Merge pull request #1964 from bungoboingo/feat/multi-window-support

[Feature] 🪟 Multi Window 🪟 .. redux!

.github/ISSUE_TEMPLATE/BUG-REPORT.yml

@@ -25,7 +25,6 @@ body:
         Before filing an issue...
 
         - If you are using `wgpu`, you need an environment that supports Vulkan, Metal, or DirectX 12. Please, make sure you can run [the `wgpu` examples].
-        - If you are using `glow`, you need support for OpenGL 2.1+. Please, make sure you can run [the `glow` examples].
 
         If you have any issues running any of the examples, make sure your graphics drivers are up-to-date. If the issues persist, please report them to the authors of the libraries directly!
 

Cargo.toml

@@ -49,6 +49,8 @@ web-colors = ["iced_renderer/web-colors"]
 webgl = ["iced_renderer/webgl"]
 # Enables the syntax `highlighter` module
 highlighter = ["iced_highlighter"]
+# Enables experimental multi-window support.
+multi-window = ["iced_winit/multi-window"]
 # Enables the advanced module
 advanced = []
 

ECOSYSTEM.md

@@ -45,7 +45,7 @@ The widgets of a _graphical_ user interface produce some primitives that eventua
 Currently, there are two different official renderers:
 
 - [`iced_wgpu`] is powered by [`wgpu`] and supports Vulkan, DirectX 12, and Metal.
-- [`iced_glow`] is powered by [`glow`] and supports OpenGL 2.1+ and OpenGL ES 2.0+.
+- [`tiny-skia`] is used as a fallback software renderer when `wgpu` is not supported.
 
 Additionally, the [`iced_graphics`] subcrate contains a bunch of backend-agnostic types that can be leveraged to build renderers. Both of the renderers rely on the graphical foundations provided by this crate.
 
@@ -54,10 +54,7 @@ The widgets of a graphical user _interface_ are interactive. __Shells__ gather a
 
 Normally, a shell will be responsible of creating a window and managing the lifecycle of a user interface, implementing a runtime of [The Elm Architecture].
 
-As of now, there are two official shells:
-
-- [`iced_winit`] implements a shell runtime on top of [`winit`].
-- [`iced_glutin`] is similar to [`iced_winit`], but it also deals with [OpenGL context creation].
+As of now, there is one official shell: [`iced_winit`] implements a shell runtime on top of [`winit`].
 
 ## The web target
 The Web platform provides all the abstractions necessary to draw widgets and gather users interactions.
@@ -91,5 +88,4 @@ Finally, [`iced`] unifies everything into a simple abstraction to create cross-p
 [`winit`]: https://github.com/rust-windowing/winit
 [`glutin`]: https://github.com/rust-windowing/glutin
 [`dodrio`]: https://github.com/fitzgen/dodrio
-[OpenGL context creation]: https://www.khronos.org/opengl/wiki/Creating_an_OpenGL_Context
 [The Elm Architecture]: https://guide.elm-lang.org/architecture/

core/Cargo.toml

@@ -23,5 +23,8 @@ palette.optional = true
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 instant.workspace = true
 
+[target.'cfg(windows)'.dependencies]
+raw-window-handle.workspace = true
+
 [dev-dependencies]
 approx = "0.5"

core/src/event.rs

@@ -19,7 +19,7 @@ pub enum Event {
     Mouse(mouse::Event),
 
     /// A window event
-    Window(window::Event),
+    Window(window::Id, window::Event),
 
     /// A touch event
     Touch(touch::Event),

core/src/point.rs

@@ -1,26 +1,34 @@
 use crate::Vector;
 
+use num_traits::{Float, Num};
+use std::fmt;
+
 /// A 2D point.
-#[derive(Debug, Clone, Copy, PartialEq, Default)]
-pub struct Point {
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub struct Point<T = f32> {
     /// The X coordinate.
-    pub x: f32,
+    pub x: T,
 
     /// The Y coordinate.
-    pub y: f32,
+    pub y: T,
 }
 
 impl Point {
     /// The origin (i.e. a [`Point`] at (0, 0)).
-    pub const ORIGIN: Point = Point::new(0.0, 0.0);
+    pub const ORIGIN: Self = Self::new(0.0, 0.0);
+}
 
+impl<T: Num> Point<T> {
     /// Creates a new [`Point`] with the given coordinates.
-    pub const fn new(x: f32, y: f32) -> Self {
+    pub const fn new(x: T, y: T) -> Self {
         Self { x, y }
     }
 
     /// Computes the distance to another [`Point`].
-    pub fn distance(&self, to: Point) -> f32 {
+    pub fn distance(&self, to: Self) -> T
+    where
+        T: Float,
+    {
         let a = self.x - to.x;
         let b = self.y - to.y;
 
@@ -34,9 +42,9 @@ impl From<[f32; 2]> for Point {
     }
 }
 
-impl From<[u16; 2]> for Point {
+impl From<[u16; 2]> for Point<u16> {
     fn from([x, y]: [u16; 2]) -> Self {
-        Point::new(x.into(), y.into())
+        Point::new(x, y)
     }
 }
 
@@ -46,10 +54,13 @@ impl From<Point> for [f32; 2] {
     }
 }
 
-impl std::ops::Add<Vector> for Point {
+impl<T> std::ops::Add<Vector<T>> for Point<T>
+where
+    T: std::ops::Add<Output = T>,
+{
     type Output = Self;
 
-    fn add(self, vector: Vector) -> Self {
+    fn add(self, vector: Vector<T>) -> Self {
         Self {
             x: self.x + vector.x,
             y: self.y + vector.y,
@@ -57,10 +68,13 @@ impl std::ops::Add<Vector> for Point {
     }
 }
 
-impl std::ops::Sub<Vector> for Point {
+impl<T> std::ops::Sub<Vector<T>> for Point<T>
+where
+    T: std::ops::Sub<Output = T>,
+{
     type Output = Self;
 
-    fn sub(self, vector: Vector) -> Self {
+    fn sub(self, vector: Vector<T>) -> Self {
         Self {
             x: self.x - vector.x,
             y: self.y - vector.y,
@@ -68,10 +82,22 @@ impl std::ops::Sub<Vector> for Point {
     }
 }
 
-impl std::ops::Sub<Point> for Point {
-    type Output = Vector;
+impl<T> std::ops::Sub<Point<T>> for Point<T>
+where
+    T: std::ops::Sub<Output = T>,
+{
+    type Output = Vector<T>;
 
-    fn sub(self, point: Point) -> Vector {
+    fn sub(self, point: Self) -> Vector<T> {
         Vector::new(self.x - point.x, self.y - point.y)
     }
 }
+
+impl<T> fmt::Display for Point<T>
+where
+    T: fmt::Display,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "Point {{ x: {}, y: {} }}", self.x, self.y)
+    }
+}

core/src/widget/tree.rs

@@ -67,7 +67,7 @@ impl Tree {
         }
     }
 
-    /// Reconciliates the children of the tree with the provided list of widgets.
+    /// Reconciles the children of the tree with the provided list of widgets.
     pub fn diff_children<'a, Message, Renderer>(
         &mut self,
         new_children: &[impl Borrow<dyn Widget<Message, Renderer> + 'a>],

core/src/window.rs

@@ -1,15 +1,21 @@
 //! Build window-based GUI applications.
 pub mod icon;
+pub mod settings;
 
 mod event;
+mod id;
 mod level;
 mod mode;
+mod position;
 mod redraw_request;
 mod user_attention;
 
 pub use event::Event;
 pub use icon::Icon;
+pub use id::Id;
 pub use level::Level;
 pub use mode::Mode;
+pub use position::Position;
 pub use redraw_request::RedrawRequest;
+pub use settings::Settings;
 pub use user_attention::UserAttention;

core/src/window/event.rs

@@ -1,10 +1,27 @@
 use crate::time::Instant;
+use crate::{Point, Size};
 
 use std::path::PathBuf;
 
 /// A window-related event.
-#[derive(PartialEq, Eq, Clone, Debug)]
+#[derive(PartialEq, Clone, Debug)]
 pub enum Event {
+    /// A window was opened.
+    Opened {
+        /// The position of the opened window. This is relative to the top-left corner of the desktop
+        /// the window is on, including virtual desktops. Refers to window's "inner" position,
+        /// or the client area, in logical pixels.
+        ///
+        /// **Note**: Not available in Wayland.
+        position: Option<Point>,
+        /// The size of the created window. This is its "inner" size, or the size of the
+        /// client area, in logical pixels.
+        size: Size,
+    },
+
+    /// A window was closed.
+    Closed,
+
     /// A window was moved.
     Moved {
         /// The new logical x location of the window
@@ -27,9 +44,6 @@ pub enum Event {
     RedrawRequested(Instant),
 
     /// The user has requested for the window to close.
-    ///
-    /// Usually, you will want to terminate the execution whenever this event
-    /// occurs.
     CloseRequested,
 
     /// A window was focused.

core/src/window/id.rs

@@ -0,0 +1,21 @@
+use std::hash::Hash;
+
+use std::sync::atomic::{self, AtomicU64};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
+/// The id of the window.
+///
+/// Internally Iced reserves `window::Id::MAIN` for the first window spawned.
+pub struct Id(u64);
+
+static COUNT: AtomicU64 = AtomicU64::new(1);
+
+impl Id {
+    /// The reserved window [`Id`] for the first window in an Iced application.
+    pub const MAIN: Self = Id(0);
+
+    /// Creates a new unique window [`Id`].
+    pub fn unique() -> Id {
+        Id(COUNT.fetch_add(1, atomic::Ordering::Relaxed))
+    }
+}

core/src/window/position.rs

@@ -1,5 +1,7 @@
+use crate::Point;
+
 /// The position of a window in a given screen.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq)]
 pub enum Position {
     /// The platform-specific default position for a new window.
     Default,
@@ -12,7 +14,7 @@ pub enum Position {
     /// position. So if you have decorations enabled and want the window to be
     /// at (0, 0) you would have to set the position to
     /// `(PADDING_X, PADDING_Y)`.
-    Specific(i32, i32),
+    Specific(Point),
 }
 
 impl Default for Position {

core/src/window/settings.rs

@@ -1,21 +1,47 @@
+//! Configure your windows.
+#[cfg(target_os = "windows")]
+#[path = "settings/windows.rs"]
+mod platform;
+
+#[cfg(target_os = "macos")]
+#[path = "settings/macos.rs"]
+mod platform;
+
+#[cfg(target_os = "linux")]
+#[path = "settings/linux.rs"]
+mod platform;
+
+#[cfg(target_arch = "wasm32")]
+#[path = "settings/wasm.rs"]
+mod platform;
+
+#[cfg(not(any(
+    target_os = "windows",
+    target_os = "macos",
+    target_os = "linux",
+    target_arch = "wasm32"
+)))]
+#[path = "settings/other.rs"]
+mod platform;
+
 use crate::window::{Icon, Level, Position};
+use crate::Size;
 
-pub use iced_winit::settings::PlatformSpecific;
-
+pub use platform::PlatformSpecific;
 /// The window settings of an application.
 #[derive(Debug, Clone)]
 pub struct Settings {
-    /// The initial size of the window.
-    pub size: (u32, u32),
+    /// The initial logical dimensions of the window.
+    pub size: Size,
 
     /// The initial position of the window.
     pub position: Position,
 
     /// The minimum size of the window.
-    pub min_size: Option<(u32, u32)>,
+    pub min_size: Option<Size>,
 
     /// The maximum size of the window.
-    pub max_size: Option<(u32, u32)>,
+    pub max_size: Option<Size>,
 
     /// Whether the window should be visible or not.
     pub visible: bool,
@@ -37,12 +63,22 @@ pub struct Settings {
 
     /// Platform specific settings.
     pub platform_specific: PlatformSpecific,
+
+    /// Whether the window will close when the user requests it, e.g. when a user presses the
+    /// close button.
+    ///
+    /// This can be useful if you want to have some behavior that executes before the window is
+    /// actually destroyed. If you disable this, you must manually close the window with the
+    /// `window::close` command.
+    ///
+    /// By default this is enabled.
+    pub exit_on_close_request: bool,
 }
 
 impl Default for Settings {
-    fn default() -> Settings {
-        Settings {
-            size: (1024, 768),
+    fn default() -> Self {
+        Self {
+            size: Size::new(1024.0, 768.0),
             position: Position::default(),
             min_size: None,
             max_size: None,
@@ -52,25 +88,8 @@ impl Default for Settings {
             transparent: false,
             level: Level::default(),
             icon: None,
+            exit_on_close_request: true,
             platform_specific: PlatformSpecific::default(),
         }
     }
 }
-
-impl From<Settings> for iced_winit::settings::Window {
-    fn from(settings: Settings) -> Self {
-        Self {
-            size: settings.size,
-            position: iced_winit::Position::from(settings.position),
-            min_size: settings.min_size,
-            max_size: settings.max_size,
-            visible: settings.visible,
-            resizable: settings.resizable,
-            decorations: settings.decorations,
-            transparent: settings.transparent,
-            level: settings.level,
-            icon: settings.icon.map(Icon::into),
-            platform_specific: settings.platform_specific,
-        }
-    }
-}

examples/events/src/main.rs

@@ -10,7 +10,10 @@ use iced::{
 
 pub fn main() -> iced::Result {
     Events::run(Settings {
-        exit_on_close_request: false,
+        window: window::Settings {
+            exit_on_close_request: false,
+            ..window::Settings::default()
+        },
         ..Settings::default()
     })
 }
@@ -54,8 +57,9 @@ impl Application for Events {
                 Command::none()
             }
             Message::EventOccurred(event) => {
-                if let Event::Window(window::Event::CloseRequested) = event {
-                    window::close()
+                if let Event::Window(id, window::Event::CloseRequested) = event
+                {
+                    window::close(id)
                 } else {
                     Command::none()
                 }
@@ -65,7 +69,7 @@ impl Application for Events {
 
