winit/src/platform_impl/linux/wayland/event_loop/mod.rs

//! The event-loop routines.

use std::cell::RefCell;
use std::error::Error;
use std::io::Result as IOResult;
use std::marker::PhantomData;
use std::mem;
use std::process;
use std::rc::Rc;
use std::sync::atomic::Ordering;
use std::time::{Duration, Instant};

use raw_window_handle::{RawDisplayHandle, WaylandDisplayHandle};

use sctk::reexports::calloop;
use sctk::reexports::client::globals;
use sctk::reexports::client::{Connection, Proxy, QueueHandle, WaylandSource};

use crate::dpi::{LogicalSize, PhysicalSize};
use crate::event::{Event, StartCause, WindowEvent};
use crate::event_loop::{ControlFlow, EventLoopWindowTarget as RootEventLoopWindowTarget};
use crate::platform_impl::platform::sticky_exit_callback;
use crate::platform_impl::EventLoopWindowTarget as PlatformEventLoopWindowTarget;

mod proxy;
pub mod sink;

pub use proxy::EventLoopProxy;
use sink::EventSink;

use super::state::{WindowCompositorUpdate, WinitState};
use super::{DeviceId, WindowId};

type WaylandDispatcher = calloop::Dispatcher<'static, WaylandSource<WinitState>, WinitState>;

/// The Wayland event loop.
pub struct EventLoop<T: 'static> {
    /// Sender of user events.
    user_events_sender: calloop::channel::Sender<T>,

    // XXX can't remove RefCell out of here, unless we can plumb generics into the `Window`, which
    // we don't really want, since it'll break public API by a lot.
    /// Pending events from the user.
    pending_user_events: Rc<RefCell<Vec<T>>>,

    /// The Wayland dispatcher to has raw access to the queue when needed, such as
    /// when creating a new window.
    wayland_dispatcher: WaylandDispatcher,

    /// Connection to the wayland server.
    connection: Connection,

    /// Event loop window target.
    window_target: RootEventLoopWindowTarget<T>,

    // XXX drop after everything else, just to be safe.
    /// Calloop's event loop.
    event_loop: calloop::EventLoop<'static, WinitState>,
}

impl<T: 'static> EventLoop<T> {
    pub fn new() -> Result<EventLoop<T>, Box<dyn Error>> {
        let connection = Connection::connect_to_env()?;

        let (globals, mut event_queue) = globals::registry_queue_init(&connection)?;
        let queue_handle = event_queue.handle();

        let event_loop = calloop::EventLoop::<WinitState>::try_new()?;

        let mut winit_state = WinitState::new(&globals, &queue_handle, event_loop.handle())?;

        // NOTE: do a roundtrip after binding the globals to prevent potential
        // races with the server.
        event_queue.roundtrip(&mut winit_state)?;

        // Register Wayland source.
        let wayland_source = WaylandSource::new(event_queue)?;
        let wayland_dispatcher =
            calloop::Dispatcher::new(wayland_source, |_, queue, winit_state| {
                queue.dispatch_pending(winit_state)
            });

        event_loop
            .handle()
            .register_dispatcher(wayland_dispatcher.clone())?;

        // Setup the user proxy.
        let pending_user_events = Rc::new(RefCell::new(Vec::new()));
        let pending_user_events_clone = pending_user_events.clone();
        let (user_events_sender, user_events_channel) = calloop::channel::channel();
        event_loop
            .handle()
            .insert_source(user_events_channel, move |event, _, _| {
                if let calloop::channel::Event::Msg(msg) = event {
                    pending_user_events_clone.borrow_mut().push(msg);
                }
            })?;

        // An event's loop awakener to wake up for window events from winit's windows.
        let (event_loop_awakener, event_loop_awakener_source) = calloop::ping::make_ping()?;
        event_loop
            .handle()
            .insert_source(event_loop_awakener_source, move |_, _, _| {
                // No extra handling is required, we just need to wake-up.
            })?;

        let window_target = EventLoopWindowTarget {
            connection: connection.clone(),
            wayland_dispatcher: wayland_dispatcher.clone(),
            event_loop_awakener,
            queue_handle,
            state: RefCell::new(winit_state),
            _marker: PhantomData,
        };

        let event_loop = Self {
            connection,
            wayland_dispatcher,
            user_events_sender,
            pending_user_events,
            event_loop,
            window_target: RootEventLoopWindowTarget {
                p: PlatformEventLoopWindowTarget::Wayland(window_target),
                _marker: PhantomData,
            },
        };

