QDialog Showmaximized not working

[Seb Tur]

After days of research I found that the bug is still there almost 10 years after report.
This is important for anybody using QinputDialog Ubuntu (I tested on Ubuntu 22.04) : showMaximized() and showNormal() have issues changing the state. This makes setGeometry troublesome as well.

https://bugreports.qt.io/browse/QTBUG-16034

I spend hours searching this forum and others finally finding the bug report.

So if moderators allow let's have it here for record of others searching for the cause.

[JonB]

@Seb-Tur
That issue refers to "metacity" under GNOME. I don't know that it has general/any applicability nowadays. It also is about whether min/max buttons can be shown on a dialog, whereas you seem to be asking about code.

FWIW I tried under 22.04 and it seemed to work OK. Default GNOME/Mutter. showMaximized() seem to work from code. I cannot be sure what else you saw for "troublesome".

[Seb Tur]

@JonB

tested again on mine,

   QDialog dialog(parent_widget);
   dialog.setObjectName("messageDialog");
   dialog.setWindowIcon(icon);
   dialog.setWindowTitle(title);
   dialog.setWindowFlags(Qt::Window);
   dialog.showMaximized();
   bool res = dialog.exec()

if I skip setWindowFlags(Qt::Window) then dialog is not maximized at all

[JonB]

@Seb-Tur
Tested on mine: Ubuntu 22.04, Qt 5.15.3, GNOME. Works fine (maximizes) with or without setWindowFlags(Qt::Window).

Check you are running under Xorg, not Wayland? Wayland may not allow such stuff?

[Seb Tur]

Reopening,
now I tried to make a windows10 build for my app and show dialog.showMaxmized() does not work, the window is just a fraction of the screen.

this is how i do it:

    if (touchscreen) {
        qDebug()<<"Showing maximized, it is touchscreen";
        setWindowFlags(windowFlags() | Qt::Window);
        setSizePolicy(QSizePolicy::Maximum,QSizePolicy::Maximum);
        showMaximized();
    } else {
        qDebug()<<"no touchscreen, getting screen geometry and calculate the size to occupy half of the screen";;
        QRect screenGeometry = QApplication::primaryScreen()->geometry();
        int width = screenGeometry.width() / 2;
        int height = screenGeometry.height() / 2;
        int x = (screenGeometry.width() - width) / 2;
        int y = (screenGeometry.height() - height) / 2;

        // Set the geometry of the dialog to be centered and occupy half the screen
        setGeometry(x, y, width, height);
        show();
    }

    exec();

[jsulm]

@Seb-Tur said in QDialog Showmaximized not working:

Showing maximized, it is touchscreen

Is this printed if you run your app?

[Seb Tur]

yes it is printed
I also do check
qDebug()<<"isMaximized: "<<isMaximized();
which returns 1 after showMaximized() even if the window does not get maximized.

my dirty trick right now is to add

#ifdef Q_OS_WIN
        QWidget *parentWidget = static_cast<QWidget *>(parent());
        if (parentWidget)
            setGeometry(parentWidget->geometry());
#endif

just after showMaximized()

[Seb Tur]

what is strange that showFullScreen() works ok

[Pl45m4]

@Seb-Tur said in QDialog Showmaximized not working:

what is strange that showFullScreen() works ok

Therefore check this topic.