I mean, the user can press cancel, that's when QColorDialog returns an invalid color.
If there was a concept like an invalid font we could do the same here, but there's no such concept in QFont.
So yep, no better way.

In D28774#647157, @dfaure wrote:

I mean, the user can press cancel, that's when QColorDialog returns an invalid color.
If there was a concept like an invalid font we could do the same here, but there's no such concept in QFont.
So yep, no better way.

Looking at the code, if the user presses cancel, "theFont" is returned unchanged; seems pretty good to me:

int KFontChooserDialog::getFont(QFont &theFont, const KFontChooser::DisplayFlags &flags, QWidget *parent)
{
    KFontChooserDialog dlg(flags, parent);
    dlg.setObjectName(QStringLiteral("Font Selector"));
    dlg.setFont(theFont, flags & KFontChooser::FixedFontsOnly);

    const int result = dlg.exec();
    if (result == Accepted) {
        theFont = dlg.d->chooser->font();
        stripRegularStyleName(theFont);
    }
    return result;
}

QFontDialog::getFont() returns a QFont, and one may pass a bool * to check the dialog result code:
QFont QFontDialog::getFont(bool *ok, const QFont &initial, QWidget *parent, const QString &title, FontDialogOptions options)

which is standard Qt behaviour from other dialogs/widgets that handle user yes/no use cases, IIRC.

The KFontChooer* approach is more "economical", the "initial" font and the font you get from the dialog if you press OK, are the same object, and the function returns the dialog result code. As some wise old builder once said "there's no right or wrong way to lay bricks, as long as it works".

Why not add support for QPlatformTheme::FontDialog in KdePlatformTheme::createPlatformDialogHelper()?

In D28774#676000, @volkov wrote:

Why not add support for QPlatformTheme::FontDialog in KdePlatformTheme::createPlatformDialogHelper()?

Sorry about the late reply; I had looked into the platformtheme integration stuff, but at the time I didn't think it was a viable solution (nor was it easy for me to port); see https://phabricator.kde.org/D27808 for more details.