Critical information for every developer.
In typical, native, Qt setting, modal windows allocated on stack and block upon opening. To manage the modal window, Qt spins up a second event loop. However, that is not technically possible in Web-Assembly environment. (This might be solved in new Qt with “asyncify” build flag, but it does not work with currently used Qt 5.15.2)
QMessageBox msg;
msg.exec();QMessageBox::critical("Hello");The .exec() method and single line call are typical warning signs.
Some parts of code employ special code for Web-Assembly (like HTML file selector) and the native part may use blocking solution. However, in performance non-critical parts (which most dialogs are), unified asynchronous solution is preferred.
The modal window object has to be allocated dynamically and started using asynchronous method open. Answer has to be
obtained via connect callback.
For ease of use, wrapper functions are prepared in gui/helper/async_modal.h.
Free can be accomplished using special call msg->setAttribute(Qt::WA_DeleteOnClose) before opening. This method is
automatically employed in async_modal.h.
Docs: WA_DeleteOnClose , QCloseEvent