WEFT_OS/crates/weft-servo-shell/src/embedder.rs

#![cfg(feature = "servo-embed")]

use std::path::Path;
use std::rc::Rc;
use std::sync::{Arc, Mutex};

use servo::{
    EventLoopWaker, ServoBuilder, ServoDelegate, ServoUrl, WebViewBuilder, WebViewDelegate,
};
use winit::{
    application::ApplicationHandler,
    event::WindowEvent,
    event_loop::{ActiveEventLoop, EventLoop, EventLoopProxy},
    window::{Window, WindowAttributes, WindowId},
};

// ── Event loop waker ──────────────────────────────────────────────────────────

#[derive(Clone)]
struct WeftEventLoopWaker {
    proxy: Arc<Mutex<EventLoopProxy<ServoWake>>>,
}

#[derive(Debug, Clone)]
struct ServoWake;

impl EventLoopWaker for WeftEventLoopWaker {
    fn clone_box(&self) -> Box<dyn EventLoopWaker> {
        Box::new(self.clone())
    }

    fn wake(&self) {
        let _ = self
            .proxy
            .lock()
            .unwrap_or_else(|p| p.into_inner())
            .send_event(ServoWake);
    }
}

// ── Servo delegate ────────────────────────────────────────────────────────────

struct WeftServoDelegate;

impl ServoDelegate for WeftServoDelegate {
    fn notify_error(&self, error: servo::ServoError) {
        tracing::error!(?error, "Servo error");
    }
}

// ── WebView delegate ──────────────────────────────────────────────────────────

struct WeftWebViewDelegate {
    redraw_requested: Arc<std::sync::atomic::AtomicBool>,
}

impl WebViewDelegate for WeftWebViewDelegate {
    fn notify_new_frame_ready(&self, _webview: servo::WebView) {
        self.redraw_requested
            .store(true, std::sync::atomic::Ordering::Relaxed);
    }
}

// ── Application state ─────────────────────────────────────────────────────────

struct App {
    url: ServoUrl,
    window: Option<Arc<Window>>,
    servo: Option<servo::Servo>,
    webview: Option<servo::WebView>,
    redraw_requested: Arc<std::sync::atomic::AtomicBool>,
    waker: WeftEventLoopWaker,
    shutting_down: bool,
}

impl App {
    fn new(url: ServoUrl, waker: WeftEventLoopWaker) -> Self {
        Self {
            url,
            window: None,
            servo: None,
            webview: None,
            redraw_requested: Arc::new(std::sync::atomic::AtomicBool::new(false)),
            waker,
            shutting_down: false,
        }
    }

    fn blit_to_window(window: &Arc<Window>, rendering_context: &servo::SoftwareRenderingContext) {
        let size = window.inner_size();
        let Some(pixels) = rendering_context.read_pixels() else {
            return;
        };
        let ctx = softbuffer::Context::new(Arc::clone(window)).expect("softbuffer context");
        let mut surface =
            softbuffer::Surface::new(&ctx, Arc::clone(window)).expect("softbuffer surface");
        let _ = surface.resize(
            std::num::NonZeroU32::new(size.width).unwrap_or(std::num::NonZeroU32::new(1).unwrap()),
            std::num::NonZeroU32::new(size.height).unwrap_or(std::num::NonZeroU32::new(1).unwrap()),
        );
        let Ok(mut buf) = surface.buffer_mut() else {
            return;
        };
        for (dst, src) in buf.iter_mut().zip(pixels.chunks(4)) {
            *dst = u32::from_be_bytes([0, src[0], src[1], src[2]]);
        }
        let _ = buf.present();
    }
}

impl ApplicationHandler<ServoWake> for App {
    fn resumed(&mut self, event_loop: &ActiveEventLoop) {
        if self.window.is_some() {
            return;
        }

        let attrs = WindowAttributes::default().with_title("WEFT Shell");
        let window = Arc::new(
            event_loop
                .create_window(attrs)
                .expect("failed to create shell window"),
        );
        let size = window.inner_size();
        self.window = Some(Arc::clone(&window));

        let servo = ServoBuilder::default()
            .event_loop_waker(Box::new(self.waker.clone()))
            .build();

        servo.set_delegate(Rc::new(WeftServoDelegate));

        let rendering_context = Rc::new(
            servo::SoftwareRenderingContext::new(servo::euclid::Size2D::new(
                size.width,
                size.height,
            ))
            .expect("SoftwareRenderingContext"),
        );

        let webview = WebViewBuilder::new(&servo, Rc::clone(&rendering_context))
            .delegate(Rc::new(WeftWebViewDelegate {
                redraw_requested: Arc::clone(&self.redraw_requested),
            }))
            .url(self.url.clone())
            .build();

        self.servo = Some(servo);
        self.webview = Some(webview);
    }

    fn user_event(&mut self, _event_loop: &ActiveEventLoop, _event: ServoWake) {
        if let Some(servo) = &self.servo {
            servo.spin_event_loop();
        }
    }

    fn about_to_wait(&mut self, event_loop: &ActiveEventLoop) {
        if self.shutting_down {
            event_loop.exit();
            return;
        }
        if let Some(servo) = &self.servo {
            servo.spin_event_loop();
        }
        if self
            .redraw_requested
            .swap(false, std::sync::atomic::Ordering::Relaxed)
        {
            if let Some(w) = &self.window {
                w.request_redraw();
            }
        }
    }

    fn window_event(
        &mut self,
        event_loop: &ActiveEventLoop,
        _window_id: WindowId,
        event: WindowEvent,
    ) {
        match event {
            WindowEvent::RedrawRequested => {
                if let (Some(window), Some(servo)) = (&self.window, &self.servo) {
                    if let Some(wv) = &self.webview {
                        let rc = wv.rendering_context();
                        Self::blit_to_window(window, rc);
                    }
                    servo.spin_event_loop();
                }
            }
            WindowEvent::Resized(new_size) => {
                if let Some(wv) = &self.webview {
                    wv.resize(servo::euclid::Size2D::new(new_size.width, new_size.height));
                }
            }
            WindowEvent::CloseRequested => {
                self.shutting_down = true;
                if let Some(servo) = &self.servo {
                    servo.start_shutting_down();
                }
                event_loop.exit();
            }
            _ => {}
        }
    }
}

// ── Public entry point ────────────────────────────────────────────────────────

pub fn run(html_path: &Path, _ws_port: u16) -> anyhow::Result<()> {
    let url_str = format!("file://{}", html_path.display());
    let url =
        ServoUrl::parse(&url_str).map_err(|e| anyhow::anyhow!("invalid URL {url_str}: {e}"))?;

    let event_loop = EventLoop::<ServoWake>::with_user_event()
        .build()
        .map_err(|e| anyhow::anyhow!("event loop: {e}"))?;

    let waker = WeftEventLoopWaker {
        proxy: Arc::new(Mutex::new(event_loop.create_proxy())),
    };

    let mut app = App::new(url, waker);
    event_loop
        .run_app(&mut app)
        .map_err(|e| anyhow::anyhow!("event loop run: {e}"))
}