Setting QFont from QFontDatabase sets all labels to monospaced font? Qt C++

Question

I am trying to set one QLabel to a monospaced font. By default, I have all my other labels set to "Arame-Regular" in the designer. Normally, trying to set any of my labels to "Arame-Mono" (the monospaced font) in the designer does not work. They stay regular.

After this bit of code in my mainwindow.cpp, every label in the application turns to monospaced:

    QFontDatabase::addApplicationFont("/path/to/the/fonts/Arame-Mono.ttf");
    QFont monospace("Arame-Mono");
    ui->labelFontTest->setFont(monospace);

Which solves part of the problem, a monospaced font is able to be used I guess, but I don't want every label in the application to be set to monospaced. How can I only address this one specific label to apply the monospaced font to it, and keep all other label how they were?

Another side effect of this is I am getting this message on launch:

qt.qpa.fonts: Populating font family aliases took 159 ms. Replace uses of missing font family "Arame-Mono" with one that exists to avoid this cost.

I both have the fonts installed locally on my Mac and added to my .pro file. The fonts are inside the fonts folder inside the project directory:

DISTFILES += \
    Fonts/Arame-Mono.ttf \
    Fonts/Arame-Regular.ttf \

Any help appreciated!

Check the [QFontDatabase::addApplicationFont](https://doc.qt.io/qt-5/qfontdatabase.html#addApplicationFont) return value. Maybe your application is not loading the font correctly. — Andrea Ricchi, Jun 09 '20 at 14:09
@AndreaRicchi I am checking the font with the line: `if (monoid != -1 && !QFontDatabase::applicationFontFamilies(monoid).isEmpty()){` and the font loads properly. Afterwards I can set every label to monospaced with `QApplication::setFont(regfamily, "QLabel");`. But I can not set a specific label to monospaced after this with `ui->label_speed_3->setFont(QFont("0Arame"));` and `monofont.setStyleHint(QFont::Monospace);`. I want the opposite effect: either not affect every label and only set one label to monospaced, OR set all labels to regular, then set one specifc label to monospaced after. — 956MB, Jun 09 '20 at 14:38

score 2 · Accepted Answer · answered Jun 11 '20 at 07:30

I've created a simple demo; it shows three labels where only the last one is set manually to monospace:

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

    using QFD = QFontDatabase;
    if (QFD::addApplicationFont(QStringLiteral(":/Roboto/Roboto-Regular.ttf")) == -1) {
        qWarning() << "Failed to load Roboto-Regular.ttf";
    }
    if (QFD::addApplicationFont(QStringLiteral(":/Roboto_Mono/RobotoMono-Regular.ttf")) == -1) {
        qWarning() << "Failed to load RobotoMono-Regular.ttf";
    }

    QFont regular("Roboto");
    QApplication::setFont(regular);

    MainWindow w;
    w.show();

    return a.exec();
}

    QFont mono("RobotoMono");
    ui->label_3->setFont(mono);

This works flawlessly. In your case, I suggest in the main to set the regular font for the application. Then only when needed use the monospace one. Also, remember that if you plan to ship the application you should embed the fonts in the executable using a QtResources (.qrc) file.

Thank you. This solves my immediate problem of setting an application wide font, and then being able to set other fonts on top of that. Now I just have a naming issue with setting the monospaced typeface of the same font. Which I suppose is a topic for somewhere else. — 956MB, Jun 11 '20 at 13:42

Setting QFont from QFontDatabase sets all labels to monospaced font? Qt C++

1 Answers1