Introduce daemon API and unify shell runtimes

Cargo.toml

@@ -66,7 +66,7 @@ iced_core.workspace = true
 iced_futures.workspace = true
 iced_renderer.workspace = true
 iced_widget.workspace = true
-iced_winit.features = ["application"]
+iced_winit.features = ["program"]
 iced_winit.workspace = true
 
 iced_highlighter.workspace = true

examples/arc/src/main.rs

@@ -7,7 +7,7 @@ use iced::widget::canvas::{
 use iced::{Element, Length, Point, Rectangle, Renderer, Subscription, Theme};
 
 pub fn main() -> iced::Result {
-    iced::program("Arc - Iced", Arc::update, Arc::view)
+    iced::application("Arc - Iced", Arc::update, Arc::view)
         .subscription(Arc::subscription)
         .theme(|_| Theme::Dark)
         .antialiasing(true)

examples/bezier_tool/src/main.rs

@@ -4,7 +4,7 @@ use iced::widget::{button, container, horizontal_space, hover};
 use iced::{Element, Length, Theme};
 
 pub fn main() -> iced::Result {
-    iced::program("Bezier Tool - Iced", Example::update, Example::view)
+    iced::application("Bezier Tool - Iced", Example::update, Example::view)
         .theme(|_| Theme::CatppuccinMocha)
         .antialiasing(true)
         .run()

examples/checkbox/src/main.rs

@@ -4,7 +4,7 @@ use iced::{Element, Font};
 const ICON_FONT: Font = Font::with_name("icons");
 
 pub fn main() -> iced::Result {
-    iced::program("Checkbox - Iced", Example::update, Example::view)
+    iced::application("Checkbox - Iced", Example::update, Example::view)
         .font(include_bytes!("../fonts/icons.ttf").as_slice())
         .run()
 }

examples/clock/src/main.rs

@@ -11,7 +11,7 @@ use iced::{
 pub fn main() -> iced::Result {
     tracing_subscriber::fmt::init();
 
-    iced::program("Clock - Iced", Clock::update, Clock::view)
+    iced::application("Clock - Iced", Clock::update, Clock::view)
         .subscription(Clock::subscription)
         .theme(Clock::theme)
         .antialiasing(true)

examples/color_palette/src/main.rs

@@ -11,7 +11,7 @@ use std::marker::PhantomData;
 use std::ops::RangeInclusive;
 
 pub fn main() -> iced::Result {
-    iced::program(
+    iced::application(
         "Color Palette - Iced",
         ColorPalette::update,
         ColorPalette::view,

examples/custom_shader/src/main.rs

@@ -9,7 +9,11 @@ use iced::window;
 use iced::{Alignment, Color, Element, Length, Subscription};
 
 fn main() -> iced::Result {
-    iced::program("Custom Shader - Iced", IcedCubes::update, IcedCubes::view)
+    iced::application(
+        "Custom Shader - Iced",
+        IcedCubes::update,
+        IcedCubes::view,
+    )
     .subscription(IcedCubes::subscription)
     .run()
 }

examples/download_progress/src/main.rs

@@ -4,7 +4,11 @@ use iced::widget::{button, center, column, progress_bar, text, Column};
 use iced::{Alignment, Element, Subscription};
 
 pub fn main() -> iced::Result {
-    iced::program("Download Progress - Iced", Example::update, Example::view)
+    iced::application(
+        "Download Progress - Iced",
+        Example::update,
+        Example::view,
+    )
     .subscription(Example::subscription)
     .run()
 }

examples/editor/src/main.rs

@@ -12,7 +12,7 @@ use std::path::{Path, PathBuf};
 use std::sync::Arc;
 
 pub fn main() -> iced::Result {
-    iced::program("Editor - Iced", Editor::update, Editor::view)
+    iced::application("Editor - Iced", Editor::update, Editor::view)
         .load(Editor::load)
         .subscription(Editor::subscription)
         .theme(Editor::theme)

examples/events/src/main.rs

@@ -5,7 +5,7 @@ use iced::window;
 use iced::{Alignment, Element, Length, Subscription, Task};
 
 pub fn main() -> iced::Result {
-    iced::program("Events - Iced", Events::update, Events::view)
+    iced::application("Events - Iced", Events::update, Events::view)
         .subscription(Events::subscription)
         .exit_on_close_request(false)
         .run()

examples/exit/src/main.rs

@@ -3,7 +3,7 @@ use iced::window;
 use iced::{Alignment, Element, Task};
 
 pub fn main() -> iced::Result {
-    iced::program("Exit - Iced", Exit::update, Exit::view).run()
+    iced::application("Exit - Iced", Exit::update, Exit::view).run()
 }
 
 #[derive(Default)]

examples/ferris/src/main.rs

@@ -9,7 +9,7 @@ use iced::{
 };
 
 pub fn main() -> iced::Result {
-    iced::program("Ferris - Iced", Image::update, Image::view)
+    iced::application("Ferris - Iced", Image::update, Image::view)
         .subscription(Image::subscription)
         .theme(|_| Theme::TokyoNight)
         .run()

examples/game_of_life/src/main.rs

@@ -15,7 +15,11 @@ use std::time::Duration;
 pub fn main() -> iced::Result {
     tracing_subscriber::fmt::init();
 
-    iced::program("Game of Life - Iced", GameOfLife::update, GameOfLife::view)
+    iced::application(
+        "Game of Life - Iced",
+        GameOfLife::update,
+        GameOfLife::view,
+    )
     .subscription(GameOfLife::subscription)
     .theme(|_| Theme::Dark)
     .antialiasing(true)

examples/gradient/src/main.rs

@@ -1,5 +1,5 @@
+use iced::application;
 use iced::gradient;
-use iced::program;
 use iced::widget::{
     checkbox, column, container, horizontal_space, row, slider, text,
 };
@@ -8,7 +8,7 @@ use iced::{Alignment, Color, Element, Length, Radians, Theme};
 pub fn main() -> iced::Result {
     tracing_subscriber::fmt::init();
 
-    iced::program("Gradient - Iced", Gradient::update, Gradient::view)
+    iced::application("Gradient - Iced", Gradient::update, Gradient::view)
         .style(Gradient::style)
         .transparent(true)
         .run()
@@ -95,11 +95,11 @@ impl Gradient {
         .into()
     }
 
-    fn style(&self, theme: &Theme) -> program::Appearance {
-        use program::DefaultStyle;
+    fn style(&self, theme: &Theme) -> application::Appearance {
+        use application::DefaultStyle;
 
         if self.transparent {
-            program::Appearance {
+            application::Appearance {
                 background_color: Color::TRANSPARENT,
                 text_color: theme.palette().text,
             }

examples/layout/src/main.rs

@@ -10,7 +10,7 @@ use iced::{
 };
 
 pub fn main() -> iced::Result {
-    iced::program(Layout::title, Layout::update, Layout::view)
+    iced::application(Layout::title, Layout::update, Layout::view)
         .subscription(Layout::subscription)
         .theme(Layout::theme)
         .run()

examples/loading_spinners/src/main.rs

@@ -11,7 +11,7 @@ use circular::Circular;
 use linear::Linear;
 
 pub fn main() -> iced::Result {
-    iced::program(
+    iced::application(
         "Loading Spinners - Iced",
         LoadingSpinners::update,
         LoadingSpinners::view,

examples/modal/src/main.rs

@@ -10,7 +10,7 @@ use iced::{Alignment, Color, Element, Length, Subscription, Task};
 use std::fmt;
 
 pub fn main() -> iced::Result {
-    iced::program("Modal - Iced", App::update, App::view)
+    iced::application("Modal - Iced", App::update, App::view)
         .subscription(App::subscription)
         .run()
 }

examples/multi_window/src/main.rs

@@ -1,18 +1,21 @@
-use iced::executor;
-use iced::multi_window::{self, Application};
 use iced::widget::{
     button, center, column, container, horizontal_space, scrollable, text,
     text_input,
 };
 use iced::window;
-use iced::{
-    Alignment, Element, Length, Settings, Subscription, Task, Theme, Vector,
-};
+use iced::{Alignment, Element, Length, Subscription, Task, Theme, Vector};
 
 use std::collections::BTreeMap;
 
 fn main() -> iced::Result {
-    Example::run(Settings::default())
+    iced::daemon(Example::title, Example::update, Example::view)
+        .load(|| {
+            window::open(window::Settings::default()).map(Message::WindowOpened)
+        })
+        .subscription(Example::subscription)
+        .theme(Example::theme)
+        .scale_factor(Example::scale_factor)
+        .run()
 }
 
 #[derive(Default)]
@@ -39,21 +42,7 @@ enum Message {
     TitleChanged(window::Id, String),
 }
 
-impl multi_window::Application for Example {
-    type Executor = executor::Default;
-    type Message = Message;
-    type Theme = Theme;
-    type Flags = ();
-
-    fn new(_flags: ()) -> (Self, Task<Message>) {
-        (
-            Example {
-                windows: BTreeMap::from([(window::Id::MAIN, Window::new(1))]),
-            },
-            Task::none(),
-        )
-    }
-
+impl Example {
     fn title(&self, window: window::Id) -> String {
         self.windows
             .get(&window)
@@ -97,8 +86,12 @@ impl multi_window::Application for Example {
             Message::WindowClosed(id) => {
                 self.windows.remove(&id);
 
+                if self.windows.is_empty() {
+                    iced::exit()
+                } else {
                     Task::none()
                 }
+            }
             Message::ScaleInputChanged(id, scale) => {
                 if let Some(window) = self.windows.get_mut(&id) {
                     window.scale_input = scale;
@@ -149,7 +142,7 @@ impl multi_window::Application for Example {
             .unwrap_or(1.0)
     }
 
-    fn subscription(&self) -> Subscription<Self::Message> {
+    fn subscription(&self) -> Subscription<Message> {
         window::close_events().map(Message::WindowClosed)
     }
 }

examples/multitouch/src/main.rs

@@ -13,7 +13,7 @@ use std::collections::HashMap;
 pub fn main() -> iced::Result {
     tracing_subscriber::fmt::init();
 
-    iced::program("Multitouch - Iced", Multitouch::update, Multitouch::view)
+    iced::application("Multitouch - Iced", Multitouch::update, Multitouch::view)
         .antialiasing(true)
         .centered()
         .run()

examples/pane_grid/src/main.rs

@@ -7,7 +7,7 @@ use iced::widget::{
 use iced::{Color, Element, Length, Size, Subscription};
 
 pub fn main() -> iced::Result {
-    iced::program("Pane Grid - Iced", Example::update, Example::view)
+    iced::application("Pane Grid - Iced", Example::update, Example::view)
         .subscription(Example::subscription)
         .run()
 }

examples/pokedex/src/main.rs

@@ -3,7 +3,7 @@ use iced::widget::{self, center, column, image, row, text};
 use iced::{Alignment, Element, Length, Task};
 
 pub fn main() -> iced::Result {
-    iced::program(Pokedex::title, Pokedex::update, Pokedex::view)
+    iced::application(Pokedex::title, Pokedex::update, Pokedex::view)
         .load(Pokedex::search)
         .run()
 }

examples/qr_code/src/main.rs

@@ -2,7 +2,7 @@ use iced::widget::{center, column, pick_list, qr_code, row, text, text_input};
 use iced::{Alignment, Element, Theme};
 
 pub fn main() -> iced::Result {
-    iced::program(
+    iced::application(
         "QR Code Generator - Iced",
         QRGenerator::update,
         QRGenerator::view,

examples/screenshot/src/main.rs

@@ -13,7 +13,7 @@ use ::image::ColorType;
 fn main() -> iced::Result {
     tracing_subscriber::fmt::init();
 
-    iced::program("Screenshot - Iced", Example::update, Example::view)
+    iced::application("Screenshot - Iced", Example::update, Example::view)
         .subscription(Example::subscription)
         .run()
 }

examples/scrollable/src/main.rs

@@ -10,7 +10,7 @@ use once_cell::sync::Lazy;
 static SCROLLABLE_ID: Lazy<scrollable::Id> = Lazy::new(scrollable::Id::unique);
 
 pub fn main() -> iced::Result {
-    iced::program(
+    iced::application(
         "Scrollable - Iced",
         ScrollableDemo::update,
         ScrollableDemo::view,

examples/sierpinski_triangle/src/main.rs

@@ -8,7 +8,7 @@ use rand::Rng;
 use std::fmt::Debug;
 
 fn main() -> iced::Result {
-    iced::program(
+    iced::application(
         "Sierpinski Triangle - Iced",
         SierpinskiEmulator::update,
         SierpinskiEmulator::view,

examples/solar_system/src/main.rs

@@ -22,7 +22,7 @@ use std::time::Instant;
 pub fn main() -> iced::Result {
     tracing_subscriber::fmt::init();
 
