KConfigDialog

For a configuration dialog in a QtWidgets application, use KConfigDialog, from sonic-frameworks-settings-ui (find_package(KF6 REQUIRED COMPONENTS ConfigWidgets), KF6::ConfigWidgets).

KConfigDialog enables and disables its buttons, creates the dialog and deletes its widgets. Through KConfigDialogManager it also restores the settings, resets them to their defaults and saves them.

For that, each widget that edits a setting must be named after the setting's entry with the prefix kcfg_: the widget kcfg_MyOption edits the entry MyOption. The settings come from a KConfig XT class (a KCoreConfigSkeleton).

An example:

void KCoolApp::showSettings(){
    if (KConfigDialog::showDialog(QStringLiteral("settings"))) {
      return;
    }
    KConfigDialog *dialog = new KConfigDialog(this, QStringLiteral("settings"), MySettings::self());
    dialog->setFaceType(KPageDialog::List);
    dialog->addPage(new General(nullptr, "General"), i18n("General"));
    dialog->addPage(new Appearance(nullptr, "Style"), i18n("Appearance"));
    connect(dialog, &KConfigDialog::settingsChanged, mainWidget, &Bar::loadSettings);
    connect(dialog, &KConfigDialog::settingsChanged, this, &Foo::loadSettings);
    dialog->show();
}

showDialog() shows the dialog called settings if it already exists, so it is only created once. General and Appearance stand for your own page widgets.

Besides this code, each class whose settings are in the dialog should have a slot like loadSettings() that reads the settings and applies them; the dialog's settingsChanged() signal calls it.

For the dialog's appearance (buttons, default button, …) see KPageDialog.

For more, see the KConfigDialog API reference.