wry: Deadlock creating a new window on the IPC handler on Windows

Describe the bug On Tauri, we allow users to create a window from a IPC handler. This results in a deadlock on Windows on the create_controller function (the second closure is never called). This might be an issue on the windows crate instead.

Steps To Reproduce I’ve changed the multi_window example to reproduce this issue (note that I’m not using the event loop proxy to send a message because Tauri needs a response from the event loop (the window id).

// Copyright 2019-2021 Tauri Programme within The Commons Conservancy
// SPDX-License-Identifier: Apache-2.0
// SPDX-License-Identifier: MIT

fn main() -> wry::Result<()> {
  use std::collections::HashMap;
  use std::ops::Deref;
  use wry::{
    application::{
      event::{Event, WindowEvent},
      event_loop::{ControlFlow, EventLoop, EventLoopProxy, EventLoopWindowTarget},
      window::{Window, WindowBuilder, WindowId},
    },
    webview::{WebView, WebViewBuilder},
  };

  #[derive(Clone)]
  enum UserEvents {
    CloseWindow(WindowId),
    NewWindow(),
  }

  fn create_new_window(
    title: String,
    event_loop: EventLoopWindowTarget<UserEvents>,
    proxy: EventLoopProxy<UserEvents>,
  ) -> (WindowId, WebView) {
    let window = WindowBuilder::new()
      .with_title(title)
      .build(&event_loop)
      .unwrap();
    let window_id = window.id();
    let event_loop_ = event_loop.clone();
    let handler = move |window: &Window, req: String| match req.as_str() {
      "new-window" => {
        //let _ = proxy.send_event(UserEvents::NewWindow());
        create_new_window("something".into(), event_loop_.clone(), proxy.clone());
      }
      "close" => {
        let _ = proxy.send_event(UserEvents::CloseWindow(window.id()));
      }
      _ if req.starts_with("change-title") => {
        let title = req.replace("change-title:", "");
        window.set_title(title.as_str());
      }
      _ => {}
    };

    let webview = WebViewBuilder::new(window)
      .unwrap()
      .with_html(
        r#"
          <button onclick="window.ipc.postMessage('new-window')">Open a new window</button>
          <button onclick="window.ipc.postMessage('close')">Close current window</button>
          <input oninput="window.ipc.postMessage(`change-title:${this.value}`)" />
      "#,
      )
      .unwrap()
      .with_ipc_handler(handler)
      .build()
      .unwrap();
    (window_id, webview)
  }

  let event_loop = EventLoop::<UserEvents>::with_user_event();
  let mut webviews = HashMap::new();
  let proxy = event_loop.create_proxy();

  let new_window = create_new_window(
    format!("Window {}", webviews.len() + 1),
    event_loop.deref().clone(),
    proxy.clone(),
  );
  webviews.insert(new_window.0, new_window.1);

  event_loop.run(move |event, event_loop, control_flow| {
    *control_flow = ControlFlow::Wait;

    match event {
      Event::WindowEvent {
        event, window_id, ..
      } => match event {
        WindowEvent::CloseRequested => {
          webviews.remove(&window_id);
          if webviews.is_empty() {
            *control_flow = ControlFlow::Exit
          }
        }
        WindowEvent::Resized(_) => {
          let _ = webviews[&window_id].resize();
        }
        _ => (),
      },
      Event::UserEvent(UserEvents::NewWindow()) => {
        let new_window = create_new_window(
          format!("Window {}", webviews.len() + 1),
          event_loop.clone(),
          proxy.clone(),
        );
        webviews.insert(new_window.0, new_window.1);
      }
      Event::UserEvent(UserEvents::CloseWindow(id)) => {
        webviews.remove(&id);
        if webviews.is_empty() {
          *control_flow = ControlFlow::Exit
        }
      }
      _ => (),
    }
  });
}

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Platform and Versions (please complete the following information): OS: Rustc:

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• Yes
• No

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