QTabWidget hides a child widget and cannot show it again (Qt 5.12.2, mingw64, Windows 7)

Ejok88

Qt 5.12.2, mingw64, Windows 7
I need to create a tab with two widgets: custom widget and a button. I did:

    auto vbox = new QVBoxLayout;
    vbox->addWidget(customWidget);
    auto pb = new QPushButton("my button");
    vbox->addWidget(pb);
    vbox->addStretch();
    auto w = new QWidget();
    w->setLayout(vbox);
    tw_main = new QTabWidget;
    tw_main->addTab(w, "my tab");

And the first time there are no problems. And "w" widget is shown all. But when I close the tw_main widget and then open it again, there is only a button in "my tab".
When I debug this behavior, I find out that the customWidget is not shown again (file qwidget.cpp, in func showChildren(bool)) because it has the Qt::WA_WState_Hidden attribute.
If I insert the customWidget without the proxy widget w, I get normal behavior.

Now I cope with this problem by next code:

void MyMainForm::showEvent(QShowEvent *ev)
{
    if (customWidget)
    {
        customWidget->setVisible(true);
    }
}

SGaist

Hi,

What version of Qt ?
What OS ?
Can you provide a complete minimal example that shows that behavior ?

JoeCFD

w is not a child of tw_main or customWidget. Therefore it is not displayed when tw_main->setVisible( true ), right? make customWidget to be w's parent. Try it again.

Ejok88

@JoeCFD I read about addTab function: "Ownership of page is passed on to the QTabWidget." Why do you think that w is not a child of tw_main? And I read about w->setLayout(): "The QWidget will take ownership of layout." Then I read about vbox->addWidget: "When you use a layout, you do not need to pass a parent when constructing the child widgets. The layout will automatically reparent the widgets (using QWidget::setParent()) so that they are children of the widget on which the layout is installed." So tw_main owns w and w owns customWidget. (And I saw the customWidget in the child list of w in the debug mode)

Christian Ehrlicher

Please check with a more recent Qt version (5.12.8 will be enought if you can't update to 5.15). I think there was a bug around not showing dialogs after the first show somewhere in 5.12.x but don't know if this also affected QTabWidgets. Maybe also search the bugtracker.