-    iced::program(
+    iced::application(
         "Solar System - Iced",
         SolarSystem::update,
         SolarSystem::view,

examples/stopwatch/src/main.rs

@@ -7,7 +7,7 @@ use iced::{Alignment, Element, Subscription, Theme};
 use std::time::{Duration, Instant};
 
 pub fn main() -> iced::Result {
-    iced::program("Stopwatch - Iced", Stopwatch::update, Stopwatch::view)
+    iced::application("Stopwatch - Iced", Stopwatch::update, Stopwatch::view)
         .subscription(Stopwatch::subscription)
         .theme(Stopwatch::theme)
         .run()

examples/styling/src/main.rs

@@ -6,7 +6,7 @@ use iced::widget::{
 use iced::{Alignment, Element, Length, Theme};
 
 pub fn main() -> iced::Result {
-    iced::program("Styling - Iced", Styling::update, Styling::view)
+    iced::application("Styling - Iced", Styling::update, Styling::view)
         .theme(Styling::theme)
         .run()
 }

examples/system_information/src/main.rs

@@ -2,7 +2,11 @@ use iced::widget::{button, center, column, text};
 use iced::{system, Element, Task};
 
 pub fn main() -> iced::Result {
-    iced::program("System Information - Iced", Example::update, Example::view)
+    iced::application(
+        "System Information - Iced",
+        Example::update,
+        Example::view,
+    )
     .run()
 }
 

examples/the_matrix/src/main.rs

@@ -11,7 +11,7 @@ use std::cell::RefCell;
 pub fn main() -> iced::Result {
     tracing_subscriber::fmt::init();
 
-    iced::program("The Matrix - Iced", TheMatrix::update, TheMatrix::view)
+    iced::application("The Matrix - Iced", TheMatrix::update, TheMatrix::view)
         .subscription(TheMatrix::subscription)
         .antialiasing(true)
         .run()

examples/toast/src/main.rs

@@ -9,7 +9,7 @@ use iced::{Alignment, Element, Length, Subscription, Task};
 use toast::{Status, Toast};
 
 pub fn main() -> iced::Result {
-    iced::program("Toast - Iced", App::update, App::view)
+    iced::application("Toast - Iced", App::update, App::view)
         .subscription(App::subscription)
         .run()
 }

examples/todos/src/main.rs

@@ -17,7 +17,7 @@ pub fn main() -> iced::Result {
     #[cfg(not(target_arch = "wasm32"))]
     tracing_subscriber::fmt::init();
 
-    iced::program(Todos::title, Todos::update, Todos::view)
+    iced::application(Todos::title, Todos::update, Todos::view)
         .load(Todos::load)
         .subscription(Todos::subscription)
         .font(include_bytes!("../fonts/icons.ttf").as_slice())

examples/tour/src/main.rs

@@ -16,7 +16,7 @@ pub fn main() -> iced::Result {
     #[cfg(not(target_arch = "wasm32"))]
     tracing_subscriber::fmt::init();
 
-    iced::program(Tour::title, Tour::update, Tour::view)
+    iced::application(Tour::title, Tour::update, Tour::view)
         .centered()
         .run()
 }

examples/url_handler/src/main.rs

@@ -3,7 +3,7 @@ use iced::widget::{center, text};
 use iced::{Element, Subscription};
 
 pub fn main() -> iced::Result {
-    iced::program("URL Handler - Iced", App::update, App::view)
+    iced::application("URL Handler - Iced", App::update, App::view)
         .subscription(App::subscription)
         .run()
 }

examples/vectorial_text/src/main.rs

@@ -6,7 +6,7 @@ use iced::widget::{
 use iced::{Element, Length, Point, Rectangle, Renderer, Theme, Vector};
 
 pub fn main() -> iced::Result {
-    iced::program(
+    iced::application(
         "Vectorial Text - Iced",
         VectorialText::update,
         VectorialText::view,

examples/visible_bounds/src/main.rs

@@ -10,7 +10,7 @@ use iced::{
 };
 
 pub fn main() -> iced::Result {
-    iced::program("Visible Bounds - Iced", Example::update, Example::view)
+    iced::application("Visible Bounds - Iced", Example::update, Example::view)
         .subscription(Example::subscription)
         .theme(|_| Theme::Dark)
         .run()

examples/websocket/src/main.rs

@@ -8,7 +8,7 @@ use iced::{color, Element, Length, Subscription, Task};
 use once_cell::sync::Lazy;
 
 pub fn main() -> iced::Result {
-    iced::program("WebSocket - Iced", WebSocket::update, WebSocket::view)
+    iced::application("WebSocket - Iced", WebSocket::update, WebSocket::view)
         .load(WebSocket::load)
         .subscription(WebSocket::subscription)
         .run()

runtime/src/lib.rs

@@ -70,6 +70,12 @@ pub enum Action<T> {
 
     /// Run a system action.
     System(system::Action),
+
+    /// Exits the runtime.
+    ///
+    /// This will normally close any application windows and
+    /// terminate the runtime loop.
+    Exit,
 }
 
 impl<T> Action<T> {
@@ -88,6 +94,7 @@ impl<T> Action<T> {
             Action::Clipboard(action) => Err(Action::Clipboard(action)),
             Action::Window(action) => Err(Action::Window(action)),
             Action::System(action) => Err(Action::System(action)),
+            Action::Exit => Err(Action::Exit),
         }
     }
 }
@@ -110,6 +117,15 @@ where
             }
             Action::Window(_) => write!(f, "Action::Window"),
             Action::System(action) => write!(f, "Action::System({action:?})"),
+            Action::Exit => write!(f, "Action::Exit"),
         }
     }
 }
+
+/// Creates a [`Task`] that exits the iced runtime.
+///
+/// This will normally close any application windows and
+/// terminate the runtime loop.
+pub fn exit<T>() -> Task<T> {
+    Task::effect(Action::Exit)
+}

src/advanced.rs

@@ -1,5 +1,4 @@
 //! Leverage advanced concepts like custom widgets.
-pub use crate::application::Application;
 pub use crate::core::clipboard::{self, Clipboard};
 pub use crate::core::image;
 pub use crate::core::layout::{self, Layout};

src/application.rs

@@ -1,278 +1,426 @@
-//! Build interactive cross-platform applications.
-use crate::core::text;
-use crate::graphics::compositor;
-use crate::shell::application;
-use crate::{Element, Executor, Settings, Subscription, Task};
+//! Create and run iced applications step by step.
+//!
+//! # Example
+//! ```no_run
+//! use iced::widget::{button, column, text, Column};
+//! use iced::Theme;
+//!
+//! pub fn main() -> iced::Result {
+//!     iced::application("A counter", update, view)
+//!         .theme(|_| Theme::Dark)
+//!         .centered()
+//!         .run()
+//! }
+//!
+//! #[derive(Debug, Clone)]
+//! enum Message {
+//!     Increment,
+//! }
+//!
+//! fn update(value: &mut u64, message: Message) {
+//!     match message {
+//!         Message::Increment => *value += 1,
+//!     }
+//! }
+//!
+//! fn view(value: &u64) -> Column<Message> {
+//!     column![
+//!         text(value),
+//!         button("+").on_press(Message::Increment),
+//!     ]
+//! }
+//! ```
+use crate::program::{self, Program};
+use crate::window;
+use crate::{Element, Font, Result, Settings, Size, Subscription, Task};
 
-pub use application::{Appearance, DefaultStyle};
+use std::borrow::Cow;
 
-/// An interactive cross-platform application.
-///
-/// This trait is the main entrypoint of Iced. Once implemented, you can run
-/// your GUI application by simply calling [`run`](#method.run).
-///
-/// - On native platforms, it will run in its own window.
-/// - On the web, it will take control of the `<title>` and the `<body>` of the
-///   document.
-///
-/// An [`Application`] can execute asynchronous actions by returning a
-/// [`Task`] in some of its methods.
-///
-/// When using an [`Application`] with the `debug` feature enabled, a debug view
-/// can be toggled by pressing `F12`.
-///
-/// # Examples
-/// [The repository has a bunch of examples] that use the [`Application`] trait:
-///
-/// - [`clock`], an application that uses the [`Canvas`] widget to draw a clock
-/// and its hands to display the current time.
-/// - [`download_progress`], a basic application that asynchronously downloads
-/// a dummy file of 100 MB and tracks the download progress.
-/// - [`events`], a log of native events displayed using a conditional
-/// [`Subscription`].
-/// - [`game_of_life`], an interactive version of the [Game of Life], invented
-/// by [John Horton Conway].
-/// - [`pokedex`], an application that displays a random Pokédex entry (sprite
-/// included!) by using the [PokéAPI].
-/// - [`solar_system`], an animated solar system drawn using the [`Canvas`] widget
-/// and showcasing how to compose different transforms.
-/// - [`stopwatch`], a watch with start/stop and reset buttons showcasing how
-/// to listen to time.
-/// - [`todos`], a todos tracker inspired by [TodoMVC].
-///
-/// [The repository has a bunch of examples]: https://github.com/iced-rs/iced/tree/0.12/examples
-/// [`clock`]: https://github.com/iced-rs/iced/tree/0.12/examples/clock
-/// [`download_progress`]: https://github.com/iced-rs/iced/tree/0.12/examples/download_progress
-/// [`events`]: https://github.com/iced-rs/iced/tree/0.12/examples/events
-/// [`game_of_life`]: https://github.com/iced-rs/iced/tree/0.12/examples/game_of_life
-/// [`pokedex`]: https://github.com/iced-rs/iced/tree/0.12/examples/pokedex
-/// [`solar_system`]: https://github.com/iced-rs/iced/tree/0.12/examples/solar_system
-/// [`stopwatch`]: https://github.com/iced-rs/iced/tree/0.12/examples/stopwatch
-/// [`todos`]: https://github.com/iced-rs/iced/tree/0.12/examples/todos
-/// [`Sandbox`]: crate::Sandbox
-/// [`Canvas`]: crate::widget::Canvas
-/// [PokéAPI]: https://pokeapi.co/
-/// [TodoMVC]: http://todomvc.com/
-///
-/// ## A simple "Hello, world!"
-///
-/// If you just want to get started, here is a simple [`Application`] that
-/// says "Hello, world!":
+pub use crate::shell::program::{Appearance, DefaultStyle};
+
+/// Creates an iced [`Application`] given its title, update, and view logic.
 ///
+/// # Example
 /// ```no_run
-/// use iced::advanced::Application;
-/// use iced::executor;
-/// use iced::{Task, Element, Settings, Theme, Renderer};
+/// use iced::widget::{button, column, text, Column};
 ///
 /// pub fn main() -> iced::Result {
-///     Hello::run(Settings::default())
+///     iced::application("A counter", update, view).run()
 /// }
 ///
-/// struct Hello;
-///
-/// impl Application for Hello {
-///     type Executor = executor::Default;
-///     type Flags = ();
-///     type Message = ();
-///     type Theme = Theme;
-///     type Renderer = Renderer;
-///
-///     fn new(_flags: ()) -> (Hello, Task<Self::Message>) {
-///         (Hello, Task::none())
+/// #[derive(Debug, Clone)]
+/// enum Message {
+///     Increment,
 /// }
 ///
-///     fn title(&self) -> String {
-///         String::from("A cool application")
+/// fn update(value: &mut u64, message: Message) {
+///     match message {
+///         Message::Increment => *value += 1,
+///     }
 /// }
 ///
-///     fn update(&mut self, _message: Self::Message) -> Task<Self::Message> {
-///         Task::none()
-///     }
-///
-///     fn view(&self) -> Element<Self::Message> {
-///         "Hello, world!".into()
-///     }
+/// fn view(value: &u64) -> Column<Message> {
+///     column![
+///         text(value),
+///         button("+").on_press(Message::Increment),
+///     ]
 /// }
 /// ```
-pub trait Application: Sized
+pub fn application<State, Message, Theme, Renderer>(
+    title: impl Title<State>,
+    update: impl Update<State, Message>,
+    view: impl for<'a> self::View<'a, State, Message, Theme, Renderer>,
+) -> Application<impl Program<State = State, Message = Message, Theme = Theme>>
 where
-    Self::Theme: DefaultStyle,
+    State: 'static,
+    Message: Send + std::fmt::Debug + 'static,
+    Theme: Default + DefaultStyle,
+    Renderer: program::Renderer,
 {
-    /// The [`Executor`] that will run commands and subscriptions.
-    ///
-    /// The [default executor] can be a good starting point!
-    ///
-    /// [`Executor`]: Self::Executor
-    /// [default executor]: crate::executor::Default
-    type Executor: Executor;
+    use std::marker::PhantomData;
 
