Added Undo and Redo

ViewModels/MainWindowViewModel.cs

@@ -84,7 +84,8 @@ public class MainWindowViewModel : ViewModelBase
     private void OnCanvasPointerPressed(PointerPressedEventArgs? e)
     {
         if (e == null) return;
-        
+        if(UndoDrawingPoints.Count > 0) UndoDrawingPoints.Clear();
+
         IsDrawing = true;
         DrawingPoints.Add(new DrawingPoints(Brush, BrushThickness));
         DrawingPoint = DrawingPoints[^1];
@@ -111,4 +112,26 @@ public class MainWindowViewModel : ViewModelBase
     {
         IsDrawing = false;
     }
+
+    public void GlobalKeyUpHandler(KeyEventArgs e)
+    {
+        if (e.KeyModifiers != KeyModifiers.Control) return;
+        switch (e.Key)
+        {
+            case Key.Z:
+                if (DrawingPoints.Count > 0)
+                {
+                    UndoDrawingPoints.Add(DrawingPoints[^1]);
+                    DrawingPoints.Remove(DrawingPoints[^1]);
+                }
+                break;
+            case Key.Y:
+                if (UndoDrawingPoints.Count > 0)
+                {
+                    DrawingPoints.Add(UndoDrawingPoints[^1]);
+                    UndoDrawingPoints.Remove(UndoDrawingPoints[^1]);
+                }
+                break;
+        }
+    }
 }