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ScrollTrigger.cs
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ScrollTrigger.cs
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using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Interactivity;
using System.Windows.Media;
namespace Sharp.Utils.Wpf
{
/// <summary>
/// Invokes actions when the scroll position changes.
/// </summary>
public class ScrollTrigger : TriggerBase<FrameworkElement>
{
/// <summary>
/// Called after the trigger is attached to an AssociatedObject.
/// </summary>
protected override void OnAttached()
{
AssociatedObject.Loaded += new RoutedEventHandler(AssociatedObject_Loaded);
}
private void AssociatedObject_Loaded(object sender, RoutedEventArgs e)
{
foreach (var scrollViewer in GetScrollViewers())
scrollViewer.ScrollChanged += scrollViewer_ScrollChanged;
}
private void scrollViewer_ScrollChanged(object sender, ScrollChangedEventArgs e)
{
const double changeTolerance = 1e-6;
if (Math.Abs(e.VerticalChange) < changeTolerance && Math.Abs(e.HorizontalChange) < changeTolerance)
return;
InvokeActions(e.OriginalSource);
}
private IEnumerable<ScrollViewer> GetScrollViewers()
{
for (DependencyObject element = AssociatedObject; element != null; element = VisualTreeHelper.GetParent(element))
if (element is ScrollViewer)
yield return element as ScrollViewer;
}
}
}