Make new_window asynchronous (#4297)

* Make new_window asynchronous

* fix clippy

packages/desktop/src/webview.rs

@@ -1,6 +1,7 @@
 use crate::element::DesktopElement;
 use crate::file_upload::DesktopFileDragEvent;
 use crate::menubar::DioxusMenu;
+use crate::PendingDesktopContext;
 use crate::{
     app::SharedContext,
     assets::AssetHandlerRegistry,
@@ -207,6 +208,7 @@ impl WebviewInstance {
 
         // https://developer.apple.com/documentation/appkit/nswindowcollectionbehavior/nswindowcollectionbehaviormanaged
         #[cfg(target_os = "macos")]
+        #[allow(deprecated)]
         {
             use cocoa::appkit::NSWindowCollectionBehavior;
             use cocoa::base::id;
@@ -524,3 +526,33 @@ impl SynchronousEventResponse {
         Self { prevent_default }
     }
 }
+
+/// A webview that is queued to be created. We can't spawn webviews outside of the main event loop because it may
+/// block on windows so we queue them into the shared context and then create them when the main event loop is ready.
+pub(crate) struct PendingWebview {
+    dom: VirtualDom,
+    cfg: Config,
+    sender: tokio::sync::oneshot::Sender<DesktopContext>,
+}
+
+impl PendingWebview {
+    pub(crate) fn new(dom: VirtualDom, cfg: Config) -> (Self, PendingDesktopContext) {
+        let (sender, receiver) = tokio::sync::oneshot::channel();
+        let webview = Self { dom, cfg, sender };
+        let pending = PendingDesktopContext { receiver };
+        (webview, pending)
+    }
+
+    pub(crate) fn create_window(self, shared: &Rc<SharedContext>) -> WebviewInstance {
+        let window = WebviewInstance::new(self.cfg, self.dom, shared.clone());
+
+        let cx = window.dom.in_runtime(|| {
+            ScopeId::ROOT
+                .consume_context::<Rc<DesktopService>>()
+                .unwrap()
+        });
+        _ = self.sender.send(cx);
+
+        window
+    }
+}