Allow objects to listen for changes to the equipment list

megamek/build.gradle

@@ -9,14 +9,20 @@ plugins {
     id 'jacoco'
     id 'java'
     id 'org.ec4j.editorconfig' version '0.1.0'
-
+    id 'org.openjfx.javafxplugin' version '0.1.0'
 }
 
 java {
     sourceCompatibility = JavaVersion.VERSION_17
     targetCompatibility = JavaVersion.VERSION_17
 }
 
+javafx {
+    // Version 23 requires JDK 21
+    version = "22.0.2"
+    modules = [ 'javafx.base' ]
+}
+
 sourceSets {
     main {
         java {

megamek/src/megamek/common/Entity.java

@@ -15,6 +15,9 @@
 package megamek.common;
 
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+import javafx.collections.FXCollections;
+import javafx.collections.ListChangeListener;
+import javafx.collections.ObservableList;
 import megamek.MMConstants;
 import megamek.client.bot.princess.FireControl;
 import megamek.client.ui.Base64Image;
@@ -50,6 +53,10 @@
 import megamek.utilities.xml.MMXMLUtility;
 
 import java.awt.*;
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.Serial;
 import java.math.BigInteger;
 import java.util.List;
 import java.util.*;
@@ -453,7 +460,7 @@ public enum InvalidSourceBuildReason {
     /**
      * A list of all mounted equipment. (Weapons, ammo, and misc)
      */
-    protected List<Mounted<?>> equipmentList = new ArrayList<>();
+    protected transient ObservableList<Mounted<?>> equipmentList = FXCollections.observableArrayList();
 
     /**
      * A list of all mounted weapons. This only includes regular weapons, not
@@ -15846,4 +15853,54 @@ public boolean canonUnitWithInvalidBuild() {
         return false;
     }
 
+    private final List<ListChangeListener<Mounted<?>>> equipmentListeners = new ArrayList<>();
+
+    /**
+     * Adds a listener to this entity's equipment list
+     * @param listener an object which will be informed when the entity's equipment changes
+     */
+    public void addEquipmentChangedListener(ListChangeListener<Mounted<?>> listener) {
+        equipmentList.addListener(listener);
+        equipmentListeners.add(listener);
+    }
+
+    /**
+     * Removes a listener from this entity's equipment list
+     * @param listener the listener to rmove
+     */
+    public void removeEquipmentChangedListener(ListChangeListener<Mounted<?>> listener) {
+        equipmentList.removeListener(listener);
+        equipmentListeners.remove(listener);
+    }
+
+    /**
+     * Replaces any existing equipment listeners with a new one.
+     * Only listeners of the exact same class of the listener are replaced.
+     * This can help prevent memory leaks, if a listening object is no longer needed it will be removed from the list of listeners by the replacing object.
+     * @param listener The new listener to add.
+     */
+    public void replaceEquipmentChangedListener(ListChangeListener<Mounted<?>> listener) {
+        for (Iterator<ListChangeListener<Mounted<?>>> iterator = equipmentListeners.iterator(); iterator.hasNext(); ) {
+            var existing = iterator.next();
+            if (listener.getClass().equals(existing.getClass())) {
+                equipmentList.removeListener(existing);
+                iterator.remove();
+            }
+        }
+
+        equipmentList.addListener(listener);
+        equipmentListeners.add(listener);
+    }
+
+    @Serial
+    private void writeObject(ObjectOutputStream out) throws IOException {
+        out.defaultWriteObject();
+        out.writeObject(new ArrayList<>(equipmentList));
+    }
+
+    @Serial
+    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
+        in.defaultReadObject();
+        equipmentList = FXCollections.observableArrayList((ArrayList<Mounted<?>>) in.readObject());
+    }
 }