iced/glutin/src/multi_window.rs

//! Create interactive, native cross-platform applications.
use crate::mouse;
use crate::{Error, Executor, Runtime};

pub use iced_winit::multi_window::{self, Application, StyleSheet};

use iced_winit::conversion;
use iced_winit::futures;
use iced_winit::futures::channel::mpsc;
use iced_winit::renderer;
use iced_winit::user_interface;
use iced_winit::window;
use iced_winit::winit;
use iced_winit::{Clipboard, Command, Debug, Proxy, Settings};

use glutin::config::{
    Config, ConfigSurfaceTypes, ConfigTemplateBuilder, GlConfig,
};
use glutin::context::{
    ContextApi, ContextAttributesBuilder, NotCurrentContext,
    NotCurrentGlContextSurfaceAccessor, PossiblyCurrentGlContext,
};
use glutin::display::{Display, DisplayApiPreference, GlDisplay};
use glutin::surface::{GlSurface, SwapInterval};
use raw_window_handle::{HasRawDisplayHandle, HasRawWindowHandle};

use crate::application::gl_surface;
use iced_winit::multi_window::Event;
use std::collections::HashMap;
use std::ffi::CString;
use std::mem::ManuallyDrop;
use std::num::NonZeroU32;

use iced_native::widget::operation;
#[cfg(feature = "tracing")]
use tracing::{info_span, instrument::Instrument};

#[allow(unsafe_code)]
const ONE: NonZeroU32 = unsafe { NonZeroU32::new_unchecked(1) };

/// Runs an [`Application`] with an executor, compositor, and the provided
/// settings.
pub fn run<A, E, C>(
    settings: Settings<A::Flags>,
    compositor_settings: C::Settings,
) -> Result<(), Error>
where
    A: Application + 'static,
    E: Executor + 'static,
    C: iced_graphics::window::GLCompositor<Renderer = A::Renderer> + 'static,
    <A::Renderer as iced_native::Renderer>::Theme: StyleSheet,
{
    use futures::task;
    use futures::Future;
    use winit::event_loop::EventLoopBuilder;
    use winit::platform::run_return::EventLoopExtRunReturn;

    #[cfg(feature = "trace")]
    let _guard = iced_winit::Profiler::init();

    let mut debug = Debug::new();
    debug.startup_started();

    #[cfg(feature = "tracing")]
    let _ = info_span!("Application::Glutin", "RUN").entered();

    let mut event_loop = EventLoopBuilder::with_user_event().build();
    let proxy = event_loop.create_proxy();

    let runtime = {
        let executor = E::new().map_err(Error::ExecutorCreationFailed)?;
        let proxy = Proxy::new(event_loop.create_proxy());

        Runtime::new(executor, proxy)
    };

    let (application, init_command) = {
        let flags = settings.flags;

        runtime.enter(|| A::new(flags))
    };

    let builder = settings.window.into_builder(
        &application.title(window::Id::MAIN),
        event_loop.primary_monitor(),
        settings.id,
    );

    log::info!("Window builder: {:#?}", builder);

    #[allow(unsafe_code)]
    let (display, window, configuration, surface, context) = unsafe {
        struct Configuration(Config);
        use std::fmt;
        impl fmt::Debug for Configuration {
            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
                let config = &self.0;

                f.debug_struct("Configuration")
                    .field("raw", &config)
                    .field("samples", &config.num_samples())
                    .field("buffer_type", &config.color_buffer_type())
                    .field("surface_type", &config.config_surface_types())
                    .field("depth", &config.depth_size())
                    .field("alpha", &config.alpha_size())
                    .field("stencil", &config.stencil_size())
                    .field("float_pixels", &config.float_pixels())
                    .field("srgb", &config.srgb_capable())
                    .field("api", &config.api())
                    .finish()
            }
        }

        impl AsRef<Config> for Configuration {
            fn as_ref(&self) -> &Config {
                &self.0
            }
        }

        let display_handle = event_loop.raw_display_handle();

        #[cfg(all(
            any(windows, target_os = "macos"),
            not(target_arch = "wasm32")
        ))]
        let (window, window_handle) = {
            let window = builder
                .build(&event_loop)
                .map_err(Error::WindowCreationFailed)?;

            let handle = window.raw_window_handle();

            (window, handle)
        };

