Add #[derive(QEnum)]

see rust-lang/rust#8730

Author: Guiguiprim

qmetaobject/src/lib.rs

@@ -409,6 +409,22 @@ pub trait QGadget {
         Self: Sized;
 }
 
+/// Trait that is implemented by the QEnum custom derive macro
+///
+/// Do not implement this trait yourself, use `#[derive(QEnum)]`.
+pub trait QEnum {
+    /// Returns a pointer to a meta object
+    fn static_meta_object() -> *const QMetaObject
+    where
+        Self: Sized;
+
+    fn from_raw_value(raw: i32) -> Option<Self>
+    where
+        Self: Sized;
+
+    fn to_raw_value(&self) -> i32;
+}
+
 #[doc(hidden)]
 #[no_mangle]
 pub unsafe extern "C" fn RustObject_metaObject(p: *mut RefCell<QObject>) -> *const QMetaObject {
@@ -445,7 +461,8 @@ pub struct QMetaObject {
     pub superdata: *const QMetaObject,
     pub string_data: *const u8,
     pub data: *const u32,
-    pub static_metacall: extern "C" fn(o: *mut c_void, c: u32, idx: u32, a: *const *mut c_void),
+    pub static_metacall:
+        Option<extern "C" fn(o: *mut c_void, c: u32, idx: u32, a: *const *mut c_void)>,
     pub r: *const c_void,
     pub e: *const c_void,
 }

qmetaobject/src/qtdeclarative.rs

@@ -239,6 +239,27 @@ pub fn qml_register_type<T: QObject + Default + Sized>(
     })}
 }
 
+/// Register the given enum as a QML type
+///
+/// Refer to the Qt documentation for qmlRegisterUncreatableMetaObject.
+pub fn qml_register_enum<T: QEnum>(
+    uri: &std::ffi::CStr,
+    version_major: u32,
+    version_minor: u32,
+    qml_name: &std::ffi::CStr,
+)
+{
+    let uri_ptr = uri.as_ptr();
+    let qml_name_ptr = qml_name.as_ptr();
+    let meta_object = T::static_meta_object();
+
+    unsafe { cpp!([qml_name_ptr as "char*", uri_ptr as "char*", version_major as "int",
+                    version_minor as "int", meta_object as "const QMetaObject *"]{
+        qmlRegisterUncreatableMetaObject(*meta_object, uri_ptr, version_major,
+            version_minor, qml_name_ptr, "Access to enums & flags only");
+    })}
+}
+
 /// A QObject-like trait to inherit from QQuickItem.
 ///
 /// Work in progress

qmetaobject/tests/tests.rs

@@ -606,3 +606,44 @@ fn panic_when_moved_setter() {
     do_test(my_obj, "Item { function doTest() { _obj.prop_y = 45; } }");
 }
 */
+
+#[derive(QEnum)]
+#[repr(u8)]
+enum MyEnum {
+    None,
+    First = 1,
+    Four = 4,
+}
+
+#[derive(QObject, Default)]
+struct MyEnumObject {
+    base: qt_base_class!(trait QObject),
+}
+
+#[test]
+fn enum_properties() {
+    qml_register_enum::<MyEnum>(
+        CStr::from_bytes_with_nul(b"MyEnumLib\0").unwrap(),
+        1,
+        0,
+        CStr::from_bytes_with_nul(b"MyEnum\0").unwrap(),
+    );
+    let my_obj = MyObject::default();
+    assert!(do_test(
+        my_obj,
+        "import MyEnumLib 1.0
+        Item {
+        function doTest() {
+            if(MyEnum.None != 0) {
+                return false;
+            }
+            if(MyEnum.First != 1) {
+                return false;
+            }
+            if(MyEnum.Four != 4) {
+                return false;
+            }
+            return true;
+        }}"
+    ));
+}

qmetaobject_impl/src/lib.rs

@@ -70,6 +70,12 @@ pub fn qgadget_impl(input: TokenStream) -> TokenStream {
     qobject_impl::generate(input, false)
 }
 
+/// Implementation of #[derive(QEnum)]
+#[proc_macro_derive(QEnum, attributes(QMetaObjectCrate))]
+pub fn qenum_impl(input: TokenStream) -> TokenStream {
+    qobject_impl::generate_enum(input)
+}
+
 /// Implementation of the qmetaobject::qrc! macro
 #[proc_macro]
 pub fn qrc_internal(input: TokenStream) -> TokenStream {