-    /// The type of __messages__ your [`Application`] will produce.
-    type Message: std::fmt::Debug + Send;
-
-    /// The theme of your [`Application`].
-    type Theme: Default;
-
-    /// The renderer of your [`Application`].
-    type Renderer: text::Renderer + compositor::Default;
-
-    /// The data needed to initialize your [`Application`].
-    type Flags;
-
-    /// Initializes the [`Application`] with the flags provided to
-    /// [`run`] as part of the [`Settings`].
-    ///
-    /// Here is where you should return the initial state of your app.
-    ///
-    /// Additionally, you can return a [`Task`] if you need to perform some
-    /// async action in the background on startup. This is useful if you want to
-    /// load state from a file, perform an initial HTTP request, etc.
-    ///
-    /// [`run`]: Self::run
-    fn new(flags: Self::Flags) -> (Self, Task<Self::Message>);
-
-    /// Returns the current title of the [`Application`].
-    ///
-    /// This title can be dynamic! The runtime will automatically update the
-    /// title of your application when necessary.
-    fn title(&self) -> String;
-
-    /// Handles a __message__ and updates the state of the [`Application`].
-    ///
-    /// This is where you define your __update logic__. All the __messages__,
-    /// produced by either user interactions or commands, will be handled by
-    /// this method.
-    ///
-    /// Any [`Task`] returned will be executed immediately in the background.
-    fn update(&mut self, message: Self::Message) -> Task<Self::Message>;
-
-    /// Returns the widgets to display in the [`Application`].
-    ///
-    /// These widgets can produce __messages__ based on user interaction.
-    fn view(&self) -> Element<'_, Self::Message, Self::Theme, Self::Renderer>;
-
-    /// Returns the current [`Theme`] of the [`Application`].
-    ///
-    /// [`Theme`]: Self::Theme
-    fn theme(&self) -> Self::Theme {
-        Self::Theme::default()
+    struct Instance<State, Message, Theme, Renderer, Update, View> {
+        update: Update,
+        view: View,
+        _state: PhantomData<State>,
+        _message: PhantomData<Message>,
+        _theme: PhantomData<Theme>,
+        _renderer: PhantomData<Renderer>,
     }
 
-    /// Returns the current [`Appearance`] of the [`Application`].
-    fn style(&self, theme: &Self::Theme) -> Appearance {
-        theme.default_style()
+    impl<State, Message, Theme, Renderer, Update, View> Program
+        for Instance<State, Message, Theme, Renderer, Update, View>
+    where
+        Message: Send + std::fmt::Debug + 'static,
+        Theme: Default + DefaultStyle,
+        Renderer: program::Renderer,
+        Update: self::Update<State, Message>,
+        View: for<'a> self::View<'a, State, Message, Theme, Renderer>,
+    {
+        type State = State;
+        type Message = Message;
+        type Theme = Theme;
+        type Renderer = Renderer;
+        type Executor = iced_futures::backend::default::Executor;
+
+        fn load(&self) -> Task<Self::Message> {
+            Task::none()
         }
 
-    /// Returns the event [`Subscription`] for the current state of the
-    /// application.
-    ///
-    /// A [`Subscription`] will be kept alive as long as you keep returning it,
-    /// and the __messages__ produced will be handled by
-    /// [`update`](#tymethod.update).
-    ///
-    /// By default, this method returns an empty [`Subscription`].
-    fn subscription(&self) -> Subscription<Self::Message> {
-        Subscription::none()
+        fn update(
+            &self,
+            state: &mut Self::State,
+            message: Self::Message,
+        ) -> Task<Self::Message> {
+            self.update.update(state, message).into()
         }
 
-    /// Returns the scale factor of the [`Application`].
-    ///
-    /// It can be used to dynamically control the size of the UI at runtime
-    /// (i.e. zooming).
-    ///
-    /// For instance, a scale factor of `2.0` will make widgets twice as big,
-    /// while a scale factor of `0.5` will shrink them to half their size.
-    ///
-    /// By default, it returns `1.0`.
-    fn scale_factor(&self) -> f64 {
-        1.0
+        fn view<'a>(
+            &self,
+            state: &'a Self::State,
+            _window: window::Id,
+        ) -> Element<'a, Self::Message, Self::Theme, Self::Renderer> {
+            self.view.view(state).into()
+        }
     }
 
+    Application {
+        raw: Instance {
+            update,
+            view,
+            _state: PhantomData,
+            _message: PhantomData,
+            _theme: PhantomData,
+            _renderer: PhantomData,
+        },
+        settings: Settings::default(),
+        window: window::Settings::default(),
+    }
+    .title(title)
+}
+
+/// The underlying definition and configuration of an iced application.
+///
+/// You can use this API to create and run iced applications
+/// step by step—without coupling your logic to a trait
+/// or a specific type.
+///
+/// You can create an [`Application`] with the [`application`] helper.
+#[derive(Debug)]
+pub struct Application<P: Program> {
+    raw: P,
+    settings: Settings,
+    window: window::Settings,
+}
+
+impl<P: Program> Application<P> {
     /// Runs the [`Application`].
     ///
-    /// On native platforms, this method will take control of the current thread
-    /// until the [`Application`] exits.
+    /// The state of the [`Application`] must implement [`Default`].
+    /// If your state does not implement [`Default`], use [`run_with`]
+    /// instead.
     ///
-    /// On the web platform, this method __will NOT return__ unless there is an
-    /// [`Error`] during startup.
-    ///
-    /// [`Error`]: crate::Error
-    fn run(settings: Settings<Self::Flags>) -> crate::Result
+    /// [`run_with`]: Self::run_with
+    pub fn run(self) -> Result
     where
         Self: 'static,
+        P::State: Default,
     {
-        #[allow(clippy::needless_update)]
-        let renderer_settings = crate::graphics::Settings {
-            default_font: settings.default_font,
-            default_text_size: settings.default_text_size,
-            antialiasing: if settings.antialiasing {
-                Some(crate::graphics::Antialiasing::MSAAx4)
-            } else {
-                None
+        self.run_with(P::State::default)
+    }
+
+    /// Runs the [`Application`] with a closure that creates the initial state.
+    pub fn run_with<I>(self, initialize: I) -> Result
+    where
+        Self: 'static,
+        I: Fn() -> P::State + Clone + 'static,
+    {
+        self.raw
+            .run_with(self.settings, Some(self.window), initialize)
+    }
+
+    /// Sets the [`Settings`] that will be used to run the [`Application`].
+    pub fn settings(self, settings: Settings) -> Self {
+        Self { settings, ..self }
+    }
+
+    /// Sets the [`Settings::antialiasing`] of the [`Application`].
+    pub fn antialiasing(self, antialiasing: bool) -> Self {
+        Self {
+            settings: Settings {
+                antialiasing,
+                ..self.settings
             },
-            ..crate::graphics::Settings::default()
-        };
-
-        Ok(crate::shell::application::run::<
-            Instance<Self>,
-            Self::Executor,
-            <Self::Renderer as compositor::Default>::Compositor,
-        >(settings.into(), renderer_settings)?)
+            ..self
         }
     }
 
-struct Instance<A>(A)
-where
-    A: Application,
-    A::Theme: DefaultStyle;
+    /// Sets the default [`Font`] of the [`Application`].
+    pub fn default_font(self, default_font: Font) -> Self {
+        Self {
+            settings: Settings {
+                default_font,
+                ..self.settings
+            },
+            ..self
+        }
+    }
 
-impl<A> crate::runtime::Program for Instance<A>
+    /// Adds a font to the list of fonts that will be loaded at the start of the [`Application`].
+    pub fn font(mut self, font: impl Into<Cow<'static, [u8]>>) -> Self {
+        self.settings.fonts.push(font.into());
+        self
+    }
+
+    /// Sets the [`window::Settings::position`] to [`window::Position::Centered`] in the [`Application`].
+    pub fn centered(self) -> Self {
+        Self {
+            window: window::Settings {
+                position: window::Position::Centered,
+                ..self.window
+            },
+            ..self
+        }
+    }
+
+    /// Sets the [`window::Settings::exit_on_close_request`] of the [`Application`].
+    pub fn exit_on_close_request(self, exit_on_close_request: bool) -> Self {
+        Self {
+            window: window::Settings {
+                exit_on_close_request,
+                ..self.window
+            },
+            ..self
+        }
+    }
+
+    /// Sets the [`window::Settings::size`] of the [`Application`].
+    pub fn window_size(self, size: impl Into<Size>) -> Self {
+        Self {
+            window: window::Settings {
+                size: size.into(),
+                ..self.window
+            },
+            ..self
+        }
+    }
+
+    /// Sets the [`window::Settings::transparent`] of the [`Application`].
+    pub fn transparent(self, transparent: bool) -> Self {
+        Self {
+            window: window::Settings {
+                transparent,
+                ..self.window
+            },
+            ..self
+        }
+    }
+
+    /// Sets the [`Title`] of the [`Application`].
+    pub(crate) fn title(
+        self,
+        title: impl Title<P::State>,
+    ) -> Application<
+        impl Program<State = P::State, Message = P::Message, Theme = P::Theme>,
+    > {
+        Application {
+            raw: program::with_title(self.raw, move |state, _window| {
+                title.title(state)
+            }),
+            settings: self.settings,
+            window: self.window,
+        }
+    }
+
+    /// Runs the [`Task`] produced by the closure at startup.
+    pub fn load(
+        self,
+        f: impl Fn() -> Task<P::Message>,
+    ) -> Application<
+        impl Program<State = P::State, Message = P::Message, Theme = P::Theme>,
+    > {
+        Application {
+            raw: program::with_load(self.raw, f),
+            settings: self.settings,
+            window: self.window,
+        }
+    }
+
+    /// Sets the subscription logic of the [`Application`].
+    pub fn subscription(
+        self,
+        f: impl Fn(&P::State) -> Subscription<P::Message>,
+    ) -> Application<
+        impl Program<State = P::State, Message = P::Message, Theme = P::Theme>,
+    > {
+        Application {
+            raw: program::with_subscription(self.raw, f),
+            settings: self.settings,
+            window: self.window,
+        }
+    }
+
+    /// Sets the theme logic of the [`Application`].
+    pub fn theme(
+        self,
+        f: impl Fn(&P::State) -> P::Theme,
+    ) -> Application<
+        impl Program<State = P::State, Message = P::Message, Theme = P::Theme>,
+    > {
+        Application {
+            raw: program::with_theme(self.raw, move |state, _window| f(state)),
+            settings: self.settings,
+            window: self.window,
+        }
+    }
+
+    /// Sets the style logic of the [`Application`].
+    pub fn style(
+        self,
+        f: impl Fn(&P::State, &P::Theme) -> Appearance,
+    ) -> Application<
+        impl Program<State = P::State, Message = P::Message, Theme = P::Theme>,
+    > {
+        Application {
+            raw: program::with_style(self.raw, f),
+            settings: self.settings,
+            window: self.window,
+        }
+    }
+
+    /// Sets the scale factor of the [`Application`].
+    pub fn scale_factor(
+        self,
+        f: impl Fn(&P::State) -> f64,
+    ) -> Application<
+        impl Program<State = P::State, Message = P::Message, Theme = P::Theme>,
+    > {
+        Application {
+            raw: program::with_scale_factor(self.raw, move |state, _window| {
+                f(state)
+            }),
+            settings: self.settings,
+            window: self.window,
+        }
+    }
+}
+
+/// The title logic of some [`Application`].
+///
+/// This trait is implemented both for `&static str` and
+/// any closure `Fn(&State) -> String`.
+///
+/// This trait allows the [`application`] builder to take any of them.
+pub trait Title<State> {
+    /// Produces the title of the [`Application`].
+    fn title(&self, state: &State) -> String;
+}
+
+impl<State> Title<State> for &'static str {
+    fn title(&self, _state: &State) -> String {
+        self.to_string()
+    }
+}
+
+impl<T, State> Title<State> for T
 where
-    A: Application,
-    A::Theme: DefaultStyle,
+    T: Fn(&State) -> String,
 {
-    type Message = A::Message;
-    type Theme = A::Theme;
-    type Renderer = A::Renderer;
-
-    fn update(&mut self, message: Self::Message) -> Task<Self::Message> {
-        self.0.update(message)
-    }
-
-    fn view(&self) -> Element<'_, Self::Message, Self::Theme, Self::Renderer> {
-        self.0.view()
+    fn title(&self, state: &State) -> String {
+        self(state)
     }
 }
 