                 Command::none()
             }
-            Message::Exit => window::close(),
+            Message::Exit => window::close(window::Id::MAIN),
         }
     }
 

examples/exit/src/main.rs

@@ -34,7 +34,7 @@ impl Application for Exit {
 
     fn update(&mut self, message: Message) -> Command<Message> {
         match message {
-            Message::Confirm => window::close(),
+            Message::Confirm => window::close(window::Id::MAIN),
             Message::Exit => {
                 self.show_confirm = true;
 

examples/integration/src/main.rs

@@ -6,13 +6,17 @@ use scene::Scene;
 
 use iced_wgpu::graphics::Viewport;
 use iced_wgpu::{wgpu, Backend, Renderer, Settings};
+use iced_winit::conversion;
 use iced_winit::core::mouse;
 use iced_winit::core::renderer;
+use iced_winit::core::window;
 use iced_winit::core::{Color, Font, Pixels, Size};
+use iced_winit::futures;
 use iced_winit::runtime::program;
 use iced_winit::runtime::Debug;
 use iced_winit::style::Theme;
-use iced_winit::{conversion, futures, winit, Clipboard};
+use iced_winit::winit;
+use iced_winit::Clipboard;
 
 use winit::{
     event::{Event, ModifiersState, WindowEvent},
@@ -180,6 +184,7 @@ pub fn main() -> Result<(), Box<dyn std::error::Error>> {
 
                 // Map window event to iced event
                 if let Some(event) = iced_winit::conversion::window_event(
+                    window::Id::MAIN,
                     &event,
                     window.scale_factor(),
                     modifiers,

examples/loading_spinners/src/circular.rs

@@ -279,7 +279,7 @@ where
 
         let state = tree.state.downcast_mut::<State>();
 
-        if let Event::Window(window::Event::RedrawRequested(now)) = event {
+        if let Event::Window(_, window::Event::RedrawRequested(now)) = event {
             state.animation = state.animation.timed_transition(
                 self.cycle_duration,
                 self.rotation_duration,

examples/loading_spinners/src/linear.rs

@@ -200,7 +200,7 @@ where
 
         let state = tree.state.downcast_mut::<State>();
 
-        if let Event::Window(window::Event::RedrawRequested(now)) = event {
+        if let Event::Window(_, window::Event::RedrawRequested(now)) = event {
             *state = state.timed_transition(self.cycle_duration, now);
 
             shell.request_redraw(RedrawRequest::At(

examples/multi_window/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "multi_window"
+version = "0.1.0"
+authors = ["Bingus <shankern@protonmail.com>"]
+edition = "2021"
+publish = false
+
+[dependencies]
+iced = { path = "../..", features = ["debug", "multi-window"] }

examples/multi_window/src/main.rs

@@ -0,0 +1,215 @@
+use iced::event;
+use iced::executor;
+use iced::multi_window::{self, Application};
+use iced::widget::{button, column, container, scrollable, text, text_input};
+use iced::window;
+use iced::{
+    Alignment, Command, Element, Length, Point, Settings, Subscription, Theme,
+    Vector,
+};
+
+use std::collections::HashMap;
+
+fn main() -> iced::Result {
+    Example::run(Settings::default())
+}
+
+#[derive(Default)]
+struct Example {
+    windows: HashMap<window::Id, Window>,
+    next_window_pos: window::Position,
+}
+
+#[derive(Debug)]
+struct Window {
+    title: String,
+    scale_input: String,
+    current_scale: f64,
+    theme: Theme,
+    input_id: iced::widget::text_input::Id,
+}
+
+#[derive(Debug, Clone)]
+enum Message {
+    ScaleInputChanged(window::Id, String),
+    ScaleChanged(window::Id, String),
+    TitleChanged(window::Id, String),
+    CloseWindow(window::Id),
+    WindowOpened(window::Id, Option<Point>),
+    WindowClosed(window::Id),
+    NewWindow,
+}
+
+impl multi_window::Application for Example {
+    type Executor = executor::Default;
+    type Message = Message;
+    type Theme = Theme;
+    type Flags = ();
+
+    fn new(_flags: ()) -> (Self, Command<Message>) {
+        (
+            Example {
+                windows: HashMap::from([(window::Id::MAIN, Window::new(1))]),
+                next_window_pos: window::Position::Default,
+            },
+            Command::none(),
+        )
+    }
+
+    fn title(&self, window: window::Id) -> String {
+        self.windows
+            .get(&window)
+            .map(|window| window.title.clone())
+            .unwrap_or("Example".to_string())
+    }
+
+    fn update(&mut self, message: Message) -> Command<Message> {
+        match message {
+            Message::ScaleInputChanged(id, scale) => {
+                let window =
+                    self.windows.get_mut(&id).expect("Window not found!");
+                window.scale_input = scale;
+
+                Command::none()
+            }
+            Message::ScaleChanged(id, scale) => {
+                let window =
+                    self.windows.get_mut(&id).expect("Window not found!");
+
+                window.current_scale = scale
+                    .parse::<f64>()
+                    .unwrap_or(window.current_scale)
+                    .clamp(0.5, 5.0);
+
+                Command::none()
+            }
+            Message::TitleChanged(id, title) => {
+                let window =
+                    self.windows.get_mut(&id).expect("Window not found.");
+
+                window.title = title;
+
+                Command::none()
+            }
+            Message::CloseWindow(id) => window::close(id),
+            Message::WindowClosed(id) => {
+                self.windows.remove(&id);
+                Command::none()
+            }
+            Message::WindowOpened(id, position) => {
+                if let Some(position) = position {
+                    self.next_window_pos = window::Position::Specific(
+                        position + Vector::new(20.0, 20.0),
+                    );
+                }
+
+                if let Some(window) = self.windows.get(&id) {
+                    text_input::focus(window.input_id.clone())
+                } else {
+                    Command::none()
+                }
+            }
+            Message::NewWindow => {
+                let count = self.windows.len() + 1;
+
+                let (id, spawn_window) = window::spawn(window::Settings {
+                    position: self.next_window_pos,
+                    exit_on_close_request: count % 2 == 0,
+                    ..Default::default()
+                });
+
+                self.windows.insert(id, Window::new(count));
+
+                spawn_window
+            }
+        }
+    }
+
+    fn view(&self, window: window::Id) -> Element<Message> {
+        let content = self.windows.get(&window).unwrap().view(window);
+
+        container(content)
+            .width(Length::Fill)
+            .height(Length::Fill)
+            .center_x()
+            .center_y()
+            .into()
+    }
+
+    fn theme(&self, window: window::Id) -> Self::Theme {
+        self.windows.get(&window).unwrap().theme.clone()
+    }
+
+    fn scale_factor(&self, window: window::Id) -> f64 {
+        self.windows
+            .get(&window)
+            .map(|window| window.current_scale)
+            .unwrap_or(1.0)
+    }
+
+    fn subscription(&self) -> Subscription<Self::Message> {
+        event::listen_with(|event, _| {
+            if let iced::Event::Window(id, window_event) = event {
+                match window_event {
+                    window::Event::CloseRequested => {
+                        Some(Message::CloseWindow(id))
+                    }
+                    window::Event::Opened { position, .. } => {
+                        Some(Message::WindowOpened(id, position))
+                    }
+                    window::Event::Closed => Some(Message::WindowClosed(id)),
+                    _ => None,
+                }
+            } else {
+                None
+            }
+        })
+    }
+}
+
+impl Window {
+    fn new(count: usize) -> Self {
+        Self {
+            title: format!("Window_{}", count),
+            scale_input: "1.0".to_string(),
+            current_scale: 1.0,
+            theme: if count % 2 == 0 {
+                Theme::Light
+            } else {
+                Theme::Dark
+            },
+            input_id: text_input::Id::unique(),
+        }
+    }
+
+    fn view(&self, id: window::Id) -> Element<Message> {
+        let scale_input = column![
+            text("Window scale factor:"),
+            text_input("Window Scale", &self.scale_input)
+                .on_input(move |msg| { Message::ScaleInputChanged(id, msg) })
+                .on_submit(Message::ScaleChanged(
+                    id,
+                    self.scale_input.to_string()
+                ))
+        ];
+
+        let title_input = column![
+            text("Window title:"),
+            text_input("Window Title", &self.title)
+                .on_input(move |msg| { Message::TitleChanged(id, msg) })
+                .id(self.input_id.clone())
+        ];
+
+        let new_window_button =
+            button(text("New Window")).on_press(Message::NewWindow);
+
+        let content = scrollable(
+            column![scale_input, title_input, new_window_button]
+                .spacing(50)
+                .width(Length::Fill)
+                .align_items(Alignment::Center),
+        );
+
+        container(content).width(200).center_x().into()
+    }
+}

examples/screenshot/src/main.rs

@@ -1,8 +1,8 @@
-use iced::alignment;
 use iced::keyboard::KeyCode;
 use iced::theme::{Button, Container};
 use iced::widget::{button, column, container, image, row, text, text_input};
 use iced::window::screenshot::{self, Screenshot};
+use iced::{alignment, window};
 use iced::{
     event, executor, keyboard, Alignment, Application, Command, ContentFit,
     Element, Event, Length, Rectangle, Renderer, Subscription, Theme,
@@ -70,7 +70,10 @@ impl Application for Example {
     fn update(&mut self, message: Self::Message) -> Command<Self::Message> {
         match message {
             Message::Screenshot => {
-                return iced::window::screenshot(Message::ScreenshotData);
+                return iced::window::screenshot(
+                    window::Id::MAIN,
+                    Message::ScreenshotData,
+                );
             }
             Message::ScreenshotData(screenshot) => {
                 self.screenshot = Some(screenshot);

examples/solar_system/src/main.rs

@@ -114,14 +114,14 @@ impl State {
 
     pub fn new() -> State {
         let now = Instant::now();
-        let (width, height) = window::Settings::default().size;
+        let size = window::Settings::default().size;
 
         State {
             space_cache: canvas::Cache::default(),
             system_cache: canvas::Cache::default(),
             start: now,
             now,
-            stars: Self::generate_stars(width, height),
+            stars: Self::generate_stars(size.width, size.height),
         }
     }
 
@@ -130,7 +130,7 @@ impl State {
         self.system_cache.clear();
     }
 
-    fn generate_stars(width: u32, height: u32) -> Vec<(Point, f32)> {
+    fn generate_stars(width: f32, height: f32) -> Vec<(Point, f32)> {
         use rand::Rng;
 
         let mut rng = rand::thread_rng();
@@ -139,12 +139,8 @@ impl State {
             .map(|_| {
                 (
                     Point::new(
-                        rng.gen_range(
-                            (-(width as f32) / 2.0)..(width as f32 / 2.0),
-                        ),
-                        rng.gen_range(
-                            (-(height as f32) / 2.0)..(height as f32 / 2.0),
-                        ),
+                        rng.gen_range((-width / 2.0)..(width / 2.0)),
+                        rng.gen_range((-height / 2.0)..(height / 2.0)),
                     ),
                     rng.gen_range(0.5..1.0),
                 )

examples/toast/src/main.rs

@@ -539,7 +539,9 @@ mod toast {
             clipboard: &mut dyn Clipboard,
             shell: &mut Shell<'_, Message>,
         ) -> event::Status {
-            if let Event::Window(window::Event::RedrawRequested(now)) = &event {
+            if let Event::Window(_, window::Event::RedrawRequested(now)) =
+                &event
+            {
                 let mut next_redraw: Option<window::RedrawRequest> = None;
 
                 self.instants.iter_mut().enumerate().for_each(

examples/todos/src/main.rs

@@ -8,7 +8,7 @@ use iced::widget::{
 };
 use iced::window;
 use iced::{Application, Element};
-use iced::{Color, Command, Length, Settings, Subscription};
+use iced::{Color, Command, Length, Settings, Size, Subscription};
 
 use once_cell::sync::Lazy;
 use serde::{Deserialize, Serialize};
@@ -22,7 +22,7 @@ pub fn main() -> iced::Result {
 
     Todos::run(Settings {
         window: window::Settings {
-            size: (500, 800),
+            size: Size::new(500.0, 800.0),
             ..window::Settings::default()
         },
         ..Settings::default()
@@ -54,7 +54,7 @@ enum Message {
     FilterChanged(Filter),
     TaskMessage(usize, TaskMessage),
     TabPressed { shift: bool },
-    ChangeWindowMode(window::Mode),
+    ToggleFullscreen(window::Mode),
 }
 
 impl Application for Todos {
@@ -165,8 +165,8 @@ impl Application for Todos {
                             widget::focus_next()
                         }
                     }
-                    Message::ChangeWindowMode(mode) => {
-                        window::change_mode(mode)
+                    Message::ToggleFullscreen(mode) => {
+                        window::change_mode(window::Id::MAIN, mode)
                     }
                     _ => Command::none(),
                 };
@@ -272,10 +272,10 @@ impl Application for Todos {
                     shift: modifiers.shift(),
                 }),
                 (keyboard::KeyCode::Up, keyboard::Modifiers::SHIFT) => {
-                    Some(Message::ChangeWindowMode(window::Mode::Fullscreen))
+                    Some(Message::ToggleFullscreen(window::Mode::Fullscreen))
                 }
                 (keyboard::KeyCode::Down, keyboard::Modifiers::SHIFT) => {
-                    Some(Message::ChangeWindowMode(window::Mode::Windowed))
+                    Some(Message::ToggleFullscreen(window::Mode::Windowed))
                 }
                 _ => None,
             }

examples/visible_bounds/src/main.rs

@@ -167,7 +167,7 @@ impl Application for Example {
             Event::Mouse(mouse::Event::CursorMoved { position }) => {
                 Some(Message::MouseMoved(position))
             }
-            Event::Window(window::Event::Resized { .. }) => {
+            Event::Window(_, window::Event::Resized { .. }) => {
                 Some(Message::WindowResized)
             }
             _ => None,

futures/src/event.rs

@@ -35,7 +35,7 @@ where
     subscription::filter_map(
         (EventsWith, f),
         move |event, status| match event {
-            Event::Window(window::Event::RedrawRequested(_)) => None,
+            Event::Window(_, window::Event::RedrawRequested(_)) => None,
             _ => f(event, status),
         },
     )

graphics/src/compositor.rs

@@ -22,7 +22,10 @@ pub trait Compositor: Sized {
     fn new<W: HasRawWindowHandle + HasRawDisplayHandle>(
         settings: Self::Settings,
         compatible_window: Option<&W>,
-    ) -> Result<(Self, Self::Renderer), Error>;
+    ) -> Result<Self, Error>;
+
+    /// Creates a [`Self::Renderer`] for the [`Compositor`].
+    fn create_renderer(&self) -> Self::Renderer;
 
