Switch to custom scene root

app/src/main/java/com/annimon/hotarufx/ui/control/NodesGroup.java

@@ -0,0 +1,47 @@
+package com.annimon.hotarufx.ui.control;
+
+import javafx.collections.ObservableList;
+import javafx.scene.Group;
+import javafx.scene.Node;
+
+public class NodesGroup extends Group {
+
+    private final double width, height;
+
+    public NodesGroup(double width, double height) {
+        this.width = width;
+        this.height = height;
+        setAutoSizeChildren(false);
+        setManaged(false);
+    }
+
+    @Override
+    public ObservableList<Node> getChildren() {
+        return super.getChildren();
+    }
+
+    @Override
+    public double prefWidth(double unused) {
+        return width;
+    }
+
+    @Override
+    public double prefHeight(double unused) {
+        return height;
+    }
+
+    @Override
+    protected double computePrefWidth(double unused) {
+        return width;
+    }
+
+    @Override
+    protected double computePrefHeight(double unused) {
+        return height;
+    }
+
+    @Override
+    public boolean isResizable() {
+        return false;
+    }
+}

app/src/main/java/com/annimon/hotarufx/visual/Composition.java

@@ -1,6 +1,6 @@
 package com.annimon.hotarufx.visual;
 
-import javafx.scene.Group;
+import com.annimon.hotarufx.ui.control.NodesGroup;
 import javafx.scene.Scene;
 import javafx.scene.input.KeyCode;
 import javafx.scene.paint.Color;
@@ -54,7 +54,7 @@ public class Composition {
     }
 
     private VirtualScene newScene() {
-        val group = new Group();
+        val group = new NodesGroup(sceneWidth, sceneHeight);
         group.setScaleX(1d / factor);
         group.setScaleY(1d / factor);
         group.setTranslateX(sceneWidth / 2);

app/src/main/java/com/annimon/hotarufx/visual/VirtualScene.java

@@ -1,6 +1,6 @@
 package com.annimon.hotarufx.visual;
 
-import javafx.scene.Group;
+import com.annimon.hotarufx.ui.control.NodesGroup;
 import javafx.scene.Node;
 import lombok.Getter;
 import lombok.RequiredArgsConstructor;
@@ -9,7 +9,7 @@ import lombok.RequiredArgsConstructor;
 public class VirtualScene {
 
     @Getter
-    private final Group group;
+    private final NodesGroup group;
 
     @Getter
     private final int virtualWidth, virtualHeight;