Ticket #15118: menu-disable.patch

src/org/openstreetmap/josm/gui/JosmMenu.java

@@ +1 @@
+// License: GPL. For details, see LICENSE file.
+
+package org.openstreetmap.josm.gui;
+
+import javax.swing.JMenu;
+import javax.swing.JMenuItem;
+import java.awt.Component;
+import java.awt.event.ContainerEvent;
+import java.awt.event.ContainerListener;
+import java.beans.PropertyChangeEvent;
+import java.beans.PropertyChangeListener;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Objects;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+
+/**
+ * Represents a menu containing a popup menu.
+ */
+public class JosmMenu extends JMenu {
+
+    /**
+     * Constructs a new instance of {@link JosmMenu}.
+     * @param label The label to be displayed on the menu.
+     */
+    public JosmMenu(String label) {
+        super(label);
+    }
+
+    /**
+     * Gets a stream of {@link JMenuItem} objects contained within this menu.
+     * @return A stream of {@link JMenuItem} contained within this menu.
+     */
+    public Stream<JMenuItem> streamMenuItems() {
+        return IntStream.range(0, this.getItemCount())
+                .mapToObj(this::getItem)
+                .filter(Objects::nonNull)
+                .filter(JMenuItem.class::isInstance);
+    }
+
+    /**
+     * Adds a listener to the underlying {@link javax.swing.JPopupMenu} to react
+     * on {@link JMenuItem} addition/removal. Mainly, adds {@link PropertyChangeListener} to every
+     * item that disables the menu if none of containing items are enabled.
+     */
+    public void addPopupContainerListener() {
+        enabledPropertyChangeListener(null); // initial check
+
+        super.getPopupMenu().addContainerListener(new ContainerListener() {
+
+            /**
+             * Keeps references to all listeners that were added, in order to be able to
+             * delete them later if needed.
+             */
+            private final List<PropertyChangeListener> listeners = new ArrayList<>();
+
+            @Override
+            public void componentAdded(ContainerEvent e) {
+                Component child = e.getChild();
+                if (child != null && child instanceof JMenuItem) {
+                    PropertyChangeListener l = ev -> enabledPropertyChangeListener(ev);
+                    listeners.add(l);
+                    child.addPropertyChangeListener("enabled", l);
+
+                    enabledPropertyChangeListener(null);
+                }
+            }
+
+            @Override
+            public void componentRemoved(ContainerEvent e) {
+                Component child = e.getChild();
+                if (child != null && child instanceof JMenuItem) {
+                    PropertyChangeListener[] ls = child.getPropertyChangeListeners("enabled");
+                    Arrays.stream(ls)
+                            .filter(this.listeners::contains)
+                            .findFirst()
+                            .ifPresent(l -> {
+                                this.listeners.remove(l);
+                                child.removePropertyChangeListener("enabled", l);
+
+                                enabledPropertyChangeListener(null);
+                            });
+                }
+            }
+        });
+    }
+
+    private void enabledPropertyChangeListener(PropertyChangeEvent ev) {
+        boolean enable = this.streamMenuItems().anyMatch(Component::isEnabled);
+        this.setEnabled(enable);
+    }
+}

src/org/openstreetmap/josm/gui/MainMenu.java

@@ -608 +608 @@
      * @return the newly created menu
      */
     public JMenu addMenu(String name, String translatedName, int mnemonicKey, int position, String relativeHelpTopic) {
-        final JMenu menu = new JMenu(translatedName);
+        final JosmMenu menu = new JosmMenu(translatedName);
+        menu.addPopupContainerListener();
+
         if (!GraphicsEnvironment.isHeadless()) {
             MenuScroller.setScrollerFor(menu);
         }