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using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
namespace MediaBrowser.UI.Controls
{
/// <summary>
/// Provides a ScrollViewer that can be scrolled by dragging the mouse
/// </summary>
public class EnhancedScrollViewer : ScrollViewer
{
private Point _scrollTarget;
private Point _scrollStartPoint;
private Point _scrollStartOffset;
private const int PixelsToMoveToBeConsideredScroll = 5;
protected override void OnPreviewMouseDown(MouseButtonEventArgs e)
{
if (IsMouseOver)
{
// Save starting point, used later when determining how much to scroll.
_scrollStartPoint = e.GetPosition(this);
_scrollStartOffset.X = HorizontalOffset;
_scrollStartOffset.Y = VerticalOffset;
// Update the cursor if can scroll or not.
Cursor = (ExtentWidth > ViewportWidth) ||
(ExtentHeight > ViewportHeight) ?
Cursors.ScrollAll : Cursors.Arrow;
CaptureMouse();
}
base.OnPreviewMouseDown(e);
}
protected override void OnPreviewMouseMove(MouseEventArgs e)
{
if (IsMouseCaptured)
{
Point currentPoint = e.GetPosition(this);
// Determine the new amount to scroll.
var delta = new Point(_scrollStartPoint.X - currentPoint.X, _scrollStartPoint.Y - currentPoint.Y);
if (Math.Abs(delta.X) < PixelsToMoveToBeConsideredScroll &&
Math.Abs(delta.Y) < PixelsToMoveToBeConsideredScroll)
return;
_scrollTarget.X = _scrollStartOffset.X + delta.X;
_scrollTarget.Y = _scrollStartOffset.Y + delta.Y;
// Scroll to the new position.
ScrollToHorizontalOffset(_scrollTarget.X);
ScrollToVerticalOffset(_scrollTarget.Y);
}
base.OnPreviewMouseMove(e);
}
protected override void OnPreviewMouseUp(MouseButtonEventArgs e)
{
if (IsMouseCaptured)
{
Cursor = Cursors.Arrow;
ReleaseMouseCapture();
}
base.OnPreviewMouseUp(e);
}
}
}
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