-impl<A> application::Application for Instance<A>
+/// The update logic of some [`Application`].
+///
+/// This trait allows the [`application`] builder to take any closure that
+/// returns any `Into<Task<Message>>`.
+pub trait Update<State, Message> {
+    /// Processes the message and updates the state of the [`Application`].
+    fn update(
+        &self,
+        state: &mut State,
+        message: Message,
+    ) -> impl Into<Task<Message>>;
+}
+
+impl<T, State, Message, C> Update<State, Message> for T
 where
-    A: Application,
-    A::Theme: DefaultStyle,
+    T: Fn(&mut State, Message) -> C,
+    C: Into<Task<Message>>,
 {
-    type Flags = A::Flags;
-
-    fn new(flags: Self::Flags) -> (Self, Task<A::Message>) {
-        let (app, command) = A::new(flags);
-
-        (Instance(app), command)
-    }
-
-    fn title(&self) -> String {
-        self.0.title()
-    }
-
-    fn theme(&self) -> A::Theme {
-        self.0.theme()
-    }
-
-    fn style(&self, theme: &A::Theme) -> Appearance {
-        self.0.style(theme)
-    }
-
-    fn subscription(&self) -> Subscription<Self::Message> {
-        self.0.subscription()
-    }
-
-    fn scale_factor(&self) -> f64 {
-        self.0.scale_factor()
+    fn update(
+        &self,
+        state: &mut State,
+        message: Message,
+    ) -> impl Into<Task<Message>> {
+        self(state, message)
+    }
+}
+
+/// The view logic of some [`Application`].
+///
+/// This trait allows the [`application`] builder to take any closure that
+/// returns any `Into<Element<'_, Message>>`.
+pub trait View<'a, State, Message, Theme, Renderer> {
+    /// Produces the widget of the [`Application`].
+    fn view(
+        &self,
+        state: &'a State,
+    ) -> impl Into<Element<'a, Message, Theme, Renderer>>;
+}
+
+impl<'a, T, State, Message, Theme, Renderer, Widget>
+    View<'a, State, Message, Theme, Renderer> for T
+where
+    T: Fn(&'a State) -> Widget,
+    State: 'static,
+    Widget: Into<Element<'a, Message, Theme, Renderer>>,
+{
+    fn view(
+        &self,
+        state: &'a State,
+    ) -> impl Into<Element<'a, Message, Theme, Renderer>> {
+        self(state)
     }
 }

src/daemon.rs

@@ -0,0 +1,298 @@
+//! Create and run daemons that run in the background.
+use crate::application;
+use crate::program::{self, Program};
+use crate::window;
+use crate::{Element, Font, Result, Settings, Subscription, Task};
+
+use std::borrow::Cow;
+
+pub use crate::shell::program::{Appearance, DefaultStyle};
+
+/// Creates an iced [`Daemon`] given its title, update, and view logic.
+///
+/// A [`Daemon`] will not open a window by default, but will run silently
+/// instead until a [`Task`] from [`window::open`] is returned by its update logic.
+///
+/// Furthermore, a [`Daemon`] will not stop running when all its windows are closed.
+/// In order to completely terminate a [`Daemon`], its process must be interrupted or
+/// its update logic must produce a [`Task`] from [`exit`].
+///
+/// [`exit`]: crate::exit
+pub fn daemon<State, Message, Theme, Renderer>(
+    title: impl Title<State>,
+    update: impl application::Update<State, Message>,
+    view: impl for<'a> self::View<'a, State, Message, Theme, Renderer>,
+) -> Daemon<impl Program<State = State, Message = Message, Theme = Theme>>
+where
+    State: 'static,
+    Message: Send + std::fmt::Debug + 'static,
+    Theme: Default + DefaultStyle,
+    Renderer: program::Renderer,
+{
+    use std::marker::PhantomData;
+
+    struct Instance<State, Message, Theme, Renderer, Update, View> {
+        update: Update,
+        view: View,
+        _state: PhantomData<State>,
+        _message: PhantomData<Message>,
+        _theme: PhantomData<Theme>,
+        _renderer: PhantomData<Renderer>,
+    }
+
+    impl<State, Message, Theme, Renderer, Update, View> Program
+        for Instance<State, Message, Theme, Renderer, Update, View>
+    where
+        Message: Send + std::fmt::Debug + 'static,
+        Theme: Default + DefaultStyle,
+        Renderer: program::Renderer,
+        Update: application::Update<State, Message>,
+        View: for<'a> self::View<'a, State, Message, Theme, Renderer>,
+    {
+        type State = State;
+        type Message = Message;
+        type Theme = Theme;
+        type Renderer = Renderer;
+        type Executor = iced_futures::backend::default::Executor;
+
+        fn load(&self) -> Task<Self::Message> {
+            Task::none()
+        }
+
+        fn update(
+            &self,
+            state: &mut Self::State,
+            message: Self::Message,
+        ) -> Task<Self::Message> {
+            self.update.update(state, message).into()
+        }
+
+        fn view<'a>(
+            &self,
+            state: &'a Self::State,
+            window: window::Id,
+        ) -> Element<'a, Self::Message, Self::Theme, Self::Renderer> {
+            self.view.view(state, window).into()
+        }
+    }
+
+    Daemon {
+        raw: Instance {
+            update,
+            view,
+            _state: PhantomData,
+            _message: PhantomData,
+            _theme: PhantomData,
+            _renderer: PhantomData,
+        },
+        settings: Settings::default(),
+    }
+    .title(title)
+}
+
+/// The underlying definition and configuration of an iced daemon.
+///
+/// You can use this API to create and run iced applications
+/// step by step—without coupling your logic to a trait
+/// or a specific type.
+///
+/// You can create a [`Daemon`] with the [`daemon`] helper.
+#[derive(Debug)]
+pub struct Daemon<P: Program> {
+    raw: P,
+    settings: Settings,
+}
+
+impl<P: Program> Daemon<P> {
+    /// Runs the [`Daemon`].
+    ///
+    /// The state of the [`Daemon`] must implement [`Default`].
+    /// If your state does not implement [`Default`], use [`run_with`]
+    /// instead.
+    ///
+    /// [`run_with`]: Self::run_with
+    pub fn run(self) -> Result
+    where
+        Self: 'static,
+        P::State: Default,
+    {
+        self.run_with(P::State::default)
+    }
+
+    /// Runs the [`Daemon`] with a closure that creates the initial state.
+    pub fn run_with<I>(self, initialize: I) -> Result
+    where
+        Self: 'static,
+        I: Fn() -> P::State + Clone + 'static,
+    {
+        self.raw.run_with(self.settings, None, initialize)
+    }
+
+    /// Sets the [`Settings`] that will be used to run the [`Daemon`].
+    pub fn settings(self, settings: Settings) -> Self {
+        Self { settings, ..self }
+    }
+
+    /// Sets the [`Settings::antialiasing`] of the [`Daemon`].
+    pub fn antialiasing(self, antialiasing: bool) -> Self {
+        Self {
+            settings: Settings {
+                antialiasing,
+                ..self.settings
+            },
+            ..self
+        }
+    }
+
+    /// Sets the default [`Font`] of the [`Daemon`].
+    pub fn default_font(self, default_font: Font) -> Self {
+        Self {
+            settings: Settings {
+                default_font,
+                ..self.settings
+            },
+            ..self
+        }
+    }
+
+    /// Adds a font to the list of fonts that will be loaded at the start of the [`Daemon`].
+    pub fn font(mut self, font: impl Into<Cow<'static, [u8]>>) -> Self {
+        self.settings.fonts.push(font.into());
+        self
+    }
+
+    /// Sets the [`Title`] of the [`Daemon`].
+    pub(crate) fn title(
+        self,
+        title: impl Title<P::State>,
+    ) -> Daemon<
+        impl Program<State = P::State, Message = P::Message, Theme = P::Theme>,
+    > {
+        Daemon {
+            raw: program::with_title(self.raw, move |state, window| {
+                title.title(state, window)
+            }),
+            settings: self.settings,
+        }
+    }
+
+    /// Runs the [`Task`] produced by the closure at startup.
+    pub fn load(
+        self,
+        f: impl Fn() -> Task<P::Message>,
+    ) -> Daemon<
+        impl Program<State = P::State, Message = P::Message, Theme = P::Theme>,
+    > {
+        Daemon {
+            raw: program::with_load(self.raw, f),
+            settings: self.settings,
+        }
+    }
+
+    /// Sets the subscription logic of the [`Daemon`].
+    pub fn subscription(
+        self,
+        f: impl Fn(&P::State) -> Subscription<P::Message>,
+    ) -> Daemon<
+        impl Program<State = P::State, Message = P::Message, Theme = P::Theme>,
+    > {
+        Daemon {
+            raw: program::with_subscription(self.raw, f),
+            settings: self.settings,
+        }
+    }
+
+    /// Sets the theme logic of the [`Daemon`].
+    pub fn theme(
+        self,
+        f: impl Fn(&P::State, window::Id) -> P::Theme,
+    ) -> Daemon<
+        impl Program<State = P::State, Message = P::Message, Theme = P::Theme>,
+    > {
+        Daemon {
+            raw: program::with_theme(self.raw, f),
+            settings: self.settings,
+        }
+    }
+
+    /// Sets the style logic of the [`Daemon`].
+    pub fn style(
+        self,
+        f: impl Fn(&P::State, &P::Theme) -> Appearance,
+    ) -> Daemon<
+        impl Program<State = P::State, Message = P::Message, Theme = P::Theme>,
+    > {
+        Daemon {
+            raw: program::with_style(self.raw, f),
+            settings: self.settings,
+        }
+    }
+
+    /// Sets the scale factor of the [`Daemon`].
+    pub fn scale_factor(
+        self,
+        f: impl Fn(&P::State, window::Id) -> f64,
+    ) -> Daemon<
+        impl Program<State = P::State, Message = P::Message, Theme = P::Theme>,
+    > {
+        Daemon {
+            raw: program::with_scale_factor(self.raw, f),
+            settings: self.settings,
+        }
+    }
+}
+
+/// The title logic of some [`Daemon`].
+///
+/// This trait is implemented both for `&static str` and
+/// any closure `Fn(&State, window::Id) -> String`.
+///
+/// This trait allows the [`daemon`] builder to take any of them.
+pub trait Title<State> {
+    /// Produces the title of the [`Daemon`].
+    fn title(&self, state: &State, window: window::Id) -> String;
+}
+
+impl<State> Title<State> for &'static str {
+    fn title(&self, _state: &State, _window: window::Id) -> String {
+        self.to_string()
+    }
+}
+
+impl<T, State> Title<State> for T
+where
+    T: Fn(&State, window::Id) -> String,
+{
+    fn title(&self, state: &State, window: window::Id) -> String {
+        self(state, window)
+    }
+}
+
+/// The view logic of some [`Daemon`].
+///
+/// This trait allows the [`daemon`] builder to take any closure that
+/// returns any `Into<Element<'_, Message>>`.
+pub trait View<'a, State, Message, Theme, Renderer> {
+    /// Produces the widget of the [`Daemon`].
+    fn view(
+        &self,
+        state: &'a State,
+        window: window::Id,
+    ) -> impl Into<Element<'a, Message, Theme, Renderer>>;
+}
+
+impl<'a, T, State, Message, Theme, Renderer, Widget>
+    View<'a, State, Message, Theme, Renderer> for T
+where
+    T: Fn(&'a State, window::Id) -> Widget,
+    State: 'static,
+    Widget: Into<Element<'a, Message, Theme, Renderer>>,
+{
+    fn view(
+        &self,
+        state: &'a State,
+        window: window::Id,
+    ) -> impl Into<Element<'a, Message, Theme, Renderer>> {
+        self(state, window)
+    }
+}

src/lib.rs

@@ -158,11 +158,11 @@
 //!   1. Draw the resulting user interface.
 //!
 //! # Usage
-//! Use [`run`] or the [`program`] builder.
+//! Use [`run`] or the [`application`] builder.
 //!
 //! [Elm]: https://elm-lang.org/
 //! [The Elm Architecture]: https://guide.elm-lang.org/architecture/
-//! [`program`]: program()
+//! [`application`]: application()
 #![doc(
     html_logo_url = "https://raw.githubusercontent.com/iced-rs/iced/9ab6923e943f784985e9ef9ca28b10278297225d/docs/logo.svg"
 )]
@@ -179,10 +179,11 @@ pub use iced_futures::futures;
 #[cfg(feature = "highlighter")]
 pub use iced_highlighter as highlighter;
 
-mod application;
 mod error;
+mod program;
 
-pub mod program;
+pub mod application;
+pub mod daemon;
 pub mod settings;
 pub mod time;
 pub mod window;
@@ -190,9 +191,6 @@ pub mod window;
 #[cfg(feature = "advanced")]
 pub mod advanced;
 
-#[cfg(feature = "multi-window")]
-pub mod multi_window;
-
 pub use crate::core::alignment;
 pub use crate::core::border;
 pub use crate::core::color;
@@ -203,7 +201,7 @@ pub use crate::core::{
     Length, Padding, Pixels, Point, Radians, Rectangle, Rotation, Shadow, Size,
     Theme, Transformation, Vector,
 };
-pub use crate::runtime::Task;
+pub use crate::runtime::{exit, Task};
 
 pub mod clipboard {
     //! Access the clipboard.
@@ -308,11 +306,12 @@ pub mod widget {
     mod runtime {}
 }
 
