Lib: add Broadcast Channel and Shared Worker bindings

API-STATUS.md

@@ -64,7 +64,7 @@ This document lists standard JavaScript/Web APIs and their support status in js_
 |-----|------|-----|---------------------|
 | Web Workers | Yes | Yes | `Worker` · Brr: `Brr_webworkers.Worker` |
 | Service Workers | Yes | Yes | `ServiceWorker` · Brr: `Brr_webworkers.Service_worker` |
-| Shared Workers | No | Yes | Brr: `Brr_webworkers.Worker.Shared` |
+| Shared Workers | Yes | Yes | `SharedWorker` · Brr: `Brr_webworkers.Worker.Shared` |
 
 ## File & Binary Data
 
@@ -156,7 +156,7 @@ This document lists standard JavaScript/Web APIs and their support status in js_
 | Web Components (Custom Elements, Shadow DOM) | Partial | No | `Dom_html` (Shadow DOM — `attachShadow`, `shadowRoot`, `assignedSlot`, `slot`); Custom Elements not bound |
 | Web Crypto API | Yes | Yes | `Crypto` · Brr: `Brr_webcrypto` |
 | Notifications API | Yes | Yes | `Notification` · Brr: `Brr_io.Notification` |
-| Broadcast Channel API | No | Yes | Brr: `Brr_io.Message.Broadcast_channel` |
+| Broadcast Channel API | Yes | Yes | `BroadcastChannel` · Brr: `Brr_io.Message.Broadcast_channel` |
 | AbortController / AbortSignal | Yes | Yes | `Abort` · Brr: `Brr.Abort` |
 
 ---
@@ -180,11 +180,9 @@ Worker/iframe/window communication.
 
 | API | Issue | In Brr | Why |
 |-----|-------|--------|-----|
-| Broadcast Channel API | — | Yes | Cross-tab communication (sync auth state, shared data). Simple API. |
 | Web Audio API | — | Yes | Audio processing, games, music apps. Large API surface but well-defined. |
 | Media Capture (getUserMedia) | — | Yes | Video calls, camera/mic access. Growing use with remote work tooling. |
 | Encoding API (TextEncoder/TextDecoder) | — | Partial | Needed for binary protocol work and streaming text. Small surface. |
-| Shared Workers | — | Yes | Shared state across tabs. Niche but Brr covers it. |
 | IndexedDB | — | No | Client-side database for offline apps. Large API but important for data-heavy PWAs. |
 | Streams API | — | No | Modern data processing. Fetch response bodies are ReadableStreams. Increasingly foundational. |
 | History API (upgrade to full) | — | Yes | SPA routing depends on pushState/replaceState. Current binding is limited. |
@@ -205,5 +203,5 @@ Worker/iframe/window communication.
 
 ### Suggested implementation order
 
-1. **Broadcast Channel** — small API that fills out the
-   remaining communication gaps.
+1. **Encoding API** — small surface, needed for binary protocol
+   work and streaming text.

CHANGES.md

@@ -1,6 +1,11 @@
 # dev
 
 ## Features/Changes
+* Lib: add `BroadcastChannel` and `SharedWorker` — bindings to the Broadcast
+  Channel API and to shared workers (the page-side `SharedWorker` constructors
+  with their options, and the worker-side `SharedWorkerGlobalScope` with a
+  `set_onconnect` helper). The wasm runtime no longer loses `connect` events
+  received while the module is being instantiated (#2400)
 * Lib: add `WebGL2` — bindings to the WebGL2 rendering context. The context
   inherits every method and constant of `WebGL`, and adds the WebGL2 objects
   (vertex array objects, queries, samplers, syncs, transform feedback), 3D and

lib/js_of_ocaml/broadcastChannel.ml

@@ -0,0 +1,42 @@
+(* Js_of_ocaml library
+ * http://www.ocsigen.org/js_of_ocaml/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, with linking exception;
+ * either version 2.1 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *)
+
+open! Import
+
+class type broadcastChannel = object ('self)
+  inherit Dom_html.eventTarget
+
+  method name : Js.js_string Js.t Js.readonly_prop
+
+  method postMessage : 'a. 'a -> unit Js.meth
+
+  method close : unit Js.meth
+
+  method onmessage :
+    ('self Js.t, ('self, Js.Unsafe.any) Dom_html.messageEvent Js.t) Dom.event_listener
+    Js.writeonly_prop
+
+  method onmessageerror :
+    ('self Js.t, ('self, Js.Unsafe.any) Dom_html.messageEvent Js.t) Dom.event_listener
+    Js.writeonly_prop
+end
+
+let broadcastChannel : (Js.js_string Js.t -> broadcastChannel Js.t) Js.constr =
+  Js.Unsafe.global##._BroadcastChannel
+
+let is_supported () = Js.Optdef.test Js.Unsafe.global##._BroadcastChannel

