add mouse scroll to zoom functionality

lib/core/controller/controller.dart

@@ -208,8 +208,9 @@ class LazyCanvasController with ChangeNotifier {
   }
 
   /// Increment or decrement the scale by an additive delta value.
-  void updateScalebyDelta(double delta) {
-    final focalPoint = Offset(canvasSize.width / 2, canvasSize.height / 2);
+  void updateScalebyDelta(double delta, {Offset? focalPoint}) {
+    // added focalPoint param
+    focalPoint ??= Offset(canvasSize.width / 2, canvasSize.height / 2);
     final newScale = _scale + delta;
     _gsTopLeftOffset = newGsTopLeftOnScaling(_gsTopLeftOffset, focalPoint, _scale, newScale);
     _scale = newScale;

lib/core/render.dart

@@ -1,5 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
+import 'package:flutter/services.dart'; // added for LogicalKeyboardKey
+import 'package:flutter/gestures.dart'; // added for PointerScrollEvent
 import '../utils/offset_extensions.dart';
 
 import '../utils/styles.dart';
@@ -33,7 +35,21 @@ class _LazyCanvasState extends State<LazyCanvas> with TickerProviderStateMixin<L
   @override
   Widget build(BuildContext context) {
     widget.controller.setBuildContext(context);
-    return GestureDetector(
+    return Listener(
+      behavior: HitTestBehavior.translucent, // ensure scroll signals are captured even on empty space
+      onPointerSignal: (event) {
+        if (event is PointerScrollEvent) {
+          final pressed = RawKeyboard.instance.keysPressed;
+          if (pressed.contains(LogicalKeyboardKey.controlLeft) || pressed.contains(LogicalKeyboardKey.controlRight)) {
+            // Typical mouse wheel up gives negative dy on many platforms; invert if needed
+            final delta = (-event.scrollDelta.dy) * 0.0015; // sensitivity
+            if (delta != 0) {
+              widget.controller.updateScalebyDelta(delta, focalPoint: event.localPosition);
+            }
+          }
+        }
+      },
+      child: GestureDetector(
         behavior: HitTestBehavior.translucent,
         onScaleUpdate: widget.controller.onScaleUpdate,
         onScaleStart: widget.controller.onScaleStart,
@@ -74,6 +90,7 @@ class _LazyCanvasState extends State<LazyCanvas> with TickerProviderStateMixin<L
             }
           },
         ),
+      ),
     );
   }
 }
@@ -217,7 +234,6 @@ class _CanvasRenderBox extends RenderBox
       childParentData.id = _childrenIds[index];
       childParentData.scale = _scale;
       index++;
-      // loosen so like a stack can take it's own size inside parent
       child.layout(constraints.loosen(), parentUsesSize: true);
 
       // notify the controller about the size of the child