How to set a color scheme for a QMainWindow?

Mark81

In Qt 6.8.2 Desktop application that runs on Ubuntu 24.10, I have this main.cpp:

#include "mainwindow.h"

#include <QStyleHints>
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QGuiApplication::styleHints()->setColorScheme(Qt::ColorScheme::Light);

    MainWindow w;
    w.show();
    return a.exec();
}

but this is the actual appearance:

so it still follows the system theme regardless the explictly setting of the light color scheme.
By the way if I write:

QGuiApplication::styleHints()->setColorScheme(Qt::ColorScheme::Light);
qDebug() << QGuiApplication::styleHints()->colorScheme();

it outputs:

Qt::ColorScheme::Dark

It seems it silently ignores the request.
Is there anything else I should add to force the desired color scheme?

SGaist

From a quick look at the code, the platform plugins currently don't handle that request yet.

SGaist

Hi,

Which desktop environment are you using ?

Mark81

@SGaist said in How to set a color scheme for a QMainWindow?:

Which desktop environment are you using ?

The default one that comes with Ubuntu 24.10:

GNOME Shell 47.0

SGaist

From a quick look at the code, the platform plugins currently don't handle that request yet.

Mark81

@SGaist Got it. Out of curiosity, I RTFM but I wasn't able to find this information. Actually, the docs say:

Sets the color scheme used by the application to an explicit scheme, or revert to the system's current color scheme if scheme is Qt::ColorScheme::Unknown.

There is no mention that this function is not implemented yet.
Are you saying there is no way to know this besides inspect the source code, aren't you?

SGaist

I would expect to have somewhere a list of the platform where the value is in use. I haven't checked all the platform backends. Just the Linux ones where I haven't seen the value in use.