        #[cfg(target_arch = "wasm32")]
        let preference = Err(Error::GraphicsCreationFailed(
            iced_graphics::Error::BackendError(format!(
                "target not supported by backend"
            )),
        ))?;

        #[cfg(all(windows, not(target_arch = "wasm32")))]
        let preference = DisplayApiPreference::WglThenEgl(Some(window_handle));

        #[cfg(all(target_os = "macos", not(target_arch = "wasm32")))]
        let preference = DisplayApiPreference::Cgl;

        #[cfg(all(
            unix,
            not(target_os = "macos"),
            not(target_arch = "wasm32")
        ))]
        let preference = DisplayApiPreference::GlxThenEgl(Box::new(
            winit::platform::unix::register_xlib_error_hook,
        ));

        let display =
            Display::new(display_handle, preference).map_err(|error| {
                Error::GraphicsCreationFailed(
                    iced_graphics::Error::BackendError(format!(
                        "failed to create display: {error}"
                    )),
                )
            })?;

        log::debug!("Display: {}", display.version_string());

        let samples = C::sample_count(&compositor_settings) as u8;
        let mut template = ConfigTemplateBuilder::new()
            .with_surface_type(ConfigSurfaceTypes::WINDOW);

        if samples != 0 {
            template = template.with_multisampling(samples);
        }

        #[cfg(all(windows, not(target_arch = "wasm32")))]
        let template = template.compatible_with_native_window(window_handle);

        log::debug!("Searching for display configurations");
        let configuration = display
            .find_configs(template.build())
            .map_err(|_| {
                Error::GraphicsCreationFailed(
                    iced_graphics::Error::NoAvailablePixelFormat,
                )
            })?
            .map(Configuration)
            .inspect(|config| {
                log::trace!("{config:#?}");
            })
            .min_by_key(|config| {
                config.as_ref().num_samples().saturating_sub(samples)
            })
            .ok_or(Error::GraphicsCreationFailed(
                iced_graphics::Error::NoAvailablePixelFormat,
            ))?;

        log::debug!("Selected: {configuration:#?}");

        #[cfg(all(
            unix,
            not(target_os = "macos"),
            not(target_arch = "wasm32")
        ))]
        let (window, window_handle) = {
            use glutin::platform::x11::X11GlConfigExt;
            let builder =
                if let Some(visual) = configuration.as_ref().x11_visual() {
                    use winit::platform::unix::WindowBuilderExtUnix;
                    builder.with_x11_visual(visual.into_raw())
                } else {
                    builder
                };

            let window = builder
                .build(&event_loop)
                .map_err(Error::WindowCreationFailed)?;

            let handle = window.raw_window_handle();

            (window, handle)
        };

        let attributes =
            ContextAttributesBuilder::new().build(Some(window_handle));
        let fallback_attributes = ContextAttributesBuilder::new()
            .with_context_api(ContextApi::Gles(None))
            .build(Some(window_handle));

        let context = display
            .create_context(configuration.as_ref(), &attributes)
            .or_else(|_| {
                display.create_context(
                    configuration.as_ref(),
                    &fallback_attributes,
                )
            })
            .map_err(|error| {
                Error::GraphicsCreationFailed(
                    iced_graphics::Error::BackendError(format!(
                        "failed to create context: {error}"
                    )),
                )
            })?;

        let surface = gl_surface(&display, configuration.as_ref(), &window)
            .map_err(|error| {
                Error::GraphicsCreationFailed(
                    iced_graphics::Error::BackendError(format!(
                        "failed to create surface: {error}"
                    )),
                )
            })?;

        (display, window, configuration.0, surface, context)
    };

    let windows: HashMap<window::Id, winit::window::Window> =
        HashMap::from([(window::Id::MAIN, window)]);

    // need to make context current before trying to load GL functions
    let context = context
        .make_current(&surface)
        .expect("Make context current.");

    #[allow(unsafe_code)]
    let (compositor, renderer) = unsafe {
        C::new(compositor_settings, |address| {
            let address = CString::new(address).expect("address error");
            display.get_proc_address(address.as_c_str())
        })?
    };

    let context = context.make_not_current().expect("Make not current.");

    let (mut sender, receiver) = mpsc::unbounded();

    let mut instance = Box::pin({
        let run_instance = run_instance::<A, E, C>(
            application,
            compositor,
            renderer,
            runtime,
            proxy,
            debug,
            receiver,
            display,
            windows,
            configuration,
            context,
            init_command,
            settings.exit_on_close_request,
        );

