QLineEdit - wrong placeholderText's color on Linux Mint dark theme

Kobid

Ok I have installed PhantonStyle and it also has black placeholder (on the right):

Here is for example my app written in wxWidgets with GTK and placeholder is correct:

cristian-adam

I think it has something to do with the default palette, which can vary from operating system to operating system.

If I look at https://doc.qt.io/qt-6/qpalette.html it could be that for some entry, like QPalette::PlaceholderText the light theme color value is being used instead of the dark theme one.

cristian-adam

You can change the QPalette::PlaceholderText to something else, see:

int main(int argc, char *argv[])
{        
    QApplication a(argc, argv);

    QPalette pal = QApplication::palette();
    pal.setColor(QPalette::PlaceholderText, pal.color(QPalette::Mid));
    QApplication::setPalette(pal);

Kobid

Thank you @cristian-adam . Found something interesting. The QPalette::Mid was too much alike to edit background so I played with different types to get something close to GTK placeholder color. Finally did something stupid just for curiosity:

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    //QApplication::setStyle(new PhantomStyle);

    QPalette pal = QApplication::palette();
    pal.setColor(QPalette::PlaceholderText, pal.color(QPalette::PlaceholderText));
    QApplication::setPalette(pal);

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

And the result is:

What happened there? Palette don't have initialized color for QPalette::PlaceholderText color role?

cristian-adam

It looks like a bug. Please do open up a bug report at https://bugreports.qt.io

Hopefully the Qt Widgets maintainers have more ideas why this is happening. But now you have a workaround.

Does:

   QPalette pal = QApplication::palette();
    QApplication::setPalette(pal);

work? Or you have to explicitly set QPalette::PlaceholderText ?

Kobid

No. That doesn't work.
Ok I'll submit a bug report.
Thank you

Christian Ehrlicher

You should check it with a recent Qt version first before creating a bug report

Kobid

Yo mean preview version? Because I have recent stable 6.9

Christian Ehrlicher

In your images above you use Qt5

Kobid

The installed one in linux mint (Keepassx installed this version) is 5.15. For my project I'm using 6.9 in custom installation

Christian Ehrlicher

Ok, then all is fine, create a bug report. Looks like a problem with the gtk platform plugin.
Maybe it's also related to https://bugreports.qt.io/browse/QTBUG-86195

Kobid

Created ticket if someone come here with similar problem:
https://bugreports.qt.io/browse/QTBUG-136075

Kobid

@Christian-Ehrlicher said in QLineEdit - wrong placeholderText's color on Linux Mint dark theme:

Ok, then all is fine, create a bug report. Looks like a problem with the gtk platform plugin.
Maybe it's also related to https://bugreports.qt.io/browse/QTBUG-86195

Weird, I searched first for placeholdertext keyword and didn't find anything. Anyway, that one is for Windows 10 reported in 2023

Christian Ehrlicher

@Kobid said in QLineEdit - wrong placeholderText's color on Linux Mint dark theme:

Anyway, that one is for Windows 10 reported in 2023

Please read the full bug report. It's also for linux.

Kobid

You are right