Defold: Implement JsToDef functionality as part of `html5` module

[AGulev]

Task (REQUIRED):
It would be nice to implement JsToDef functionality as part of html5 module.

On Lua side:

local function js_listener(self, message)
...
end

html5.add_listener("listener_id", js_listener)
--or
html5.add_listener(hash("listener_id"), js_listener)

html5.remove_listener("listener_id", js_listener)
--or
html5.remove_listener(hash("listener_id"), js_listener)

html5.remove_all_listeners("listener_id")
--or
html5.remove_all_listeners(hash("listener_id"))

On JS side:

//Module or some other module
Module.send("listener_id", "custom message");
Module.send("listener_id", {foo:"bar", num:16, isAv:true});
Module.send("listener_id", 19.2);
Module.send("listener_id", 18);
Module.send("listener_id", "custom string");
Module.send("listener_id");
Module.send("listener_id", true);
Module.send("listener_id", false);

Expected outcome (REQUIRED):
JsToDef provides functionality that's is really important and basic for html5 developers. It should be part of the engine as a method in html5 module.

[britzl]

I agree with you @AGulev. I think this is really useful functionality.

We need to discuss the API though. On the JS side I think we should have a Defold.* namespace and not hide it in Module if possible.

I'd also like to discuss the "listener_id", is this needed? And should it be html5.add_listener() and html5remove_listener() or simply html5.set_listener()?

Perhaps more closely replicating on_message(self, message_id, message):

html5.set_listener(function(self, message_id, message)
end)

Defold.post("ad_ready", { placement: 1 })

[AGulev]

Yes, maybe.
Now jstodef supports multiple callbacks. The idea was to create an easier way of separated logic for different modules.

For example if we connect 2 different SDK on JS side, probably we want to use two different script/lua files on Defold side.
Also, it would be easier to publish such integration as separate module which contains lua+js (based only on this new functionality) without cpp at all.

But in case with single listener it will be much harder to do in a nice way.
That's why I moved message_id ("listener_id") in my example as part of registration and sending data, not receiving.

[britzl]

Ah, yes, good point with the multiple callbacks to more easily support multiple modules. Ok, so. no html5.set_listener(). Instead we should have html5.add_listener() and html5.remove_listener().