        #[cfg(feature = "tracing")]
        let run_instance =
            run_instance.instrument(info_span!("Application", "LOOP"));

        run_instance
    });

    let mut context = task::Context::from_waker(task::noop_waker_ref());

    let _ = event_loop.run_return(move |event, event_loop, control_flow| {
        use winit::event_loop::ControlFlow;

        if let ControlFlow::ExitWithCode(_) = control_flow {
            return;
        }

        let event = match event {
            winit::event::Event::WindowEvent {
                event:
                    winit::event::WindowEvent::ScaleFactorChanged {
                        new_inner_size,
                        ..
                    },
                window_id,
            } => Some(winit::event::Event::WindowEvent {
                event: winit::event::WindowEvent::Resized(*new_inner_size),
                window_id,
            }),
            winit::event::Event::UserEvent(Event::NewWindow {
                id,
                settings,
                title,
            }) => {
                let window = settings
                    .into_builder(&title, event_loop.primary_monitor(), None)
                    .build(event_loop)
                    .expect("Failed to build window");

                Some(winit::event::Event::UserEvent(Event::WindowCreated(
                    id, window,
                )))
            }
            _ => event.to_static(),
        };

        if let Some(event) = event {
            sender.start_send(event).expect("Send event");

            let poll = instance.as_mut().poll(&mut context);

            *control_flow = match poll {
                task::Poll::Pending => ControlFlow::Wait,
                task::Poll::Ready(_) => ControlFlow::Exit,
            };
        }
    });

    Ok(())
}

async fn run_instance<A, E, C>(
    mut application: A,
    mut compositor: C,
    mut renderer: A::Renderer,
    mut runtime: Runtime<E, Proxy<Event<A::Message>>, Event<A::Message>>,
    mut proxy: winit::event_loop::EventLoopProxy<Event<A::Message>>,
    mut debug: Debug,
    mut receiver: mpsc::UnboundedReceiver<
        winit::event::Event<'_, Event<A::Message>>,
    >,
    display: Display,
    mut windows: HashMap<window::Id, winit::window::Window>,
    configuration: Config,
    mut context: NotCurrentContext,
    init_command: Command<A::Message>,
    _exit_on_close_request: bool,
) where
    A: Application + 'static,
    E: Executor + 'static,
    C: iced_graphics::window::GLCompositor<Renderer = A::Renderer> + 'static,
    <A::Renderer as iced_native::Renderer>::Theme: StyleSheet,
{
    use iced_winit::futures::stream::StreamExt;
    use winit::event;

    let mut clipboard =
        Clipboard::connect(windows.values().next().expect("No window found"));
    let mut caches = HashMap::new();
    let mut current_context_window = None;
    let mut window_ids: HashMap<_, _> = windows
        .iter()
        .map(|(&id, window)| (window.id(), id))
        .collect();
    let mut states = HashMap::new();
    let mut surfaces = HashMap::new();
    let mut interfaces = ManuallyDrop::new(HashMap::new());

    for (&id, window) in windows.keys().zip(windows.values()) {
        let surface = gl_surface(&display, &configuration, &window)
            .expect("Create surface.");
        let current_context =
            context.make_current(&surface).expect("Make current.");
        let state = multi_window::State::new(&application, id, &window);
        let physical_size = state.physical_size();

        surface.resize(
            &current_context,
            NonZeroU32::new(physical_size.width).unwrap_or(ONE),
            NonZeroU32::new(physical_size.height).unwrap_or(ONE),
        );

        let user_interface = multi_window::build_user_interface(
            &application,
            user_interface::Cache::default(),
            &mut renderer,
            state.logical_size(),
            &mut debug,
            id,
        );

        context = current_context
            .make_not_current()
            .expect("Make not current.");

        let _ = states.insert(id, state);
        let _ = surfaces.insert(id, surface);
        let _ = interfaces.insert(id, user_interface);
    }

    run_command(
        &application,
        &mut caches,
        &states,
        &mut renderer,
        init_command,
        &mut runtime,
        &mut clipboard,
        &mut proxy,
        &mut debug,
        &windows,
        || compositor.fetch_information(),
    );

    runtime.track(application.subscription().map(Event::Application));

    let mut mouse_interaction = mouse::Interaction::default();
    let mut events = Vec::new();
    let mut messages = Vec::new();

    debug.startup_finished();

