private void ZoomSliderOnValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
{
ZoomTransform.ScaleX = e.NewValue;
ZoomTransform.ScaleY = e.NewValue;
var centerOfViewport = new Point(ZoomViewer.ViewportWidth/2, ZoomViewer.ViewportHeight/2);
_lastCenterPositionOnTarget = ZoomViewer.TranslatePoint(centerOfViewport, ZoomGrid);
}
private void ZoomViewer_ScrollChanged(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(ZoomViewer.ViewportWidth/2, ZoomViewer.ViewportHeight/2);
Point centerOfTargetNow = ZoomViewer.TranslatePoint(centerOfViewport, ZoomGrid);
targetBefore = _lastCenterPositionOnTarget;
targetNow = centerOfTargetNow;
}
}
else
{
targetBefore = _lastMousePositionOnTarget;
targetNow = Mouse.GetPosition(ZoomGrid);
_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/ZoomGrid.Width;
double multiplicatorY = e.ExtentHeight/ZoomGrid.Height;
double newOffsetX = ZoomViewer.HorizontalOffset - dXInTargetPixels*multiplicatorX;
double newOffsetY = ZoomViewer.VerticalOffset - dYInTargetPixels*multiplicatorY;
if (double.IsNaN(newOffsetX) || double.IsNaN(newOffsetY))
{
return;
}
ZoomViewer.ScrollToHorizontalOffset(newOffsetX);
ZoomViewer.ScrollToVerticalOffset(newOffsetY);
}
}
}