     /// Crates a new [`Surface`] for the given window.
     ///

renderer/src/compositor.rs

@@ -26,7 +26,7 @@ impl<Theme> crate::graphics::Compositor for Compositor<Theme> {
     fn new<W: HasRawWindowHandle + HasRawDisplayHandle>(
         settings: Self::Settings,
         compatible_window: Option<&W>,
-    ) -> Result<(Self, Self::Renderer), Error> {
+    ) -> Result<Self, Error> {
         let candidates =
             Candidate::list_from_env().unwrap_or(Candidate::default_list());
 
@@ -34,9 +34,7 @@ impl<Theme> crate::graphics::Compositor for Compositor<Theme> {
 
         for candidate in candidates {
             match candidate.build(settings, compatible_window) {
-                Ok((compositor, renderer)) => {
-                    return Ok((compositor, renderer))
-                }
+                Ok(compositor) => return Ok(compositor),
                 Err(new_error) => {
                     error = new_error;
                 }
@@ -46,6 +44,18 @@ impl<Theme> crate::graphics::Compositor for Compositor<Theme> {
         Err(error)
     }
 
+    fn create_renderer(&self) -> Self::Renderer {
+        match self {
+            Compositor::TinySkia(compositor) => {
+                Renderer::TinySkia(compositor.create_renderer())
+            }
+            #[cfg(feature = "wgpu")]
+            Compositor::Wgpu(compositor) => {
+                Renderer::Wgpu(compositor.create_renderer())
+            }
+        }
+    }
+
     fn create_surface<W: HasRawWindowHandle + HasRawDisplayHandle>(
         &mut self,
         window: &W,
@@ -220,24 +230,21 @@ impl Candidate {
         self,
         settings: Settings,
         _compatible_window: Option<&W>,
-    ) -> Result<(Compositor<Theme>, Renderer<Theme>), Error> {
+    ) -> Result<Compositor<Theme>, Error> {
         match self {
             Self::TinySkia => {
-                let (compositor, backend) =
-                    iced_tiny_skia::window::compositor::new();
+                let compositor = iced_tiny_skia::window::compositor::new(
+                    iced_tiny_skia::Settings {
+                        default_font: settings.default_font,
+                        default_text_size: settings.default_text_size,
+                    },
+                );
 
-                Ok((
-                    Compositor::TinySkia(compositor),
-                    Renderer::TinySkia(iced_tiny_skia::Renderer::new(
-                        backend,
-                        settings.default_font,
-                        settings.default_text_size,
-                    )),
-                ))
+                Ok(Compositor::TinySkia(compositor))
             }
             #[cfg(feature = "wgpu")]
             Self::Wgpu => {
-                let (compositor, backend) = iced_wgpu::window::compositor::new(
+                let compositor = iced_wgpu::window::compositor::new(
                     iced_wgpu::Settings {
                         default_font: settings.default_font,
                         default_text_size: settings.default_text_size,
@@ -247,14 +254,7 @@ impl Candidate {
                     _compatible_window,
                 )?;
 
-                Ok((
-                    Compositor::Wgpu(compositor),
-                    Renderer::Wgpu(iced_wgpu::Renderer::new(
-                        backend,
-                        settings.default_font,
-                        settings.default_text_size,
-                    )),
-                ))
+                Ok(Compositor::Wgpu(compositor))
             }
             #[cfg(not(feature = "wgpu"))]
             Self::Wgpu => {

runtime/Cargo.toml

@@ -12,6 +12,7 @@ keywords.workspace = true
 
 [features]
 debug = []
+multi-window = []
 
 [dependencies]
 iced_core.workspace = true

runtime/src/command/action.rs

@@ -84,7 +84,9 @@ impl<T> fmt::Debug for Action<T> {
             Self::Clipboard(action) => {
                 write!(f, "Action::Clipboard({action:?})")
             }
-            Self::Window(action) => write!(f, "Action::Window({action:?})"),
+            Self::Window(action) => {
+                write!(f, "Action::Window({action:?})")
+            }
             Self::System(action) => write!(f, "Action::System({action:?})"),
             Self::Widget(_action) => write!(f, "Action::Widget"),
             Self::LoadFont { .. } => write!(f, "Action::LoadFont"),

runtime/src/lib.rs

@@ -26,6 +26,9 @@ pub mod system;
 pub mod user_interface;
 pub mod window;
 
+#[cfg(feature = "multi-window")]
+pub mod multi_window;
+
 // We disable debug capabilities on release builds unless the `debug` feature
 // is explicitly enabled.
 #[cfg(feature = "debug")]

runtime/src/multi_window.rs

@@ -0,0 +1,6 @@
+//! A multi-window application.
+pub mod program;
+pub mod state;
+
+pub use program::Program;
+pub use state::State;

runtime/src/multi_window/program.rs

@@ -0,0 +1,32 @@
+//! Build interactive programs using The Elm Architecture.
+use crate::core::text;
+use crate::core::window;
+use crate::core::{Element, Renderer};
+use crate::Command;
+
+/// The core of a user interface for a multi-window application following The Elm Architecture.
+pub trait Program: Sized {
+    /// The graphics backend to use to draw the [`Program`].
+    type Renderer: Renderer + text::Renderer;
+
+    /// The type of __messages__ your [`Program`] will produce.
+    type Message: std::fmt::Debug + Send;
+
+    /// 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 [`Command`] returned will be executed immediately in the
+    /// background by shells.
+    fn update(&mut self, message: Self::Message) -> Command<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::Renderer>;
+}

runtime/src/multi_window/state.rs

@@ -0,0 +1,280 @@
+//! The internal state of a multi-window [`Program`].
+use crate::core::event::{self, Event};
+use crate::core::mouse;
+use crate::core::renderer;
+use crate::core::widget::operation::{self, Operation};
+use crate::core::{Clipboard, Size};
+use crate::user_interface::{self, UserInterface};
+use crate::{Command, Debug, Program};
+
+/// The execution state of a multi-window [`Program`]. It leverages caching, event
+/// processing, and rendering primitive storage.
+#[allow(missing_debug_implementations)]
+pub struct State<P>
+where
+    P: Program + 'static,
+{
+    program: P,
+    caches: Option<Vec<user_interface::Cache>>,
+    queued_events: Vec<Event>,
+    queued_messages: Vec<P::Message>,
+    mouse_interaction: mouse::Interaction,
+}
+
+impl<P> State<P>
+where
+    P: Program + 'static,
+{
+    /// Creates a new [`State`] with the provided [`Program`], initializing its
+    /// primitive with the given logical bounds and renderer.
+    pub fn new(
+        program: P,
+        bounds: Size,
+        renderer: &mut P::Renderer,
+        debug: &mut Debug,
+    ) -> Self {
+        let user_interface = build_user_interface(
+            &program,
+            user_interface::Cache::default(),
+            renderer,
+            bounds,
+            debug,
+        );
+
+        let caches = Some(vec![user_interface.into_cache()]);
+
+        State {
+            program,
+            caches,
+            queued_events: Vec::new(),
+            queued_messages: Vec::new(),
+            mouse_interaction: mouse::Interaction::Idle,
+        }
+    }
+
+    /// Returns a reference to the [`Program`] of the [`State`].
+    pub fn program(&self) -> &P {
+        &self.program
+    }
+
+    /// Queues an event in the [`State`] for processing during an [`update`].
+    ///
+    /// [`update`]: Self::update
+    pub fn queue_event(&mut self, event: Event) {
+        self.queued_events.push(event);
+    }
+
+    /// Queues a message in the [`State`] for processing during an [`update`].
+    ///
+    /// [`update`]: Self::update
+    pub fn queue_message(&mut self, message: P::Message) {
+        self.queued_messages.push(message);
+    }
+
+    /// Returns whether the event queue of the [`State`] is empty or not.
+    pub fn is_queue_empty(&self) -> bool {
+        self.queued_events.is_empty() && self.queued_messages.is_empty()
+    }
+
+    /// Returns the current [`mouse::Interaction`] of the [`State`].
+    pub fn mouse_interaction(&self) -> mouse::Interaction {
+        self.mouse_interaction
+    }
+
+    /// Processes all the queued events and messages, rebuilding and redrawing
+    /// the widgets of the linked [`Program`] if necessary.
+    ///
+    /// Returns a list containing the instances of [`Event`] that were not
+    /// captured by any widget, and the [`Command`] obtained from [`Program`]
+    /// after updating it, only if an update was necessary.
+    pub fn update(
+        &mut self,
+        bounds: Size,
+        cursor: mouse::Cursor,
+        renderer: &mut P::Renderer,
+        theme: &<P::Renderer as iced_core::Renderer>::Theme,
+        style: &renderer::Style,
+        clipboard: &mut dyn Clipboard,
+        debug: &mut Debug,
+    ) -> (Vec<Event>, Option<Command<P::Message>>) {
+        let mut user_interfaces = build_user_interfaces(
+            &self.program,
+            self.caches.take().unwrap(),
+            renderer,
+            bounds,
+            debug,
+        );
+
+        debug.event_processing_started();
+        let mut messages = Vec::new();
+
+        let uncaptured_events = user_interfaces.iter_mut().fold(
+            vec![],
+            |mut uncaptured_events, ui| {
+                let (_, event_statuses) = ui.update(
+                    &self.queued_events,
+                    cursor,
+                    renderer,
+                    clipboard,
+                    &mut messages,
+                );
+
+                uncaptured_events.extend(
+                    self.queued_events
+                        .iter()
+                        .zip(event_statuses)
+                        .filter_map(|(event, status)| {
+                            matches!(status, event::Status::Ignored)
+                                .then_some(event)
+                        })
+                        .cloned(),
+                );
+                uncaptured_events
+            },
+        );
+
+        self.queued_events.clear();
+        messages.append(&mut self.queued_messages);
+        debug.event_processing_finished();
+
+        let commands = if messages.is_empty() {
+            debug.draw_started();
+
+            for ui in &mut user_interfaces {
+                self.mouse_interaction =
+                    ui.draw(renderer, theme, style, cursor);
+            }
+
+            debug.draw_finished();
+
+            self.caches = Some(
+                user_interfaces
+                    .drain(..)
+                    .map(UserInterface::into_cache)
+                    .collect(),
+            );
+
+            None
+        } else {
+            let temp_caches = user_interfaces
+                .drain(..)
+                .map(UserInterface::into_cache)
+                .collect();
+
+            drop(user_interfaces);
+
+            let commands = Command::batch(messages.into_iter().map(|msg| {
+                debug.log_message(&msg);
+
+                debug.update_started();
+                let command = self.program.update(msg);
+                debug.update_finished();
+
+                command
+            }));
+
+            let mut user_interfaces = build_user_interfaces(
+                &self.program,
+                temp_caches,
+                renderer,
+                bounds,
+                debug,
+            );
+
+            debug.draw_started();
+            for ui in &mut user_interfaces {
+                self.mouse_interaction =
+                    ui.draw(renderer, theme, style, cursor);
+            }
+            debug.draw_finished();
+
+            self.caches = Some(
+                user_interfaces
+                    .drain(..)
+                    .map(UserInterface::into_cache)
+                    .collect(),
+            );
+
+            Some(commands)
+        };
+
+        (uncaptured_events, commands)
+    }
+
+    /// Applies widget [`Operation`]s to the [`State`].
+    pub fn operate(
+        &mut self,
+        renderer: &mut P::Renderer,
+        operations: impl Iterator<Item = Box<dyn Operation<P::Message>>>,
+        bounds: Size,
+        debug: &mut Debug,
+    ) {
+        let mut user_interfaces = build_user_interfaces(
+            &self.program,
+            self.caches.take().unwrap(),
+            renderer,
+            bounds,
+            debug,
+        );
+
+        for operation in operations {
+            let mut current_operation = Some(operation);
+
+            while let Some(mut operation) = current_operation.take() {
+                for ui in &mut user_interfaces {
+                    ui.operate(renderer, operation.as_mut());
+                }
+
+                match operation.finish() {
+                    operation::Outcome::None => {}
+                    operation::Outcome::Some(message) => {
+                        self.queued_messages.push(message);
+                    }
+                    operation::Outcome::Chain(next) => {
+                        current_operation = Some(next);
+                    }
+                };
+            }
+        }
+
+        self.caches = Some(
+            user_interfaces
+                .drain(..)
+                .map(UserInterface::into_cache)
+                .collect(),
+        );
+    }
+}
+
+fn build_user_interfaces<'a, P: Program>(
+    program: &'a P,
+    mut caches: Vec<user_interface::Cache>,
+    renderer: &mut P::Renderer,
+    size: Size,
+    debug: &mut Debug,
+) -> Vec<UserInterface<'a, P::Message, P::Renderer>> {
+    caches
+        .drain(..)
+        .map(|cache| {
+            build_user_interface(program, cache, renderer, size, debug)
+        })
+        .collect()
+}
+
+fn build_user_interface<'a, P: Program>(
+    program: &'a P,
+    cache: user_interface::Cache,
+    renderer: &mut P::Renderer,
+    size: Size,
+    debug: &mut Debug,
+) -> UserInterface<'a, P::Message, P::Renderer> {
+    debug.view_started();
+    let view = program.view();
+    debug.view_finished();
+
+    debug.layout_started();
+    let user_interface = UserInterface::build(view, size, cache, renderer);
+    debug.layout_finished();
+
+    user_interface
+}

runtime/src/window.rs

@@ -8,95 +8,113 @@ pub use screenshot::Screenshot;
 
 use crate::command::{self, Command};
 use crate::core::time::Instant;
-use crate::core::window::{Event, Icon, Level, Mode, UserAttention};
-use crate::core::Size;
+use crate::core::window::{
+    Event, Icon, Id, Level, Mode, Settings, UserAttention,
+};
+use crate::core::{Point, Size};
 use crate::futures::event;
 use crate::futures::Subscription;
 
