[SOLVED] QMdiArea::addSubWindow() issue

[Seba84]

Hi everyone,

It is the first time I'm using MdiArea object and to test it I did a little program.

I created a MainWindow with a QMdiArea as central widget, a toolbox and a statusbar. In the toolbox there is a new button that should open a new sub window, inside the sub window there is only a QPushButton. When I click on the "New" button (actionNew) the confirmation message appears on the statusbar but no sub window is opened. I searched on the qt help and on the net, I did several changes on the code but all without success.

Below the code:

@class MainWindow : public QMainWindow {
Q_OBJECT
Ui::MainWindow *ui;

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

public slots:
void _add_subwin();
void statusbar_msg(const QString &);
};

MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MainWindow) {
// SETUP USER-INTERFACE
ui->setupUi(this);
// ADDS A SUB-WINDOW (NOT WANTED!!)
QMdiSubWindow *subwin1 = ui->mdiArea->addSubWindow(new QPushButton(this));
subwin1->setAttribute(Qt::WA_DeleteOnClose);

// CONNECTIONS
connect(ui->actionNew, SIGNAL(triggered()), this, SLOT(_add_subwin()));
}

MainWindow::~MainWindow() {
ui->mdiArea->closeAllSubWindows();
delete ui;
}

void MainWindow::_add_subwin() {
// ADDS THE SUB-WINDOW
QMdiSubWindow *subwin1 = ui->mdiArea->addSubWindow(new QPushButton(this));
subwin1->setAttribute(Qt::WA_DeleteOnClose);
//subwin->show();
//ui->mdiArea->update();

// STATUSBAR MESSAGE
statusbar_msg("New window added");
}

void MainWindow::statusbar_msg(const QString &msg) {
// SENDS TO THE STATUS BAR A MESSAGE (TIMEOUT = 5 seconds)
ui->statusBar->showMessage(msg, 5000);
}@

As you can see, the only way I managed to open a subwindow is from the constructor (not the behavior wanted).
I tried QMdiSubWindow::show() and QMdiArea::update() from the MainWindow::_add_subwin() function but doesn't works.

Thanks in advance for your help.
Sebastian

[joeuser]

I've had focusing issues when opening multiple subwindows unless I create them in the following manner:

@
QMdiSubWindow* sw = new QMdiSubWindow( ui->mdiArea );
sw->setWidget( new QPushButton( sw ) );
sw->setAttribute( Qt::WA_DeleteOnClose );
ui->mdiArea->addSubWindow( sw );
sw->show();
@

perhaps the above pattern could work for you.

[Seba84]

Hello joeuser,

Thanks, this solved the problem! But I would like to understand why.

From the code above, the reasons I see are:

1. that I didn't declare as parent of the subwindow the mdiArea object (tested: not true)
2. that the call of show() is mandatory (tested: true)

But, in the original code, I called show and nothing happend...

Anyone has an idea what the problem was?

[Seba84]

The problem was show(). I tested the old code with show() and now it works:

@QMdiSubWindow *subwin1 = ui->mdiArea->addSubWindow(new QPushButton);
subwin1->setAttribute(Qt::WA_DeleteOnClose);
subwin1->show();@

Thanks again joeuser.