    'main: while let Some(event) = receiver.next().await {
        match event {
            event::Event::MainEventsCleared => {
                for id in windows.keys().copied() {
                    let (filtered, remaining): (Vec<_>, Vec<_>) =
                        events.iter().cloned().partition(
                            |(window_id, _event): &(
                                Option<window::Id>,
                                iced_native::event::Event,
                            )| {
                                *window_id == Some(id) || *window_id == None
                            },
                        );

                    events.retain(|el| remaining.contains(el));
                    let filtered: Vec<_> = filtered
                        .into_iter()
                        .map(|(_id, event)| event)
                        .collect();

                    let cursor_position =
                        states.get(&id).unwrap().cursor_position();
                    let window = windows.get(&id).unwrap();

                    if filtered.is_empty() && messages.is_empty() {
                        continue;
                    }

                    debug.event_processing_started();

                    let (interface_state, statuses) = {
                        let user_interface = interfaces.get_mut(&id).unwrap();
                        user_interface.update(
                            &filtered,
                            cursor_position,
                            &mut renderer,
                            &mut clipboard,
                            &mut messages,
                        )
                    };

                    debug.event_processing_finished();

                    for event in filtered.into_iter().zip(statuses.into_iter())
                    {
                        runtime.broadcast(event);
                    }

                    if !messages.is_empty()
                        || matches!(
                            interface_state,
                            user_interface::State::Outdated
                        )
                    {
                        let user_interfaces: HashMap<_, _> =
                            ManuallyDrop::into_inner(interfaces)
                                .drain()
                                .map(|(id, interface)| {
                                    (id, interface.into_cache())
                                })
                                .collect();

                        // Update application
                        update(
                            &mut application,
                            &mut caches,
                            &states,
                            &mut renderer,
                            &mut runtime,
                            &mut clipboard,
                            &mut proxy,
                            &mut debug,
                            &mut messages,
                            &windows,
                            || compositor.fetch_information(),
                        );

                        // Update window
                        states.get_mut(&id).unwrap().synchronize(
                            &application,
                            id,
                            windows.get(&id).expect("No window found with ID."),
                        );

                        let should_exit = application.should_exit();

                        interfaces = ManuallyDrop::new(build_user_interfaces(
                            &application,
                            &mut renderer,
                            &mut debug,
                            &states,
                            user_interfaces,
                        ));

                        if should_exit {
                            break 'main;
                        }
                    }

                    debug.draw_started();
                    let new_mouse_interaction = {
                        let user_interface = interfaces.get_mut(&id).unwrap();
                        let state = states.get(&id).unwrap();

                        user_interface.draw(
                            &mut renderer,
                            state.theme(),
                            &renderer::Style {
                                text_color: state.text_color(),
                            },
                            state.cursor_position(),
                        )
                    };
                    debug.draw_finished();

                    if new_mouse_interaction != mouse_interaction {
                        window.set_cursor_icon(conversion::mouse_interaction(
                            new_mouse_interaction,
                        ));

                        mouse_interaction = new_mouse_interaction;
                    }

                    window.request_redraw();
                }
            }
            event::Event::PlatformSpecific(event::PlatformSpecific::MacOS(
                event::MacOS::ReceivedUrl(url),
            )) => {
                use iced_native::event;
                events.push((
                    None,
                    iced_native::Event::PlatformSpecific(
                        event::PlatformSpecific::MacOS(
                            event::MacOS::ReceivedUrl(url),
                        ),
                    ),
                ));
            }
            event::Event::UserEvent(event) => match event {
                Event::Application(message) => messages.push(message),
                Event::WindowCreated(id, window) => {
                    let state =
                        multi_window::State::new(&application, id, &window);
                    let user_interface = multi_window::build_user_interface(
                        &application,
                        user_interface::Cache::default(),
                        &mut renderer,
                        state.logical_size(),
                        &mut debug,
                        id,
                    );

                    let surface = gl_surface(&display, &configuration, &window)
                        .expect("Create surface.");

