how to center a Qt mainform on the screen?

Question

I've tried these in my mainform's constructor:

QRect desktopRect = QApplication::desktop()->availableGeometry(this);
move(desktopRect.center() - frameGeometry().center());

QRect desktopRect = QApplication::desktop()->availableGeometry(this);
move(desktopRect.center() - rect().center());

but both put the bottom right corner of the form at about the center of the screen, instead of centering the form. Any ideas?

score 15 · Accepted Answer · edited Apr 26 '19 at 18:38

I've tried these in my mainform's constructor

That's likely the problem. You probably don't have valid geometry information at this point because the object isn't visible.

When the object is first constructed, it's essentially positioned at (0,0) with it's expected (width,height), as such:

frame geometry at construction:  QRect(0,0 639x479)

But, after being shown:

frame geometry rect:  QRect(476,337 968x507)

Thus, you can't yet rely on your frameGeometry() information.

EDIT: With that said, I presume you can easily move it as desired, but for completeness I'm dropping in Patrice's code which doesn't depend on the frame geometry information:

QRect desktopRect = QApplication::desktop()->availableGeometry(this);
QPoint center = desktopRect.center();

move(center.x() - width() * 0.5, center.y() - height() * 0.5);

I found it works if I call `this->resize(width_I_want, height_I_want)` before the code to center it. Thanks! — David Burson, Aug 06 '10 at 18:08
That's interesting. How does that change the frame geometry? — Kaleb Pederson, Aug 06 '10 at 19:16

score 4 · Answer 2 · answered Aug 06 '10 at 15:25

The move function (see QWidget doc) takes one QPoint or two int as parameter. This corresponds to the coordinates of the top-left corner of your Widget (relative to its parent; Here OS Desktop). Try:

QRect desktopRect = QApplication::desktop()->availableGeometry(this);
QPoint center = desktopRect.center();

move(center.x()-width*0.5, center.y()-height*0.5);

score 4 · Answer 3 · answered Sep 04 '18 at 14:08

4

availableGeometry() is deprecated.

move(pos() + (QGuiApplication::primaryScreen()->geometry().center() - geometry().center()));

answered Sep 04 '18 at 14:08

score 2 · Answer 4 · answered Oct 20 '17 at 02:16

#include <QStyle>
#include <QDesktopWidget>

window->setGeometry(
    QStyle::alignedRect(
        Qt::LeftToRight,
        Qt::AlignCenter,
        window->size(),
        qApp->desktop()->availableGeometry()
    )
);

https://wiki.qt.io/How_to_Center_a_Window_on_the_Screen

score 1 · Answer 5 · answered Jun 18 '21 at 13:14

1

move(QGuiApplication::primaryScreen()->geometry().center() - rect().center());

answered Jun 18 '21 at 13:14

trig-ger

1,195
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score 0 · Answer 6 · answered Aug 21 '18 at 15:08

0

PyQT Python Version

# Center Window
desktopRect = QApplication.desktop().availableGeometry(self.window)
center = desktopRect.center();
self.window.move(center.x()-self.window.width()  * 0.5,
                 center.y()-self.window.height() * 0.5);

answered Aug 21 '18 at 15:08

Jonathan

6,741
7
52
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score -1 · Answer 7 · answered Sep 19 '16 at 21:25

-1

Another solution, assuming the window in question is 800×800:

QRect rec = QApplication::desktop()->availableGeometry();
move(QPoint((rec.width()-800)/2, (rec.height()-800)/2));

answered Sep 19 '16 at 21:25

Neurotransmitter

6,289
2
51
38

I'm not a fan of assuming window sizes, especially in the age of high-DPI displays and ever changing landscape of mobile devices. – Jonathan Aug 21 '18 at 15:03

how to center a Qt mainform on the screen?

7 Answers7

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