lib/js_of_ocaml/broadcastChannel.mli

@@ -0,0 +1,56 @@
+(* Js_of_ocaml library
+ * http://www.ocsigen.org/js_of_ocaml/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, with linking exception;
+ * either version 2.1 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *)
+
+(** Broadcast Channel API.
+
+    A [BroadcastChannel] delivers every posted message to all other channels
+    with the same name in the same origin (other tabs, windows, workers).
+
+    @see <https://developer.mozilla.org/en-US/docs/Web/API/Broadcast_Channel_API>
+    @see <https://html.spec.whatwg.org/multipage/web-messaging.html#broadcasting-to-other-browsing-contexts> *)
+
+open Js
+
+class type broadcastChannel = object ('self)
+  inherit Dom_html.eventTarget
+
+  method name : js_string t readonly_prop
+  (** The channel name given to the constructor. *)
+
+  method postMessage : 'a. 'a -> unit meth
+  (** [chan##postMessage msg] delivers a structured clone of [msg] to every
+      other channel with the same name in the same origin. Raises once the
+      channel has been closed. *)
+
+  method close : unit meth
+
+  method onmessage :
+    ('self t, ('self, Unsafe.any) Dom_html.messageEvent t) Dom.event_listener
+    writeonly_prop
+
+  method onmessageerror :
+    ('self t, ('self, Unsafe.any) Dom_html.messageEvent t) Dom.event_listener
+    writeonly_prop
+end
+
+val broadcastChannel : (js_string t -> broadcastChannel t) constr
+(** [new%js broadcastChannel name] joins the broadcast channel [name]. *)
+
+val is_supported : unit -> bool
+(** Whether the [BroadcastChannel] global is available in the current
+    environment. *)

lib/js_of_ocaml/js_of_ocaml.ml

@@ -22,6 +22,7 @@
     {b This library is provided by the [js_of_ocaml] opam package.} *)
 
 module Abort = Abort
+module BroadcastChannel = BroadcastChannel
 module CSS = CSS
 module Cache = Cache
 module Clipboard = Clipboard
@@ -55,6 +56,7 @@ module Promise = Promise
 module ResizeObserver = ResizeObserver
 module Regexp = Regexp
 module ServiceWorker = ServiceWorker
+module SharedWorker = SharedWorker
 module Sys_js = Sys_js
 module Typed_array = Typed_array
 module Url = Url

lib/js_of_ocaml/sharedWorker.ml

@@ -0,0 +1,77 @@
+(* Js_of_ocaml library
+ * http://www.ocsigen.org/js_of_ocaml/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, with linking exception;
+ * either version 2.1 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *)
+
+open! Import
+
+class type sharedWorker = object ('self)
+  inherit Dom_html.eventTarget
+
+  method port : MessageChannel.messagePort Js.t Js.readonly_prop
+
+  method onerror :
+    ('self Js.t, Worker.errorEvent Js.t) Dom.event_listener Js.writeonly_prop
+end
+
+class type workerOptions = object
+  method name : Js.js_string Js.t Js.writeonly_prop
+
+  method _type : Js.js_string Js.t Js.writeonly_prop
+
+  method credentials : Js.js_string Js.t Js.writeonly_prop
+end
+
+let empty_worker_options () : workerOptions Js.t = Js.Unsafe.obj [||]
+
+let sharedWorker : (Js.js_string Js.t -> sharedWorker Js.t) Js.constr =
+  Js.Unsafe.global##._SharedWorker
+
+let sharedWorker_withName :
+    (Js.js_string Js.t -> Js.js_string Js.t -> sharedWorker Js.t) Js.constr =
+  Js.Unsafe.global##._SharedWorker
+
+let sharedWorker_withOptions :
+    (Js.js_string Js.t -> workerOptions Js.t -> sharedWorker Js.t) Js.constr =
+  Js.Unsafe.global##._SharedWorker
+
+let is_supported () = Js.Optdef.test Js.Unsafe.global##._SharedWorker
+
+class type sharedWorkerGlobalScope = object ('self)
+  inherit Dom_html.eventTarget
+
+  method name : Js.js_string Js.t Js.readonly_prop
+
+  method close : unit Js.meth
+
+  method onconnect :
+    ('self Js.t, ('self, Js.Unsafe.any) Dom_html.messageEvent Js.t) Dom.event_listener
+    Js.writeonly_prop
+end
+
+let global () : sharedWorkerGlobalScope Js.t = Js.Unsafe.global
+
+let set_onconnect handler =
+  if not (Js.Optdef.test Js.Unsafe.global##.onconnect)
+  then invalid_arg "SharedWorker.set_onconnect: onconnect is undefined";
+  let js_handler (ev : (_, _) Dom_html.messageEvent Js.t) =
+    let port : MessageChannel.messagePort Js.t =
+      Js.Unsafe.coerce
+        (Js.Optdef.get (Js.array_get ev##.ports 0) (fun () -> assert false))
+    in
+    handler port
+  in
+  Js.Unsafe.global##.onconnect := Js.wrap_callback js_handler