                    let _ = states.insert(id, state);
                    let _ = interfaces.insert(id, user_interface);
                    let _ = window_ids.insert(window.id(), id);
                    let _ = windows.insert(id, window);
                    let _ = surfaces.insert(id, surface);
                }
                Event::CloseWindow(id) => {
                    // TODO(derezzedex): log errors
                    if let Some(window) = windows.get(&id) {
                        if window_ids.remove(&window.id()).is_none() {
                            println!("Failed to remove from `window_ids`!");
                        }
                    }
                    if states.remove(&id).is_none() {
                        println!("Failed to remove from `states`!")
                    }
                    if interfaces.remove(&id).is_none() {
                        println!("Failed to remove from `interfaces`!");
                    }
                    if surfaces.remove(&id).is_none() {
                        println!("Failed to remove from `surfaces`!")
                    }
                    if windows.remove(&id).is_none() {
                        println!("Failed to remove from `windows`!")
                    }

                    if windows.is_empty() {
                        break 'main;
                    }
                }
                Event::NewWindow { .. } => unreachable!(),
            },
            event::Event::RedrawRequested(id) => {
                #[cfg(feature = "tracing")]
                let _ = info_span!("Application", "FRAME").entered();

                let state = window_ids
                    .get(&id)
                    .and_then(|id| states.get_mut(id))
                    .unwrap();
                let window =
                    window_ids.get(&id).and_then(|id| windows.get(id)).unwrap();

                let surface = window_ids
                    .get(&id)
                    .and_then(|id| surfaces.get(id))
                    .unwrap();

                debug.render_started();

                let current_context =
                    context.make_current(&surface).expect("Make current.");

                if current_context_window != Some(id) {
                    current_context_window = Some(id);
                }

                if state.viewport_changed() {
                    let physical_size = state.physical_size();
                    let logical_size = state.logical_size();

                    let mut user_interface = window_ids
                        .get(&id)
                        .and_then(|id| interfaces.remove(id))
                        .unwrap();

                    debug.layout_started();
                    user_interface =
                        user_interface.relayout(logical_size, &mut renderer);
                    debug.layout_finished();

                    debug.draw_started();
                    let new_mouse_interaction = user_interface.draw(
                        &mut renderer,
                        state.theme(),
                        &renderer::Style {
                            text_color: state.text_color(),
                        },
                        state.cursor_position(),
                    );
                    debug.draw_finished();

                    if new_mouse_interaction != mouse_interaction {
                        window.set_cursor_icon(conversion::mouse_interaction(
                            new_mouse_interaction,
                        ));

                        mouse_interaction = new_mouse_interaction;
                    }

                    surface.resize(
                        &current_context,
                        NonZeroU32::new(physical_size.width).unwrap_or(ONE),
                        NonZeroU32::new(physical_size.height).unwrap_or(ONE),
                    );

                    if let Err(_) = surface.set_swap_interval(
                        &current_context,
                        SwapInterval::Wait(ONE),
                    ) {
                        log::error!("Could not set swap interval for surface attached to window id: {:?}", id);
                    }

                    compositor.resize_viewport(physical_size);

                    let _ = interfaces
                        .insert(*window_ids.get(&id).unwrap(), user_interface);
                }

                compositor.present(
                    &mut renderer,
                    state.viewport(),
                    state.background_color(),
                    &debug.overlay(),
                );

                surface
                    .swap_buffers(&current_context)
                    .expect("Swap buffers");

                context = current_context
                    .make_not_current()
                    .expect("Make not current.");
                debug.render_finished();
                // TODO: Handle animations!
                // Maybe we can use `ControlFlow::WaitUntil` for this.
            }
            event::Event::WindowEvent {
                event: window_event,
                window_id,
            } => {
                // dbg!(window_id);
                if let Some(window) =
                    window_ids.get(&window_id).and_then(|id| windows.get(id))
                {
                    if let Some(state) = window_ids
                        .get(&window_id)
                        .and_then(|id| states.get_mut(id))
                    {
                        if multi_window::requests_exit(
                            &window_event,
                            state.modifiers(),
                        ) {
                            if let Some(id) =
                                window_ids.get(&window_id).cloned()
                            {
                                let message = application.close_requested(id);
                                messages.push(message);
                            }
                        }

                        state.update(window, &window_event, &mut debug);

                        if let Some(event) = conversion::window_event(
                            *window_ids.get(&window_id).unwrap(),
                            &window_event,
                            state.scale_factor(),
                            state.modifiers(),
                        ) {
                            events.push((
                                window_ids.get(&window_id).cloned(),
                                event,
                            ));
                        }
                    } else {
                        log::error!(
                            "Window state not found for id: {:?}",
                            window_id
                        );
                    }
                } else {
                    log::error!("Window not found for id: {:?}", window_id);
                }
            }
            _ => {}
        }
    }