+pub use application::{application, Application};
+pub use daemon::{daemon, Daemon};
 pub use error::Error;
 pub use event::Event;
 pub use executor::Executor;
 pub use font::Font;
-pub use program::Program;
 pub use renderer::Renderer;
 pub use settings::Settings;
 pub use subscription::Subscription;
@@ -327,13 +326,13 @@ pub type Element<
     Renderer = crate::Renderer,
 > = crate::core::Element<'a, Message, Theme, Renderer>;
 
-/// The result of running a [`Program`].
+/// The result of running an iced program.
 pub type Result = std::result::Result<(), Error>;
 
 /// Runs a basic iced application with default [`Settings`] given its title,
 /// update, and view logic.
 ///
-/// This is equivalent to chaining [`program`] with [`Program::run`].
+/// This is equivalent to chaining [`application()`] with [`Application::run`].
 ///
 /// [`program`]: program()
 ///
@@ -364,9 +363,10 @@ pub type Result = std::result::Result<(), Error>;
 /// }
 /// ```
 pub fn run<State, Message, Theme, Renderer>(
-    title: impl program::Title<State> + 'static,
-    update: impl program::Update<State, Message> + 'static,
-    view: impl for<'a> program::View<'a, State, Message, Theme, Renderer> + 'static,
+    title: impl application::Title<State> + 'static,
+    update: impl application::Update<State, Message> + 'static,
+    view: impl for<'a> application::View<'a, State, Message, Theme, Renderer>
+        + 'static,
 ) -> Result
 where
     State: Default + 'static,
@@ -374,8 +374,5 @@ where
     Theme: Default + program::DefaultStyle + 'static,
     Renderer: program::Renderer + 'static,
 {
-    program(title, update, view).run()
+    application(title, update, view).run()
 }
-
-#[doc(inline)]
-pub use program::program;

src/multi_window.rs

@@ -1,254 +0,0 @@
-//! Leverage multi-window support in your application.
-use crate::window;
-use crate::{Element, Executor, Settings, Subscription, Task};
-
-pub use crate::application::{Appearance, DefaultStyle};
-
-/// An interactive cross-platform multi-window application.
-///
-/// This trait is the main entrypoint of Iced. Once implemented, you can run
-/// your GUI application by simply calling [`run`](#method.run).
-///
-/// - On native platforms, it will run in its own windows.
-/// - On the web, it will take control of the `<title>` and the `<body>` of the
-///   document and display only the contents of the `window::Id::MAIN` window.
-///
-/// An [`Application`] can execute asynchronous actions by returning a
-/// [`Task`] in some of its methods.
-///
-/// When using an [`Application`] with the `debug` feature enabled, a debug view
-/// can be toggled by pressing `F12`.
-///
-/// # Examples
-/// See the `examples/multi-window` example to see this multi-window `Application` trait in action.
-///
-/// ## A simple "Hello, world!"
-///
-/// If you just want to get started, here is a simple [`Application`] that
-/// says "Hello, world!":
-///
-/// ```no_run
-/// use iced::{executor, window};
-/// use iced::{Task, Element, Settings, Theme};
-/// use iced::multi_window::{self, Application};
-///
-/// pub fn main() -> iced::Result {
-///     Hello::run(Settings::default())
-/// }
-///
-/// struct Hello;
-///
-/// impl multi_window::Application for Hello {
-///     type Executor = executor::Default;
-///     type Flags = ();
-///     type Message = ();
-///     type Theme = Theme;
-///
-///     fn new(_flags: ()) -> (Hello, Task<Self::Message>) {
-///         (Hello, Task::none())
-///     }
-///
-///     fn title(&self, _window: window::Id) -> String {
-///         String::from("A cool application")
-///     }
-///
-///     fn update(&mut self, _message: Self::Message) -> Task<Self::Message> {
-///         Task::none()
-///     }
-///
-///     fn view(&self, _window: window::Id) -> Element<Self::Message> {
-///         "Hello, world!".into()
-///     }
-/// }
-/// ```
-///
-/// [`Sandbox`]: crate::Sandbox
-pub trait Application: Sized
-where
-    Self::Theme: DefaultStyle,
-{
-    /// The [`Executor`] that will run commands and subscriptions.
-    ///
-    /// The [default executor] can be a good starting point!
-    ///
-    /// [`Executor`]: Self::Executor
-    /// [default executor]: crate::executor::Default
-    type Executor: Executor;
-
-    /// The type of __messages__ your [`Application`] will produce.
-    type Message: std::fmt::Debug + Send;
-
-    /// The theme of your [`Application`].
-    type Theme: Default;
-
-    /// The data needed to initialize your [`Application`].
-    type Flags;
-
-    /// Initializes the [`Application`] with the flags provided to
-    /// [`run`] as part of the [`Settings`].
-    ///
-    /// Here is where you should return the initial state of your app.
-    ///
-    /// Additionally, you can return a [`Task`] if you need to perform some
-    /// async action in the background on startup. This is useful if you want to
-    /// load state from a file, perform an initial HTTP request, etc.
-    ///
-    /// [`run`]: Self::run
-    fn new(flags: Self::Flags) -> (Self, Task<Self::Message>);
-
-    /// Returns the current title of the `window` of the [`Application`].
-    ///
-    /// This title can be dynamic! The runtime will automatically update the
-    /// title of your window when necessary.
-    fn title(&self, window: window::Id) -> String;
-
-    /// Handles a __message__ and updates the state of the [`Application`].
-    ///
-    /// This is where you define your __update logic__. All the __messages__,
-    /// produced by either user interactions or commands, will be handled by
-    /// this method.
-    ///
-    /// Any [`Task`] returned will be executed immediately in the background.
-    fn update(&mut self, message: Self::Message) -> Task<Self::Message>;
-
-    /// Returns the widgets to display in the `window` of the [`Application`].
-    ///
-    /// These widgets can produce __messages__ based on user interaction.
-    fn view(
-        &self,
-        window: window::Id,
-    ) -> Element<'_, Self::Message, Self::Theme, crate::Renderer>;
-
-    /// Returns the current [`Theme`] of the `window` of the [`Application`].
-    ///
-    /// [`Theme`]: Self::Theme
-    #[allow(unused_variables)]
-    fn theme(&self, window: window::Id) -> Self::Theme {
-        Self::Theme::default()
-    }
-
-    /// Returns the current `Style` of the [`Theme`].
-    ///
-    /// [`Theme`]: Self::Theme
-    fn style(&self, theme: &Self::Theme) -> Appearance {
-        Self::Theme::default_style(theme)
-    }
-
-    /// Returns the event [`Subscription`] for the current state of the
-    /// application.
-    ///
-    /// A [`Subscription`] will be kept alive as long as you keep returning it,
-    /// and the __messages__ produced will be handled by
-    /// [`update`](#tymethod.update).
-    ///
-    /// By default, this method returns an empty [`Subscription`].
-    fn subscription(&self) -> Subscription<Self::Message> {
-        Subscription::none()
-    }
-
-    /// Returns the scale factor of the `window` of the [`Application`].
-    ///
-    /// It can be used to dynamically control the size of the UI at runtime
-    /// (i.e. zooming).
-    ///
-    /// For instance, a scale factor of `2.0` will make widgets twice as big,
-    /// while a scale factor of `0.5` will shrink them to half their size.
-    ///
-    /// By default, it returns `1.0`.
-    #[allow(unused_variables)]
-    fn scale_factor(&self, window: window::Id) -> f64 {
-        1.0
-    }
-
-    /// Runs the multi-window [`Application`].
-    ///
-    /// On native platforms, this method will take control of the current thread
-    /// until the [`Application`] exits.
-    ///
-    /// On the web platform, this method __will NOT return__ unless there is an
-    /// [`Error`] during startup.
-    ///
-    /// [`Error`]: crate::Error
-    fn run(settings: Settings<Self::Flags>) -> crate::Result
-    where
-        Self: 'static,
-    {
-        #[allow(clippy::needless_update)]
-        let renderer_settings = crate::graphics::Settings {
-            default_font: settings.default_font,
-            default_text_size: settings.default_text_size,
-            antialiasing: if settings.antialiasing {
-                Some(crate::graphics::Antialiasing::MSAAx4)
-            } else {
-                None
-            },
-            ..crate::graphics::Settings::default()
-        };
-
-        Ok(crate::shell::multi_window::run::<
-            Instance<Self>,
-            Self::Executor,
-            crate::renderer::Compositor,
-        >(settings.into(), renderer_settings)?)
-    }
-}
-
-struct Instance<A>(A)
-where
-    A: Application,
-    A::Theme: DefaultStyle;
-
-impl<A> crate::runtime::multi_window::Program for Instance<A>
-where
-    A: Application,
-    A::Theme: DefaultStyle,
-{
-    type Message = A::Message;
-    type Theme = A::Theme;
-    type Renderer = crate::Renderer;
-
-    fn update(&mut self, message: Self::Message) -> Task<Self::Message> {
-        self.0.update(message)
-    }
-
-    fn view(
-        &self,
-        window: window::Id,
-    ) -> Element<'_, Self::Message, Self::Theme, Self::Renderer> {
-        self.0.view(window)
-    }
-}
-
-impl<A> crate::shell::multi_window::Application for Instance<A>
-where
-    A: Application,
-    A::Theme: DefaultStyle,
-{
-    type Flags = A::Flags;
-
-    fn new(flags: Self::Flags) -> (Self, Task<A::Message>) {
-        let (app, command) = A::new(flags);
-
-        (Instance(app), command)
-    }
-
-    fn title(&self, window: window::Id) -> String {
-        self.0.title(window)
-    }
-
-    fn theme(&self, window: window::Id) -> A::Theme {
-        self.0.theme(window)
-    }
-
-    fn style(&self, theme: &Self::Theme) -> Appearance {
-        self.0.style(theme)
-    }
-
-    fn subscription(&self) -> Subscription<Self::Message> {
-        self.0.subscription()
-    }
-
-    fn scale_factor(&self, window: window::Id) -> f64 {
-        self.0.scale_factor(window)
-    }
-}

src/settings.rs

@@ -1,30 +1,17 @@
 //! Configure your application.
-use crate::window;
 use crate::{Font, Pixels};
 
 use std::borrow::Cow;
 
-/// The settings of an iced [`Program`].
-///
-/// [`Program`]: crate::Program
+/// The settings of an iced program.
 #[derive(Debug, Clone)]
-pub struct Settings<Flags = ()> {
+pub struct Settings {
     /// The identifier of the application.
     ///
     /// If provided, this identifier may be used to identify the application or
     /// communicate with it through the windowing system.
     pub id: Option<String>,
 
-    /// The window settings.
-    ///
-    /// They will be ignored on the Web.
-    pub window: window::Settings,
-
-    /// The data needed to initialize the [`Program`].
-    ///
-    /// [`Program`]: crate::Program
-    pub flags: Flags,
-
     /// The fonts to load on boot.
     pub fonts: Vec<Cow<'static, [u8]>>,
 
@@ -50,34 +37,10 @@ pub struct Settings<Flags = ()> {
     pub antialiasing: bool,
 }
 
-impl<Flags> Settings<Flags> {
-    /// Initialize [`Program`] settings using the given data.
-    ///
-    /// [`Program`]: crate::Program
-    pub fn with_flags(flags: Flags) -> Self {
-        let default_settings = Settings::<()>::default();
-
-        Self {
-            flags,
-            id: default_settings.id,
-            window: default_settings.window,
-            fonts: default_settings.fonts,
-            default_font: default_settings.default_font,
-            default_text_size: default_settings.default_text_size,
-            antialiasing: default_settings.antialiasing,
-        }
-    }
-}
-
-impl<Flags> Default for Settings<Flags>
-where
-    Flags: Default,
-{
+impl Default for Settings {
     fn default() -> Self {
         Self {
             id: None,
-            window: window::Settings::default(),
-            flags: Default::default(),
             fonts: Vec::new(),
             default_font: Font::default(),
             default_text_size: Pixels(16.0),
@@ -86,12 +49,10 @@ where
     }
 }
 
