QPaintDevice: Cannot destroy paint device that is being painted?

Pauly

I'm getting this message at the application output in QtCreator, as the following function exits. This code seems to run ok thought. What is the problem and how can I fix it? Thank you.

void MyClass::ThisFunc() {
//some code before this
QImage image(size, size, QImage::Format_Mono);
QPainter painter(&image);
painter.setBrush(background);
painter.setPen(Qt::NoPen);
painter.drawRect(0, 0, size, size);
//and other painter operation

if(image.save(path)){ 
//do something
}
} //message is thrown at this point. I guess image can not be destroy? why?

koahnig

@Pauly

Some things you cannot destroy while you are working on those a slot function. My guess is that there is your problem.

void MyClass::ThisFunc() {
//some code before this
QImage image(size, size, QImage::Format_Mono);
QPainter *painter = new QPainter (&image) ;
painter->setBrush(background);
painter->setPen(Qt::NoPen);
painter->drawRect(0, 0, size, size);
//and other painter operation

if(image.save(path)){ 
//do something
}
painter->deleteLater();   // will delete the paint device outside of this slot by event loop
} //message is thrown at this point. I guess image can not be destroy? why?

See, if it helps

SGaist

Hi,

Aren't you missing a call to QPainter::end ?

Pauly

@koahnig said in QPaintDevice: Cannot destroy paint device that is being painted?:

painter->deleteLater();

It said 2165: error: 'class QPainter' has no member named 'deleteLater' painter->deleteLater();

am I missing something?

Pauly

@SGaist

I tried added painter.end();, but the problem persists.

SGaist

QPainter is not a QObject.

Pauly

Thank you all for the help.

Following the lead, I think the problem is that QImage "image" can not be destroyed as QPainterDevice. So I double check the code and I found I assign something to image along the way, I think that causes the problem. I assign it to new QImage and leave along the original QImage image, the error seems to go way. Do you think this makes sense? Thank you.

void MyClass::ThisFunc() {
//some code before this
QImage image(size, size, QImage::Format_Mono);
QPainter painter(&image);
painter.setBrush(background);
painter.setPen(Qt::NoPen);
painter.drawRect(0, 0, size, size);
//and other painter operation

**image=something_else**

if(image.save(path)){ 
//do something
}
}

SGaist

Do you mean you assigned a new value to your image variable before calling painter.end() ?