I need help with my Deno Qt/QML bindings - QGuiApplication::exec is blocking
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Hello,
I've been working on my QML bindings for Deno, the new JavaScript runtime. You can view them here: https://deno.land/x/qml@v0.1.5
But there are problems.First off, some things you need to know.
- Deno has a new (unstable) FFI API for calling native code.
- Only C functions can be used. No C++ classes.
- Buffers (aka strings) can be passed as input parameters, but they cannot be return values.
- Because of this, the only way to make Qt work at this time is to declare a
thread_local std::unique_ptr<App>
global class and initialize QGuiApplication in aninit()
function. - FFI blocks the entire Deno event loop until the function returns.
- It uses
QGuiApplication
andQQmlApplicationEngine
.
The problem is that
int exec() { return qGuiApp->exec(); }
is blocking. I need to replace it with something like:while (true) { processQtEvents(); if (isDone()) break; }
No matter how hard I tried, I can't figure out how to do it!
Things I've tried:
QEventLoop loop; while (loop.isRunning()) { loop.processEvents(QEventLoop::AllEvents | QEventLoop::WaitForMoreEvents | QEventLoop::EventLoopExec); } while (true) { qGuiApp->processEvents(QEventLoop::AllEvents, 6000); if (qGuiApp->closingDown()) break; } qGuiApp->eventDispatcher()->processEvents(QEventLoop::AllEvents);
None of them work. The most common problem is that when the window is closed, the application still keeps running (aka the only way to end it is with CTRL+C). Signals such as
QQmlApplicationEngine::quit
andQQmlApplicationEngine::exit
do not fire either.I even tried making everything live in a global C++ thread class (not QThread) and passing data using mutexes and conditional variables, so that I could just have
qGuiApp->exec()
running in a separate thread and callisDone()
from Deno. Still doesn't work.ThreadedApplication::operator()()
andThreadedApplication::setData()
are in different threads, which Qt hates.In simplest terms: can QGuiApplication::exec() be replaced with a while() loop?
I apologize if I'm not being clear about something. I'm at wits end to try and figure this out.
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Hi and welcome to devnet,
Did you try to integrate Qt's event loop with the one from Deno ?
AFAIK, QAbstractEventDispatcher is the starting for that.
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