added zoom feature

DelauneyTriangulation/Views/MainWindow.axaml.cs

@@ -1,9 +1,13 @@
+using System;
+using System.Linq;
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Controls.Shapes;
 using Avalonia.Input;
 using Avalonia.Interactivity;
 using Avalonia.Media;
+using Avalonia.VisualTree;
+using DelauneyTriangulation.ViewModels;
 
 namespace DelauneyTriangulation.Views;
 
@@ -12,12 +16,24 @@ public partial class MainWindow : Window
     private bool _isPanning;
     private Point _panStart;
     private Vector _panOffset = new();
+    
+    private double _scale = 1.0;
+    private const double MinScale = 0.2;
+    private const double MaxScale = 8.0;
+
     private readonly TranslateTransform _panTransform = new();
+    private readonly ScaleTransform _scaleTransform = new();
+    private readonly TransformGroup _transformGroup = new();
     
     public MainWindow()
     {
         InitializeComponent();
-        SceneContent.RenderTransform = _panTransform;
+        
+        _transformGroup.Children.Add(_scaleTransform);
+        _transformGroup.Children.Add(_panTransform);
+        SceneContent.RenderTransform = _transformGroup;
+        
+        if (DataContext is MainWindowViewModel vm) vm.View = this;
     }
     
     private void OnTitleBarPointerPressed(object? sender, PointerPressedEventArgs e)
@@ -64,6 +80,24 @@ public partial class MainWindow : Window
 
     private void Scene_OnWheel(object? sender, PointerWheelEventArgs e)
     {
+        var mouse = e.GetPosition(Scene);
 
+        var oldScale = _scale;
+        var factor = Math.Pow(1.1, e.Delta.Y);
+        var newScale = Math.Clamp(oldScale * factor, MinScale, MaxScale);
+        var applied = newScale / oldScale;
+
+        _scale = newScale;
+        _scaleTransform.ScaleX = _scaleTransform.ScaleY = _scale;
+        
+        _panOffset = new Vector(
+            mouse.X - applied * (mouse.X - _panOffset.X),
+            mouse.Y - applied * (mouse.Y - _panOffset.Y)
+        );
+
+        _panTransform.X = _panOffset.X;
+        _panTransform.Y = _panOffset.Y;
+
+        e.Handled = true;
     }
 }