learn how workspaces + proc macros work & restructure everything

core/src/layout/view.rs

@@ -0,0 +1,17 @@
+use crate::layout::{Widget, WidgetLike, WidgetRef};
+use std::marker::Unsize;
+
+pub trait WidgetView {
+    type Widget: Widget + ?Sized + Unsize<dyn Widget> = dyn Widget;
+    fn view(&self) -> &WidgetRef<Self::Widget>;
+}
+
+pub struct ViewTag;
+
+impl<WV: WidgetView> WidgetLike<ViewTag> for WV {
+    type Widget = WV::Widget;
+
+    fn add(self, _ui: &mut super::Ui) -> WidgetRef<Self::Widget> {
+        self.view().clone()
+    }
+}