        Ok(event_loop)
    }

    pub fn run<F>(mut self, callback: F) -> !
    where
        F: FnMut(Event<'_, T>, &RootEventLoopWindowTarget<T>, &mut ControlFlow) + 'static,
    {
        let exit_code = self.run_return(callback);
        process::exit(exit_code);
    }

    pub fn run_return<F>(&mut self, mut callback: F) -> i32
    where
        F: FnMut(Event<'_, T>, &RootEventLoopWindowTarget<T>, &mut ControlFlow),
    {
        let mut control_flow = ControlFlow::Poll;

        // XXX preallocate certian structures to avoid allocating on each loop iteration.
        let mut window_ids = Vec::<WindowId>::new();
        let mut compositor_updates = Vec::<WindowCompositorUpdate>::new();
        let mut buffer_sink = EventSink::new();

        callback(
            Event::NewEvents(StartCause::Init),
            &self.window_target,
            &mut control_flow,
        );

        // XXX For consistency all platforms must emit a 'Resumed' event even though Wayland
        // applications don't themselves have a formal suspend/resume lifecycle.
        callback(Event::Resumed, &self.window_target, &mut control_flow);

        // XXX We break on errors from dispatches, since if we've got protocol error
        // libwayland-client/wayland-rs will inform us anyway, but crashing downstream is not
        // really an option. Instead we inform that the event loop got destroyed. We may
        // communicate an error that something was terminated, but winit doesn't provide us
        // with an API to do that via some event.
        // Still, we set the exit code to the error's OS error code, or to 1 if not possible.
        let exit_code = loop {
            // Flush the connection.
            let _ = self.connection.flush();

            // During the run of the user callback, some other code monitoring and reading the
            // Wayland socket may have been run (mesa for example does this with vsync), if that
            // is the case, some events may have been enqueued in our event queue.
            //
            // If some messages are there, the event loop needs to behave as if it was instantly
            // woken up by messages arriving from the Wayland socket, to avoid delaying the
            // dispatch of these events until we're woken up again.
            let instant_wakeup = {
                let mut wayland_source = self.wayland_dispatcher.as_source_mut();
                let queue = wayland_source.queue();
                let state = match &mut self.window_target.p {
                    PlatformEventLoopWindowTarget::Wayland(window_target) => {
                        window_target.state.get_mut()
                    }
                    #[cfg(x11_platform)]
                    _ => unreachable!(),
                };

                match queue.dispatch_pending(state) {
                    Ok(dispatched) => dispatched > 0,
                    Err(error) => {
                        error!("Error dispatching wayland queue: {}", error);
                        break 1;
                    }
                }
            };

            match control_flow {
                ControlFlow::ExitWithCode(code) => break code,
                ControlFlow::Poll => {
                    // Non-blocking dispatch.
                    let timeout = Duration::ZERO;
                    if let Err(error) = self.loop_dispatch(Some(timeout)) {
                        break error.raw_os_error().unwrap_or(1);
                    }

                    callback(
                        Event::NewEvents(StartCause::Poll),
                        &self.window_target,
                        &mut control_flow,
                    );
                }
                ControlFlow::Wait => {
                    let timeout = if instant_wakeup {
                        Some(Duration::ZERO)
                    } else {
                        None
                    };

                    if let Err(error) = self.loop_dispatch(timeout) {
                        break error.raw_os_error().unwrap_or(1);
                    }

                    callback(
                        Event::NewEvents(StartCause::WaitCancelled {
                            start: Instant::now(),
                            requested_resume: None,
                        }),
                        &self.window_target,
                        &mut control_flow,
                    );
                }
                ControlFlow::WaitUntil(deadline) => {
                    let start = Instant::now();

