[Gtk4] Support MenuListener adding sub menues

Map SHOW/HIDE signals for all menues. Dynamically recreate the menu
model on each such signal to allow MenuListeners to add/remove
MenuItems.

Author: akurtakov

bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/gtk4.c

@@ -2200,6 +2200,18 @@ JNIEXPORT jlong JNICALL GTK4_NATIVE(gtk_1popover_1menu_1bar_1new_1from_1model)
 }
 #endif
 
+#ifndef NO_gtk_1popover_1menu_1get_1menu_1model
+JNIEXPORT jlong JNICALL GTK4_NATIVE(gtk_1popover_1menu_1get_1menu_1model)
+	(JNIEnv *env, jclass that, jlong arg0)
+{
+	jlong rc = 0;
+	GTK4_NATIVE_ENTER(env, that, gtk_1popover_1menu_1get_1menu_1model_FUNC);
+	rc = (jlong)gtk_popover_menu_get_menu_model((GtkPopoverMenu *)arg0);
+	GTK4_NATIVE_EXIT(env, that, gtk_1popover_1menu_1get_1menu_1model_FUNC);
+	return rc;
+}
+#endif
+
 #ifndef NO_gtk_1popover_1menu_1new_1from_1model_1full
 JNIEXPORT jlong JNICALL GTK4_NATIVE(gtk_1popover_1menu_1new_1from_1model_1full)
 	(JNIEnv *env, jclass that, jlong arg0, jint arg1)

bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/gtk4_stats.h

@@ -180,6 +180,7 @@ typedef enum {
 	gtk_1picture_1set_1can_1shrink_FUNC,
 	gtk_1picture_1set_1paintable_FUNC,
 	gtk_1popover_1menu_1bar_1new_1from_1model_FUNC,
+	gtk_1popover_1menu_1get_1menu_1model_FUNC,
 	gtk_1popover_1menu_1new_1from_1model_1full_FUNC,
 	gtk_1popover_1menu_1set_1menu_1model_FUNC,
 	gtk_1popover_1set_1has_1arrow_FUNC,

bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk4/GTK4.java

@@ -549,6 +549,11 @@ public class GTK4 {
 	 * @param flags cast=(GtkPopoverMenuFlags)
 	 */
 	public static final native long gtk_popover_menu_new_from_model_full(long model, int flags);
+	/**
+	 * @param popover cast=(GtkPopoverMenu *)
+	 * @return cast=(GMenuModel *)
+	 */
+	public static final native long gtk_popover_menu_get_menu_model(long popover);
 	/**
 	 * @param popover cast=(GtkPopoverMenu *)
 	 * @param model cast=(GMenuModel *)

bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Menu.java

@@ -824,13 +824,22 @@ public boolean getVisible () {
 
 @Override
 long gtk_map (long widget) {
-	if (GTK.GTK4 && (style & SWT.BAR) != 0) {
-		/*
-		 * The GtkPopoverMenuBar has been mapped, which means its internal
-		 * GtkPopoverMenuBarItem children now exist. Find the GtkPopoverMenu child for each,
-		 * and connect SHOW/HIDE signals so that SWT MenuListeners on DROP_DOWN are notified.
-		 */
-		connectDropDownMenuSignals();
+	if (GTK.GTK4) {
+		if ((style & SWT.BAR) != 0) {
+			/*
+			 * The GtkPopoverMenuBar has been mapped, which means its internal
+			 * GtkPopoverMenuBarItem children now exist. Find the GtkPopoverMenu child for each,
+			 * and connect SHOW/HIDE signals so that SWT MenuListeners on DROP_DOWN are notified.
+			 */
+			connectDropDownMenuSignals();
+		} else if ((style & SWT.POP_UP) != 0) {
+			/*
+			 * The POP_UP GtkPopoverMenu has been mapped. Its handle IS the GtkPopoverMenu,
+			 * and nested GtkPopoverMenu children for any CASCADE submenus already exist in
+			 * its widget tree. Connect SHOW/HIDE signals for those nested submenus now.
+			 */
+			connectCascadeSubMenuSignals(this, handle);
+		}
 	}
 	return super.gtk_map(widget);
 }
@@ -845,16 +854,67 @@ private void connectDropDownMenuSignals() {
 		if (menuItem.menu != null && menuItem.menu.popoverHandle == 0) {
 			long popover = findGtkPopoverMenuChild(barItem);
 			if (popover != 0) {
+				OS.g_object_ref(popover);
 				menuItem.menu.popoverHandle = popover;
 				display.addWidget(popover, menuItem.menu);
 				OS.g_signal_connect_closure_by_id(popover, display.signalIds[SHOW], 0, display.getClosure(SHOW), false);
 				OS.g_signal_connect_closure_by_id(popover, display.signalIds[HIDE], 0, display.getClosure(HIDE), false);
+				/*
+				 * Also connect SHOW/HIDE signals for nested CASCADE submenus.
+				 */
+				connectCascadeSubMenuSignals(menuItem.menu);
 			}
 		}
 		barItem = GTK4.gtk_widget_get_next_sibling(barItem);
 	}
 }
 
