Add MessageChannel

Author: karlseguin

src/browser/dom/Animation.zig

@@ -1,4 +1,4 @@
-// Copyright (C) 2023-2025s  Lightpanda (Selecy SAS)
+// Copyright (C) 2023-2025  Lightpanda (Selecy SAS)
 //
 // Francis Bouvier <[email protected]>
 // Pierre Tachoire <[email protected]>

src/browser/dom/MessageChannel.zig

@@ -0,0 +1,361 @@
+// Copyright (C) 2023-2025  Lightpanda (Selecy SAS)
+//
+// Francis Bouvier <[email protected]>
+// Pierre Tachoire <[email protected]>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+const std = @import("std");
+const log = @import("../../log.zig");
+const parser = @import("../netsurf.zig");
+
+const Env = @import("../env.zig").Env;
+const Page = @import("../page.zig").Page;
+const EventTarget = @import("../dom/event_target.zig").EventTarget;
+const EventHandler = @import("../events/event.zig").EventHandler;
+
+const JsObject = Env.JsObject;
+const Function = Env.Function;
+const Allocator = std.mem.Allocator;
+
+const MAX_QUEUE_SIZE = 10;
+
+pub const Interfaces = .{ MessageChannel, MessagePort };
+
+const MessageChannel = @This();
+
+port1: *MessagePort,
+port2: *MessagePort,
+
+pub fn constructor(page: *Page) !MessageChannel {
+    // Why do we allocate this rather than storing directly in the struct?
+    // https://github.com/lightpanda-io/project/discussions/165
+    const port1 = try page.arena.create(MessagePort);
+    const port2 = try page.arena.create(MessagePort);
+    port1.* = .{
+        .pair = port2,
+    };
+    port2.* = .{
+        .pair = port1,
+    };
+
+    return .{
+        .port1 = port1,
+        .port2 = port2,
+    };
+}
+
+pub fn get_port1(self: *const MessageChannel) *MessagePort {
+    return self.port1;
+}
+
+pub fn get_port2(self: *const MessageChannel) *MessagePort {
+    return self.port2;
+}
+
+pub const MessagePort = struct {
+    pub const prototype = *EventTarget;
+
+    proto: parser.EventTargetTBase = .{ .internal_target_type = .message_port },
+
+    pair: *MessagePort,
+    closed: bool = false,
+    started: bool = false,
+    onmessage_cbk: ?Function = null,
+    onmessageerror_cbk: ?Function = null,
+    // This is the queue of messages to dispatch to THIS MessagePort when the
+    // MessagePort is started.
+    queue: std.ArrayListUnmanaged(JsObject) = .empty,
+
+    pub const PostMessageOption = union(enum) {
+        transfer: JsObject,
+        options: Opts,
+
+        pub const Opts = struct {
+            transfer: JsObject,
+        };
+    };
+
+    pub fn _postMessage(self: *MessagePort, obj: JsObject, opts_: ?PostMessageOption, page: *Page) !void {
+        if (self.closed) {
+            return;
+        }
+
+        if (opts_ != null) {
+            log.warn(.web_api, "not implemented", .{ .feature = "MessagePort postMessage options" });
+            return error.NotImplemented;
+        }
+
+        try self.pair.dispatchOrQueue(obj, page.arena);
+    }
+
+    // Start impacts the ability to receive a message.
+    // Given pair1 (started) and pair2 (not started), then:
+    //    pair2.postMessage('x'); //will be dispatched to pair1.onmessage
+    //    pair1.postMessage('x'); // will be queued until pair2 is started
+    pub fn _start(self: *MessagePort) !void {
+        if (self.started) {
+            return;
+        }
+        self.started = true;
+        for (self.queue.items) |data| {
+            try self.dispatch(data);
+        }
+        // we'll never use this queue again, but it's allocated with an arena
+        // we don't even need to clear it, but it seems a bit safer to do at
+        // least that
+        self.queue.clearRetainingCapacity();
+    }
+
+    // Closing seems to stop both the publishing and receiving of messages,
+    // effectively rendering the channel useless. It cannot be reversed.
+    pub fn _close(self: *MessagePort) void {
+        self.closed = true;
+        self.pair.closed = true;
+    }
+
+    pub fn get_onmessage(self: *MessagePort) ?Function {
+        return self.onmessage_cbk;
+    }
+    pub fn get_onmessageerror(self: *MessagePort) ?Function {
+        return self.onmessageerror_cbk;
+    }
+
+    pub fn set_onmessage(self: *MessagePort, listener: EventHandler.Listener, page: *Page) !void {
+        if (self.onmessage_cbk) |cbk| {
+            try self.unregister("message", cbk.id);
+        }
+        self.onmessage_cbk = try self.register(page.arena, "message", listener);