    // Manually drop the user interface
    // drop(ManuallyDrop::into_inner(user_interface));
}

/// Updates an [`Application`] by feeding it the provided messages, spawning any
/// resulting [`Command`], and tracking its [`Subscription`].
pub fn update<A: Application, E: Executor>(
    application: &mut A,
    caches: &mut HashMap<window::Id, user_interface::Cache>,
    states: &HashMap<window::Id, multi_window::State<A>>,
    renderer: &mut A::Renderer,
    runtime: &mut Runtime<E, Proxy<Event<A::Message>>, Event<A::Message>>,
    clipboard: &mut Clipboard,
    proxy: &mut winit::event_loop::EventLoopProxy<Event<A::Message>>,
    debug: &mut Debug,
    messages: &mut Vec<A::Message>,
    windows: &HashMap<window::Id, winit::window::Window>,
    graphics_info: impl FnOnce() -> iced_graphics::compositor::Information + Copy,
) where
    A: Application + 'static,
    <A::Renderer as crate::Renderer>::Theme: StyleSheet,
{
    for message in messages.drain(..) {
        debug.log_message(&message);

        debug.update_started();
        let command = runtime.enter(|| application.update(message));
        debug.update_finished();

        run_command(
            application,
            caches,
            &states,
            renderer,
            command,
            runtime,
            clipboard,
            proxy,
            debug,
            windows,
            graphics_info,
        );
    }

    let subscription = application.subscription().map(Event::Application);
    runtime.track(subscription);
}

/// Runs the actions of a [`Command`].
pub fn run_command<A, E>(
    application: &A,
    caches: &mut HashMap<window::Id, user_interface::Cache>,
    states: &HashMap<window::Id, multi_window::State<A>>,
    renderer: &mut A::Renderer,
    command: Command<A::Message>,
    runtime: &mut Runtime<E, Proxy<Event<A::Message>>, Event<A::Message>>,
    clipboard: &mut Clipboard,
    proxy: &mut winit::event_loop::EventLoopProxy<Event<A::Message>>,
    debug: &mut Debug,
    windows: &HashMap<window::Id, winit::window::Window>,
    _graphics_info: impl FnOnce() -> iced_graphics::compositor::Information + Copy,
) where
    A: Application + 'static,
    E: Executor,
    <A::Renderer as crate::Renderer>::Theme: StyleSheet,
{
    use iced_native::command;
    use iced_native::system;
    use iced_native::window;
    use iced_winit::clipboard;
    use iced_winit::futures::FutureExt;

    for action in command.actions() {
        match action {
            command::Action::Future(future) => {
                runtime.spawn(Box::pin(future.map(Event::Application)));
            }
            command::Action::Clipboard(action) => match action {
                clipboard::Action::Read(tag) => {
                    let message = tag(clipboard.read());

                    proxy
                        .send_event(Event::Application(message))
                        .expect("Send message to event loop");
                }
                clipboard::Action::Write(contents) => {
                    clipboard.write(contents);
                }
            },
            command::Action::Window(id, action) => match action {
                window::Action::Spawn { settings } => {
                    proxy
                        .send_event(Event::NewWindow {
                            id,
                            settings: settings.into(),
                            title: application.title(id),
                        })
                        .expect("Send message to event loop");
                }
                window::Action::Close => {
                    proxy
                        .send_event(Event::CloseWindow(id))
                        .expect("Send message to event loop");
                }
                window::Action::Drag => {
                    let window = windows.get(&id).expect("No window found");
                    let _res = window.drag_window();
                }
                window::Action::Resize { width, height } => {
                    let window = windows.get(&id).expect("No window found");
                    window.set_inner_size(winit::dpi::LogicalSize {
                        width,
                        height,
                    });
                }
                window::Action::Move { x, y } => {
                    let window = windows.get(&id).expect("No window found");
                    window.set_outer_position(winit::dpi::LogicalPosition {
                        x,
                        y,
                    });
                }
                window::Action::ChangeMode(mode) => {
                    let window = windows.get(&id).expect("No window found");
                    window.set_visible(conversion::visible(mode));
                    window.set_fullscreen(conversion::fullscreen(
                        window.primary_monitor(),
                        mode,
                    ));
                }
                window::Action::FetchMode(tag) => {
                    let window = windows.get(&id).expect("No window found");
                    let mode = if window.is_visible().unwrap_or(true) {
                        conversion::mode(window.fullscreen())
                    } else {
                        window::Mode::Hidden
                    };

