Gui: Qt6 port

* QString::indexOf() is now marked as [[nodiscard]]
* Replace deprecated methods of QMessageBox
* QMouseEvent::globalPos() is deprecated, use globalPosition().toPoint()
* QWidget::enterEvent() requires a QEnterEvent as argument
* QLibraryInfo::location() is deprecated, use path()
* QVariant::Type is deprecated, use QMetaType::Type
* QVariant::canConvert(int) is deprecated, use QVariant::canConvert(QMetaType) or QVariant::canConvert<T>()
* QMessageBox::standardIcon is deprecated, use QStyle::standardIcon()
* Replace deprecated method QMessageBox::question(), ...
* QApplication::fontMetrics() is deprecated
* QDropEvent::mouseButtons() is deprecated, use buttons()
* QDropEvent::keyboardModifiers() is deprecated, use modifiers()
* Constructor of QFontDatabase is deprecated, use static methods instead
* Qt::AA_DisableHighDpiScaling is deprecated
* Qt::AA_EnableHighDpiScaling is deprecated
* Qt::AA_UseHighDpiPixmaps is deprecated

src/Gui/DlgExpressionInput.cpp

@@ -65,7 +65,7 @@ DlgExpressionInput::DlgExpressionInput(const App::ObjectIdentifier & _path,
     }
     else {
         QVariant text = parent->property("text");
-        if (text.canConvert(QMetaType::QString)) {
+        if (text.canConvert<QString>()) {
             ui->expression->setText(text.toString());
         }
     }