-impl<Flags> From<Settings<Flags>> for iced_winit::Settings<Flags> {
-    fn from(settings: Settings<Flags>) -> iced_winit::Settings<Flags> {
+impl From<Settings> for iced_winit::Settings {
+    fn from(settings: Settings) -> iced_winit::Settings {
         iced_winit::Settings {
             id: settings.id,
-            window: settings.window,
-            flags: settings.flags,
             fonts: settings.fonts,
         }
     }

winit/Cargo.toml

@@ -17,7 +17,7 @@ workspace = true
 default = ["x11", "wayland", "wayland-dlopen", "wayland-csd-adwaita"]
 debug = ["iced_runtime/debug"]
 system = ["sysinfo"]
-application = []
+program = []
 x11 = ["winit/x11"]
 wayland = ["winit/wayland"]
 wayland-dlopen = ["winit/wayland-dlopen"]

winit/src/application/state.rs

@@ -1,221 +0,0 @@
-use crate::application;
-use crate::conversion;
-use crate::core::mouse;
-use crate::core::{Color, Size};
-use crate::graphics::Viewport;
-use crate::runtime::Debug;
-use crate::Application;
-
-use std::marker::PhantomData;
-use winit::event::{Touch, WindowEvent};
-use winit::window::Window;
-
-/// The state of a windowed [`Application`].
-#[allow(missing_debug_implementations)]
-pub struct State<A: Application>
-where
-    A::Theme: application::DefaultStyle,
-{
-    title: String,
-    scale_factor: f64,
-    viewport: Viewport,
-    viewport_version: usize,
-    cursor_position: Option<winit::dpi::PhysicalPosition<f64>>,
-    modifiers: winit::keyboard::ModifiersState,
-    theme: A::Theme,
-    appearance: application::Appearance,
-    application: PhantomData<A>,
-}
-
-impl<A: Application> State<A>
-where
-    A::Theme: application::DefaultStyle,
-{
-    /// Creates a new [`State`] for the provided [`Application`] and window.
-    pub fn new(application: &A, window: &Window) -> Self {
-        let title = application.title();
-        let scale_factor = application.scale_factor();
-        let theme = application.theme();
-        let appearance = application.style(&theme);
-
-        let viewport = {
-            let physical_size = window.inner_size();
-
-            Viewport::with_physical_size(
-                Size::new(physical_size.width, physical_size.height),
-                window.scale_factor() * scale_factor,
-            )
-        };
-
-        Self {
-            title,
-            scale_factor,
-            viewport,
-            viewport_version: 0,
-            cursor_position: None,
-            modifiers: winit::keyboard::ModifiersState::default(),
-            theme,
-            appearance,
-            application: PhantomData,
-        }
-    }
-
-    /// Returns the current [`Viewport`] of the [`State`].
-    pub fn viewport(&self) -> &Viewport {
-        &self.viewport
-    }
-
-    /// Returns the version of the [`Viewport`] of the [`State`].
-    ///
-    /// The version is incremented every time the [`Viewport`] changes.
-    pub fn viewport_version(&self) -> usize {
-        self.viewport_version
-    }
-
-    /// Returns the physical [`Size`] of the [`Viewport`] of the [`State`].
-    pub fn physical_size(&self) -> Size<u32> {
-        self.viewport.physical_size()
-    }
-
-    /// Returns the logical [`Size`] of the [`Viewport`] of the [`State`].
-    pub fn logical_size(&self) -> Size<f32> {
-        self.viewport.logical_size()
-    }
-
-    /// Returns the current scale factor of the [`Viewport`] of the [`State`].
-    pub fn scale_factor(&self) -> f64 {
-        self.viewport.scale_factor()
-    }
-
-    /// Returns the current cursor position of the [`State`].
-    pub fn cursor(&self) -> mouse::Cursor {
-        self.cursor_position
-            .map(|cursor_position| {
-                conversion::cursor_position(
-                    cursor_position,
-                    self.viewport.scale_factor(),
-                )
-            })
-            .map(mouse::Cursor::Available)
-            .unwrap_or(mouse::Cursor::Unavailable)
-    }
-
-    /// Returns the current keyboard modifiers of the [`State`].
-    pub fn modifiers(&self) -> winit::keyboard::ModifiersState {
-        self.modifiers
-    }
-
-    /// Returns the current theme of the [`State`].
-    pub fn theme(&self) -> &A::Theme {
-        &self.theme
-    }
-
-    /// Returns the current background [`Color`] of the [`State`].
-    pub fn background_color(&self) -> Color {
-        self.appearance.background_color
-    }
-
-    /// Returns the current text [`Color`] of the [`State`].
-    pub fn text_color(&self) -> Color {
-        self.appearance.text_color
-    }
-
-    /// Processes the provided window event and updates the [`State`]
-    /// accordingly.
-    pub fn update(
-        &mut self,
-        window: &Window,
-        event: &WindowEvent,
-        _debug: &mut Debug,
-    ) {
-        match event {
-            WindowEvent::Resized(new_size) => {
-                let size = Size::new(new_size.width, new_size.height);
-
-                self.viewport = Viewport::with_physical_size(
-                    size,
-                    window.scale_factor() * self.scale_factor,
-                );
-
-                self.viewport_version = self.viewport_version.wrapping_add(1);
-            }
-            WindowEvent::ScaleFactorChanged {
-                scale_factor: new_scale_factor,
-                ..
-            } => {
-                let size = self.viewport.physical_size();
-
-                self.viewport = Viewport::with_physical_size(
-                    size,
-                    new_scale_factor * self.scale_factor,
-                );
-
-                self.viewport_version = self.viewport_version.wrapping_add(1);
-            }
-            WindowEvent::CursorMoved { position, .. }
-            | WindowEvent::Touch(Touch {
-                location: position, ..
-            }) => {
-                self.cursor_position = Some(*position);
-            }
-            WindowEvent::CursorLeft { .. } => {
-                self.cursor_position = None;
-            }
-            WindowEvent::ModifiersChanged(new_modifiers) => {
-                self.modifiers = new_modifiers.state();
-            }
-            #[cfg(feature = "debug")]
-            WindowEvent::KeyboardInput {
-                event:
-                    winit::event::KeyEvent {
-                        logical_key:
-                            winit::keyboard::Key::Named(
-                                winit::keyboard::NamedKey::F12,
-                            ),
-                        state: winit::event::ElementState::Pressed,
-                        ..
-                    },
-                ..
-            } => _debug.toggle(),
-            _ => {}
-        }
-    }
-
-    /// Synchronizes the [`State`] with its [`Application`] and its respective
-    /// window.
-    ///
-    /// Normally an [`Application`] should be synchronized with its [`State`]
-    /// and window after calling [`crate::application::update`].
-    pub fn synchronize(&mut self, application: &A, window: &Window) {
-        // Update window title
-        let new_title = application.title();
-
-        if self.title != new_title {
-            window.set_title(&new_title);
-
-            self.title = new_title;
-        }
-
-        // Update scale factor and size
-        let new_scale_factor = application.scale_factor();
-        let new_size = window.inner_size();
-        let current_size = self.viewport.physical_size();
-
-        if self.scale_factor != new_scale_factor
-            || (current_size.width, current_size.height)
-                != (new_size.width, new_size.height)
-        {
-            self.viewport = Viewport::with_physical_size(
-                Size::new(new_size.width, new_size.height),
-                window.scale_factor() * new_scale_factor,
-            );
-            self.viewport_version = self.viewport_version.wrapping_add(1);
-
-            self.scale_factor = new_scale_factor;
-        }
-
-        // Update theme and appearance
-        self.theme = application.theme();
-        self.appearance = application.style(&self.theme);
-    }
-}

winit/src/lib.rs

@@ -5,7 +5,7 @@
 //! `iced_winit` offers some convenient abstractions on top of [`iced_runtime`]
 //! to quickstart development when using [`winit`].
 //!
-//! It exposes a renderer-agnostic [`Application`] trait that can be implemented
+//! It exposes a renderer-agnostic [`Program`] trait that can be implemented
 //! and then run with a simple call. The use of this trait is optional.
 //!
 //! Additionally, a [`conversion`] module is available for users that decide to
@@ -24,24 +24,23 @@ pub use iced_runtime::core;
 pub use iced_runtime::futures;
 pub use winit;
 
-#[cfg(feature = "multi-window")]
-pub mod multi_window;
-
-#[cfg(feature = "application")]
-pub mod application;
 pub mod clipboard;
 pub mod conversion;
 pub mod settings;
 
+#[cfg(feature = "program")]
+pub mod program;
+
 #[cfg(feature = "system")]
 pub mod system;
 
 mod error;
 mod proxy;
 
-#[cfg(feature = "application")]
-pub use application::Application;
 pub use clipboard::Clipboard;
 pub use error::Error;
 pub use proxy::Proxy;
 pub use settings::Settings;
+
+#[cfg(feature = "program")]
+pub use program::Program;

winit/src/program.rs

@@ -10,7 +10,7 @@ use crate::core::mouse;
 use crate::core::renderer;
 use crate::core::widget::operation;
 use crate::core::window;
-use crate::core::{Point, Size};
+use crate::core::{Color, Element, Point, Size, Theme};
 use crate::futures::futures::channel::mpsc;
 use crate::futures::futures::channel::oneshot;
 use crate::futures::futures::executor;
@@ -20,14 +20,12 @@ use crate::futures::subscription::{self, Subscription};
 use crate::futures::{Executor, Runtime};
 use crate::graphics;
 use crate::graphics::{compositor, Compositor};
-use crate::multi_window::window_manager::WindowManager;
-use crate::runtime::multi_window::Program;
 use crate::runtime::user_interface::{self, UserInterface};
 use crate::runtime::Debug;
-use crate::runtime::{Action, Task};
+use crate::runtime::{self, Action, Task};
 use crate::{Clipboard, Error, Proxy, Settings};
 
-pub use crate::application::{default, Appearance, DefaultStyle};
+use window_manager::WindowManager;
 
 use rustc_hash::FxHashMap;
 use std::mem::ManuallyDrop;
@@ -40,19 +38,37 @@ use std::time::Instant;
 /// your GUI application by simply calling [`run`]. It will run in
 /// its own window.
 ///
-/// An [`Application`] can execute asynchronous actions by returning a
+/// A [`Program`] can execute asynchronous actions by returning a
 /// [`Task`] in some of its methods.
 ///
-/// When using an [`Application`] with the `debug` feature enabled, a debug view
+/// When using a [`Program`] with the `debug` feature enabled, a debug view
 /// can be toggled by pressing `F12`.
-pub trait Application: Program
+pub trait Program
 where
+    Self: Sized,
     Self::Theme: DefaultStyle,
 {
-    /// The data needed to initialize your [`Application`].
+    /// The type of __messages__ your [`Program`] will produce.
+    type Message: std::fmt::Debug + Send;
+
+    /// The theme used to draw the [`Program`].
+    type Theme;
+
+    /// The [`Executor`] that will run commands and subscriptions.
+    ///
+    /// The [default executor] can be a good starting point!
+    ///
+    /// [`Executor`]: Self::Executor
+    /// [default executor]: crate::futures::backend::default::Executor
+    type Executor: Executor;
+
+    /// The graphics backend to use to draw the [`Program`].
+    type Renderer: core::Renderer + core::text::Renderer;
+
+    /// The data needed to initialize your [`Program`].
     type Flags;
 
-    /// Initializes the [`Application`] with the flags provided to
+    /// Initializes the [`Program`] with the flags provided to
     /// [`run`] as part of the [`Settings`].
     ///
     /// Here is where you should return the initial state of your app.
@@ -62,13 +78,31 @@ where
     /// load state from a file, perform an initial HTTP request, etc.
     fn new(flags: Self::Flags) -> (Self, Task<Self::Message>);
 
-    /// Returns the current title of the [`Application`].
+    /// Returns the current title of the [`Program`].
     ///
     /// This title can be dynamic! The runtime will automatically update the
     /// title of your application when necessary.
     fn title(&self, window: window::Id) -> String;
 
-    /// Returns the current `Theme` of the [`Application`].
+    /// Handles a __message__ and updates the state of the [`Program`].
+    ///
+    /// This is where you define your __update logic__. All the __messages__,
+    /// produced by either user interactions or commands, will be handled by
+    /// this method.
+    ///
+    /// Any [`Task`] returned will be executed immediately in the background by the
+    /// runtime.
+    fn update(&mut self, message: Self::Message) -> Task<Self::Message>;
+
+    /// Returns the widgets to display in the [`Program`] for the `window`.
+    ///
+    /// These widgets can produce __messages__ based on user interaction.
+    fn view(
+        &self,
+        window: window::Id,
+    ) -> Element<'_, Self::Message, Self::Theme, Self::Renderer>;
+
+    /// Returns the current `Theme` of the [`Program`].
     fn theme(&self, window: window::Id) -> Self::Theme;
 
     /// Returns the `Style` variation of the `Theme`.
@@ -89,7 +123,7 @@ where
         Subscription::none()
     }
 
-    /// Returns the scale factor of the window of the [`Application`].
+    /// Returns the scale factor of the window of the [`Program`].
     ///
     /// It can be used to dynamically control the size of the UI at runtime
     /// (i.e. zooming).
@@ -104,17 +138,49 @@ where
     }
 }
 
