[GTK] Look up the accessibility class once in os_custom.c

call_accessible_object_function() called FindClass for every accessibility
callback. The class is now looked up once and kept as a global reference,
primed when an accessible is registered, and a failed lookup clears the
pending exception instead of leaving it for the next JNI call.

FindClass resolves against the class loader of the calling Java method, so
it only finds AccessibleObject while the C code is entered from a JNI
native method.

Assisted-by: multiple AI agents and layers of automated tooling 🤖

Author: vogella

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

@@ -1040,6 +1040,23 @@ G_DEFINE_TYPE_WITH_CODE (SwtFixedAccessible, swt_fixed_accessible, GTK_TYPE_CONT
 // Fully qualified Java class name for the Java implementation of ATK functions
 const char *ACCESSIBILITY_CLASS_NAME = "org/eclipse/swt/accessibility/AccessibleObject";
 
+static jclass accessibility_class = NULL;
+
+// FindClass resolves against the class loader of the calling Java method, which only is SWT's
+// when called from a JNI native method, so the class is looked up once and kept.
+static jclass get_accessibility_class (JNIEnv *env) {
+	if (accessibility_class == NULL) {
+		jclass cls = (*env)->FindClass(env, ACCESSIBILITY_CLASS_NAME);
+		if (cls == NULL) {
+			(*env)->ExceptionClear(env);
+			return NULL;
+		}
+		accessibility_class = (*env)->NewGlobalRef(env, cls);
+		(*env)->DeleteLocalRef(env, cls);
+	}
+	return accessibility_class;
+}
+
 static void swt_fixed_accessible_init (SwtFixedAccessible *accessible) {
 	// Initialize the SwtFixedAccessiblePrivate struct
 	accessible->priv = swt_fixed_accessible_get_instance_private (accessible);
@@ -1105,6 +1122,11 @@ void swt_fixed_accessible_register_accessible (AtkObject *obj, gboolean is_nativ
 	SwtFixedAccessiblePrivate *private = fixed->priv;
 	private->has_accessible = TRUE;
 
+	JNIEnv *env;
+	if ((*JVM)->GetEnv(JVM, (void **)&env, JNI_VERSION_10) == JNI_OK) {
+		get_accessibility_class(env);
+	}
+
 	if (!is_native) {
 		gtk_accessible_set_widget (GTK_ACCESSIBLE (obj), to_map);
 		private->widget = to_map;
@@ -2122,7 +2144,7 @@ jlong call_accessible_object_function (const char *method_name, const char *meth
 	}
 
 	// Find the class pointer
-	cls = (*env)->FindClass(env, ACCESSIBILITY_CLASS_NAME);
+	cls = get_accessibility_class(env);
 	if (cls == NULL) {
 		g_critical("JNI class pointer is NULL for class %s\n", ACCESSIBILITY_CLASS_NAME);
 		return 0;