void OnSliderValueChanged(object sender, RoutedPropertyChangedEventArgs <double> e)
{
var centerOfViewport = new Point(PlanScrollViewer.ViewportWidth / 2, PlanScrollViewer.ViewportHeight / 2);
_lastCenterPositionOnTarget = PlanScrollViewer.TranslatePoint(centerOfViewport, PlanGrid);
ShowAllButton.Visibility = e.NewValue == 1 ? Visibility.Hidden : Visibility.Visible;
}
void OnScrollViewerScrollChanged(object sender, ScrollChangedEventArgs e)
{
if (_animating || (e.ExtentHeightChange == 0 && e.ExtentWidthChange == 0))
{
return;
}
Point?targetBefore = null;
Point?targetNow = null;
if (!_lastMousePositionOnTarget.HasValue)
{
if (_lastCenterPositionOnTarget.HasValue)
{
var centerOfViewport = new Point(PlanScrollViewer.ViewportWidth / 2, PlanScrollViewer.ViewportHeight / 2);
Point centerOfTargetNow = PlanScrollViewer.TranslatePoint(centerOfViewport, PlanGrid);
targetBefore = _lastCenterPositionOnTarget;
targetNow = centerOfTargetNow;
}
}
else
{
targetBefore = _lastMousePositionOnTarget;
targetNow = Mouse.GetPosition(PlanGrid);
_lastMousePositionOnTarget = null;
}
if (targetBefore.HasValue)
{
double dXInTargetPixels = targetNow.Value.X - targetBefore.Value.X;
double dYInTargetPixels = targetNow.Value.Y - targetBefore.Value.Y;
double multiplicatorX = e.ExtentWidth / PlanGrid.ActualWidth;
double multiplicatorY = e.ExtentHeight / PlanGrid.ActualHeight;
double newOffsetX = PlanScrollViewer.HorizontalOffset - dXInTargetPixels * multiplicatorX;
double newOffsetY = PlanScrollViewer.VerticalOffset - dYInTargetPixels * multiplicatorY;
if (double.IsNaN(newOffsetX) || double.IsNaN(newOffsetY))
{
return;
}
PlanScrollViewer.ScrollToHorizontalOffset(newOffsetX);
PlanScrollViewer.ScrollToVerticalOffset(newOffsetY);
}
}