<![CDATA[QOpenGLWidget says I need a QApplication before QWidget, even if I already have.]]>So I'm making a game engine, I tried to make a QOpenGLWidget attached to one of my QMainWindow tabs, but unfortunately I kept getting an error saying I need to construct a QApplication before a QWidget.

I already did that but unfortunately doesn't work.

Am I doing something wrong here?

LevelEditor.cpp:

HAEDITOR_LEVELEDITOR::HAEDITOR_LEVELEDITOR(QWidget *parent)
	: QOpenGLWidget(parent)
{
	ui.setupUi(this);

	//HATime::renderAPI = HA_RENDER_ENUM::OpenGL;

	// QOpenGLWidget* oGL = new QOpenGLWidget(parent);
	ui.gridLayout->addWidget(this);

	HAEDITOR_MAINWINDOW* mainWindow = new HAEDITOR_MAINWINDOW();
	mainWindow->ui.TabNavigation->insertTab(0, this, "Level Editor");

	initializeGL();
	paintGL();
	resizeGL(1024, 716);
}

MainWIndow.cpp

HAEDITOR_MAINWINDOW::HAEDITOR_MAINWINDOW(QWidget* parent)
	: QMainWindow(parent)
{
	ui.setupUi(this);

	HAEDITOR_LEVELEDITOR* levelEditor = new HAEDITOR_LEVELEDITOR(parent);

	ui.TabNavigation->insertTab(0, levelEditor, "Level Editor");
}

Main.cpp:

int main(int argc, char* argv[])
{
	QApplication haEditor(argc, argv);

	std::unique_ptr<HAEDITOR_MAINWINDOW> mainEditor(new HAEDITOR_MAINWINDOW());
	mainEditor->show();

	return haEditor.exec();
}
]]>https://forum.qt.io/topic/139527/qopenglwidget-says-i-need-a-qapplication-before-qwidget-even-if-i-already-haveRSS for NodeWed, 28 Oct 2026 01:36:03 GMTFri, 23 Sep 2022 14:00:29 GMT60<![CDATA[Reply to QOpenGLWidget says I need a QApplication before QWidget, even if I already have. on Sun, 25 Sep 2022 07:50:57 GMT]]>Now please remove all the stuff you don't need, only derive from QOpenGLWidget and remove all the other unneeded stuff to see if it still gives the problem. Once you stripped down your program to less than 50 lines we can try it out here.

]]>https://forum.qt.io/post/730081https://forum.qt.io/post/730081Sun, 25 Sep 2022 07:50:57 GMT<![CDATA[Reply to QOpenGLWidget says I need a QApplication before QWidget, even if I already have. on Sun, 25 Sep 2022 06:56:01 GMT]]>@Hyperspider-Software
If this were your complete main.cpp it would not compile since it does not have any #include statements, and nor would it have a "Line 29" as shown in the stack trace.

]]>https://forum.qt.io/post/730075https://forum.qt.io/post/730075Sun, 25 Sep 2022 06:56:01 GMT<![CDATA[Reply to QOpenGLWidget says I need a QApplication before QWidget, even if I already have. on Sat, 24 Sep 2022 23:26:35 GMT]]>@Christian-Ehrlicher here:

int main(int argc, char *argv[])
{
	QApplication haEditor(argc, argv);
	haEditor.setWindowIcon(QIcon
	("C:\\Users\\abora\\source\\repos\\HyperArachnid\\HAEditor\\Main\\Icon\\HyperArachnidLogo.png")
	);

	//std::unique_ptr<HATime> time(new HATime());

	QSplashScreen* splashScreen = new QSplashScreen;
	splashScreen->setPixmap(QPixmap("C:\\Users\\abora\\source\\repos\\HyperArachnid\\HAEditor\\Main\\SplashImage\\HAEditorSplashIMage.png"));
	splashScreen->show();

	QTimer::singleShot(2500, splashScreen, SLOT(close()));

	HAEDITOR_MAINWINDOW* mainEditor = new HAEDITOR_MAINWINDOW();

	HAEDITOR_LEVELGRAPH* levelEditor = new HAEDITOR_LEVELGRAPH();

	mainEditor->ui.TabNavigation->addTab(levelEditor->window(), "Level Editor");

	QTimer::singleShot(3500, mainEditor, SLOT(show()));

	return haEditor.exec();
}
]]>https://forum.qt.io/post/730065https://forum.qt.io/post/730065Sat, 24 Sep 2022 23:26:35 GMT<![CDATA[Reply to QOpenGLWidget says I need a QApplication before QWidget, even if I already have. on Sat, 24 Sep 2022 06:18:51 GMT]]>Please show your complete main.cpp - the line number in the stack trace do not match your main.cpp you posted.

]]>https://forum.qt.io/post/730014https://forum.qt.io/post/730014Sat, 24 Sep 2022 06:18:51 GMT<![CDATA[Reply to QOpenGLWidget says I need a QApplication before QWidget, even if I already have. on Fri, 23 Sep 2022 21:30:41 GMT]]>I kept seeing this message in the stack menu but couldn't find a solution.
Any other solutions?

QtProblem.png

]]>https://forum.qt.io/post/730004https://forum.qt.io/post/730004Fri, 23 Sep 2022 21:30:41 GMT<![CDATA[Reply to QOpenGLWidget says I need a QApplication before QWidget, even if I already have. on Fri, 23 Sep 2022 18:30:49 GMT]]>Hi,

@Hyperspider-Software said in QOpenGLWidget says I need a QApplication before QWidget, even if I already have.:

initializeGL();
paintGL();
resizeGL(1024, 716);

Beside what @JonB suggests, this is also wrong. These methods will be called when appropriate by Qt. Their place is not in the class constructor.

]]>https://forum.qt.io/post/729988https://forum.qt.io/post/729988Fri, 23 Sep 2022 18:30:49 GMT<![CDATA[Reply to QOpenGLWidget says I need a QApplication before QWidget, even if I already have. on Fri, 23 Sep 2022 14:03:56 GMT]]>@Hyperspider-Software
Hello and welcome.

Run in debugger and look at stack view on error. Usually this mean you have some static QWidget somewhere, at global scope, maybe in another file. You must not do that, as it executes before your main() & QApplication.

]]>https://forum.qt.io/post/729962https://forum.qt.io/post/729962Fri, 23 Sep 2022 14:03:56 GMT