Method lengthToDisplayFormat

src/Mod/Sketcher/Gui/Utils.cpp:855–908

convert value to display format %0.[digits]f. Units are displayed if preference "ShowUnits" is true, or if the unit schema in effect uses multiple units (ex. Ft/In). Digits parameter is ignored for multi-unit schemata TODO:: if the user string is delivered in 1.23e45 format, this might not work correctly.

// TODO:: if the user string is delivered in 1.23e45 format, this might not work
//        correctly.
std::string SketcherGui::lengthToDisplayFormat(double value, int digits)
{
    Base::Quantity asQuantity;
    asQuantity.setValue(value);
    asQuantity.setUnit(Base::Unit::Length);
    std::string userString = asQuantity.getUserString();
    if (Base::UnitsApi::isMultiUnitLength() || (!hideUnits() && useSystemDecimals())) {
        // just return the user string
        return userString;
    }

    // find the unit of measure
    double factor = 1.0;
    std::string unitString;
    std::string translate = Base::UnitsApi::schemaTranslate(asQuantity, factor, unitString);
    std::string unitPart = " " + unitString;

    // get the numeric part of the user string
    QRegularExpression rxNoUnits(QStringLiteral("(.*) \\D*$"));  // text before space + any non
                                                                 // digits at end of string
    QRegularExpressionMatch match = rxNoUnits.match(QString::fromStdString(userString));
    if (!match.hasMatch()) {
        // no units in userString?
        return userString;
    }
    QString matched = match.captured(1);  // matched is the numeric part of user string
    auto smatched = matched.toStdString();
    int dpPos = matched.indexOf(QLocale().decimalPoint());
    if (dpPos < 0) {
        // no decimal separator (ie an integer), return all the digits
        if (!hideUnits()) {
            smatched.append(unitPart);
        }
        return smatched;
    }

    // real number
    if (useSystemDecimals() && hideUnits()) {
        // return just the numeric part of the user string
        return smatched;
    }

    // real number and not using system decimals
    int requiredLength = dpPos + digits + 1;
    if (requiredLength > matched.size()) {
        // just take the whole thing
        requiredLength = matched.size();
    }
    auto numericPart = matched.left(requiredLength).toStdString();
    if (!hideUnits()) {
        numericPart.append(unitPart);
    }
    return numericPart;
}

// convert value to display format %0.[digits]f. Units are always displayed for
// angles - 123.456° or 12°34'56". Digits parameter is ignored for multi-unit