This requires a std::locale generated from a boost::locale::generator
The examples already in our code base used the wrong message_path while
creating the generator and as a result our message catalogs weren't found.
As with the std::locale I have added code to create a locale via
boost::locale only once instead of having each c++ file redo the work.
This code expects a message_path to set for the boost generator.
An earlier attempt queried for this path directly from within
gnc-locale-utils using gnc_get_locale_dir (from gnc-path.h).
That however broke several c++ tests depending on gnc_locale_utils as those
then also needed to be linked against gnc-path.o. I couldn't get the linker
to do this properly so I worked around it for now by splitting the boost_locale
functionality in two steps:
- an initializer step that takes the messages_path as a string and will
generate the locale
- a getter to get the locale.
The initializer should only be run once, and before the getter is called.
It won't hurt though if the initializer is called more often.
If the getter is called before the initializer it will still
generate a std::locale but without setting a messages_path. It will then
also log a warning explaining translations may not be properly found.
We can't use std::locale::global because all streams imbue it by
default and if it's not 'C' (aka std::locale::classic) then we
must imbue all the streams that we don't want localized, and that's
most of them.
Provides error checking for setting the C++ locale from the environment.
This is necessary both because the environment might have an invalid
locale, which would cause an unhandled exception crash.
On windows std::locale("") can't handle some Microsoft-style locale
strings (e.g. Spanish_Spain) so we use boost::locale's gen("") function
to set the locale--though even that can't handle a Microsoft-style
locale string with an appended charset (e.g. Spanish_Spain.1252) and
that's what glibc's setlocale(LC_ALL, NULL) emits.
