private void MapScaleSlider_OnValueChanged(object sender, RoutedPropertyChangedEventArgs <double> e)
{
MapGridScaleTransform.ScaleX = e.NewValue;
MapGridScaleTransform.ScaleY = e.NewValue;
var centerOfViewport = new Point(MapScrollViewer.ViewportWidth / 2, MapScrollViewer.ViewportHeight / 2);
_lastCenterPositionOnTarget = MapScrollViewer.TranslatePoint(centerOfViewport, MapGrid);
}
private void MapScrollViewer_OnScrollChanged(object sender, ScrollChangedEventArgs e)
{
if (e.ExtentHeightChange != 0 || e.ExtentWidthChange != 0)
{
Point?targetBefore = null;
Point?targetNow = null;
if (!_lastMousePositionOnTarget.HasValue)
{
if (_lastCenterPositionOnTarget.HasValue)
{
var centerOfViewport = new Point(MapScrollViewer.ViewportWidth / 2, MapScrollViewer.ViewportHeight / 2);
Point centerOfTargetNow = MapScrollViewer.TranslatePoint(centerOfViewport, MapGrid);
targetBefore = _lastCenterPositionOnTarget;
targetNow = centerOfTargetNow;
}
}
else
{
targetBefore = _lastMousePositionOnTarget;
targetNow = Mouse.GetPosition(MapGrid);
_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 / MapGrid.Width;
double multiplicatorY = e.ExtentHeight / MapGrid.Height;
double newOffsetX = MapScrollViewer.HorizontalOffset - dXInTargetPixels * multiplicatorX;
double newOffsetY = MapScrollViewer.VerticalOffset - dYInTargetPixels * multiplicatorY;
if (double.IsNaN(newOffsetX) || double.IsNaN(newOffsetY))
{
return;
}
MapScrollViewer.ScrollToHorizontalOffset(newOffsetX);
MapScrollViewer.ScrollToVerticalOffset(newOffsetY);
}
}
}
