2DLightPathSimulator/LensSimulatorWPF/MainWindow.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace LensSimulatorWPF
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private Point _lastDragPoint;
        private Matrix _currentMatrix = Matrix.Identity;
        private const double ScaleRate = 1.1;
        private const double MinScale = 0.5;
        private const double MaxScale = 10.0;

        private Point lastZoomPos = new Point(0, 0);

        public MainWindow()
        {
            InitializeComponent();
            DrawGrid();
            this.MouseWheel += MainWindow_MouseWheel;
            this.MouseLeftButtonDown += MainWindow_MouseLeftButtonDown;
            this.MouseLeftButtonUp += MainWindow_MouseLeftButtonUp;
            this.MouseMove += MainWindow_MouseMove;
        }

        private void MainWindow_MouseWheel(object sender, MouseWheelEventArgs e)
        {
            var scale = e.Delta > 0 ? ScaleRate : 1 / ScaleRate;

            // Clamp the scale in between the min and max scale
            if (_currentMatrix.M11 * scale < MinScale || _currentMatrix.M11 * scale > MaxScale)
            {
                return;
            }

            // Get the mouse position in screen space (relative to canvas)
            var screenMousePos = e.GetPosition(canvas);

            // Convert the screen mouse position to the canvas space
            var matrix = _currentMatrix;
            matrix.Invert();

            var targetPointInCanvas = matrix.Transform(screenMousePos);

            lastZoomPos = targetPointInCanvas;

            // Perform the scale operation at the target point
            _currentMatrix.ScaleAtPrepend(scale, scale, canvas.ActualWidth/2, canvas.ActualHeight/ 2);

            // Apply the transformation to the canvas
            canvas.RenderTransform = new MatrixTransform(_currentMatrix);

            DrawGrid();
        }


        private void DrawGrid()
        {
            canvas.Children.Clear();

            double step = 50; // The M11 component of the matrix represents the scale in X
            double width = canvas.ActualWidth;
            double height = canvas.ActualHeight;

            for (double i = step; i < width; i += step)
            {
                canvas.Children.Add(new Line
                {
                    Stroke = Brushes.LightGray,
                    X1 = i,
                    Y1 = 0,
                    X2 = i,
                    Y2 = height
                });
            }

            for (double i = step; i < height; i += step)
            {
                canvas.Children.Add(new Line
                {
                    Stroke = Brushes.LightGray,
                    X1 = 0,
                    Y1 = i,
                    X2 = width,
                    Y2 = i
                });
            }

            var ellipse = new Ellipse
            {
                Fill = Brushes.Red,
                Width = 10,
                Height = 10
            };

            Canvas.SetLeft(ellipse, lastZoomPos.X - ellipse.Width / 2);
            Canvas.SetTop(ellipse, lastZoomPos.Y - ellipse.Height / 2);

            canvas.Children.Add(ellipse);
        }

        private void MainWindow_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            var mousePos = e.GetPosition(this);
            _lastDragPoint = new Point(mousePos.X - _currentMatrix.OffsetX, mousePos.Y - _currentMatrix.OffsetY);
            Mouse.Capture(this);
        }

        private void MainWindow_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            Mouse.Capture(null);
        }

        private void MainWindow_MouseMove(object sender, MouseEventArgs e)
        {
            if (e.LeftButton == MouseButtonState.Pressed)
            {
                var posNow = e.GetPosition(this);

                var deltaX = posNow.X - _lastDragPoint.X - _currentMatrix.OffsetX;
                var deltaY = posNow.Y - _lastDragPoint.Y - _currentMatrix.OffsetY;

                _currentMatrix.Translate(deltaX, deltaY);
                canvas.RenderTransform = new MatrixTransform(_currentMatrix);
                _lastDragPoint = new Point(posNow.X - _currentMatrix.OffsetX, posNow.Y - _currentMatrix.OffsetY);
            }
        }
    }
}