Drag and drop has never worked very well in QtWebAssembly.
But it is working in 6.6.0beta1 single threaded release.

You need to use asyncify though:
https://doc.qt.io/qt-6/wasm.html#asyncify

Good news is, you no longer have to rebuild Qt to get asyncify, you just need to add a linker argument.
cmake: target_link_options(<target> PUBLIC -sASYNCIFY -Os)
qmake: QMAKE_LFLAGS += -sASYNCIFY -Os

It is indeed a bug, see: https://bugreports.qt.io/browse/QTBUG-106707

@lorn-potter I try asap

In Qt 6.4 (on macos) Debug build does not generate javascript file...

https://bugreports.qt.io/browse/QTBUG-84392

With Qt 6.2, you can use qt-cmake to build examples, which does not have this issue.

after contact the qt support, they suggest me to replace

win32: LIBS += -L$$PWD/../../TinyLib/build-TinyLib-Qt_5_15_0_WebAssembly-Debug/ -lTinyLib

with

wasm:LIBS += -L$$PWD/../../TinyLib/build-TinyLib-Qt_5_15_0_WebAssembly-Debug/ -lTinyLib

Building OpenSSL with the no-threads option solve the problem in my case.

I don't really search deeper what is the consequences of that build option but maybe it can help someone ;)

I am not sure Qt signals would work. You should certainly be able to so callbacks though.

It is possible to call c/c++ functions from javascript as well as call javascript from c/c++.
Look at
https://emscripten.org/docs/porting/connecting_cpp_and_javascript/Interacting-with-code.html

@lorn-potter

I figured out how to export custom functions, but there's still a problem with exporting the runtime ones. I am adding the -s EXPORTED_RUNTIME_METHODS=UTF8ToString argument and keep receiving "Uncaught RuntimeError: Aborted('UTF8ToString' was not exported. add it to EXPORTED_RUNTIME_METHODS (see the FAQ))" error.

I just saw that a QNetworkReply::TimeoutError code exists. Shouldn't this code be set when a timeout occurred ? Is this a bug or did I misunderstand something ?

@lorn-potter Thanks for getting back to me!

I'm trying to build this project:
https://github.com/herewegoblueno/cs1230-final
Just to provide context, this works well when built for Mac.

And yes I am importing GL/glew.h myself.

Also by the way I've also noticed that the compilers don't recognize the standard libraries like <vector>, <map>, etc (or maybe that's just the static checker? not sure if those will result in compile time errors since I can't build due to glew anyways)

Found the problem: I had installed Qt v 6.0.0 with emscripten 1.39.8. documents say 1.39.8 should work with Qt v5.15.0. Works after installing the correct Qt version.

Problem solved by removing the emrun flag. I can now specify custom arguments in the qtloader.js using emscripten's Module.arguments like this :

Module['arguments'] = ['FirstArg', 'SecondArg'];

Hi @SGaist ,
One thing that made me skeptical about the info on the introduction page, was the affirmative that webassembly doesn't support threads, which is not an absolute true, in fact is relatively simple to enable thread support with the correct emscripten version.
But everything so far is telling me that is not possible, or at least it will be very hard to compile wasm as shared.