+
+        // When onmessage is set directly, then it's like start() was called.
+        // If addEventListener('message') is used, the app has to call start()
+        // explicitly.
+        try self._start();
+    }
+
+    pub fn set_onmessageerror(self: *MessagePort, listener: EventHandler.Listener, page: *Page) !void {
+        if (self.onmessageerror_cbk) |cbk| {
+            try self.unregister("messageerror", cbk.id);
+        }
+        self.onmessageerror_cbk = try self.register(page.arena, "messageerror", listener);
+    }
+
+    // called from our pair. If port1.postMessage("x") is called, then this
+    // will be called on port2.
+    fn dispatchOrQueue(self: *MessagePort, obj: JsObject, arena: Allocator) !void {
+        // our pair should have checked this already
+        std.debug.assert(self.closed == false);
+
+        if (self.started) {
+            return self.dispatch(try obj.persist());
+        }
+
+        if (self.queue.items.len > MAX_QUEUE_SIZE) {
+            // This isn't part of the spec, but not putting a limit is reckless
+            return error.MessageQueueLimit;
+        }
+        return self.queue.append(arena, try obj.persist());
+    }
+
+    fn dispatch(self: *MessagePort, obj: JsObject) !void {
+        // obj is already persisted, don't use `MessageEvent.constructor`, but
+        // go directly to `init`, which assumes persisted objects.
+        var evt = try MessageEvent.init(.{ .data = obj });
+        _ = try parser.eventTargetDispatchEvent(
+            parser.toEventTarget(MessagePort, self),
+            @as(*parser.Event, @ptrCast(&evt)),
+        );
+    }
+
+    fn register(
+        self: *MessagePort,
+        alloc: Allocator,
+        typ: []const u8,
+        listener: EventHandler.Listener,
+    ) !?Function {
+        const target = @as(*parser.EventTarget, @ptrCast(self));
+        const eh = (try EventHandler.register(alloc, target, typ, listener, null)) orelse unreachable;
+        return eh.callback;
+    }
+
+    fn unregister(self: *MessagePort, typ: []const u8, cbk_id: usize) !void {
+        const et = @as(*parser.EventTarget, @ptrCast(self));
+        const lst = try parser.eventTargetHasListener(et, typ, false, cbk_id);
+        if (lst == null) {
+            return;
+        }
+        try parser.eventTargetRemoveEventListener(et, typ, lst.?, false);
+    }
+};
+
+pub const MessageEvent = struct {
+    const Event = @import("../events/event.zig").Event;
+    const DOMException = @import("exceptions.zig").DOMException;
+
+    pub const prototype = *Event;
+    pub const Exception = DOMException;
+    pub const union_make_copy = true;
+
+    proto: parser.Event,
+    data: ?JsObject,
+
+    // You would think if port1 sends to port2, the source would be port2
+    // (which is how I read the documentation), but it appears to always be
+    // null. It can always be set explicitly via the constructor;
+    source: ?JsObject,
+
+    origin: []const u8,
+
+    // This is used for Server-Sent events. Appears to always be an empty
+    // string for MessagePort messages.
+    last_event_id: []const u8,
+
+    // This might be related to the "transfer" option of postMessage which
+    // we don't yet support. For "normal" message, it's always an empty array.
+    // Though it could be set explicitly via the constructor
+    ports: []*MessagePort,
+
+    const Options = struct {
+        data: ?JsObject = null,
+        source: ?JsObject = null,
+        origin: []const u8 = "",
+        lastEventId: []const u8 = "",
+        ports: []*MessagePort = &.{},
+    };
+
+    pub fn constructor(opts: Options) !MessageEvent {
+        return init(.{
+            .data = if (opts.data) |obj| try obj.persist() else null,
+            .source = if (opts.source) |obj| try obj.persist() else null,
+            .ports = opts.ports,
+            .origin = opts.origin,
+            .lastEventId = opts.lastEventId,
+        });
+    }
+
+    // This is like "constructor", but it assumes JsObjects have already been
+    // persisted. Necessary because this `new MessageEvent()` can be called
+    // directly from JS OR from a port.postMessage. In the latter case, data
+    // may have already been persisted (as it might need to be queued);
+    fn init(opts: Options) !MessageEvent {
+        const event = try parser.eventCreate();