 /// Subscribes to the frames of the window of the running application.
 ///
 /// The resulting [`Subscription`] will produce items at a rate equal to the
-/// refresh rate of the window. Note that this rate may be variable, as it is
+/// refresh rate of the first application window. Note that this rate may be variable, as it is
 /// normally managed by the graphics driver and/or the OS.
 ///
 /// In any case, this [`Subscription`] is useful to smoothly draw application-driven
 /// animations without missing any frames.
 pub fn frames() -> Subscription<Instant> {
     event::listen_raw(|event, _status| match event {
-        iced_core::Event::Window(Event::RedrawRequested(at)) => Some(at),
+        crate::core::Event::Window(_, Event::RedrawRequested(at)) => Some(at),
         _ => None,
     })
 }
 
-/// Closes the current window and exits the application.
-pub fn close<Message>() -> Command<Message> {
-    Command::single(command::Action::Window(Action::Close))
+/// Spawns a new window with the given `settings`.
+///
+/// Returns the new window [`Id`] alongside the [`Command`].
+pub fn spawn<Message>(settings: Settings) -> (Id, Command<Message>) {
+    let id = Id::unique();
+
+    (
+        id,
+        Command::single(command::Action::Window(Action::Spawn(id, settings))),
+    )
+}
+
+/// Closes the window with `id`.
+pub fn close<Message>(id: Id) -> Command<Message> {
+    Command::single(command::Action::Window(Action::Close(id)))
 }
 
 /// Begins dragging the window while the left mouse button is held.
-pub fn drag<Message>() -> Command<Message> {
-    Command::single(command::Action::Window(Action::Drag))
+pub fn drag<Message>(id: Id) -> Command<Message> {
+    Command::single(command::Action::Window(Action::Drag(id)))
 }
 
 /// Resizes the window to the given logical dimensions.
-pub fn resize<Message>(new_size: Size<u32>) -> Command<Message> {
-    Command::single(command::Action::Window(Action::Resize(new_size)))
+pub fn resize<Message>(id: Id, new_size: Size) -> Command<Message> {
+    Command::single(command::Action::Window(Action::Resize(id, new_size)))
 }
 
-/// Fetches the current window size in logical dimensions.
+/// Fetches the window's size in logical dimensions.
 pub fn fetch_size<Message>(
-    f: impl FnOnce(Size<u32>) -> Message + 'static,
+    id: Id,
+    f: impl FnOnce(Size) -> Message + 'static,
 ) -> Command<Message> {
-    Command::single(command::Action::Window(Action::FetchSize(Box::new(f))))
+    Command::single(command::Action::Window(Action::FetchSize(id, Box::new(f))))
 }
 
 /// Maximizes the window.
-pub fn maximize<Message>(maximized: bool) -> Command<Message> {
-    Command::single(command::Action::Window(Action::Maximize(maximized)))
+pub fn maximize<Message>(id: Id, maximized: bool) -> Command<Message> {
+    Command::single(command::Action::Window(Action::Maximize(id, maximized)))
 }
 
-/// Minimes the window.
-pub fn minimize<Message>(minimized: bool) -> Command<Message> {
-    Command::single(command::Action::Window(Action::Minimize(minimized)))
+/// Minimizes the window.
+pub fn minimize<Message>(id: Id, minimized: bool) -> Command<Message> {
+    Command::single(command::Action::Window(Action::Minimize(id, minimized)))
 }
 
-/// Moves a window to the given logical coordinates.
-pub fn move_to<Message>(x: i32, y: i32) -> Command<Message> {
-    Command::single(command::Action::Window(Action::Move { x, y }))
+/// Moves the window to the given logical coordinates.
+pub fn move_to<Message>(id: Id, position: Point) -> Command<Message> {
+    Command::single(command::Action::Window(Action::Move(id, position)))
 }
 
 /// Changes the [`Mode`] of the window.
-pub fn change_mode<Message>(mode: Mode) -> Command<Message> {
-    Command::single(command::Action::Window(Action::ChangeMode(mode)))
+pub fn change_mode<Message>(id: Id, mode: Mode) -> Command<Message> {
+    Command::single(command::Action::Window(Action::ChangeMode(id, mode)))
 }
 
 /// Fetches the current [`Mode`] of the window.
 pub fn fetch_mode<Message>(
+    id: Id,
     f: impl FnOnce(Mode) -> Message + 'static,
 ) -> Command<Message> {
-    Command::single(command::Action::Window(Action::FetchMode(Box::new(f))))
+    Command::single(command::Action::Window(Action::FetchMode(id, Box::new(f))))
 }
 
 /// Toggles the window to maximized or back.
-pub fn toggle_maximize<Message>() -> Command<Message> {
-    Command::single(command::Action::Window(Action::ToggleMaximize))
+pub fn toggle_maximize<Message>(id: Id) -> Command<Message> {
+    Command::single(command::Action::Window(Action::ToggleMaximize(id)))
 }
 
 /// Toggles the window decorations.
-pub fn toggle_decorations<Message>() -> Command<Message> {
-    Command::single(command::Action::Window(Action::ToggleDecorations))
+pub fn toggle_decorations<Message>(id: Id) -> Command<Message> {
+    Command::single(command::Action::Window(Action::ToggleDecorations(id)))
 }
 
-/// Request user attention to the window, this has no effect if the application
+/// Request user attention to the window. This has no effect if the application
 /// is already focused. How requesting for user attention manifests is platform dependent,
 /// see [`UserAttention`] for details.
 ///
 /// Providing `None` will unset the request for user attention. Unsetting the request for
 /// user attention might not be done automatically by the WM when the window receives input.
 pub fn request_user_attention<Message>(
+    id: Id,
     user_attention: Option<UserAttention>,
 ) -> Command<Message> {
     Command::single(command::Action::Window(Action::RequestUserAttention(
+        id,
         user_attention,
     )))
 }
@@ -107,30 +125,36 @@ pub fn request_user_attention<Message>(
 /// This [`Command`] steals input focus from other applications. Do not use this method unless
 /// you are certain that's what the user wants. Focus stealing can cause an extremely disruptive
 /// user experience.
-pub fn gain_focus<Message>() -> Command<Message> {
-    Command::single(command::Action::Window(Action::GainFocus))
+pub fn gain_focus<Message>(id: Id) -> Command<Message> {
+    Command::single(command::Action::Window(Action::GainFocus(id)))
 }
 
 /// Changes the window [`Level`].
-pub fn change_level<Message>(level: Level) -> Command<Message> {
-    Command::single(command::Action::Window(Action::ChangeLevel(level)))
+pub fn change_level<Message>(id: Id, level: Level) -> Command<Message> {
+    Command::single(command::Action::Window(Action::ChangeLevel(id, level)))
 }
 
-/// Fetches an identifier unique to the window.
+/// Fetches an identifier unique to the window, provided by the underlying windowing system. This is
+/// not to be confused with [`Id`].
 pub fn fetch_id<Message>(
+    id: Id,
     f: impl FnOnce(u64) -> Message + 'static,
 ) -> Command<Message> {
-    Command::single(command::Action::Window(Action::FetchId(Box::new(f))))
+    Command::single(command::Action::Window(Action::FetchId(id, Box::new(f))))
 }
 
 /// Changes the [`Icon`] of the window.
-pub fn change_icon<Message>(icon: Icon) -> Command<Message> {
-    Command::single(command::Action::Window(Action::ChangeIcon(icon)))
+pub fn change_icon<Message>(id: Id, icon: Icon) -> Command<Message> {
+    Command::single(command::Action::Window(Action::ChangeIcon(id, icon)))
 }
 
 /// Captures a [`Screenshot`] from the window.
 pub fn screenshot<Message>(
+    id: Id,
     f: impl FnOnce(Screenshot) -> Message + Send + 'static,
 ) -> Command<Message> {
-    Command::single(command::Action::Window(Action::Screenshot(Box::new(f))))
+    Command::single(command::Action::Window(Action::Screenshot(
+        id,
+        Box::new(f),
+    )))
 }

runtime/src/window/action.rs

@@ -1,5 +1,5 @@
-use crate::core::window::{Icon, Level, Mode, UserAttention};
-use crate::core::Size;
+use crate::core::window::{Icon, Id, Level, Mode, Settings, UserAttention};
+use crate::core::{Point, Size};
 use crate::futures::MaybeSend;
 use crate::window::Screenshot;
 
@@ -7,43 +7,40 @@ use std::fmt;
 
 /// An operation to be performed on some window.
 pub enum Action<T> {
-    /// Close the current window and exits the application.
-    Close,
+    /// Spawns a new window with some [`Settings`].
+    Spawn(Id, Settings),
+    /// Close the window and exits the application.
+    Close(Id),
     /// Move the window with the left mouse button until the button is
     /// released.
     ///
     /// There’s no guarantee that this will work unless the left mouse
     /// button was pressed immediately before this function is called.
-    Drag,
-    /// Resize the window.
-    Resize(Size<u32>),
-    /// Fetch the current size of the window.
-    FetchSize(Box<dyn FnOnce(Size<u32>) -> T + 'static>),
+    Drag(Id),
+    /// Resize the window to the given logical dimensions.
+    Resize(Id, Size),
+    /// Fetch the current logical dimensions of the window.
+    FetchSize(Id, Box<dyn FnOnce(Size) -> T + 'static>),
     /// Set the window to maximized or back
-    Maximize(bool),
+    Maximize(Id, bool),
     /// Set the window to minimized or back
-    Minimize(bool),
-    /// Move the window.
+    Minimize(Id, bool),
+    /// Move the window to the given logical coordinates.
     ///
     /// Unsupported on Wayland.
-    Move {
-        /// The new logical x location of the window
-        x: i32,
-        /// The new logical y location of the window
-        y: i32,
-    },
+    Move(Id, Point),
     /// Change the [`Mode`] of the window.
-    ChangeMode(Mode),
+    ChangeMode(Id, Mode),
     /// Fetch the current [`Mode`] of the window.
-    FetchMode(Box<dyn FnOnce(Mode) -> T + 'static>),
+    FetchMode(Id, Box<dyn FnOnce(Mode) -> T + 'static>),
     /// Toggle the window to maximized or back
-    ToggleMaximize,
+    ToggleMaximize(Id),
     /// Toggle whether window has decorations.
     ///
     /// ## Platform-specific
     /// - **X11:** Not implemented.
     /// - **Web:** Unsupported.
-    ToggleDecorations,
+    ToggleDecorations(Id),
     /// Request user attention to the window, this has no effect if the application
     /// is already focused. How requesting for user attention manifests is platform dependent,
     /// see [`UserAttention`] for details.
@@ -57,7 +54,7 @@ pub enum Action<T> {
     /// - **macOS:** `None` has no effect.
     /// - **X11:** Requests for user attention must be manually cleared.
     /// - **Wayland:** Requires `xdg_activation_v1` protocol, `None` has no effect.
-    RequestUserAttention(Option<UserAttention>),
+    RequestUserAttention(Id, Option<UserAttention>),
     /// Bring the window to the front and sets input focus. Has no effect if the window is
     /// already in focus, minimized, or not visible.
     ///
@@ -68,11 +65,11 @@ pub enum Action<T> {
     /// ## Platform-specific
     ///
     /// - **Web / Wayland:** Unsupported.
-    GainFocus,
+    GainFocus(Id),
     /// Change the window [`Level`].
-    ChangeLevel(Level),
-    /// Fetch an identifier unique to the window.
-    FetchId(Box<dyn FnOnce(u64) -> T + 'static>),
+    ChangeLevel(Id, Level),
+    /// Fetch the raw identifier unique to the window.
+    FetchId(Id, Box<dyn FnOnce(u64) -> T + 'static>),
     /// Change the window [`Icon`].
     ///
     /// On Windows and X11, this is typically the small icon in the top-left
@@ -87,9 +84,9 @@ pub enum Action<T> {
     ///
     /// - **X11:** Has no universal guidelines for icon sizes, so you're at the whims of the WM. That
     ///   said, it's usually in the same ballpark as on Windows.
-    ChangeIcon(Icon),
+    ChangeIcon(Id, Icon),
     /// Screenshot the viewport of the window.
-    Screenshot(Box<dyn FnOnce(Screenshot) -> T + 'static>),
+    Screenshot(Id, Box<dyn FnOnce(Screenshot) -> T + 'static>),
 }
 