-/// Runs an [`Application`] with an executor, compositor, and the provided
+/// The appearance of a program.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct Appearance {
+    /// The background [`Color`] of the application.
+    pub background_color: Color,
+
+    /// The default text [`Color`] of the application.
+    pub text_color: Color,
+}
+
+/// The default style of a [`Program`].
+pub trait DefaultStyle {
+    /// Returns the default style of a [`Program`].
+    fn default_style(&self) -> Appearance;
+}
+
+impl DefaultStyle for Theme {
+    fn default_style(&self) -> Appearance {
+        default(self)
+    }
+}
+
+/// The default [`Appearance`] of a [`Program`] with the built-in [`Theme`].
+pub fn default(theme: &Theme) -> Appearance {
+    let palette = theme.extended_palette();
+
+    Appearance {
+        background_color: palette.background.base.color,
+        text_color: palette.background.base.text,
+    }
+}
+/// Runs a [`Program`] with an executor, compositor, and the provided
 /// settings.
-pub fn run<A, E, C>(
-    settings: Settings<A::Flags>,
+pub fn run<P, C>(
+    settings: Settings,
     graphics_settings: graphics::Settings,
+    window_settings: Option<window::Settings>,
+    flags: P::Flags,
 ) -> Result<(), Error>
 where
-    A: Application + 'static,
-    E: Executor + 'static,
-    C: Compositor<Renderer = A::Renderer> + 'static,
-    A::Theme: DefaultStyle,
+    P: Program + 'static,
+    C: Compositor<Renderer = P::Renderer> + 'static,
+    P::Theme: DefaultStyle,
 {
     use winit::event_loop::EventLoop;
 
@@ -128,30 +194,24 @@ where
     let (proxy, worker) = Proxy::new(event_loop.create_proxy());
 
     let mut runtime = {
-        let executor = E::new().map_err(Error::ExecutorCreationFailed)?;
+        let executor =
+            P::Executor::new().map_err(Error::ExecutorCreationFailed)?;
         executor.spawn(worker);
 
         Runtime::new(executor, proxy.clone())
     };
 
-    let (application, task) = {
-        let flags = settings.flags;
-
-        runtime.enter(|| A::new(flags))
-    };
+    let (application, task) = runtime.enter(|| P::new(flags));
 
     if let Some(stream) = task.into_stream() {
         runtime.run(stream);
     }
 
-    let id = settings.id;
-    let title = application.title(window::Id::MAIN);
-
     let (boot_sender, boot_receiver) = oneshot::channel();
     let (event_sender, event_receiver) = mpsc::unbounded();
     let (control_sender, control_receiver) = mpsc::unbounded();
 
-    let instance = Box::pin(run_instance::<A, E, C>(
+    let instance = Box::pin(run_instance::<P, C>(
         application,
         runtime,
         proxy,
@@ -166,6 +226,7 @@ where
     struct Runner<Message: 'static, F, C> {
         instance: std::pin::Pin<Box<F>>,
         context: task::Context<'static>,
+        id: Option<String>,
         boot: Option<BootConfig<C>>,
         sender: mpsc::UnboundedSender<Event<Message>>,
         receiver: mpsc::UnboundedReceiver<Control>,
@@ -174,20 +235,17 @@ where
 
     struct BootConfig<C> {
         sender: oneshot::Sender<Boot<C>>,
-        id: Option<String>,
-        title: String,
-        window_settings: window::Settings,
+        window_settings: Option<window::Settings>,
         graphics_settings: graphics::Settings,
     }
 
     let mut runner = Runner {
         instance,
         context,
+        id: settings.id,
         boot: Some(BootConfig {
             sender: boot_sender,
-            id,
-            title,
-            window_settings: settings.window,
+            window_settings,
             graphics_settings,
         }),
         sender: event_sender,
@@ -204,8 +262,6 @@ where
         fn resumed(&mut self, event_loop: &winit::event_loop::ActiveEventLoop) {
             let Some(BootConfig {
                 sender,
-                id,
-                title,
                 window_settings,
                 graphics_settings,
             }) = self.boot.take()
@@ -213,20 +269,9 @@ where
                 return;
             };
 
-            let should_be_visible = window_settings.visible;
-            let exit_on_close_request = window_settings.exit_on_close_request;
-
-            let window_attributes = conversion::window_attributes(
-                window_settings,
-                &title,
-                event_loop.primary_monitor(),
-                id,
-            )
-            .with_visible(false);
-
-            log::debug!("Window attributes: {window_attributes:#?}");
-
-            let window = match event_loop.create_window(window_attributes) {
+            let window = match event_loop.create_window(
+                winit::window::WindowAttributes::default().with_visible(false),
+            ) {
                 Ok(window) => Arc::new(window),
                 Err(error) => {
                     self.error = Some(Error::WindowCreationFailed(error));
@@ -235,16 +280,17 @@ where
                 }
             };
 
+            let clipboard = Clipboard::connect(&window);
+
             let finish_boot = async move {
                 let compositor =
                     C::new(graphics_settings, window.clone()).await?;
 
                 sender
                     .send(Boot {
-                        window,
                         compositor,
-                        should_be_visible,
-                        exit_on_close_request,
+                        clipboard,
+                        window_settings,
                     })
                     .ok()
                     .expect("Send boot event");
@@ -386,7 +432,12 @@ where
                                 let window = event_loop
                                     .create_window(
                                         conversion::window_attributes(
-                                            settings, &title, monitor, None,
+                                            settings,
+                                            &title,
+                                            monitor
+                                                .or(event_loop
+                                                    .primary_monitor()),
+                                            self.id.clone(),
                                         ),
                                     )
                                     .expect("Create window");
@@ -423,10 +474,9 @@ where
 }
 
 struct Boot<C> {
-    window: Arc<winit::window::Window>,
     compositor: C,
-    should_be_visible: bool,
-    exit_on_close_request: bool,
+    clipboard: Clipboard,
+    window_settings: Option<window::Settings>,
 }
 
 enum Event<Message: 'static> {
@@ -449,62 +499,37 @@ enum Control {
     },
 }
 
-async fn run_instance<A, E, C>(
-    mut application: A,
-    mut runtime: Runtime<E, Proxy<A::Message>, Action<A::Message>>,
-    mut proxy: Proxy<A::Message>,
+async fn run_instance<P, C>(
+    mut program: P,
+    mut runtime: Runtime<P::Executor, Proxy<P::Message>, Action<P::Message>>,
+    mut proxy: Proxy<P::Message>,
     mut debug: Debug,
     mut boot: oneshot::Receiver<Boot<C>>,
-    mut event_receiver: mpsc::UnboundedReceiver<Event<Action<A::Message>>>,
+    mut event_receiver: mpsc::UnboundedReceiver<Event<Action<P::Message>>>,
     mut control_sender: mpsc::UnboundedSender<Control>,
 ) where
-    A: Application + 'static,
-    E: Executor + 'static,
-    C: Compositor<Renderer = A::Renderer> + 'static,
-    A::Theme: DefaultStyle,
+    P: Program + 'static,
+    C: Compositor<Renderer = P::Renderer> + 'static,
+    P::Theme: DefaultStyle,
 {
     use winit::event;
     use winit::event_loop::ControlFlow;
 
     let Boot {
-        window: main_window,
         mut compositor,
-        should_be_visible,
-        exit_on_close_request,
+        mut clipboard,
+        window_settings,
     } = boot.try_recv().ok().flatten().expect("Receive boot");
 
     let mut window_manager = WindowManager::new();
 
-    let _ = window_manager.insert(
-        window::Id::MAIN,
-        main_window,
-        &application,
-        &mut compositor,
-        exit_on_close_request,
-    );
-
-    let main_window = window_manager
-        .get_mut(window::Id::MAIN)
-        .expect("Get main window");
-
-    if should_be_visible {
-        main_window.raw.set_visible(true);
-    }
-
-    let mut clipboard = Clipboard::connect(&main_window.raw);
-    let mut events = {
-        vec![(
-            window::Id::MAIN,
-            core::Event::Window(window::Event::Opened {
-                position: main_window.position(),
-                size: main_window.size(),
-            }),
-        )]
-    };
+    let mut events = Vec::new();
+    let mut messages = Vec::new();
+    let mut actions = 0;
 
     let mut ui_caches = FxHashMap::default();
     let mut user_interfaces = ManuallyDrop::new(build_user_interfaces(
-        &application,
+        &program,
         &mut debug,
         &mut window_manager,
         FxHashMap::from_iter([(
@@ -513,15 +538,19 @@ async fn run_instance<A, E, C>(
         )]),
     ));
 
-    runtime.track(
-        application
-            .subscription()
-            .map(Action::Output)
-            .into_recipes(),
-    );
+    runtime.track(program.subscription().map(Action::Output).into_recipes());
 
-    let mut messages = Vec::new();
-    let mut user_events = 0;
+    let is_daemon = window_settings.is_none();
+
+    if let Some(window_settings) = window_settings {
+        let (sender, _receiver) = oneshot::channel();
+
+        proxy.send_action(Action::Window(runtime::window::Action::Open(
+            window::Id::unique(),
+            window_settings,
+            sender,
+        )));
+    }
 
     debug.startup_finished();
 
@@ -535,7 +564,7 @@ async fn run_instance<A, E, C>(
                 let window = window_manager.insert(
                     id,
                     Arc::new(window),
-                    &application,
+                    &program,
                     &mut compositor,
                     exit_on_close_request,
                 );
@@ -545,7 +574,7 @@ async fn run_instance<A, E, C>(
                 let _ = user_interfaces.insert(
                     id,
                     build_user_interface(
-                        &application,
+                        &program,
                         user_interface::Cache::default(),
                         &mut window.renderer,
                         logical_size,
@@ -591,7 +620,7 @@ async fn run_instance<A, E, C>(
                     event::Event::UserEvent(action) => {
                         run_action(
                             action,
-                            &application,
+                            &program,
                             &mut compositor,
                             &mut messages,
                             &mut clipboard,
@@ -601,7 +630,7 @@ async fn run_instance<A, E, C>(
                             &mut window_manager,
                             &mut ui_caches,
                         );
-                        user_events += 1;
+                        actions += 1;
                     }
                     event::Event::WindowEvent {
                         window_id: id,
@@ -782,6 +811,16 @@ async fn run_instance<A, E, C>(
                         event: window_event,
                         window_id,
                     } => {
+                        if !is_daemon
+                            && matches!(
+                                window_event,
+                                winit::event::WindowEvent::Destroyed
+                            )
+                            && window_manager.is_empty()
+                        {
+                            break 'main;
+                        }
+
                         let Some((id, window)) =
                             window_manager.get_mut_alias(window_id)
                         else {
@@ -801,10 +840,6 @@ async fn run_instance<A, E, C>(
                                 id,
                                 core::Event::Window(window::Event::Closed),
                             ));
-
-                            if window_manager.is_empty() {
-                                break 'main;
-                            }
                         } else {
                             window.state.update(
                                 &window.raw,
@@ -903,7 +938,7 @@ async fn run_instance<A, E, C>(
 
                             // Update application
                             update(
-                                &mut application,
+                                &mut program,
                                 &mut runtime,
                                 &mut debug,
                                 &mut messages,
@@ -913,7 +948,7 @@ async fn run_instance<A, E, C>(
                             // application update since we don't know what changed
                             for (id, window) in window_manager.iter_mut() {
                                 window.state.synchronize(
-                                    &application,
+                                    &program,
                                     id,
                                     &window.raw,
                                 );
@@ -926,15 +961,15 @@ async fn run_instance<A, E, C>(
                             // rebuild UIs with the synchronized states
                             user_interfaces =
                                 ManuallyDrop::new(build_user_interfaces(
-                                    &application,
+                                    &program,
                                     &mut debug,
                                     &mut window_manager,
                                     cached_interfaces,
                                 ));
 
-                            if user_events > 0 {
-                                proxy.free_slots(user_events);
-                                user_events = 0;
+                            if actions > 0 {
+                                proxy.free_slots(actions);
+                                actions = 0;
                             }
                         }
                     }
@@ -947,17 +982,17 @@ async fn run_instance<A, E, C>(
     let _ = ManuallyDrop::into_inner(user_interfaces);
 }
 
-/// Builds a window's [`UserInterface`] for the [`Application`].
-fn build_user_interface<'a, A: Application>(
-    application: &'a A,
+/// Builds a window's [`UserInterface`] for the [`Program`].
+fn build_user_interface<'a, P: Program>(
+    application: &'a P,
     cache: user_interface::Cache,
-    renderer: &mut A::Renderer,
+    renderer: &mut P::Renderer,
     size: Size,
     debug: &mut Debug,
     id: window::Id,
-) -> UserInterface<'a, A::Message, A::Theme, A::Renderer>
+) -> UserInterface<'a, P::Message, P::Theme, P::Renderer>
 where
-    A::Theme: DefaultStyle,
+    P::Theme: DefaultStyle,
 {
     debug.view_started();
     let view = application.view(id);
@@ -970,13 +1005,13 @@ where
     user_interface
 }
 
