/// <summary>
/// Handler for when the IsScrolling dependency property changes
/// </summary>
/// <param name="source">The object that has the property</param>
/// <param name="e">Args</param>
static void IsScrollingPropertyChanged(DependencyObject source, DependencyPropertyChangedEventArgs e)
{
LazyListBox listbox = source as LazyListBox;
// The property is supposed to be read-only, although we are allowed to change it ourselves
if (listbox.allowChangesToIsScrolling != true)
{
listbox.IsScrolling = (bool)e.OldValue;
throw new InvalidOperationException("IsScrolling property is read-only");
}
if ((bool)e.NewValue == true)
{
// Ask all the items in the list to pause what they're doing
foreach (LazyListBoxItem item in listbox.visibleItems)
{
item.Pause();
}
}
// Call the virtual notification method for anyone who derives from this class
ScrollingStateChangedEventArgs scrollingArgs = new ScrollingStateChangedEventArgs((bool)e.OldValue, (bool)e.NewValue);
listbox.OnScrollingStateChanged(scrollingArgs);
// Raise the event, if anyone is listening to it
var handler = listbox.ScrollingStateChanged;
if (handler != null)
{
handler(listbox, scrollingArgs);
}
// If the list has stopped scrolling, recompute the visible items on the next tick
if ((bool)e.NewValue == false)
{
#if ONLISTCHANGESCOMPLETE_LOGGING
Debug.WriteLine("IsScrollingPropertyChanged calling DeferredOnListChangesComplete because scrolling just finished");
#endif
listbox.DeferredOnListChangesComplete();
}
}
/// <summary>
/// Notification that the scrolling state has changed
/// </summary>
/// <param name="e">Scrolling parameters</param>
/// <remarks>
/// The default implementation does nothing
/// </remarks>
protected virtual void OnScrollingStateChanged(ScrollingStateChangedEventArgs e)
{
}