WebAssembly - Qt 6.6.0 - Embind

just_a_developer

Hello,

I compiled my app for WebAssembly with Qt 6.4.1 so far.

My embedding website is sending messages to the Qt app via a Javascript interface which is registered in C++ this way :

#ifdef EMSCRIPTEN

#include <emscripten/bind.h>

EMSCRIPTEN_BINDINGS(javascriptPublicInterface)
{
	emscripten::class_<JavascriptPublicInterface>("JavascriptPublicInterface")
		.function("myProperty", &JavascriptPublicInterface::myPropertyEMS)
		.function("setMyProperty", &JavascriptPublicInterface::setMyPropertyEMS);
	emscripten::function("self", &JavascriptPublicInterface::self, emscripten::allow_raw_pointers());
}

#endif

So my embedding website could call :

module.self().setMyProperty("something")

Now I am working on updating my app to be built using Qt 6.6.0 .
As far as I understand the app compiles, and it is running, but I don't have access to module any more (it's undefined).

Using the web browser's Javascript debugger, I can see, that this function in myapp.js is running, and it receives an unwind exception :

function callMain(args = []) {
  assert(runDependencies == 0, 'cannot call main when async dependencies remain! (listen on Module["onRuntimeInitialized"])');
  assert(__ATPRERUN__.length == 0, 'cannot call main when preRun functions remain to be called');

  var entryFunction = _main;

  args.unshift(thisProgram);

  var argc = args.length;
  var argv = stackAlloc((argc + 1) * 4);
  var argv_ptr = argv >> 2;
  args.forEach((arg) => {
    HEAP32[argv_ptr++] = stringToUTF8OnStack(arg);
  });
  HEAP32[argv_ptr] = 0;

  try {

    var ret = entryFunction(argc, argv);

    // if we're not running an evented main loop, it's time to exit
    exitJS(ret, /* implicit = */ true);
    return ret;
  }
  catch (e) {
    return handleException(e);
  }
}

When the breakpoint in the exception handler is hit, I can access to Module (with upper case first letter) from the Javascript console. As soon as I let the debugger continue, I don't have access to Module any more, but the app seems to continue running.

How could I get the access back to my Javascript public interface?

Thank you four your help in advance!

just_a_developer

I realized that I can easily get access to my JavascriptPublicInterface again, by slightly modifying the generated myapp.html :
so from :

        async function init()
        {
            const spinner = document.querySelector('#qtspinner');
            const screen = document.querySelector('#screen');
            const status = document.querySelector('#qtstatus');

            const showUi = (ui) => {
                [spinner, screen].forEach(element => element.style.display = 'none');
                if (screen === ui)
                    screen.style.position = 'default';
                ui.style.display = 'block';
            }

            try {
                showUi(spinner);
                status.innerHTML = 'Loading...';

                const instance = await qtLoad({

I updated to :

        var instance = null 
        async function init()
        {
            const spinner = document.querySelector('#qtspinner');
            const screen = document.querySelector('#screen');
            const status = document.querySelector('#qtstatus');

            const showUi = (ui) => {
                [spinner, screen].forEach(element => element.style.display = 'none');
                if (screen === ui)
                    screen.style.position = 'default';
                ui.style.display = 'block';
            }

            try {
                showUi(spinner);
                status.innerHTML = 'Loading...';

                instance = await qtLoad({

so now I can call instance.self().setMyProperty("something") .