Implement stub singleton for UIScreen

src/frameworks/uikit.rs

@@ -10,12 +10,14 @@ use crate::export_c_func;
 pub mod ui_application;
 pub mod ui_nib;
 pub mod ui_responder;
+pub mod ui_screen;
 pub mod ui_view;
 pub mod ui_window;
 
 #[derive(Default)]
 pub struct State {
     ui_application: ui_application::State,
+    ui_screen: ui_screen::State,
 }
 
 pub const FUNCTIONS: FunctionExports = {

src/frameworks/uikit/ui_screen.rs

@@ -0,0 +1,38 @@
+//! `UIScreen`.
+
+use crate::objc::{id, objc_classes, ClassExports, TrivialHostObject};
+
+#[derive(Default)]
+pub struct State {
+    main_screen: Option<id>,
+}
+
+pub const CLASSES: ClassExports = objc_classes! {
+
+(env, this, _cmd);
+
+@implementation UIScreen: NSObject
+
+// For now this is a singleton (the only instance is returned by mainScreen)
++ (id)mainScreen {
+    if let Some(screen) = env.framework_state.uikit.ui_screen.main_screen {
+        screen
+    } else {
+        let new = env.objc.alloc_static_object(
+            this,
+            Box::new(TrivialHostObject),
+            &mut env.mem
+        );
+        env.framework_state.uikit.ui_screen.main_screen = Some(new);
+        new
+   }
+}
+- (id)retain { this }
+- (())release {}
+- (id)autorelease { this }
+
+// TODO: accessors
+
+@end
+
+};

src/objc/classes/class_lists.rs

@@ -19,6 +19,7 @@ pub const CLASS_LISTS: &[super::ClassExports] = &[
     uikit::ui_application::CLASSES,
     uikit::ui_nib::CLASSES,
     uikit::ui_responder::CLASSES,
+    uikit::ui_screen::CLASSES,
     uikit::ui_view::CLASSES,
     uikit::ui_window::CLASSES,
 ];