Fix GTK4 crash when creating and closing many shells

Add signal handler tracking for GdkSurface signals in Shell.java.
Store handler IDs when connecting signals and disconnect them in releaseWidget().
Add test for creating and disposing multiple shells.

Co-authored-by: laeubi <1331477+laeubi@users.noreply.github.com>

Author: Copilot

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

@@ -133,6 +133,7 @@ public class Shell extends Decorations {
 	boolean ignoreFocusOut, ignoreFocusIn;
 	boolean ignoreFocusOutAfterGrab, grabbedFocus;
 	Region originalRegion;
+	long gdkSurfaceNotifyStateHandler, gdkSurfaceComputeSizeHandler;
 
 	static final int MAXIMUM_TRIM = 128;
 	static final int BORDER = 3;
@@ -965,8 +966,8 @@ void hookEvents () {
 		// Replaced "window-state-event" with GdkSurface "notify::state", pass shellHandle as user_data
 		GTK.gtk_widget_realize(shellHandle);
 		long gdkSurface = gtk_widget_get_surface (shellHandle);
-		OS.g_signal_connect (gdkSurface, OS.notify_state, display.notifyProc, shellHandle);
-		OS.g_signal_connect (gdkSurface, OS.compute_size, display.computeSizeProc, shellHandle);
+		gdkSurfaceNotifyStateHandler = OS.g_signal_connect (gdkSurface, OS.notify_state, display.notifyProc, shellHandle);
+		gdkSurfaceComputeSizeHandler = OS.g_signal_connect (gdkSurface, OS.compute_size, display.computeSizeProc, shellHandle);
 		OS.g_signal_connect(shellHandle, OS.notify_default_height, display.notifyProc, Widget.NOTIFY_DEFAULT_HEIGHT);
 		OS.g_signal_connect(shellHandle, OS.notify_default_width, display.notifyProc, Widget.NOTIFY_DEFAULT_WIDTH);
 		OS.g_signal_connect(shellHandle, OS.notify_maximized, display.notifyProc, Widget.NOTIFY_MAXIMIZED);
@@ -3431,6 +3432,20 @@ void releaseWidget () {
 	if (group != 0) OS.g_object_unref (group);
 	group = modalGroup = 0;
 	lastActive = null;
+	// Disconnect GdkSurface signal handlers for GTK4
+	if (GTK.GTK4 && shellHandle != 0) {
+		long gdkSurface = gtk_widget_get_surface(shellHandle);
+		if (gdkSurface != 0) {
+			if (gdkSurfaceNotifyStateHandler != 0) {
+				OS.g_signal_handler_disconnect(gdkSurface, gdkSurfaceNotifyStateHandler);
+				gdkSurfaceNotifyStateHandler = 0;
+			}
+			if (gdkSurfaceComputeSizeHandler != 0) {
+				OS.g_signal_handler_disconnect(gdkSurface, gdkSurfaceComputeSizeHandler);
+				gdkSurfaceComputeSizeHandler = 0;
+			}
+		}
+	}
 	if (regionToDispose != null) {
 		regionToDispose.dispose();
 	}

tests/org.eclipse.swt.tests/JUnit Tests/org/eclipse/swt/tests/junit/Test_org_eclipse_swt_widgets_Shell.java

@@ -1004,6 +1004,22 @@ public void test_Issue450_NoShellActivateOnSetFocus() {
 	}
 }
 
+@Test
+public void test_createAndDisposeMultipleShells() {
+	// Test for GTK4 crash when creating and disposing many shells
+	// See https://github.com/eclipse-platform/eclipse.platform.swt/issues/XXXX
+	Display display = shell.getDisplay();
+	for (int i = 0; i < 100; i++) {
+		Shell testShell = new Shell(display);
+		testShell.open();
+		while (display.readAndDispatch()) {
+			// Process events
+		}
+		testShell.close();
+		testShell.dispose();
+	}
+}
+
 @Override
 public void test_setLocationLorg_eclipse_swt_graphics_Point() {
 	//Setting location for Windows is not supported in GTK4