                    // Compute the amount of time we'll block for.
                    let duration = if deadline > start && !instant_wakeup {
                        deadline - start
                    } else {
                        Duration::ZERO
                    };

                    if let Err(error) = self.loop_dispatch(Some(duration)) {
                        break error.raw_os_error().unwrap_or(1);
                    }

                    let now = Instant::now();

                    if now < deadline {
                        callback(
                            Event::NewEvents(StartCause::WaitCancelled {
                                start,
                                requested_resume: Some(deadline),
                            }),
                            &self.window_target,
                            &mut control_flow,
                        )
                    } else {
                        callback(
                            Event::NewEvents(StartCause::ResumeTimeReached {
                                start,
                                requested_resume: deadline,
                            }),
                            &self.window_target,
                            &mut control_flow,
                        )
                    }
                }
            }

            // Handle pending user events. We don't need back buffer, since we can't dispatch
            // user events indirectly via callback to the user.
            for user_event in self.pending_user_events.borrow_mut().drain(..) {
                sticky_exit_callback(
                    Event::UserEvent(user_event),
                    &self.window_target,
                    &mut control_flow,
                    &mut callback,
                );
            }

            // Drain the pending compositor updates.
            self.with_state(|state| {
                compositor_updates.append(&mut state.window_compositor_updates)
            });

            for mut compositor_update in compositor_updates.drain(..) {
                let window_id = compositor_update.window_id;
                if let Some(scale_factor) = compositor_update.scale_factor {
                    let mut physical_size = self.with_state(|state| {
                        let windows = state.windows.get_mut();
                        let mut window = windows.get(&window_id).unwrap().lock().unwrap();

                        // Set the new scale factor.
                        window.set_scale_factor(scale_factor);
                        let window_size = compositor_update.size.unwrap_or(window.inner_size());
                        logical_to_physical_rounded(window_size, scale_factor)
                    });

                    // Stash the old window size.
                    let old_physical_size = physical_size;

                    sticky_exit_callback(
                        Event::WindowEvent {
                            window_id: crate::window::WindowId(window_id),
                            event: WindowEvent::ScaleFactorChanged {
                                scale_factor,
                                new_inner_size: &mut physical_size,
                            },
                        },
                        &self.window_target,
                        &mut control_flow,
                        &mut callback,
                    );

                    let new_logical_size = physical_size.to_logical(scale_factor);

                    // Resize the window when user altered the size.
                    if old_physical_size != physical_size {
                        self.with_state(|state| {
                            let windows = state.windows.get_mut();
                            let mut window = windows.get(&window_id).unwrap().lock().unwrap();
                            window.resize(new_logical_size);
                        });
                    }

                    // Make it queue resize.
                    compositor_update.size = Some(new_logical_size);
                }

                if let Some(size) = compositor_update.size.take() {
                    let physical_size = self.with_state(|state| {
                        let windows = state.windows.get_mut();
                        let window = windows.get(&window_id).unwrap().lock().unwrap();

                        let scale_factor = window.scale_factor();
                        let physical_size = logical_to_physical_rounded(size, scale_factor);

                        // TODO could probably bring back size reporting optimization.

                        // Mark the window as needed a redraw.
                        state
                            .window_requests
                            .get_mut()
                            .get_mut(&window_id)
                            .unwrap()
                            .redraw_requested
                            .store(true, Ordering::Relaxed);

                        physical_size
                    });

                    sticky_exit_callback(
                        Event::WindowEvent {
                            window_id: crate::window::WindowId(window_id),
                            event: WindowEvent::Resized(physical_size),
                        },
                        &self.window_target,
                        &mut control_flow,
                        &mut callback,
                    );
                }

                if compositor_update.close_window {
                    sticky_exit_callback(
                        Event::WindowEvent {
                            window_id: crate::window::WindowId(window_id),
                            event: WindowEvent::CloseRequested,
                        },
                        &self.window_target,
                        &mut control_flow,
                        &mut callback,
                    );
                }
            }

            // Push the events directly from the window.
            self.with_state(|state| {
                buffer_sink.append(&mut state.window_events_sink.lock().unwrap());
            });
            for event in buffer_sink.drain() {
                let event = event.map_nonuser_event().unwrap();
                sticky_exit_callback(event, &self.window_target, &mut control_flow, &mut callback);
            }

