[Kde-finance-apps] Porting KLocale::formatMoney()/readMoney() to Qt5/KF5, best practise?

[Friedrich W. H. Kossebau]

Hi developers of finance apps & Calligra Sheets & Calligra Plan,

(please keep cross-posting to both ml for now)

I (not only with my Calligra developer hat on) would like to collect 
experiences and ideas for conversion of curreny values to and from 
strings when using Qt5/KF5, especially when porting from kdelibs4's 
KLocale.


PROBLEM

QLocale is rather limited (as of Qt 5.5):
- no currency string parsing method
- string formatting method toCurrencyString() does not allow
  to control precision

KLocale and its currency related methods seem the last blocker to get 
rid of kdelibs4support in Calligra in the Qt5/KF5 port. Plan uses them 
for handling the costs of resources, and Sheets for the currency 
formatted cells. And both limitations are a blocker.


APPROACHES

Long term ideally QLocale gets support in its API for that. So we 
developers of currency data handling software should organize and 
draft an API.

First and short term though, until some released & wide-spread Qt 
version has the improved QLocale, I am looking for a solution 
independent of QLocale.
Most obvious might be to duplicate all currency things from KLocale, 
which would also include duplicating the database with all currency 
formatting data. This is what I would plan to do if there is no better 
idea.
Especially the database duplication is painful though, I would like to 
avoid at least that if possible. 


QUESTIONS

How have developers of e.g. Skrooge & KMyMoney approached the issue of 
conversion of currency values to/from strings?

Do you know about any activities to improve QLocale here?

Seems that Calligra apps Plan & Sheets are the only KDE apps using 
KLocale::readMoney() ?
https://lxr.kde.org/ident?v=stable-qt4&_i=readMoney&_remember=1

But KLocale::formatMoney() might be used by KMyMoney, Skrooge, Kraft & 
others (did not check though if not custom code):
https://lxr.kde.org/ident?v=stable-qt4&_i=formatMoney&_remember=1

Cheers
Friedrich