NodeEditor/Controls/EditorCanvas.xaml.cs

using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;

namespace NodeEditor.Controls
{
    /// <summary>
    /// Interaction logic for EditorCanvas.xaml
    /// </summary>
    public partial class EditorCanvas : UserControl
    {
        private Point? _dragStart = null;

        public EditorCanvas()
        {
            InitializeComponent();
            m_EditorCanvas.MouseMove += MapCanvas_Drag;
            m_EditorCanvas.MouseDown += MapCanvas_StartDrag;
            m_EditorCanvas.MouseUp += MapCanvas_StopDrag;
            m_EditorCanvas.MouseWheel += MapCanvas_OnScroll;
        }

        private void MapCanvas_StartDrag(object sender, MouseEventArgs e)
        {
            var element = (UIElement) sender;
            // dragStart = new Point(e.GetPosition(mapCanvas).X * st.ScaleX, e.GetPosition(mapCanvas).Y * st.ScaleY);
            if (mapCanvas.RenderTransform is MatrixTransform transform)
                _dragStart = new Point(e.GetPosition(mapCanvas).X * transform.Value.M11,
                    e.GetPosition(mapCanvas).Y * transform.Value.M22);
            element.CaptureMouse();
        }
        private void MapCanvas_StopDrag(object sender, MouseEventArgs e)
        {
            var element = (UIElement)sender;
            _dragStart = null;
            element.ReleaseMouseCapture();
        }

        private void MapCanvas_Drag(object sender, MouseEventArgs e)
        {
            if (_dragStart == null || e.LeftButton != MouseButtonState.Pressed) return;
            var newPoint = e.GetPosition(m_EditorCanvas);
                
            Canvas.SetLeft(mapCanvas, newPoint.X - _dragStart.Value.X);
            Canvas.SetTop(mapCanvas, newPoint.Y - _dragStart.Value.Y);
        }

        private void MapCanvas_OnScroll(object sender, MouseWheelEventArgs e)
        {
            // if (e.Delta > 0)
            // {
            //     st.ScaleX *= 1.1;
            //     st.ScaleY *= 1.1;
            // }
            // else
            // {
            //     st.ScaleX /= 1.1;
            //     st.ScaleY /= 1.1;
            // }
            var element = sender as UIElement;
            var position = e.GetPosition(element);
            if (!(mapCanvas.RenderTransform is MatrixTransform transform)) return;
            var matrix = transform.Matrix;
            var scale = e.Delta >= 0 ? 1.1 : (1.0 / 1.1); // choose appropriate scaling factor

            matrix.ScaleAtPrepend(scale, scale, position.X, position.Y);
            transform.Matrix = matrix;
        }
    }
}