About windows and layout

The key is to add the window back to its layout , Instead of just returning its parent class
// In the maximum state , Double click the screen to display the full screen
else if(preScreen->getScreenState() == ScreenState::maxState)
{
m_screensParent[n]->setWindowFlags(Qt::Window);
When the new window is Qt::Window when , Don't change it parent;
m_screensParent[n]->showFullScreen();
preScreen->setScreenState(ScreenState::fullState);
}
// In full screen mode , Double click the screen to restore the normal display
else if(preScreen->getScreenState() == ScreenState::fullState)
{
m_screensParent[n]->setWindowFlags(Qt::Widget);
screensDivid(nowDevidedNum);
preScreen->setScreenState(ScreenState::normalState);
}
One qwidget After becoming a separate window , Break away from the original layout , You need to reset the layout to add it back . When setting the layout , The parent of the additional window is the object to which the layout belongs .
Because after the current parent Phase at the same time , Do not perform operation .
widget->setParent(m_screensParent[index],Qt::Widget);
Set the parent object with parameters .
Break the relationship with its parent class before deleting ：
The old layout must be deleted , To set a new layout .
layout->setParent(nullptr);
layout->deleteLater();
layout = nullptr;
About QWidget::setParent() Use of functions
setParent It can be used to switch one QWidget Corresponding parent window , because QT All of the widget It's all based on the relationship between father and son .

What we should pay special attention to here is ,setParent There are two interfaces , One is setParent（QWidget *parent）, One is setParent（QWidget *parent, Qt::WindowFlags f）, If the first parameter is called ,parent The flag bit of the window will be reset , If you want to keep the original window flag bit , You must specify a parameter . Let's take a simple example , If your original window flag bit is Qt::Window|Qt::FramelessWindowHint( A free form , Without Borders ), Then you need to bring this parameter to flags in , If not specified , Then its window property will be modified to QWidget 了 （ Will merge with the parent window , And will move the window position to （0,0） The location of ）