private void Canvas_MouseLeftButtonDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
var pos = e.GetPosition(zoomCanvas);
var cl = Canvas.GetLeft(this.zoomThumb);
var ct = Canvas.GetTop(this.zoomThumb);
double scale, xOffset, yOffset;
this.InvalidateScale(out scale, out xOffset, out yOffset);
var dl = pos.X - cl - (zoomThumb.Width / 2);
var dt = pos.Y - ct - (zoomThumb.Height / 2);
scrollViewer.ScrollToHorizontalOffset(scrollViewer.HorizontalOffset + dl / scale);
scrollViewer.ScrollToVerticalOffset(scrollViewer.VerticalOffset + dt / scale);
}
private void Thumb_DragDelta(object sender, DragDeltaEventArgs e)
{
if (DesignSurface != null)
{
if (scrollViewer != null)
{
double scale, xOffset, yOffset;
this.InvalidateScale(out scale, out xOffset, out yOffset);
scrollViewer.ScrollToHorizontalOffset(scrollViewer.HorizontalOffset + e.HorizontalChange / scale);
scrollViewer.ScrollToVerticalOffset(scrollViewer.VerticalOffset + e.VerticalChange / scale);
}
}
}