+        defer parser.eventDestroy(event);
+        try parser.eventInit(event, "message", .{});
+        try parser.eventSetInternalType(event, .message_event);
+
+        return .{
+            .proto = event.*,
+            .data = opts.data,
+            .source = opts.source,
+            .ports = opts.ports,
+            .origin = opts.origin,
+            .last_event_id = opts.lastEventId,
+        };
+    }
+
+    pub fn get_data(self: *const MessageEvent) !?JsObject {
+        return self.data;
+    }
+
+    pub fn get_origin(self: *const MessageEvent) []const u8 {
+        return self.origin;
+    }
+
+    pub fn get_source(self: *const MessageEvent) ?JsObject {
+        return self.source;
+    }
+
+    pub fn get_ports(self: *const MessageEvent) []*MessagePort {
+        return self.ports;
+    }
+
+    pub fn get_lastEventId(self: *const MessageEvent) []const u8 {
+        return self.last_event_id;
+    }
+};
+
+const testing = @import("../../testing.zig");
+test "Browser.MessageChannel" {
+    var runner = try testing.jsRunner(testing.tracking_allocator, .{
+        .html = "",
+    });
+    defer runner.deinit();
+
+    try runner.testCases(&.{
+        .{ "const mc1 = new MessageChannel()", null },
+        .{ "mc1.port1 == mc1.port1", "true" },
+        .{ "mc1.port2 == mc1.port2", "true" },
+        .{ "mc1.port1 != mc1.port2", "true" },
+        .{ "mc1.port1.postMessage('msg1');", "undefined" },
+        .{
+            \\ let message = null;
+            \\ let target = null;
+            \\ let currentTarget = null;
+            \\ mc1.port2.onmessage = (e) => {
+            \\   message = e.data;
+            \\   target = e.target;
+            \\   currentTarget = e.currentTarget;
+            \\ };
+            ,
+            null,
+        },
+        //  as soon as onmessage is called, queued messages are delivered
+        .{ "message", "msg1" },
+        .{ "target == mc1.port2", "true" },
+        .{ "currentTarget == mc1.port2", "true" },
+
+        .{ "mc1.port1.postMessage('msg2');", "undefined" },
+        .{ "message", "msg2" },
+        .{ "target == mc1.port2", "true" },
+        .{ "currentTarget == mc1.port2", "true" },
+
+        .{ "message = null", null },
+        .{ "mc1.port1.close();", null },
+        .{ "mc1.port1.postMessage('msg3');", "undefined" },
+        .{ "message", "null" },
+    }, .{});
+
+    try runner.testCases(&.{
+        .{ "const mc2 = new MessageChannel()", null },
+        .{ "mc2.port2.postMessage('msg1');", "undefined" },
+        .{ "mc2.port1.postMessage('msg2');", "undefined" },
+        .{
+            \\ let message1 = null;
+            \\ mc2.port1.addEventListener('message', (e) => {
+            \\   message1 = e.data;
+            \\ });
+            ,
+            null,
+        },
+        .{
+            \\ let message2 = null;
+            \\ mc2.port2.addEventListener('message', (e) => {
+            \\   message2 = e.data;
+            \\ });
+            ,
+            null,
+        },
+        .{ "message1", "null" },
+        .{ "message2", "null" },
+        .{ "mc2.port2.start()", null },
+
+        .{ "message1", "null" },
+        .{ "message2", "msg2" },
+        .{ "message2 = null", null },
+
+        .{ "mc2.port1.start()", null },
+        .{ "message1", "msg1" },
+        .{ "message2", "null" },
+    }, .{});
+}

src/browser/dom/dom.zig

@@ -53,4 +53,5 @@ pub const Interfaces = .{
     PerformanceObserver,
     @import("range.zig").Interfaces,
     @import("Animation.zig"),
+    @import("MessageChannel.zig").Interfaces,
 };

src/browser/dom/event_target.zig

@@ -30,6 +30,7 @@ pub const Union = union(enum) {
     node: nod.Union,
     xhr: *@import("../xhr/xhr.zig").XMLHttpRequest,
     plain: *parser.EventTarget,
+    message_port: *@import("MessageChannel.zig").MessagePort,
 };
 
 // EventTarget implementation
@@ -63,6 +64,9 @@ pub const EventTarget = struct {
                 const base: *XMLHttpRequestEventTarget = @fieldParentPtr("base", @as(*parser.EventTargetTBase, @ptrCast(et)));
                 return .{ .xhr = @fieldParentPtr("proto", base) };
             },
+            .message_port => {
+                return .{ .message_port = @fieldParentPtr("proto", @as(*parser.EventTargetTBase, @ptrCast(et))) };
+            },
             else => return error.MissingEventTargetType,
         }
     }