                    proxy
                        .send_event(Event::Application(tag(mode)))
                        .expect("Send message to event loop");
                }
                window::Action::Maximize(value) => {
                    let window = windows.get(&id).expect("No window found!");
                    window.set_maximized(value);
                }
                window::Action::Minimize(value) => {
                    let window = windows.get(&id).expect("No window found!");
                    window.set_minimized(value);
                }
                window::Action::ToggleMaximize => {
                    let window = windows.get(&id).expect("No window found!");
                    window.set_maximized(!window.is_maximized());
                }
                window::Action::ToggleDecorations => {
                    let window = windows.get(&id).expect("No window found!");
                    window.set_decorations(!window.is_decorated());
                }
                window::Action::RequestUserAttention(attention_type) => {
                    let window = windows.get(&id).expect("No window found!");
                    window.request_user_attention(
                        attention_type.map(conversion::user_attention),
                    );
                }
                window::Action::GainFocus => {
                    let window = windows.get(&id).expect("No window found!");
                    window.focus_window();
                }
                window::Action::ChangeAlwaysOnTop(on_top) => {
                    let window = windows.get(&id).expect("No window found!");
                    window.set_always_on_top(on_top);
                }
                window::Action::FetchId(tag) => {
                    let window = windows.get(&id).expect("No window found!");

                    proxy
                        .send_event(Event::Application(tag(window.id().into())))
                        .expect("Send message to event loop.")
                }
            },
            command::Action::System(action) => match action {
                system::Action::QueryInformation(_tag) => {
                    #[cfg(feature = "iced_winit/system")]
                    {
                        let graphics_info = _graphics_info();
                        let proxy = proxy.clone();

                        let _ = std::thread::spawn(move || {
                            let information =
                                crate::system::information(graphics_info);

                            let message = _tag(information);

                            proxy
                                .send_event(Event::Application(message))
                                .expect("Send message to event loop")
                        });
                    }
                }
            },
            command::Action::Widget(action) => {
                let mut current_caches = std::mem::take(caches);
                let mut current_operation = Some(action.into_operation());

                let mut user_interfaces = multi_window::build_user_interfaces(
                    application,
                    renderer,
                    debug,
                    states,
                    current_caches,
                );

                while let Some(mut operation) = current_operation.take() {
                    for user_interface in user_interfaces.values_mut() {
                        user_interface.operate(renderer, operation.as_mut());

                        match operation.finish() {
                            operation::Outcome::None => {}
                            operation::Outcome::Some(message) => {
                                proxy
                                    .send_event(Event::Application(message))
                                    .expect("Send message to event loop");
                            }
                            operation::Outcome::Chain(next) => {
                                current_operation = Some(next);
                            }
                        }
                    }
                }

                let user_interfaces: HashMap<_, _> = user_interfaces
                    .drain()
                    .map(|(id, interface)| (id, interface.into_cache()))
                    .collect();

                current_caches = user_interfaces;
                *caches = current_caches;
            }
        }
    }
}

/// TODO(derezzedex)
pub fn build_user_interfaces<'a, A>(
    application: &'a A,
    renderer: &mut A::Renderer,
    debug: &mut Debug,
    states: &HashMap<window::Id, multi_window::State<A>>,
    mut user_interfaces: HashMap<window::Id, user_interface::Cache>,
) -> HashMap<
    window::Id,
    iced_winit::UserInterface<
        'a,
        <A as Application>::Message,
        <A as Application>::Renderer,
    >,
>
where
    A: Application + 'static,
    <A::Renderer as crate::Renderer>::Theme: StyleSheet,
{
    let mut interfaces = HashMap::new();

    for (id, pure_state) in user_interfaces.drain() {
        let state = &states.get(&id).unwrap();

        let user_interface = multi_window::build_user_interface(
            application,
            pure_state,
            renderer,
            state.logical_size(),
            debug,
            id,
        );

        let _ = interfaces.insert(id, user_interface);
    }

    interfaces
}