public void Register(FrameworkElement element) { if (element != null) { element.GotFocus += new RoutedEventHandler(OnGotFocus); } }

Impliment OnGotFocus event handler

In this part we will manage the m_scroller instance when needed in a recursive manner. This way we will allways effect the relevant hosting ScrollViewer of the focused control.

/// GotFocus event handler private void OnGotFocus(object sender, RoutedEventArgs e) { lock (this) { m_scroller = CheckParent((FrameworkElement)e.OriginalSource); }} /// Recursive method to update the correct scrollviewer (if exists) private ScrollViewer CheckParent(FrameworkElement element) { ScrollViewer _result = element as ScrollViewer; if (element != null && _result ==null) { FrameworkElement _temp = element.Parent as FrameworkElement; _result= CheckParent(_temp); } return _result; }

Create MouseWheelController

We will create a simple singletone controller to manage the state of the current ScrollViewer.

/// MouseWheelControler class public class MouseWheelControler { private ScrollViewer m_scroller; public static MouseWheelControler Instance { get; protected set; } static MouseWheelControler() { Instance = new MouseWheelControler(); } /// /// register to the html events for all browsers /// public MouseWheelControler() { HtmlPage.Window.AttachEvent("DOMMouseScroll", OnMouseScroll); // firefox HtmlPage.Window.AttachEvent("onmousewheel", OnMouseScroll); HtmlPage.Document.AttachEvent("onmousewheel", OnMouseScroll); // ie }...

Connecting the pieces

All we need to do at this part is register the relevant page (Page.xaml) to our MouseWheelController.

///Page.xaml constructor public Page() { InitializeComponent(); MouseWheelControler.Instance.Register(this); }

Hope it makes sence
Gilad