openglContextCreated signal not emitted

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Hello everyone!

I would like to ask what's wrong with OpenGL context signal.
Previously everything was working, until I didn't upgrade QT 5.9.5 -> 5.12.5. Compilation was successful, so I wasn't expecting any problems.

Currently I am using QT 5.12.5 on embedded platform based on Yocto.

// main.qml
import QtQuick 2.0
import QtQuick.Window 2.0
import QtWebEngine 1.0

Window {
    width: 1024
    height: 600
    visible: true
    WebEngineView {
        anchors.fill: parent
        url: "http://localhost"
    }
}

// main.cpp
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QtWebEngine>
#include <QWindow>
#include <QQuickWindow>
#include <QOpenGLContext>
#include <QDebug>

void CheckOpenGLContext(QOpenGLContext* ogl_contex)
{
  qDebug() << "CheckOpenGLContext()";
}

int main(int argc, char *argv[])
{
  QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
  QCoreApplication::setAttribute(Qt::AA_ShareOpenGLContexts);

  QGuiApplication app(argc, argv);
  QtWebEngine::initialize();

  QQmlApplicationEngine engine;
  engine.load(QUrl(QUrl("./main.qml")));

  QQuickWindow* window = qobject_cast<QQuickWindow*>(engine.rootObjects().first());
  QObject::connect(window, &QQuickWindow::openglContextCreated, [&](QOpenGLContext* ogl_ctx){ CheckOpenGLContext(ogl_ctx); });

  if(window->openglContext() != nullptr) qDebug() << "isValid: " << window->openglContext()->isValid();

  qDebug() << "started";

  return app.exec();
}

Application startup:

./egl_test -platform eglfs --no-sandbox
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/var/volatile/tmp/runtime-root'
Setting framebuffer size is only available with DRM atomic API
Unable to query physical screen size, defaulting to 100 dpi.
To override, set QT_QPA_EGLFS_PHYSICAL_WIDTH and QT_QPA_EGLFS_PHYSICAL_HEIGHT (in millimeters).
isValid:  true
started

From the documentation (https://doc.qt.io/qt-5/qopenglcontext.html#isValid) I can see Returns if this context is valid, i.e. has been successfully created.. So the signal openglContextCreated wasn't emitted even if, the openglContext is valid already

Same code on 5.9.5 works without any problems. Signal is emitted and validity check is false, because OpenGL content there is not valid.

So what's wrong there?

Thank you,
Andy

Andy99

Solved by setting visible: false then calling ->show() showe the window, when I wanted. Later the signal was emitted without problems as before.