[GTK] Fire settings event on Gtk theme change

Listen for notify::gtk-theme-name signal and fire SWT.Settings even in
this case.

Author: akurtakov

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

@@ -338,6 +338,7 @@ public static String getEnvironmentalVariable (String envVarName) {
 	public static final byte[] mnemonic_activate = ascii("mnemonic-activate");
 	public static final byte[] month_changed = ascii("month-changed");
 	public static final byte[] next_month = ascii("next-month");
+	public static final byte[] notify_gtk_theme = ascii("notify::gtk-theme-name");
 	public static final byte[] prev_month = ascii("prev-month");
 	public static final byte[] next_year = ascii("next-year");
 	public static final byte[] prev_year = ascii("prev-year");

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

@@ -497,6 +497,10 @@ public void stop() {
 	long keysChangedProc;
 	Callback keysChangedCallback;
 
+	/* Settings "changed" callback */
+	long settingsChangedProc;
+	Callback settingsChangedCallback;
+
 	/* Multiple Displays. */
 	static Display Default;
 	static Display [] Displays = new Display [1];
@@ -1323,7 +1327,11 @@ void createDisplay (DeviceData data) {
 	} else {
 		keymap = GDK.gdk_keymap_get_for_display(display);
 		OS.g_signal_connect (keymap, OS.keys_changed, keysChangedProc, 0);
-	}
+		}
+
+	settingsChangedCallback = new Callback (this, "settingsChangedProc", 3); //$NON-NLS-1$
+	settingsChangedProc = settingsChangedCallback.getAddress ();
+	OS.g_signal_connect (GTK.gtk_settings_get_default(), OS.notify_gtk_theme, settingsChangedProc, 0);
 }
 
 /**
@@ -1403,6 +1411,14 @@ long keysChangedProc (long keymap, long user_data) {
 	return 0;
 }
 
+/**
+ * GtkSettings 'changed' event handler.
+ */
+long settingsChangedProc (long settings, long key, long user_data) {
+	settingsChanged = true;
+	return 0;
+}
+
 Image createImage (String name) {
 	byte[] buffer = Converter.wcsToMbcs(name, true);
 
@@ -4818,6 +4834,10 @@ void releaseDisplay () {
 	keysChangedCallback.dispose(); keysChangedCallback = null;
 	keysChangedProc = 0;
 
+	/* Dispose the settings "changed" callback */
+	settingsChangedCallback.dispose(); settingsChangedCallback = null;
+	settingsChangedProc = 0;
+
 	/* Dispose subclass */
 	if (!GTK.GTK4) {
 		long pangoLayoutType = OS.PANGO_TYPE_LAYOUT ();