Unsolved QWidget's child show doesn't work

[Milosz]

I have a strange problem:
My MainWindow is QWidget type and its constructor is like that:

...............
loggingWidget = new QWidget;
loggingWidget->setGeometry(0,0,1920,1080);
loggingWidget->setStyleSheet("background-image: url(FinalOutput_01_10.png); border: none;");

(1) QWidget *rulesWidget = new QWidget(loggingWidget);
rulesWidget->setGeometry(200,200,1020,680);
rulesWidget->setStyleSheet("background-image: url(FinalOutput.png); border: none;");

rulesWidget->show();

This operates OK.
But when I inherite QWidget into RulesWidget class and line (1) is:
RulesWidget *rulesWidget = new RulesWidget(loggingWidget);

that show() doesn't work.

definition of RulesWidget:
class RulesWidget : public QWidget
{
Q_OBJECT
public:
explicit RulesWidget(QWidget *parent = nullptr);
......

implementation
RulesWidget::RulesWidget(QWidget *parent) : QWidget(parent)
{

}

[JonB]

@Milosz said in QWidget's child show doesn't work:

My MainWindow is QWidget type

I thought it had to be QMainWindow type?

loggingWidget = new QWidget;

Where is its parent specified, or what is it added to?

I don't know if these are relevant to your issue, but I wouldn't mind understanding them anyway...

[Milosz]

Ok,
so I show all the code

MainWindow::MainWindow(QWidget *parent) :
QWidget(parent)
{

this->setWindowFlags(Qt::CustomizeWindowHint);
this->setGeometry(0,0,1920, 1080);
loggingWidget = new QWidget;
loggingWidget->setGeometry(0,0,1920,1080);
loggingWidget->setStyleSheet("background-image: url(Ekran_01_FinalOutput_01_10.png); border: none;");


RulesWidget *rulesWidget = new RulesWidget(loggingWidget);
rulesWidget->setGeometry(200,200,1020,680);
rulesWidget->setStyleSheet("background-image: url(Regulamin_FinalOutput.png); border: none;");


rulesWidget->show();


QHBoxLayout *mainLayout = new QHBoxLayout;
mainLayout->addWidget(loggingWidget);

setLayout(mainLayout);

}

and definition of MainWindow
class MainWindow : public QWidget
{
Q_OBJECT

public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();

private:

QWidget *loggingWidget;

};

[JonB]

@Milosz
At least that makes sense now!

Again, I don't know, but you call rulesWidget->show(); before you have ever added it (or anything) to the main window. I wouldn't even try to do that, seems real odd to me, can a widget deal with show() when it's not anywhere on the page? Does it make any difference if you put that as the very last line?

[Milosz]

I marked it's strange (:-)).
I have put it at the very last line but no effect :-(

[Christian Ehrlicher]

I would guess you have not implemented sizeHint() and therefore QWidget::sizeHint() is called which simply returns and invalid size since it doesn't know better.

[Milosz]

@Christian-Ehrlicher No effect.
:-(