Add AutoSize option to groups to control whether moving children resizes the group

Author: zHaytam

src/Blazor.Diagrams.Core/Behaviors/DragMovablesBehavior.cs

@@ -33,12 +33,17 @@ private void OnPointerDown(Model? model, PointerEventArgs e)
                 if (sm is not MovableModel movable || movable.Locked)
                     continue;
 
+                // Special case: groups without auto size on
+                if (sm is NodeModel node && node.Group != null && !node.Group.AutoSize)
+                    continue;
+
                 var position = movable.Position;
-                if (Diagram.Options.GridSnapToCenter && movable is NodeModel node)
+                if (Diagram.Options.GridSnapToCenter && movable is NodeModel n)
                 {
-                    position = new Point(movable.Position.X + (node.Size?.Width ?? 0) / 2,
-                        movable.Position.Y + (node.Size?.Height ?? 0) / 2);
+                    position = new Point(movable.Position.X + (n.Size?.Width ?? 0) / 2,
+                        movable.Position.Y + (n.Size?.Height ?? 0) / 2);
                 }
+
                 _initialPositions.Add(movable, position);
             }
 
@@ -61,9 +66,13 @@ private void OnPointerMove(Model? model, PointerEventArgs e)
                 var ndx = ApplyGridSize(deltaX + initialPosition.X);
                 var ndy = ApplyGridSize(deltaY + initialPosition.Y);
                 if (Diagram.Options.GridSnapToCenter && movable is NodeModel node)
+                {
                     node.SetPosition(ndx - (node.Size?.Width ?? 0) / 2, ndy - (node.Size?.Height ?? 0) / 2);
+                }
                 else
+                {
                     movable.SetPosition(ndx, ndy);
+                }
             }
         }
 

src/Blazor.Diagrams.Core/Models/GroupModel.cs

@@ -10,17 +10,19 @@ public class GroupModel : NodeModel
     {
         private readonly List<NodeModel> _children;
 
-        public GroupModel(IEnumerable<NodeModel> children, byte padding = 30)
+        public GroupModel(IEnumerable<NodeModel> children, byte padding = 30, bool autoSize = true)
         {
             _children = new List<NodeModel>();
 
             Size = Size.Zero;
             Padding = padding;
+            AutoSize = autoSize;
             Initialize(children);
         }
 
         public IReadOnlyList<NodeModel> Children => _children;
         public byte Padding { get; }
+        public bool AutoSize { get; }
 
         public void AddChild(NodeModel child)
         {

tests/Blazor.Diagrams.Core.Tests/Behaviors/DragMovablesBehaviorTests.cs

@@ -1,4 +1,3 @@
-using System.Linq;
 using Blazor.Diagrams.Core.Events;
 using Blazor.Diagrams.Core.Geometry;
 using Blazor.Diagrams.Core.Models;
@@ -101,4 +100,44 @@ public void Behavior_ShouldNotTriggerMoved_WhenMovableDidntMove()
         // Assert
         movedTrigger.Should().BeFalse();
     }
+
+    [Fact]
+    public void Behavior_ShouldNotCallSetPosition_WhenGroupHasNoAutoSize()
+    {
+        // Arrange
+        var diagram = new TestDiagram();
+        var nodeMock = new Mock<NodeModel>(Point.Zero);
+        var group = new GroupModel(new[] { nodeMock.Object }, autoSize: false);
+        var node = diagram.Nodes.Add(nodeMock.Object);
+        diagram.SelectModel(node, false);
+
+        // Act
+        diagram.TriggerPointerDown(node,
+            new PointerEventArgs(100, 100, 0, 0, false, false, false, 0, 0, 0, 0, 0, 0, string.Empty, true));
+        diagram.TriggerPointerMove(null,
+            new PointerEventArgs(150, 150, 0, 0, false, false, false, 0, 0, 0, 0, 0, 0, string.Empty, true));
+
+        // Assert
+        nodeMock.Verify(n => n.SetPosition(50, 50), Times.Never);
+    }
+
+    [Fact]
+    public void Behavior_ShouldCallSetPosition_WhenGroupHasAutoSize()
+    {
+        // Arrange
+        var diagram = new TestDiagram();
+        var nodeMock = new Mock<NodeModel>(Point.Zero);
+        var group = new GroupModel(new[] { nodeMock.Object }, autoSize: true);
+        var node = diagram.Nodes.Add(nodeMock.Object);
+        diagram.SelectModel(node, false);
+
+        // Act
+        diagram.TriggerPointerDown(node,
+            new PointerEventArgs(100, 100, 0, 0, false, false, false, 0, 0, 0, 0, 0, 0, string.Empty, true));
+        diagram.TriggerPointerMove(null,
+            new PointerEventArgs(150, 150, 0, 0, false, false, false, 0, 0, 0, 0, 0, 0, string.Empty, true));
+
+        // Assert
+        nodeMock.Verify(n => n.SetPosition(50, 50), Times.Once);
+    }
 }