Simplify Iris app initialization and task updates

examples/message_list/desktop.rs

@@ -3,24 +3,10 @@ use winit::{dpi::LogicalSize, window::WindowAttributes};
 
 #[path = "lib.rs"]
 mod app;
-use app::*;
-
-#[derive(DesktopUiState)]
-struct State {
-    ui_state: DesktopUiState,
-}
-
-impl DesktopAppState for State {
-    fn window_attributes() -> WindowAttributes {
-        WindowAttributes::default().with_inner_size(LogicalSize::new(420.0, 900.0))
-    }
-
-    fn new(mut ui_state: DesktopUiState, rsc: &mut StdRsc<Self>, _: Proxy<Self::Event>) -> Self {
-        build(rsc, &mut ui_state);
-        Self { ui_state }
-    }
-}
 
 fn main() {
-    DesktopApp::<State>::run();
+    let attributes = WindowAttributes::default().with_inner_size(LogicalSize::new(420.0, 900.0));
+    DesktopApp::<DesktopUiState>::run_with_attributes(attributes, |ui_state, rsc| {
+        app::build(rsc, ui_state)
+    });
 }