 impl<T> Action<T> {
@@ -102,29 +99,35 @@ impl<T> Action<T> {
         T: 'static,
     {
         match self {
-            Self::Close => Action::Close,
-            Self::Drag => Action::Drag,
-            Self::Resize(size) => Action::Resize(size),
-            Self::FetchSize(o) => Action::FetchSize(Box::new(move |s| f(o(s)))),
-            Self::Maximize(maximized) => Action::Maximize(maximized),
-            Self::Minimize(minimized) => Action::Minimize(minimized),
-            Self::Move { x, y } => Action::Move { x, y },
-            Self::ChangeMode(mode) => Action::ChangeMode(mode),
-            Self::FetchMode(o) => Action::FetchMode(Box::new(move |s| f(o(s)))),
-            Self::ToggleMaximize => Action::ToggleMaximize,
-            Self::ToggleDecorations => Action::ToggleDecorations,
-            Self::RequestUserAttention(attention_type) => {
-                Action::RequestUserAttention(attention_type)
+            Self::Spawn(id, settings) => Action::Spawn(id, settings),
+            Self::Close(id) => Action::Close(id),
+            Self::Drag(id) => Action::Drag(id),
+            Self::Resize(id, size) => Action::Resize(id, size),
+            Self::FetchSize(id, o) => {
+                Action::FetchSize(id, Box::new(move |s| f(o(s))))
             }
-            Self::GainFocus => Action::GainFocus,
-            Self::ChangeLevel(level) => Action::ChangeLevel(level),
-            Self::FetchId(o) => Action::FetchId(Box::new(move |s| f(o(s)))),
-            Self::ChangeIcon(icon) => Action::ChangeIcon(icon),
-            Self::Screenshot(tag) => {
-                Action::Screenshot(Box::new(move |screenshot| {
-                    f(tag(screenshot))
-                }))
+            Self::Maximize(id, maximized) => Action::Maximize(id, maximized),
+            Self::Minimize(id, minimized) => Action::Minimize(id, minimized),
+            Self::Move(id, position) => Action::Move(id, position),
+            Self::ChangeMode(id, mode) => Action::ChangeMode(id, mode),
+            Self::FetchMode(id, o) => {
+                Action::FetchMode(id, Box::new(move |s| f(o(s))))
             }
+            Self::ToggleMaximize(id) => Action::ToggleMaximize(id),
+            Self::ToggleDecorations(id) => Action::ToggleDecorations(id),
+            Self::RequestUserAttention(id, attention_type) => {
+                Action::RequestUserAttention(id, attention_type)
+            }
+            Self::GainFocus(id) => Action::GainFocus(id),
+            Self::ChangeLevel(id, level) => Action::ChangeLevel(id, level),
+            Self::FetchId(id, o) => {
+                Action::FetchId(id, Box::new(move |s| f(o(s))))
+            }
+            Self::ChangeIcon(id, icon) => Action::ChangeIcon(id, icon),
+            Self::Screenshot(id, tag) => Action::Screenshot(
+                id,
+                Box::new(move |screenshot| f(tag(screenshot))),
+            ),
         }
     }
 }
@@ -132,35 +135,46 @@ impl<T> Action<T> {
 impl<T> fmt::Debug for Action<T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            Self::Close => write!(f, "Action::Close"),
-            Self::Drag => write!(f, "Action::Drag"),
-            Self::Resize(size) => write!(f, "Action::Resize({size:?})"),
-            Self::FetchSize(_) => write!(f, "Action::FetchSize"),
-            Self::Maximize(maximized) => {
-                write!(f, "Action::Maximize({maximized})")
+            Self::Spawn(id, settings) => {
+                write!(f, "Action::Spawn({id:?}, {settings:?})")
             }
-            Self::Minimize(minimized) => {
-                write!(f, "Action::Minimize({minimized}")
+            Self::Close(id) => write!(f, "Action::Close({id:?})"),
+            Self::Drag(id) => write!(f, "Action::Drag({id:?})"),
+            Self::Resize(id, size) => {
+                write!(f, "Action::Resize({id:?}, {size:?})")
             }
-            Self::Move { x, y } => {
-                write!(f, "Action::Move {{ x: {x}, y: {y} }}")
+            Self::FetchSize(id, _) => write!(f, "Action::FetchSize({id:?})"),
+            Self::Maximize(id, maximized) => {
+                write!(f, "Action::Maximize({id:?}, {maximized})")
             }
-            Self::ChangeMode(mode) => write!(f, "Action::SetMode({mode:?})"),
-            Self::FetchMode(_) => write!(f, "Action::FetchMode"),
-            Self::ToggleMaximize => write!(f, "Action::ToggleMaximize"),
-            Self::ToggleDecorations => write!(f, "Action::ToggleDecorations"),
-            Self::RequestUserAttention(_) => {
-                write!(f, "Action::RequestUserAttention")
+            Self::Minimize(id, minimized) => {
+                write!(f, "Action::Minimize({id:?}, {minimized}")
             }
-            Self::GainFocus => write!(f, "Action::GainFocus"),
-            Self::ChangeLevel(level) => {
-                write!(f, "Action::ChangeLevel({level:?})")
+            Self::Move(id, position) => {
+                write!(f, "Action::Move({id:?}, {position})")
             }
-            Self::FetchId(_) => write!(f, "Action::FetchId"),
-            Self::ChangeIcon(_icon) => {
-                write!(f, "Action::ChangeIcon(icon)")
+            Self::ChangeMode(id, mode) => {
+                write!(f, "Action::SetMode({id:?}, {mode:?})")
             }
-            Self::Screenshot(_) => write!(f, "Action::Screenshot"),
+            Self::FetchMode(id, _) => write!(f, "Action::FetchMode({id:?})"),
+            Self::ToggleMaximize(id) => {
+                write!(f, "Action::ToggleMaximize({id:?})")
+            }
+            Self::ToggleDecorations(id) => {
+                write!(f, "Action::ToggleDecorations({id:?})")
+            }
+            Self::RequestUserAttention(id, _) => {
+                write!(f, "Action::RequestUserAttention({id:?})")
+            }
+            Self::GainFocus(id) => write!(f, "Action::GainFocus({id:?})"),
+            Self::ChangeLevel(id, level) => {
+                write!(f, "Action::ChangeLevel({id:?}, {level:?})")
+            }
+            Self::FetchId(id, _) => write!(f, "Action::FetchId({id:?})"),
+            Self::ChangeIcon(id, _icon) => {
+                write!(f, "Action::ChangeIcon({id:?})")
+            }
+            Self::Screenshot(id, _) => write!(f, "Action::Screenshot({id:?})"),
         }
     }
 }

src/lib.rs

@@ -182,6 +182,9 @@ pub mod window;
 #[cfg(feature = "advanced")]
 pub mod advanced;
 
+#[cfg(feature = "multi-window")]
+pub mod multi_window;
+
 pub use style::theme;
 
 pub use crate::core::alignment;

src/multi_window.rs

@@ -0,0 +1,4 @@
+//! Leverage multi-window support in your application.
+mod application;
+
+pub use application::Application;

src/multi_window/application.rs

@@ -0,0 +1,245 @@
+use crate::style::application::StyleSheet;
+use crate::window;
+use crate::{Command, Element, Executor, Settings, Subscription};
+
+/// 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
+/// [`Command`] in some of its methods. If you do not intend to perform any
+/// background work in your program, the [`Sandbox`] trait offers a simplified
+/// interface.
+///
+/// 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::{Command, 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, Command<Self::Message>) {
+///         (Hello, Command::none())
+///     }
+///
+///     fn title(&self, _window: window::Id) -> String {
+///         String::from("A cool application")
+///     }
+///
+///     fn update(&mut self, _message: Self::Message) -> Command<Self::Message> {
+///         Command::none()
+///     }
+///
+///     fn view(&self, _window: window::Id) -> Element<Self::Message> {
+///         "Hello, world!".into()
+///     }
+/// }
+/// ```
+///
+/// [`Sandbox`]: crate::Sandbox
+pub trait Application: Sized {
+    /// 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 + StyleSheet;
+
+    /// 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 [`Command`] 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, Command<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 [`Command`] returned will be executed immediately in the background.
+    fn update(&mut self, message: Self::Message) -> Command<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, crate::Renderer<Self::Theme>>;
+
+    /// 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) -> <Self::Theme as StyleSheet>::Style {
+        <Self::Theme as StyleSheet>::Style::default()
+    }
+
+    /// 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::renderer::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::renderer::Settings::default()
+        };
+
+        Ok(crate::shell::multi_window::run::<
+            Instance<Self>,
+            Self::Executor,
+            crate::renderer::Compositor<Self::Theme>,
+        >(settings.into(), renderer_settings)?)
+    }
+}
+
+struct Instance<A: Application>(A);
+
+impl<A> crate::runtime::multi_window::Program for Instance<A>
+where
+    A: Application,
+{
+    type Renderer = crate::Renderer<A::Theme>;
+    type Message = A::Message;
+
+    fn update(&mut self, message: Self::Message) -> Command<Self::Message> {
+        self.0.update(message)
+    }
+
+    fn view(
+        &self,
+        window: window::Id,
+    ) -> Element<'_, Self::Message, Self::Renderer> {
+        self.0.view(window)
+    }
+}
+
+impl<A> crate::shell::multi_window::Application for Instance<A>
+where
+    A: Application,
+{
+    type Flags = A::Flags;
+
+    fn new(flags: Self::Flags) -> (Self, Command<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) -> <A::Theme as StyleSheet>::Style {
+        self.0.style()
+    }
+
+    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

@@ -46,14 +46,6 @@ pub struct Settings<Flags> {
     ///
     /// [`Canvas`]: crate::widget::Canvas
     pub antialiasing: bool,
-
-    /// Whether the [`Application`] should exit when the user requests the
-    /// window to close (e.g. the user presses the close button).
-    ///
-    /// By default, it is enabled.
-    ///
-    /// [`Application`]: crate::Application
-    pub exit_on_close_request: bool,
 }
 
 impl<Flags> Settings<Flags> {
@@ -71,7 +63,6 @@ impl<Flags> Settings<Flags> {
             default_font: default_settings.default_font,
             default_text_size: default_settings.default_text_size,
             antialiasing: default_settings.antialiasing,
-            exit_on_close_request: default_settings.exit_on_close_request,
         }
     }
 }
@@ -89,7 +80,6 @@ where
             default_font: Font::default(),
             default_text_size: Pixels(16.0),
             antialiasing: false,
-            exit_on_close_request: true,
         }
     }
 }
@@ -98,10 +88,9 @@ impl<Flags> From<Settings<Flags>> for iced_winit::Settings<Flags> {
     fn from(settings: Settings<Flags>) -> iced_winit::Settings<Flags> {
         iced_winit::Settings {
             id: settings.id,
-            window: settings.window.into(),
+            window: settings.window,
             flags: settings.flags,
             fonts: settings.fonts,
-            exit_on_close_request: settings.exit_on_close_request,
         }
     }
 }

src/window.rs

@@ -1,12 +1,8 @@
 //! Configure the window of your application in native platforms.
-mod position;
-mod settings;
 
 pub mod icon;
 
 pub use icon::Icon;
-pub use position::Position;
-pub use settings::{PlatformSpecific, Settings};
 
 pub use crate::core::window::*;
 pub use crate::runtime::window::*;

src/window/position.rs

@@ -1,32 +0,0 @@
-/// The position of a window in a given screen.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum Position {
-    /// The platform-specific default position for a new window.
-    Default,
-    /// The window is completely centered on the screen.
-    Centered,
-    /// The window is positioned with specific coordinates: `(X, Y)`.
-    ///
-    /// When the decorations of the window are enabled, Windows 10 will add some
-    /// invisible padding to the window. This padding gets included in the
-    /// position. So if you have decorations enabled and want the window to be
-    /// at (0, 0) you would have to set the position to
-    /// `(PADDING_X, PADDING_Y)`.
-    Specific(i32, i32),
-}
-
-impl Default for Position {
-    fn default() -> Self {
-        Self::Default
-    }
-}
-
-impl From<Position> for iced_winit::Position {
-    fn from(position: Position) -> Self {
-        match position {
-            Position::Default => Self::Default,
-            Position::Centered => Self::Centered,
-            Position::Specific(x, y) => Self::Specific(x, y),
-        }
-    }
-}

tiny_skia/src/window/compositor.rs

@@ -8,6 +8,7 @@ use raw_window_handle::{HasRawDisplayHandle, HasRawWindowHandle};
 use std::marker::PhantomData;
 
 pub struct Compositor<Theme> {
+    settings: Settings,
     _theme: PhantomData<Theme>,
 }
 
@@ -27,17 +28,16 @@ impl<Theme> crate::graphics::Compositor for Compositor<Theme> {
     fn new<W: HasRawWindowHandle + HasRawDisplayHandle>(
         settings: Self::Settings,
         _compatible_window: Option<&W>,
-    ) -> Result<(Self, Self::Renderer), Error> {
-        let (compositor, backend) = new();
+    ) -> Result<Self, Error> {
+        Ok(new(settings))
+    }
 
-        Ok((
-            compositor,
-            Renderer::new(
-                backend,
-                settings.default_font,
-                settings.default_text_size,
-            ),
-        ))
+    fn create_renderer(&self) -> Self::Renderer {
+        Renderer::new(
+            Backend::new(),
+            self.settings.default_font,
+            self.settings.default_text_size,
+        )
     }
 
     fn create_surface<W: HasRawWindowHandle + HasRawDisplayHandle>(
@@ -121,13 +121,11 @@ impl<Theme> crate::graphics::Compositor for Compositor<Theme> {
     }
 }
 
