If I have a Sidebar/Panel/Widget thing that adds a `addon` global to the associated window, then it will be impossible to listen to the following 'X' message using the `addon` global. In Addon: thing.once('attach', function(worker) { worker.port.emit('X', 'Y'); }); In Content: <script> addon.on('X', function doStuff() {}) </script> IE `doStuff` above is never called. The only way this message passing is possible is to have the window use the `addon` to initiate the communication, or wait until the window is loaded before emit messages to the worker. At the moment the best solution I can think of is to queue these messages and emit them when the first available listener is attached. This doesn't seem ideal tho..

The example on https://github.com/mozilla/addon-sdk/wiki/JEP-Sidebars is a good example of what does not work, the same is true for panels.

I just want to see what you think Irakli, before I attempt to patch this.

Erik I'm not convinced that queuing up messages by default is a good idea, it may make sense for that specific cases, but there maybe be others when it wouldn't. I think it would make more sense to expose something like `thing.on("ready", function(port) { ... })` instead or make a helper function like `enqueue(thing, "X", "Y")` that will queue up messages.

(In reply to Irakli Gozilalishvili [:irakli] [:gozala] [@gozala] from comment #3) > `thing.on("ready", function(port) { ... })` instead or make a helper > function like `enqueue(thing, "X", "Y")` that will queue up messages. I like both of these ideas, for now I think I will former, by emitting the `show` event when the sidebar loads instead of when it starts showing. Atm my ui-sidebar branch emits `attach` when the window is created, before `show` which emits when the window loads. sidebar.on('attach', function(worker) {}); sidebar.on('show', function({worker}) {}); So I think we can close this for now. No matter when show emits we should be able to pass a worker.

Closing per the last comment.