-fn update<A: Application, E: Executor>(
-    application: &mut A,
-    runtime: &mut Runtime<E, Proxy<A::Message>, Action<A::Message>>,
+fn update<P: Program, E: Executor>(
+    application: &mut P,
+    runtime: &mut Runtime<E, Proxy<P::Message>, Action<P::Message>>,
     debug: &mut Debug,
-    messages: &mut Vec<A::Message>,
+    messages: &mut Vec<P::Message>,
 ) where
-    A::Theme: DefaultStyle,
+    P::Theme: DefaultStyle,
 {
     for message in messages.drain(..) {
         debug.log_message(&message);
@@ -994,24 +1029,24 @@ fn update<A: Application, E: Executor>(
     runtime.track(subscription.map(Action::Output).into_recipes());
 }
 
-fn run_action<A, C>(
-    action: Action<A::Message>,
-    application: &A,
+fn run_action<P, C>(
+    action: Action<P::Message>,
+    application: &P,
     compositor: &mut C,
-    messages: &mut Vec<A::Message>,
+    messages: &mut Vec<P::Message>,
     clipboard: &mut Clipboard,
     control_sender: &mut mpsc::UnboundedSender<Control>,
     debug: &mut Debug,
     interfaces: &mut FxHashMap<
         window::Id,
-        UserInterface<'_, A::Message, A::Theme, A::Renderer>,
+        UserInterface<'_, P::Message, P::Theme, P::Renderer>,
     >,
-    window_manager: &mut WindowManager<A, C>,
+    window_manager: &mut WindowManager<P, C>,
     ui_caches: &mut FxHashMap<window::Id, user_interface::Cache>,
 ) where
-    A: Application,
-    C: Compositor<Renderer = A::Renderer> + 'static,
-    A::Theme: DefaultStyle,
+    P: Program,
+    C: Compositor<Renderer = P::Renderer> + 'static,
+    P::Theme: DefaultStyle,
 {
     use crate::runtime::clipboard;
     use crate::runtime::system;
@@ -1047,12 +1082,6 @@ fn run_action<A, C>(
             window::Action::Close(id) => {
                 let _ = window_manager.remove(id);
                 let _ = ui_caches.remove(&id);
-
-                if window_manager.is_empty() {
-                    control_sender
-                        .start_send(Control::Exit)
-                        .expect("Send control action");
-                }
             }
             window::Action::Drag(id) => {
                 if let Some(window) = window_manager.get_mut(id) {
@@ -1266,19 +1295,24 @@ fn run_action<A, C>(
 
             let _ = channel.send(Ok(()));
         }
+        Action::Exit => {
+            control_sender
+                .start_send(Control::Exit)
+                .expect("Send control action");
+        }
     }
 }
 
 /// Build the user interface for every window.
-pub fn build_user_interfaces<'a, A: Application, C>(
-    application: &'a A,
+pub fn build_user_interfaces<'a, P: Program, C>(
+    application: &'a P,
     debug: &mut Debug,
-    window_manager: &mut WindowManager<A, C>,
+    window_manager: &mut WindowManager<P, C>,
     mut cached_user_interfaces: FxHashMap<window::Id, user_interface::Cache>,
-) -> FxHashMap<window::Id, UserInterface<'a, A::Message, A::Theme, A::Renderer>>
+) -> FxHashMap<window::Id, UserInterface<'a, P::Message, P::Theme, P::Renderer>>
 where
-    C: Compositor<Renderer = A::Renderer>,
-    A::Theme: DefaultStyle,
+    C: Compositor<Renderer = P::Renderer>,
+    P::Theme: DefaultStyle,
 {
     cached_user_interfaces
         .drain()
@@ -1300,7 +1334,7 @@ where
         .collect()
 }
 
-/// Returns true if the provided event should cause an [`Application`] to
+/// Returns true if the provided event should cause a [`Program`] to
 /// exit.
 pub fn user_force_quit(
     event: &winit::event::WindowEvent,

winit/src/program/state.rs

@@ -2,16 +2,16 @@ use crate::conversion;
 use crate::core::{mouse, window};
 use crate::core::{Color, Size};
 use crate::graphics::Viewport;
-use crate::multi_window::{self, Application};
+use crate::program::{self, Program};
 use std::fmt::{Debug, Formatter};
 
 use winit::event::{Touch, WindowEvent};
 use winit::window::Window;
 
-/// The state of a multi-windowed [`Application`].
-pub struct State<A: Application>
+/// The state of a multi-windowed [`Program`].
+pub struct State<P: Program>
 where
-    A::Theme: multi_window::DefaultStyle,
+    P::Theme: program::DefaultStyle,
 {
     title: String,
     scale_factor: f64,
@@ -19,13 +19,13 @@ where
     viewport_version: u64,
     cursor_position: Option<winit::dpi::PhysicalPosition<f64>>,
     modifiers: winit::keyboard::ModifiersState,
-    theme: A::Theme,
-    appearance: multi_window::Appearance,
+    theme: P::Theme,
+    appearance: program::Appearance,
 }
 
-impl<A: Application> Debug for State<A>
+impl<P: Program> Debug for State<P>
 where
-    A::Theme: multi_window::DefaultStyle,
+    P::Theme: program::DefaultStyle,
 {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         f.debug_struct("multi_window::State")
@@ -39,13 +39,13 @@ where
     }
 }
 
-impl<A: Application> State<A>
+impl<P: Program> State<P>
 where
-    A::Theme: multi_window::DefaultStyle,
+    P::Theme: program::DefaultStyle,
 {
-    /// Creates a new [`State`] for the provided [`Application`]'s `window`.
+    /// Creates a new [`State`] for the provided [`Program`]'s `window`.
     pub fn new(
-        application: &A,
+        application: &P,
         window_id: window::Id,
         window: &Window,
     ) -> Self {
@@ -121,7 +121,7 @@ where
     }
 
     /// Returns the current theme of the [`State`].
-    pub fn theme(&self) -> &A::Theme {
+    pub fn theme(&self) -> &P::Theme {
         &self.theme
     }
 
@@ -195,14 +195,14 @@ where
         }
     }
 
-    /// Synchronizes the [`State`] with its [`Application`] and its respective
+    /// Synchronizes the [`State`] with its [`Program`] and its respective
     /// window.
     ///
-    /// Normally, an [`Application`] should be synchronized with its [`State`]
+    /// Normally, a [`Program`] should be synchronized with its [`State`]
     /// and window after calling [`State::update`].
     pub fn synchronize(
         &mut self,
-        application: &A,
+        application: &P,
         window_id: window::Id,
         window: &Window,
     ) {

winit/src/program/window_manager.rs

@@ -2,28 +2,28 @@ use crate::core::mouse;
 use crate::core::window::Id;
 use crate::core::{Point, Size};
 use crate::graphics::Compositor;
-use crate::multi_window::{Application, DefaultStyle, State};
+use crate::program::{DefaultStyle, Program, State};
 
 use std::collections::BTreeMap;
 use std::sync::Arc;
 use winit::monitor::MonitorHandle;
 
 #[allow(missing_debug_implementations)]
-pub struct WindowManager<A, C>
+pub struct WindowManager<P, C>
 where
-    A: Application,
-    C: Compositor<Renderer = A::Renderer>,
-    A::Theme: DefaultStyle,
+    P: Program,
+    C: Compositor<Renderer = P::Renderer>,
+    P::Theme: DefaultStyle,
 {
     aliases: BTreeMap<winit::window::WindowId, Id>,
-    entries: BTreeMap<Id, Window<A, C>>,
+    entries: BTreeMap<Id, Window<P, C>>,
 }
 
-impl<A, C> WindowManager<A, C>
+impl<P, C> WindowManager<P, C>
 where
-    A: Application,
-    C: Compositor<Renderer = A::Renderer>,
-    A::Theme: DefaultStyle,
+    P: Program,
+    C: Compositor<Renderer = P::Renderer>,
+    P::Theme: DefaultStyle,
 {
     pub fn new() -> Self {
         Self {
@@ -36,10 +36,10 @@ where
         &mut self,
         id: Id,
         window: Arc<winit::window::Window>,
-        application: &A,
+        application: &P,
         compositor: &mut C,
         exit_on_close_request: bool,
-    ) -> &mut Window<A, C> {
+    ) -> &mut Window<P, C> {
         let state = State::new(application, id, &window);
         let viewport_version = state.viewport_version();
         let physical_size = state.physical_size();
@@ -76,18 +76,18 @@ where
 
     pub fn iter_mut(
         &mut self,
-    ) -> impl Iterator<Item = (Id, &mut Window<A, C>)> {
+    ) -> impl Iterator<Item = (Id, &mut Window<P, C>)> {
         self.entries.iter_mut().map(|(k, v)| (*k, v))
     }
 
-    pub fn get_mut(&mut self, id: Id) -> Option<&mut Window<A, C>> {
+    pub fn get_mut(&mut self, id: Id) -> Option<&mut Window<P, C>> {
         self.entries.get_mut(&id)
     }
 
     pub fn get_mut_alias(
         &mut self,
         id: winit::window::WindowId,
-    ) -> Option<(Id, &mut Window<A, C>)> {
+    ) -> Option<(Id, &mut Window<P, C>)> {
         let id = self.aliases.get(&id).copied()?;
 
         Some((id, self.get_mut(id)?))
@@ -97,7 +97,7 @@ where
         self.entries.values().last()?.raw.current_monitor()
     }
 
-    pub fn remove(&mut self, id: Id) -> Option<Window<A, C>> {
+    pub fn remove(&mut self, id: Id) -> Option<Window<P, C>> {
         let window = self.entries.remove(&id)?;
         let _ = self.aliases.remove(&window.raw.id());
 
@@ -105,11 +105,11 @@ where
     }
 }
 
-impl<A, C> Default for WindowManager<A, C>
+impl<P, C> Default for WindowManager<P, C>
 where
-    A: Application,
-    C: Compositor<Renderer = A::Renderer>,
-    A::Theme: DefaultStyle,
+    P: Program,
+    C: Compositor<Renderer = P::Renderer>,
+    P::Theme: DefaultStyle,
 {
     fn default() -> Self {
         Self::new()
@@ -117,26 +117,26 @@ where
 }
 
 #[allow(missing_debug_implementations)]
-pub struct Window<A, C>
+pub struct Window<P, C>
 where
-    A: Application,
-    C: Compositor<Renderer = A::Renderer>,
-    A::Theme: DefaultStyle,
+    P: Program,
+    C: Compositor<Renderer = P::Renderer>,
+    P::Theme: DefaultStyle,
 {
     pub raw: Arc<winit::window::Window>,
-    pub state: State<A>,
+    pub state: State<P>,
     pub viewport_version: u64,
     pub exit_on_close_request: bool,
     pub mouse_interaction: mouse::Interaction,
     pub surface: C::Surface,
-    pub renderer: A::Renderer,
+    pub renderer: P::Renderer,
 }
 
-impl<A, C> Window<A, C>
+impl<P, C> Window<P, C>
 where
-    A: Application,
-    C: Compositor<Renderer = A::Renderer>,
-    A::Theme: DefaultStyle,
+    P: Program,
+    C: Compositor<Renderer = P::Renderer>,
+    P::Theme: DefaultStyle,
 {
     pub fn position(&self) -> Option<Point> {
         self.raw

winit/src/proxy.rs

@@ -78,11 +78,22 @@ impl<T: 'static> Proxy<T> {
     /// Note: This skips the backpressure mechanism with an unbounded
     /// channel. Use sparingly!
     pub fn send(&mut self, value: T)
+    where
+        T: std::fmt::Debug,
+    {
+        self.send_action(Action::Output(value));
+    }
+
+    /// Sends an action to the event loop.
+    ///
+    /// Note: This skips the backpressure mechanism with an unbounded
+    /// channel. Use sparingly!
+    pub fn send_action(&mut self, action: Action<T>)
     where
         T: std::fmt::Debug,
     {
         self.raw
-            .send_event(Action::Output(value))
+            .send_event(action)
             .expect("Send message to event loop");
     }
 

winit/src/settings.rs

@@ -1,25 +1,15 @@
 //! Configure your application.
-use crate::core::window;
-
 use std::borrow::Cow;
 
 /// The settings of an application.
 #[derive(Debug, Clone, Default)]
-pub struct Settings<Flags> {
+pub struct Settings {
     /// The identifier of the application.
     ///
     /// If provided, this identifier may be used to identify the application or
     /// communicate with it through the windowing system.
     pub id: Option<String>,
 
-    /// The [`window::Settings`].
-    pub window: window::Settings,
-
-    /// The data needed to initialize an [`Application`].
-    ///
-    /// [`Application`]: crate::Application
-    pub flags: Flags,
-
     /// The fonts to load on boot.
     pub fonts: Vec<Cow<'static, [u8]>>,
 }