Multithreaded QOpenGLWidget embed to QMainWindow

[ytexas]

hi, everyone

what happend:

Recently I'd like add a high performance opengl display widget to our application's window. So I tried add some code on official example threadedopenglwidget. For simulate situations like embed a threaded QOpenGLWidget to a QMainWindow:

Based on the example threadedopenglwidget. I added the GLWidget as QMainWindow 's central widget. And the window has a QDockWidget and a QStatusBar at the same time. The application would got crash when floating and moving the QDockWidget hovering the window, or resize the window with QStatusBar 's handle.

So my question: is there any way to make threaded QOpenGLWidget embed to QMainWindow?

---

What I tried & thounght:

I tried check back-trace tree, find most crashes happened after the QOpenGLWidget::resizeEvent, then overrloded the resizeEvent with empty function. And the window never crashed. But the resized render was incorrect, and the official doc suggest don't overload the resizeEvent.

I think there may be two reason caused crash:

• According to the official doc & the example. For make QOpenGLWidget render in multi-thread. The QOpenGLContext must be create/init/useing in the render thread. But it seems the QOpenGLContext may used by QOpenGLWidgetPrivate in QOpenGLWidget::resizeEvent.

• Or QOpenGLWidgetPrivate::sendPaintEvent in QOpenGLWidget::resizeEvent

update 3-10:
Crash caused by makeCurrent in QOpenGLOpenGLPrivate::recreateFbo. Backtrace:

---

minimum example:

(based on official's example threadedopenglwidget)

only modified: 3 source code files:

• mainwindow.h

// mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget* parent = nullptr);
};
#endif

• mainwindow.cpp

//mainwindow.cpp
#include "mainwindow.h"
#include "glwidget.h"

#include <QDockWidget>
#include <QStackedWidget>
#include <QStatusBar>

MainWindow::MainWindow(QWidget* parent) : QMainWindow(parent)
{
    auto* glwidget1 = new GLWidget();
    setCentralWidget(glwidget1);

	setStatusBar(new QStatusBar(this));

    auto* dock = new QDockWidget;
    this->addDockWidget(Qt::LeftDockWidgetArea, dock);
}

• main.cpp

// main.cpp
#include "glwidget.h"
#include "mainwindow.h"
#include <QApplication>

int main(int argc, char **argv) {
  QApplication a(argc, argv);

 MainWindow mw1;
  mw1.show();

  return a.exec();
}

[SGaist]

Hi,

Which version of Qt are you using ?
On which platform ?
What is your graphics card ?

[ytexas]

@SGaist

• Tried 5.12.8 on Ubuntu 20.04 LTS; 5.15.3 and 6.2.3 on Archlinux.
• Graphics card: Nvidia GTX 1080Ti

[SGaist]

I think you should bring this to the bug report system. Don't forget to add the analysis you did here.