lib/js_of_ocaml/sharedWorker.mli

@@ -0,0 +1,104 @@
+(* Js_of_ocaml library
+ * http://www.ocsigen.org/js_of_ocaml/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, with linking exception;
+ * either version 2.1 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *)
+
+(** Shared Workers.
+
+    A [SharedWorker] is a worker shared by every browsing context of the same
+    origin that creates one with the same script URL and name. Each context
+    communicates with the worker through the {!MessageChannel.messagePort}
+    exposed as {!class-type:sharedWorker}'s [port]; inside the worker, each new
+    connection is delivered as a [connect] event carrying the other end of that
+    port.
+
+    @see <https://developer.mozilla.org/en-US/docs/Web/API/SharedWorker>
+    @see <https://html.spec.whatwg.org/multipage/workers.html#shared-workers-and-the-sharedworker-interface> *)
+
+open Js
+
+(** {2 Page side} *)
+
+class type sharedWorker = object ('self)
+  inherit Dom_html.eventTarget
+
+  method port : MessageChannel.messagePort t readonly_prop
+  (** The port used to communicate with the worker. When messages are received
+      through the [onmessage] property the port is started implicitly;
+      otherwise call [port##start] to begin receiving. *)
+
+  method onerror : ('self t, Worker.errorEvent t) Dom.event_listener writeonly_prop
+end
+
+(** Options for the {!sharedWorker_withOptions} constructor. All fields are
+    optional; create an empty record with {!empty_worker_options}. *)
+class type workerOptions = object
+  method name : js_string t writeonly_prop
+  (** Identifies the worker: contexts constructing a [SharedWorker] with the
+      same URL and name share a single worker instance. *)
+
+  method _type : js_string t writeonly_prop
+  (** Either ["classic"] (default) or ["module"]. *)
+
+  method credentials : js_string t writeonly_prop
+  (** One of ["omit"], ["same-origin"] (default) or ["include"]. Only used
+      with module workers. *)
+end
+
+val empty_worker_options : unit -> workerOptions t
+
+val sharedWorker : (js_string t -> sharedWorker t) constr
+(** [new%js sharedWorker url] connects to the shared worker running the script
+    at [url], starting it if it is not running yet. *)
+
+val sharedWorker_withName : (js_string t -> js_string t -> sharedWorker t) constr
+(** [new%js sharedWorker_withName url name] connects to the shared worker
+    identified by [url] and [name]. *)
+
+val sharedWorker_withOptions : (js_string t -> workerOptions t -> sharedWorker t) constr
+
+val is_supported : unit -> bool
+(** Whether the [SharedWorker] global is available in the current
+    environment. *)
+
+(** {2 Worker side} *)
+
+(** The global scope of a running shared worker (its [self]). Only meaningful
+    when the current code is actually running as a shared worker. *)
+class type sharedWorkerGlobalScope = object ('self)
+  inherit Dom_html.eventTarget
+
+  method name : js_string t readonly_prop
+  (** The name given at construction, or the empty string. *)
+
+  method close : unit meth
+
+  method onconnect :
+    ('self t, ('self, Unsafe.any) Dom_html.messageEvent t) Dom.event_listener
+    writeonly_prop
+  (** Fired each time a new context connects. The first element of the event's
+      [ports] is the {!MessageChannel.messagePort} to that context. *)
+end
+
+val global : unit -> sharedWorkerGlobalScope t
+(** The shared worker's global scope. *)
+
+val set_onconnect : (MessageChannel.messagePort t -> unit) -> unit
+(** [set_onconnect f] calls [f port] each time a new context connects to the
+    worker, where [port] is the port to that context (already extracted from
+    the [connect] event). To receive its messages, set [port##.onmessage] or
+    add a [message] listener and call [port##start]. Raises [Invalid_argument]
+    when not running in a shared worker. *)

lib/tests-browser/dune

@@ -1,5 +1,11 @@
 (executables
- (names test_beforeunload test_wheel test_fetch test_font_face)
+ (names
+  test_beforeunload
+  test_wheel
+  test_fetch
+  test_font_face
+  test_shared_worker
+  test_shared_worker_worker)
  (libraries js_of_ocaml)
  (modes js wasm)
  (preprocess
@@ -17,6 +23,9 @@
   test_fetch.html
   test_font_face.bc.js
   test_font_face.html
+  test_shared_worker.bc.js
+  test_shared_worker_worker.bc.js
+  test_shared_worker.html
   BebasNeue-Regular.ttf))
 
 (alias
@@ -31,4 +40,7 @@
   test_fetch.html
   test_font_face.bc.wasm.js
   test_font_face.html
+  test_shared_worker.bc.wasm.js
+  test_shared_worker_worker.bc.wasm.js
+  test_shared_worker.html
   BebasNeue-Regular.ttf))

lib/tests-browser/index.html

@@ -28,6 +28,10 @@ <h1>Browser tests</h1>
       <a href="test_font_face.html">test_font_face</a>
       (<a href="test_font_face.html?wasm">wasm</a>)
     </li>
+    <li>
+      <a href="test_shared_worker.html">test_shared_worker</a>
+      (<a href="test_shared_worker.html?wasm">wasm</a>)
+    </li>
   </ul>
 </body>
 </html>