-pub fn new<Theme>() -> (Compositor<Theme>, Backend) {
-    (
-        Compositor {
-            _theme: PhantomData,
-        },
-        Backend::new(),
-    )
+pub fn new<Theme>(settings: Settings) -> Compositor<Theme> {
+    Compositor {
+        settings,
+        _theme: PhantomData,
+    }
 }
 
 pub fn present<T: AsRef<str>>(

wgpu/src/window/compositor.rs

@@ -139,16 +139,14 @@ impl<Theme> Compositor<Theme> {
 pub fn new<Theme, W: HasRawWindowHandle + HasRawDisplayHandle>(
     settings: Settings,
     compatible_window: Option<&W>,
-) -> Result<(Compositor<Theme>, Backend), Error> {
+) -> Result<Compositor<Theme>, Error> {
     let compositor = futures::executor::block_on(Compositor::request(
         settings,
         compatible_window,
     ))
     .ok_or(Error::GraphicsAdapterNotFound)?;
 
-    let backend = compositor.create_backend();
-
-    Ok((compositor, backend))
+    Ok(compositor)
 }
 
 /// Presents the given primitives with the given [`Compositor`] and [`Backend`].
@@ -214,17 +212,16 @@ impl<Theme> graphics::Compositor for Compositor<Theme> {
     fn new<W: HasRawWindowHandle + HasRawDisplayHandle>(
         settings: Self::Settings,
         compatible_window: Option<&W>,
-    ) -> Result<(Self, Self::Renderer), Error> {
-        let (compositor, backend) = new(settings, compatible_window)?;
+    ) -> Result<Self, Error> {
+        new(settings, compatible_window)
+    }
 
-        Ok((
-            compositor,
-            Renderer::new(
-                backend,
-                settings.default_font,
-                settings.default_text_size,
-            ),
-        ))
+    fn create_renderer(&self) -> Self::Renderer {
+        Renderer::new(
+            self.create_backend(),
+            self.settings.default_font,
+            self.settings.default_text_size,
+        )
     }
 
     fn create_surface<W: HasRawWindowHandle + HasRawDisplayHandle>(

widget/src/shader.rs

@@ -109,7 +109,7 @@ where
                 Some(Event::Keyboard(keyboard_event))
             }
             core::Event::Touch(touch_event) => Some(Event::Touch(touch_event)),
-            core::Event::Window(window::Event::RedrawRequested(instant)) => {
+            core::Event::Window(_, window::Event::RedrawRequested(instant)) => {
                 Some(Event::RedrawRequested(instant))
             }
             _ => None,

widget/src/text_input.rs

@@ -1003,14 +1003,14 @@ where
 
             state.keyboard_modifiers = modifiers;
         }
-        Event::Window(window::Event::Unfocused) => {
+        Event::Window(_, window::Event::Unfocused) => {
             let state = state();
 
             if let Some(focus) = &mut state.is_focused {
                 focus.is_window_focused = false;
             }
         }
-        Event::Window(window::Event::Focused) => {
+        Event::Window(_, window::Event::Focused) => {
             let state = state();
 
             if let Some(focus) = &mut state.is_focused {
@@ -1020,7 +1020,7 @@ where
                 shell.request_redraw(window::RedrawRequest::NextFrame);
             }
         }
-        Event::Window(window::Event::RedrawRequested(now)) => {
+        Event::Window(_, window::Event::RedrawRequested(now)) => {
             let state = state();
 
             if let Some(focus) = &mut state.is_focused {

winit/Cargo.toml

@@ -19,6 +19,7 @@ x11 = ["winit/x11"]
 wayland = ["winit/wayland"]
 wayland-dlopen = ["winit/wayland-dlopen"]
 wayland-csd-adwaita = ["winit/wayland-csd-adwaita"]
+multi-window = ["iced_runtime/multi-window"]
 
 [dependencies]
 iced_graphics.workspace = true
@@ -26,7 +27,6 @@ iced_runtime.workspace = true
 iced_style.workspace = true
 
 log.workspace = true
-raw-window-handle.workspace = true
 thiserror.workspace = true
 tracing.workspace = true
 window_clipboard.workspace = true

winit/src/application.rs

@@ -1,6 +1,4 @@
 //! Create interactive, native cross-platform applications.
-#[cfg(feature = "trace")]
-mod profiler;
 mod state;
 
 pub use state::State;
@@ -27,11 +25,6 @@ use futures::channel::mpsc;
 
 use std::mem::ManuallyDrop;
 
-#[cfg(feature = "trace")]
-pub use profiler::Profiler;
-#[cfg(feature = "trace")]
-use tracing::{info_span, instrument::Instrument};
-
 /// An interactive, native cross-platform application.
 ///
 /// This trait is the main entrypoint of Iced. Once implemented, you can run
@@ -119,15 +112,9 @@ where
     use futures::Future;
     use winit::event_loop::EventLoopBuilder;
 
-    #[cfg(feature = "trace")]
-    let _guard = Profiler::init();
-
     let mut debug = Debug::new();
     debug.startup_started();
 
-    #[cfg(feature = "trace")]
-    let _ = info_span!("Application", "RUN").entered();
-
     let event_loop = EventLoopBuilder::with_user_event().build();
     let proxy = event_loop.create_proxy();
 
@@ -148,14 +135,15 @@ where
     let target = settings.window.platform_specific.target.clone();
 
     let should_be_visible = settings.window.visible;
-    let builder = settings
-        .window
-        .into_builder(
-            &application.title(),
-            event_loop.primary_monitor(),
-            settings.id,
-        )
-        .with_visible(false);
+    let exit_on_close_request = settings.window.exit_on_close_request;
+
+    let builder = conversion::window_settings(
+        settings.window,
+        &application.title(),
+        event_loop.primary_monitor(),
+        settings.id,
+    )
+    .with_visible(false);
 
     log::debug!("Window builder: {builder:#?}");
 
@@ -193,8 +181,8 @@ where
         };
     }
 
-    let (compositor, mut renderer) =
-        C::new(compositor_settings, Some(&window))?;
+    let compositor = C::new(compositor_settings, Some(&window))?;
+    let mut renderer = compositor.create_renderer();
 
     for font in settings.fonts {
         use crate::core::text::Renderer;
@@ -205,28 +193,20 @@ where
     let (mut event_sender, event_receiver) = mpsc::unbounded();
     let (control_sender, mut control_receiver) = mpsc::unbounded();
 
-    let mut instance = Box::pin({
-        let run_instance = run_instance::<A, E, C>(
-            application,
-            compositor,
-            renderer,
-            runtime,
-            proxy,
-            debug,
-            event_receiver,
-            control_sender,
-            init_command,
-            window,
-            should_be_visible,
-            settings.exit_on_close_request,
-        );
-
-        #[cfg(feature = "trace")]
-        let run_instance =
-            run_instance.instrument(info_span!("Application", "LOOP"));
-
-        run_instance
-    });
+    let mut instance = Box::pin(run_instance::<A, E, C>(
+        application,
+        compositor,
+        renderer,
+        runtime,
+        proxy,
+        debug,
+        event_receiver,
+        control_sender,
+        init_command,
+        window,
+        should_be_visible,
+        exit_on_close_request,
+    ));
 
     let mut context = task::Context::from_waker(task::noop_waker_ref());
 
@@ -426,6 +406,7 @@ async fn run_instance<A, E, C>(
                 // Then, we can use the `interface_state` here to decide if a redraw
                 // is needed right away, or simply wait until a specific time.
                 let redraw_event = Event::Window(
+                    window::Id::MAIN,
                     window::Event::RedrawRequested(Instant::now()),
                 );
 
@@ -488,9 +469,6 @@ async fn run_instance<A, E, C>(
                 messages.push(message);
             }
             event::Event::RedrawRequested(_) => {
-                #[cfg(feature = "trace")]
-                let _ = info_span!("Application", "FRAME").entered();
-
                 let physical_size = state.physical_size();
 
                 if physical_size.width == 0 || physical_size.height == 0 {
@@ -578,6 +556,7 @@ async fn run_instance<A, E, C>(
                 state.update(&window, &window_event, &mut debug);
 
                 if let Some(event) = conversion::window_event(
+                    window::Id::MAIN,
                     &window_event,
                     state.scale_factor(),
                     state.modifiers(),
@@ -629,24 +608,12 @@ pub fn build_user_interface<'a, A: Application>(
 where
     <A::Renderer as core::Renderer>::Theme: StyleSheet,
 {
-    #[cfg(feature = "trace")]
-    let view_span = info_span!("Application", "VIEW").entered();
-
     debug.view_started();
     let view = application.view();
-
-    #[cfg(feature = "trace")]
-    let _ = view_span.exit();
     debug.view_finished();
 
-    #[cfg(feature = "trace")]
-    let layout_span = info_span!("Application", "LAYOUT").entered();
-
     debug.layout_started();
     let user_interface = UserInterface::build(view, size, cache, renderer);
-
-    #[cfg(feature = "trace")]
-    let _ = layout_span.exit();
     debug.layout_finished();
 
     user_interface
@@ -673,16 +640,10 @@ pub fn update<A: Application, C, E: Executor>(
     <A::Renderer as core::Renderer>::Theme: StyleSheet,
 {
     for message in messages.drain(..) {
-        #[cfg(feature = "trace")]
-        let update_span = info_span!("Application", "UPDATE").entered();
-
         debug.log_message(&message);
 
         debug.update_started();
         let command = runtime.enter(|| application.update(message));
-
-        #[cfg(feature = "trace")]
-        let _ = update_span.exit();
         debug.update_finished();
 
         run_command(
@@ -752,20 +713,27 @@ pub fn run_command<A, C, E>(
                 }
             },
             command::Action::Window(action) => match action {
-                window::Action::Close => {
+                window::Action::Close(_id) => {
                     *should_exit = true;
                 }
-                window::Action::Drag => {
+                window::Action::Drag(_id) => {
                     let _res = window.drag_window();
                 }
-                window::Action::Resize(size) => {
+                window::Action::Spawn { .. } => {
+                    log::warn!(
+                        "Spawning a window is only available with \
+                        multi-window applications."
+                    );
+                }
+                window::Action::Resize(_id, size) => {
                     window.set_inner_size(winit::dpi::LogicalSize {
                         width: size.width,
                         height: size.height,
                     });
                 }
-                window::Action::FetchSize(callback) => {
-                    let size = window.inner_size();
+                window::Action::FetchSize(_id, callback) => {
+                    let size =
+                        window.inner_size().to_logical(window.scale_factor());
 
                     proxy
                         .send_event(callback(Size::new(
@@ -774,29 +742,29 @@ pub fn run_command<A, C, E>(
                         )))
                         .expect("Send message to event loop");
                 }
-                window::Action::Maximize(maximized) => {
+                window::Action::Maximize(_id, maximized) => {
                     window.set_maximized(maximized);
                 }
-                window::Action::Minimize(minimized) => {
+                window::Action::Minimize(_id, minimized) => {
                     window.set_minimized(minimized);
                 }
-                window::Action::Move { x, y } => {
+                window::Action::Move(_id, position) => {
                     window.set_outer_position(winit::dpi::LogicalPosition {
-                        x,
-                        y,
+                        x: position.x,
+                        y: position.y,
                     });
                 }
-                window::Action::ChangeMode(mode) => {
+                window::Action::ChangeMode(_id, mode) => {
                     window.set_visible(conversion::visible(mode));
                     window.set_fullscreen(conversion::fullscreen(
                         window.current_monitor(),
                         mode,
                     ));
                 }
-                window::Action::ChangeIcon(icon) => {
+                window::Action::ChangeIcon(_id, icon) => {
                     window.set_window_icon(conversion::icon(icon));
                 }
-                window::Action::FetchMode(tag) => {
+                window::Action::FetchMode(_id, tag) => {
                     let mode = if window.is_visible().unwrap_or(true) {
                         conversion::mode(window.fullscreen())
                     } else {
@@ -807,29 +775,29 @@ pub fn run_command<A, C, E>(
                         .send_event(tag(mode))
                         .expect("Send message to event loop");
                 }
-                window::Action::ToggleMaximize => {
+                window::Action::ToggleMaximize(_id) => {
                     window.set_maximized(!window.is_maximized());
                 }
-                window::Action::ToggleDecorations => {
+                window::Action::ToggleDecorations(_id) => {
                     window.set_decorations(!window.is_decorated());
                 }
-                window::Action::RequestUserAttention(user_attention) => {
+                window::Action::RequestUserAttention(_id, user_attention) => {
                     window.request_user_attention(
                         user_attention.map(conversion::user_attention),
                     );
                 }
-                window::Action::GainFocus => {
+                window::Action::GainFocus(_id) => {
                     window.focus_window();
                 }
-                window::Action::ChangeLevel(level) => {
+                window::Action::ChangeLevel(_id, level) => {
                     window.set_window_level(conversion::window_level(level));
                 }
-                window::Action::FetchId(tag) => {
+                window::Action::FetchId(_id, tag) => {
                     proxy
                         .send_event(tag(window.id().into()))
                         .expect("Send message to event loop");
                 }
-                window::Action::Screenshot(tag) => {
+                window::Action::Screenshot(_id, tag) => {
                     let bytes = compositor.screenshot(
                         renderer,
                         surface,

