feat(qmetaobject): add null and undefined functions to QJSValue

Author: Mikhail Zolotukhin

qmetaobject/src/qtdeclarative.rs

@@ -506,11 +506,7 @@ pub fn qml_register_type<T: QObject + Default + Sized>(
 ///
 /// [qt]: https://doc.qt.io/qt-5/qqmlengine.html#qmlRegisterModule
 #[cfg(qt_5_9)]
-pub fn qml_register_module(
-    uri: &CStr,
-    version_major: u32,
-    version_minor: u32,
-) {
+pub fn qml_register_module(uri: &CStr, version_major: u32, version_minor: u32) {
     let uri_ptr = uri.as_ptr();
 
     cpp!(unsafe [
@@ -937,6 +933,18 @@ pub enum QJSValueSpecialValue {
 }
 
 impl QJSValue {
+    pub fn null() -> Self {
+        cpp!(unsafe [] -> QJSValue as "QJSValue" {
+            return QJSValue(QJSValue::SpecialValue::NullValue);
+        })
+    }
+
+    pub fn undefined() -> Self {
+        cpp!(unsafe [] -> QJSValue as "QJSValue" {
+            return QJSValue(QJSValue::SpecialValue::UndefinedValue);
+        })
+    }
+
     pub fn is_bool(&self) -> bool {
         cpp!(unsafe [self as "const QJSValue *"] -> bool as "bool" {
             return self->isBool();