            // Handle non-synthetic events.
            self.with_state(|state| {
                buffer_sink.append(&mut state.events_sink);
            });
            for event in buffer_sink.drain() {
                let event = event.map_nonuser_event().unwrap();
                sticky_exit_callback(event, &self.window_target, &mut control_flow, &mut callback);
            }

            // Send events cleared.
            sticky_exit_callback(
                Event::MainEventsCleared,
                &self.window_target,
                &mut control_flow,
                &mut callback,
            );

            // Collect the window ids
            self.with_state(|state| {
                window_ids.extend(state.window_requests.get_mut().keys());
            });

            for window_id in window_ids.drain(..) {
                let request_redraw = self.with_state(|state| {
                    let window_requests = state.window_requests.get_mut();
                    if window_requests.get(&window_id).unwrap().take_closed() {
                        mem::drop(window_requests.remove(&window_id));
                        mem::drop(state.windows.get_mut().remove(&window_id));
                        false
                    } else {
                        let mut redraw_requested = window_requests
                            .get(&window_id)
                            .unwrap()
                            .take_redraw_requested();

                        // Redraw the frames while at it.
                        redraw_requested |= state
                            .windows
                            .get_mut()
                            .get_mut(&window_id)
                            .unwrap()
                            .lock()
                            .unwrap()
                            .refresh_frame();

                        redraw_requested
                    }
                });

                if request_redraw {
                    sticky_exit_callback(
                        Event::RedrawRequested(crate::window::WindowId(window_id)),
                        &self.window_target,
                        &mut control_flow,
                        &mut callback,
                    );
                }
            }

            // Send RedrawEventCleared.
            sticky_exit_callback(
                Event::RedrawEventsCleared,
                &self.window_target,
                &mut control_flow,
                &mut callback,
            );
        };

        callback(Event::LoopDestroyed, &self.window_target, &mut control_flow);
        exit_code
    }

    #[inline]
    pub fn create_proxy(&self) -> EventLoopProxy<T> {
        EventLoopProxy::new(self.user_events_sender.clone())
    }

    #[inline]
    pub fn window_target(&self) -> &RootEventLoopWindowTarget<T> {
        &self.window_target
    }

    fn with_state<'a, U: 'a, F: FnOnce(&'a mut WinitState) -> U>(&'a mut self, callback: F) -> U {
        let state = match &mut self.window_target.p {
            PlatformEventLoopWindowTarget::Wayland(window_target) => window_target.state.get_mut(),
            #[cfg(x11_platform)]
            _ => unreachable!(),
        };

        callback(state)
    }

    fn loop_dispatch<D: Into<Option<std::time::Duration>>>(&mut self, timeout: D) -> IOResult<()> {
        let state = match &mut self.window_target.p {
            PlatformEventLoopWindowTarget::Wayland(window_target) => window_target.state.get_mut(),
            #[cfg(feature = "x11")]
            _ => unreachable!(),
        };

        self.event_loop.dispatch(timeout, state).map_err(|error| {
            error!("Error dispatching event loop: {}", error);
            error.into()
        })
    }
}

pub struct EventLoopWindowTarget<T> {
    /// The event loop wakeup source.
    pub event_loop_awakener: calloop::ping::Ping,

    /// The main queue used by the event loop.
    pub queue_handle: QueueHandle<WinitState>,

    // TODO remove that RefCell once we can pass `&mut` in `Window::new`.
    /// Winit state.
    pub state: RefCell<WinitState>,

    /// Dispatcher of Wayland events.
    pub wayland_dispatcher: WaylandDispatcher,

    /// Connection to the wayland server.
    pub connection: Connection,

    _marker: std::marker::PhantomData<T>,
}

impl<T> EventLoopWindowTarget<T> {
    pub fn raw_display_handle(&self) -> RawDisplayHandle {
        let mut display_handle = WaylandDisplayHandle::empty();
        display_handle.display = self.connection.display().id().as_ptr() as *mut _;
        RawDisplayHandle::Wayland(display_handle)
    }
}

// The default routine does floor, but we need round on Wayland.
fn logical_to_physical_rounded(size: LogicalSize<u32>, scale_factor: f64) -> PhysicalSize<u32> {
    let width = size.width as f64 * scale_factor;
    let height = size.height as f64 * scale_factor;
    (width.round(), height.round()).into()
}