QPainter setFont segmentation fault on app exit.

Oen44

I'm using OpenGL to draw stuff, some of them have text. Everything works, nothing is glitching, no crashes, it's just great. The only thing that is bothering me is when I close the app, it's throwing segmentation fault. Debugger shows nothing but assembly so that wasn't helpful. I was able to narrow it down to this function:

void OTUI::MainWindow::draw(QPainter& painter)
{
    painter.save();
    painter.setPen(getColor());
    painter.setFont(getFont()); // this line is the reason
    //painter.setFont(QFont("Verdana", 11)); // same result
    painter.drawText(x(), y(), width(), 25, Qt::AlignCenter, getText());
    painter.restore();
}

What to do? If you need more info, let me know.

Oen44

@Christian-Ehrlicher Alright, started from scratch, adding as little code from previous project as possible. Made it so it's creating OTUI::MainWindow on startup, no seg fault. Started adding more, creation from context menu etc. and still no crash. Then added last pieces, StartupWindow was one of them. It's a small window with list of recent projects that you can open or create new. It's a separated window that is opening second one (the one with OpenGL and all, CoreWindow) and hiding itself. What I was missing is deleting 2nd window when the app is closed, inside StartupWindow deconstructor.

StartupWindow::~StartupWindow()
{
    delete coreWindow; // this was missing
    delete ui;
}

Christian Ehrlicher

From where do you call MainWindow::draw()? And please provide some more code - best would be a minimal, compilable example.

Oen44

@Christian-Ehrlicher From QOpenGLWidget::paintGL. You can clone project repository, nothing fancy needed to make it work straight away.
https://github.com/Oen44/OTUIEditor

Segmentation fault occurs when you create at least OTUI::MainWindow widget, even if it's then deleted. To do this, create new project, right-click on Widgets List panel on the left side and add Main Window, then simply close the app (you will be asked if you want to save the project, just press No), that's when segmentation fault happens.

Christian Ehrlicher

It would really be nice to get a small example - this will maybe also help you to find out the reason by yourself.

Oen44

@Christian-Ehrlicher Alright, started from scratch, adding as little code from previous project as possible. Made it so it's creating OTUI::MainWindow on startup, no seg fault. Started adding more, creation from context menu etc. and still no crash. Then added last pieces, StartupWindow was one of them. It's a small window with list of recent projects that you can open or create new. It's a separated window that is opening second one (the one with OpenGL and all, CoreWindow) and hiding itself. What I was missing is deleting 2nd window when the app is closed, inside StartupWindow deconstructor.

StartupWindow::~StartupWindow()
{
    delete coreWindow; // this was missing
    delete ui;
}

Christian Ehrlicher

Nice - good example why a minimal, compilable example is useful and good to track down the bug by yourself in most cases :)