+private void connectCascadeSubMenuSignals(Menu menu) {
+	connectCascadeSubMenuSignals(menu, menu.popoverHandle);
+}
+
+private void connectCascadeSubMenuSignals(Menu menu, long parentPopoverHandle) {
+	if (menu == null || parentPopoverHandle == 0 || menu.items == null) return;
+	for (MenuItem item : menu.items) {
+		if ((item.style & SWT.CASCADE) != 0 && item.menu != null) {
+			/*
+			 * item.menu is the CASCADE submenu (always SWT.DROP_DOWN style).
+			 * Its popoverHandle is 0 until we find and register its GtkPopoverMenu.
+			 * Skip if already connected (popoverHandle != 0).
+			 */
+			if (item.menu.popoverHandle != 0) continue;
+			long nestedPopover = findNestedPopoverForModel(parentPopoverHandle, item.menu.modelHandle);
+			if (nestedPopover != 0) {
+				OS.g_object_ref(nestedPopover);
+				item.menu.popoverHandle = nestedPopover;
+				display.addWidget(nestedPopover, item.menu);
+				OS.g_signal_connect_closure_by_id(nestedPopover, display.signalIds[SHOW], 0, display.getClosure(SHOW), false);
+				OS.g_signal_connect_closure_by_id(nestedPopover, display.signalIds[HIDE], 0, display.getClosure(HIDE), false);
+				// Recurse to handle further nested CASCADE submenus
+				connectCascadeSubMenuSignals(item.menu);
+			}
+		}
+	}
+}
+
+private long findNestedPopoverForModel(long parentWidget, long targetModel) {
+	if (parentWidget == 0 || targetModel == 0) return 0;
+	long child = GTK4.gtk_widget_get_first_child(parentWidget);
+	while (child != 0) {
+		if (GTK4.GTK_IS_POPOVER_MENU(child)) {
+			long model = GTK4.gtk_popover_menu_get_menu_model(child);
+			if (model == targetModel) {
+				return child;
+			}
+		}
+		long found = findNestedPopoverForModel(child, targetModel);
+		if (found != 0) return found;
+		child = GTK4.gtk_widget_get_next_sibling(child);
+	}
+	return 0;
+}
+
+
 private long findGtkPopoverMenuChild(long barItem) {
 	long child = GTK4.gtk_widget_get_first_child(barItem);
 	while (child != 0) {
@@ -955,7 +1015,7 @@ void hookEvents() {
 		if ((style & SWT.DROP_DOWN) == 0) {
 			OS.g_signal_connect_closure_by_id(handle, display.signalIds[SHOW], 0, display.getClosure(SHOW), false);
 			OS.g_signal_connect_closure_by_id(handle, display.signalIds[HIDE], 0, display.getClosure(HIDE), false);
-			if ((style & SWT.BAR) != 0) {
+			if ((style & (SWT.BAR | SWT.POP_UP)) != 0) {
 				/*
 				 * Connect MAP signal on the GtkPopoverMenuBar so that once it is
 				 * realized and its internal GtkPopoverMenuBarItem children exist,
@@ -1102,6 +1162,7 @@ void deregister() {
 	super.deregister();
 	if (GTK.GTK4 && (style & SWT.DROP_DOWN) != 0 && popoverHandle != 0) {
 		display.removeWidget(popoverHandle);
+		OS.g_object_unref(popoverHandle);
 		popoverHandle = 0;
 	}
 }