winit/src/application/profiler.rs

@@ -1,101 +0,0 @@
-//! A simple profiler for Iced.
-use std::ffi::OsStr;
-use std::path::Path;
-use std::time::Duration;
-use tracing_subscriber::prelude::*;
-use tracing_subscriber::Registry;
-#[cfg(feature = "chrome-trace")]
-use {
-    tracing_chrome::FlushGuard,
-    tracing_subscriber::fmt::{format::DefaultFields, FormattedFields},
-};
-
-/// Profiler state. This will likely need to be updated or reworked when adding new tracing backends.
-#[allow(missing_debug_implementations)]
-pub struct Profiler {
-    #[cfg(feature = "chrome-trace")]
-    /// [`FlushGuard`] must not be dropped until the application scope is dropped for accurate tracing.
-    _guard: FlushGuard,
-}
-
-impl Profiler {
-    /// Initializes the [`Profiler`].
-    pub fn init() -> Self {
-        // Registry stores the spans & generates unique span IDs
-        let subscriber = Registry::default();
-
-        let default_path = Path::new(env!("CARGO_MANIFEST_DIR"));
-        let curr_exe = std::env::current_exe()
-            .unwrap_or_else(|_| default_path.to_path_buf());
-        let out_dir = curr_exe.parent().unwrap_or(default_path).join("traces");
-
-        #[cfg(feature = "chrome-trace")]
-        let (chrome_layer, guard) = {
-            let mut layer = tracing_chrome::ChromeLayerBuilder::new();
-
-            // Optional configurable env var: CHROME_TRACE_FILE=/path/to/trace_file/file.json,
-            // for uploading to chrome://tracing (old) or ui.perfetto.dev (new).
-            if let Ok(path) = std::env::var("CHROME_TRACE_FILE") {
-                layer = layer.file(path);
-            } else if std::fs::create_dir_all(&out_dir).is_ok() {
-                let time = std::time::SystemTime::now()
-                    .duration_since(std::time::UNIX_EPOCH)
-                    .unwrap_or(Duration::from_millis(0))
-                    .as_millis();
-
-                let curr_exe_name = curr_exe
-                    .file_name()
-                    .unwrap_or_else(|| OsStr::new("trace"))
-                    .to_str()
-                    .unwrap_or("trace");
-
-                let path =
-                    out_dir.join(format!("{curr_exe_name}_trace_{time}.json"));
-
-                layer = layer.file(path);
-            } else {
-                layer = layer.file(env!("CARGO_MANIFEST_DIR"))
-            }
-
-            let (chrome_layer, guard) = layer
-                .name_fn(Box::new(|event_or_span| match event_or_span {
-                    tracing_chrome::EventOrSpan::Event(event) => {
-                        event.metadata().name().into()
-                    }
-                    tracing_chrome::EventOrSpan::Span(span) => {
-                        if let Some(fields) = span
-                            .extensions()
-                            .get::<FormattedFields<DefaultFields>>()
-                        {
-                            format!(
-                                "{}: {}",
-                                span.metadata().name(),
-                                fields.fields.as_str()
-                            )
-                        } else {
-                            span.metadata().name().into()
-                        }
-                    }
-                }))
-                .build();
-
-            (chrome_layer, guard)
-        };
-
-        let fmt_layer = tracing_subscriber::fmt::Layer::default();
-        let subscriber = subscriber.with(fmt_layer);
-
-        #[cfg(feature = "chrome-trace")]
-        let subscriber = subscriber.with(chrome_layer);
-
-        // create dispatcher which will forward span events to the subscriber
-        // this can only be set once or will panic
-        tracing::subscriber::set_global_default(subscriber)
-            .expect("Tracer could not set the global default subscriber.");
-
-        Profiler {
-            #[cfg(feature = "chrome-trace")]
-            _guard: guard,
-        }
-    }
-}

winit/src/conversion.rs

@@ -6,11 +6,128 @@ use crate::core::keyboard;
 use crate::core::mouse;
 use crate::core::touch;
 use crate::core::window;
-use crate::core::{Event, Point};
-use crate::Position;
+use crate::core::{Event, Point, Size};
+
+/// Converts some [`window::Settings`] into a `WindowBuilder` from `winit`.
+pub fn window_settings(
+    settings: window::Settings,
+    title: &str,
+    primary_monitor: Option<winit::monitor::MonitorHandle>,
+    _id: Option<String>,
+) -> winit::window::WindowBuilder {
+    let mut window_builder = winit::window::WindowBuilder::new();
+
+    window_builder = window_builder
+        .with_title(title)
+        .with_inner_size(winit::dpi::LogicalSize {
+            width: settings.size.width,
+            height: settings.size.height,
+        })
+        .with_resizable(settings.resizable)
+        .with_enabled_buttons(if settings.resizable {
+            winit::window::WindowButtons::all()
+        } else {
+            winit::window::WindowButtons::CLOSE
+                | winit::window::WindowButtons::MINIMIZE
+        })
+        .with_decorations(settings.decorations)
+        .with_transparent(settings.transparent)
+        .with_window_icon(settings.icon.and_then(icon))
+        .with_window_level(window_level(settings.level))
+        .with_visible(settings.visible);
+
+    if let Some(position) =
+        position(primary_monitor.as_ref(), settings.size, settings.position)
+    {
+        window_builder = window_builder.with_position(position);
+    }
+
+    if let Some(min_size) = settings.min_size {
+        window_builder =
+            window_builder.with_min_inner_size(winit::dpi::LogicalSize {
+                width: min_size.width,
+                height: min_size.height,
+            });
+    }
+
+    if let Some(max_size) = settings.max_size {
+        window_builder =
+            window_builder.with_max_inner_size(winit::dpi::LogicalSize {
+                width: max_size.width,
+                height: max_size.height,
+            });
+    }
+
+    #[cfg(any(
+        target_os = "dragonfly",
+        target_os = "freebsd",
+        target_os = "netbsd",
+        target_os = "openbsd"
+    ))]
+    {
+        // `with_name` is available on both `WindowBuilderExtWayland` and `WindowBuilderExtX11` and they do
+        // exactly the same thing. We arbitrarily choose `WindowBuilderExtWayland` here.
+        use ::winit::platform::wayland::WindowBuilderExtWayland;
+
+        if let Some(id) = _id {
+            window_builder = window_builder.with_name(id.clone(), id);
+        }
+    }
+
+    #[cfg(target_os = "windows")]
+    {
+        use winit::platform::windows::WindowBuilderExtWindows;
+        #[allow(unsafe_code)]
+        unsafe {
+            window_builder = window_builder
+                .with_parent_window(settings.platform_specific.parent);
+        }
+        window_builder = window_builder
+            .with_drag_and_drop(settings.platform_specific.drag_and_drop);
+    }
+
+    #[cfg(target_os = "macos")]
+    {
+        use winit::platform::macos::WindowBuilderExtMacOS;
+
+        window_builder = window_builder
+            .with_title_hidden(settings.platform_specific.title_hidden)
+            .with_titlebar_transparent(
+                settings.platform_specific.titlebar_transparent,
+            )
+            .with_fullsize_content_view(
+                settings.platform_specific.fullsize_content_view,
+            );
+    }
+
+    #[cfg(target_os = "linux")]
+    {
+        #[cfg(feature = "x11")]
+        {
+            use winit::platform::x11::WindowBuilderExtX11;
+
+            window_builder = window_builder.with_name(
+                &settings.platform_specific.application_id,
+                &settings.platform_specific.application_id,
+            );
+        }
+        #[cfg(feature = "wayland")]
+        {
+            use winit::platform::wayland::WindowBuilderExtWayland;
+
+            window_builder = window_builder.with_name(
+                &settings.platform_specific.application_id,
+                &settings.platform_specific.application_id,
+            );
+        }
+    }
+
+    window_builder
+}
 
 /// Converts a winit window event into an iced event.
 pub fn window_event(
+    id: window::Id,
     event: &winit::event::WindowEvent<'_>,
     scale_factor: f64,
     modifiers: winit::event::ModifiersState,
@@ -21,21 +138,27 @@ pub fn window_event(
         WindowEvent::Resized(new_size) => {
             let logical_size = new_size.to_logical(scale_factor);
 
-            Some(Event::Window(window::Event::Resized {
-                width: logical_size.width,
-                height: logical_size.height,
-            }))
+            Some(Event::Window(
+                id,
+                window::Event::Resized {
+                    width: logical_size.width,
+                    height: logical_size.height,
+                },
+            ))
         }
         WindowEvent::ScaleFactorChanged { new_inner_size, .. } => {
             let logical_size = new_inner_size.to_logical(scale_factor);
 
-            Some(Event::Window(window::Event::Resized {
-                width: logical_size.width,
-                height: logical_size.height,
-            }))
+            Some(Event::Window(
+                id,
+                window::Event::Resized {
+                    width: logical_size.width,
+                    height: logical_size.height,
+                },
+            ))
         }
         WindowEvent::CloseRequested => {
-            Some(Event::Window(window::Event::CloseRequested))
+            Some(Event::Window(id, window::Event::CloseRequested))
         }
         WindowEvent::CursorMoved { position, .. } => {
             let position = position.to_logical::<f64>(scale_factor);
@@ -113,19 +236,22 @@ pub fn window_event(
         WindowEvent::ModifiersChanged(new_modifiers) => Some(Event::Keyboard(
             keyboard::Event::ModifiersChanged(self::modifiers(*new_modifiers)),
         )),
-        WindowEvent::Focused(focused) => Some(Event::Window(if *focused {
-            window::Event::Focused
-        } else {
-            window::Event::Unfocused
-        })),
+        WindowEvent::Focused(focused) => Some(Event::Window(
+            id,
+            if *focused {
+                window::Event::Focused
+            } else {
+                window::Event::Unfocused
+            },
+        )),
         WindowEvent::HoveredFile(path) => {
-            Some(Event::Window(window::Event::FileHovered(path.clone())))
+            Some(Event::Window(id, window::Event::FileHovered(path.clone())))
         }
         WindowEvent::DroppedFile(path) => {
-            Some(Event::Window(window::Event::FileDropped(path.clone())))
+            Some(Event::Window(id, window::Event::FileDropped(path.clone())))
         }
         WindowEvent::HoveredFileCancelled => {
-            Some(Event::Window(window::Event::FilesHoveredLeft))
+            Some(Event::Window(id, window::Event::FilesHoveredLeft))
         }
         WindowEvent::Touch(touch) => {
             Some(Event::Touch(touch_event(*touch, scale_factor)))
@@ -134,7 +260,7 @@ pub fn window_event(
             let winit::dpi::LogicalPosition { x, y } =
                 position.to_logical(scale_factor);
 
-            Some(Event::Window(window::Event::Moved { x, y }))
+            Some(Event::Window(id, window::Event::Moved { x, y }))
         }
         _ => None,
     }
@@ -153,23 +279,23 @@ pub fn window_level(level: window::Level) -> winit::window::WindowLevel {
     }
 }
 
-/// Converts a [`Position`] to a [`winit`] logical position for a given monitor.
+/// Converts a [`window::Position`] to a [`winit`] logical position for a given monitor.
 ///
 /// [`winit`]: https://github.com/rust-windowing/winit
 pub fn position(
     monitor: Option<&winit::monitor::MonitorHandle>,
-    (width, height): (u32, u32),
-    position: Position,
+    size: Size,
+    position: window::Position,
 ) -> Option<winit::dpi::Position> {
     match position {
-        Position::Default => None,
-        Position::Specific(x, y) => {
+        window::Position::Default => None,
+        window::Position::Specific(position) => {
             Some(winit::dpi::Position::Logical(winit::dpi::LogicalPosition {
-                x: f64::from(x),
-                y: f64::from(y),
+                x: f64::from(position.x),
+                y: f64::from(position.y),
             }))
         }
-        Position::Centered => {
+        window::Position::Centered => {
             if let Some(monitor) = monitor {
                 let start = monitor.position();
 
@@ -178,8 +304,8 @@ pub fn position(
 
                 let centered: winit::dpi::PhysicalPosition<i32> =
                     winit::dpi::LogicalPosition {
-                        x: (resolution.width - f64::from(width)) / 2.0,
-                        y: (resolution.height - f64::from(height)) / 2.0,
+                        x: (resolution.width - f64::from(size.width)) / 2.0,
+                        y: (resolution.height - f64::from(size.height)) / 2.0,
                     }
                     .to_physical(monitor.scale_factor());
 

winit/src/lib.rs

@@ -33,6 +33,9 @@ pub use iced_runtime::futures;
 pub use iced_style as style;
 pub use winit;
 
+#[cfg(feature = "multi-window")]
+pub mod multi_window;
+
 #[cfg(feature = "application")]
 pub mod application;
 pub mod clipboard;
@@ -43,17 +46,11 @@ pub mod settings;
 pub mod system;
 
 mod error;
-mod position;
 mod proxy;
 
