Introduce opaque window::Id type

src/multi_window/application.rs

@@ -1,3 +1,4 @@
+use crate::window;
 use crate::{Command, Element, Executor, Settings, Subscription};
 
 pub use iced_native::application::{Appearance, StyleSheet};
@@ -45,6 +46,9 @@ pub trait Application: Sized {
     /// title of your application when necessary.
     fn title(&self) -> String;
 
+    /// TODO(derezzedex)
+    fn windows(&self) -> Vec<(window::Id, window::Settings)>;
+
     /// Handles a __message__ and updates the state of the [`Application`].
     ///
     /// This is where you define your __update logic__. All the __messages__,
@@ -160,6 +164,16 @@ where
         self.0.title()
     }
 
+    fn windows(&self) -> Vec<(window::Id, iced_winit::settings::Window)> {
+        self.0
+            .windows()
+            .into_iter()
+            .map(|(id, settings)| {
+                (id, iced_winit::settings::Window::from(settings))
+            })
+            .collect()
+    }
+
     fn update(&mut self, message: Self::Message) -> Command<Self::Message> {
         self.0.update(message)
     }