 #[cfg(feature = "application")]
 pub use application::Application;
-#[cfg(feature = "trace")]
-pub use application::Profiler;
 pub use clipboard::Clipboard;
 pub use error::Error;
-pub use position::Position;
 pub use proxy::Proxy;
 pub use settings::Settings;
-
-pub use iced_graphics::Viewport;

winit/src/multi_window/state.rs

@@ -0,0 +1,240 @@
+use crate::conversion;
+use crate::core;
+use crate::core::{mouse, window};
+use crate::core::{Color, Size};
+use crate::graphics::Viewport;
+use crate::multi_window::Application;
+use crate::style::application;
+use std::fmt::{Debug, Formatter};
+
+use iced_style::application::StyleSheet;
+use winit::event::{Touch, WindowEvent};
+use winit::window::Window;
+
+/// The state of a multi-windowed [`Application`].
+pub struct State<A: Application>
+where
+    <A::Renderer as core::Renderer>::Theme: application::StyleSheet,
+{
+    title: String,
+    scale_factor: f64,
+    viewport: Viewport,
+    viewport_version: u64,
+    cursor_position: Option<winit::dpi::PhysicalPosition<f64>>,
+    modifiers: winit::event::ModifiersState,
+    theme: <A::Renderer as core::Renderer>::Theme,
+    appearance: application::Appearance,
+}
+
+impl<A: Application> Debug for State<A>
+where
+    <A::Renderer as core::Renderer>::Theme: application::StyleSheet,
+{
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("multi_window::State")
+            .field("title", &self.title)
+            .field("scale_factor", &self.scale_factor)
+            .field("viewport", &self.viewport)
+            .field("viewport_version", &self.viewport_version)
+            .field("cursor_position", &self.cursor_position)
+            .field("appearance", &self.appearance)
+            .finish()
+    }
+}
+
+impl<A: Application> State<A>
+where
+    <A::Renderer as core::Renderer>::Theme: application::StyleSheet,
+{
+    /// Creates a new [`State`] for the provided [`Application`]'s `window`.
+    pub fn new(
+        application: &A,
+        window_id: window::Id,
+        window: &Window,
+    ) -> Self {
+        let title = application.title(window_id);
+        let scale_factor = application.scale_factor(window_id);
+        let theme = application.theme(window_id);
+        let appearance = theme.appearance(&application.style());
+
+        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::event::ModifiersState::default(),
+            theme,
+            appearance,
+        }
+    }
+
+    /// 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) -> u64 {
+        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::event::ModifiersState {
+        self.modifiers
+    }
+
+    /// Returns the current theme of the [`State`].
+    pub fn theme(&self) -> &<A::Renderer as core::Renderer>::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 crate::runtime::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,
+                new_inner_size,
+            } => {
+                let size =
+                    Size::new(new_inner_size.width, new_inner_size.height);
+
+                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;
+            }
+            #[cfg(feature = "debug")]
+            WindowEvent::KeyboardInput {
+                input:
+                    winit::event::KeyboardInput {
+                        virtual_keycode: Some(winit::event::VirtualKeyCode::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 [`State::update`].
+    pub fn synchronize(
+        &mut self,
+        application: &A,
+        window_id: window::Id,
+        window: &Window,
+    ) {
+        // Update window title
+        let new_title = application.title(window_id);
+
+        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(window_id);
+        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(window_id);
+        self.appearance = self.theme.appearance(&application.style());
+    }
+}

winit/src/multi_window/window_manager.rs

@@ -0,0 +1,156 @@
+use crate::core::mouse;
+use crate::core::window::Id;
+use crate::core::{Point, Size};
+use crate::graphics::Compositor;
+use crate::multi_window::{Application, State};
+use crate::style::application::StyleSheet;
+
+use std::collections::BTreeMap;
+use winit::monitor::MonitorHandle;
+
+#[allow(missing_debug_implementations)]
+pub struct WindowManager<A: Application, C: Compositor>
+where
+    <A::Renderer as crate::core::Renderer>::Theme: StyleSheet,
+    C: Compositor<Renderer = A::Renderer>,
+{
+    aliases: BTreeMap<winit::window::WindowId, Id>,
+    entries: BTreeMap<Id, Window<A, C>>,
+}
+
+impl<A, C> WindowManager<A, C>
+where
+    A: Application,
+    C: Compositor<Renderer = A::Renderer>,
+    <A::Renderer as crate::core::Renderer>::Theme: StyleSheet,
+{
+    pub fn new() -> Self {
+        Self {
+            aliases: BTreeMap::new(),
+            entries: BTreeMap::new(),
+        }
+    }
+
+    pub fn insert(
+        &mut self,
+        id: Id,
+        window: winit::window::Window,
+        application: &A,
+        compositor: &mut C,
+        exit_on_close_request: bool,
+    ) -> &mut Window<A, C> {
+        let state = State::new(application, id, &window);
+        let viewport_version = state.viewport_version();
+        let physical_size = state.physical_size();
+        let surface = compositor.create_surface(
+            &window,
+            physical_size.width,
+            physical_size.height,
+        );
+        let renderer = compositor.create_renderer();
+
+        let _ = self.aliases.insert(window.id(), id);
+
+        let _ = self.entries.insert(
+            id,
+            Window {
+                raw: window,
+                state,
+                viewport_version,
+                exit_on_close_request,
+                surface,
+                renderer,
+                mouse_interaction: mouse::Interaction::Idle,
+            },
+        );
+
+        self.entries
+            .get_mut(&id)
+            .expect("Get window that was just inserted")
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.entries.is_empty()
+    }
+
+    pub fn iter_mut(
+        &mut self,
+    ) -> impl Iterator<Item = (Id, &mut Window<A, C>)> {
+        self.entries.iter_mut().map(|(k, v)| (*k, v))
+    }
+
+    pub fn get_mut(&mut self, id: Id) -> Option<&mut Window<A, C>> {
+        self.entries.get_mut(&id)
+    }
+
+    pub fn get_mut_alias(
+        &mut self,
+        id: winit::window::WindowId,
+    ) -> Option<(Id, &mut Window<A, C>)> {
+        let id = self.aliases.get(&id).copied()?;
+
+        Some((id, self.get_mut(id)?))
+    }
+
+    pub fn last_monitor(&self) -> Option<MonitorHandle> {
+        self.entries.values().last()?.raw.current_monitor()
+    }
+
+    pub fn remove(&mut self, id: Id) -> Option<Window<A, C>> {
+        let window = self.entries.remove(&id)?;
+        let _ = self.aliases.remove(&window.raw.id());
+
+        Some(window)
+    }
+}
+
+impl<A, C> Default for WindowManager<A, C>
+where
+    A: Application,
+    C: Compositor<Renderer = A::Renderer>,
+    <A::Renderer as crate::core::Renderer>::Theme: StyleSheet,
+{
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[allow(missing_debug_implementations)]
+pub struct Window<A, C>
+where
+    A: Application,
+    C: Compositor<Renderer = A::Renderer>,
+    <A::Renderer as crate::core::Renderer>::Theme: StyleSheet,
+{
+    pub raw: winit::window::Window,
+    pub state: State<A>,
+    pub viewport_version: u64,
+    pub exit_on_close_request: bool,
+    pub mouse_interaction: mouse::Interaction,
+    pub surface: C::Surface,
+    pub renderer: A::Renderer,
+}
+
+impl<A, C> Window<A, C>
+where
+    A: Application,
+    C: Compositor<Renderer = A::Renderer>,
+    <A::Renderer as crate::core::Renderer>::Theme: StyleSheet,
+{
+    pub fn position(&self) -> Option<Point> {
+        self.raw
+            .inner_position()
+            .ok()
+            .map(|position| position.to_logical(self.raw.scale_factor()))
+            .map(|position| Point {
+                x: position.x,
+                y: position.y,
+            })
+    }
+
+    pub fn size(&self) -> Size {
+        let size = self.raw.inner_size().to_logical(self.raw.scale_factor());
+
+        Size::new(size.width, size.height)
+    }
+}

winit/src/settings.rs

@@ -1,40 +1,7 @@
 //! Configure your application.
-#[cfg(target_os = "windows")]
-#[path = "settings/windows.rs"]
-mod platform;
-
-#[cfg(target_os = "macos")]
-#[path = "settings/macos.rs"]
-mod platform;
-
-#[cfg(target_os = "linux")]
-#[path = "settings/linux.rs"]
-mod platform;
-
-#[cfg(target_arch = "wasm32")]
-#[path = "settings/wasm.rs"]
-mod platform;
-
-#[cfg(not(any(
-    target_os = "windows",
-    target_os = "macos",
-    target_os = "linux",
-    target_arch = "wasm32"
-)))]
-#[path = "settings/other.rs"]
-mod platform;
-
-pub use platform::PlatformSpecific;
-
-use crate::conversion;
-use crate::core::window::{Icon, Level};
-use crate::Position;
-
-use winit::monitor::MonitorHandle;
-use winit::window::WindowBuilder;
+use crate::core::window;
 
 use std::borrow::Cow;
-use std::fmt;
 
 /// The settings of an application.
 #[derive(Debug, Clone, Default)]
@@ -45,8 +12,8 @@ pub struct Settings<Flags> {
     /// communicate with it through the windowing system.
     pub id: Option<String>,
 
-    /// The [`Window`] settings.
-    pub window: Window,
+    /// The [`window::Settings`].
+    pub window: window::Settings,
 
     /// The data needed to initialize an [`Application`].
     ///
@@ -55,197 +22,4 @@ pub struct Settings<Flags> {
 
     /// The fonts to load on boot.
     pub fonts: Vec<Cow<'static, [u8]>>,
-
-    /// Whether the [`Application`] should exit when the user requests the
-    /// window to close (e.g. the user presses the close button).
-    ///
-    /// [`Application`]: crate::Application
-    pub exit_on_close_request: bool,
-}
-
-/// The window settings of an application.
-#[derive(Clone)]
-pub struct Window {
-    /// The size of the window.
-    pub size: (u32, u32),
-
-    /// The position of the window.
-    pub position: Position,
-
-    /// The minimum size of the window.
-    pub min_size: Option<(u32, u32)>,
-
-    /// The maximum size of the window.
-    pub max_size: Option<(u32, u32)>,
-
-    /// Whether the window should be visible or not.
-    pub visible: bool,
-
-    /// Whether the window should be resizable or not.
-    pub resizable: bool,
-
-    /// Whether the window should have a border, a title bar, etc.
-    pub decorations: bool,
-
-    /// Whether the window should be transparent.
-    pub transparent: bool,
-
-    /// The window [`Level`].
-    pub level: Level,
-
-    /// The window icon, which is also usually used in the taskbar
-    pub icon: Option<Icon>,
-
-    /// Platform specific settings.
-    pub platform_specific: platform::PlatformSpecific,
-}
-
-impl fmt::Debug for Window {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_struct("Window")
-            .field("size", &self.size)
-            .field("position", &self.position)
-            .field("min_size", &self.min_size)
-            .field("max_size", &self.max_size)
-            .field("visible", &self.visible)
-            .field("resizable", &self.resizable)
-            .field("decorations", &self.decorations)
-            .field("transparent", &self.transparent)
-            .field("level", &self.level)
-            .field("icon", &self.icon.is_some())
-            .field("platform_specific", &self.platform_specific)
-            .finish()
-    }
-}
-
-impl Window {
-    /// Converts the window settings into a `WindowBuilder` from `winit`.
-    pub fn into_builder(
-        self,
-        title: &str,
-        primary_monitor: Option<MonitorHandle>,
-        _id: Option<String>,
-    ) -> WindowBuilder {
-        let mut window_builder = WindowBuilder::new();
-
-        let (width, height) = self.size;
-
-        window_builder = window_builder
-            .with_title(title)
-            .with_inner_size(winit::dpi::LogicalSize { width, height })
-            .with_resizable(self.resizable)
-            .with_enabled_buttons(if self.resizable {
-                winit::window::WindowButtons::all()
-            } else {
-                winit::window::WindowButtons::CLOSE
-                    | winit::window::WindowButtons::MINIMIZE
-            })
-            .with_decorations(self.decorations)
-            .with_transparent(self.transparent)
-            .with_window_icon(self.icon.and_then(conversion::icon))
-            .with_window_level(conversion::window_level(self.level))
-            .with_visible(self.visible);
-
-        if let Some(position) = conversion::position(
-            primary_monitor.as_ref(),
-            self.size,
-            self.position,
-        ) {
-            window_builder = window_builder.with_position(position);
-        }
-
-        if let Some((width, height)) = self.min_size {
-            window_builder = window_builder
-                .with_min_inner_size(winit::dpi::LogicalSize { width, height });
-        }
-
-        if let Some((width, height)) = self.max_size {
-            window_builder = window_builder
-                .with_max_inner_size(winit::dpi::LogicalSize { width, height });
-        }
-
-        #[cfg(any(
-            target_os = "dragonfly",
-            target_os = "freebsd",
-            target_os = "netbsd",
-            target_os = "openbsd"
-        ))]
-        {
-            // `with_name` is available on both `WindowBuilderExtWayland` and `WindowBuilderExtX11` and they do
-            // exactly the same thing. We arbitrarily choose `WindowBuilderExtWayland` here.
-            use ::winit::platform::wayland::WindowBuilderExtWayland;
-
-            if let Some(id) = _id {
-                window_builder = window_builder.with_name(id.clone(), id);
-            }
-        }
-
-        #[cfg(target_os = "windows")]
-        {
-            use winit::platform::windows::WindowBuilderExtWindows;
-            #[allow(unsafe_code)]
-            unsafe {
-                window_builder = window_builder
-                    .with_parent_window(self.platform_specific.parent);
-            }
-            window_builder = window_builder
-                .with_drag_and_drop(self.platform_specific.drag_and_drop);
-        }
-
-        #[cfg(target_os = "macos")]
-        {
-            use winit::platform::macos::WindowBuilderExtMacOS;
-
-            window_builder = window_builder
-                .with_title_hidden(self.platform_specific.title_hidden)
-                .with_titlebar_transparent(
-                    self.platform_specific.titlebar_transparent,
-                )
-                .with_fullsize_content_view(
-                    self.platform_specific.fullsize_content_view,
-                );
-        }
-
-        #[cfg(target_os = "linux")]
-        {
-            #[cfg(feature = "x11")]
-            {
-                use winit::platform::x11::WindowBuilderExtX11;
-
-                window_builder = window_builder.with_name(
-                    &self.platform_specific.application_id,
-                    &self.platform_specific.application_id,
-                );
-            }
-            #[cfg(feature = "wayland")]
-            {
-                use winit::platform::wayland::WindowBuilderExtWayland;
-
-                window_builder = window_builder.with_name(
-                    &self.platform_specific.application_id,
-                    &self.platform_specific.application_id,
-                );
-            }
-        }
-
-        window_builder
-    }
-}
-
-impl Default for Window {
-    fn default() -> Window {
-        Window {
-            size: (1024, 768),
-            position: Position::default(),
-            min_size: None,
-            max_size: None,
-            visible: true,
-            resizable: true,
-            decorations: true,
-            transparent: false,
-            level: Level::default(),
-            icon: None,
-            platform_specific: PlatformSpecific::default(),
-        }
-    }
 }