If your port requires gettext, just set USE_GETTEXT to yes, and your port will grow the dependency on devel/gettext. The value of USE_GETTEXT can also specify the required version of the libintl library, the basic part of gettext, but using this feature is strongly discouraged: Your port should work with just the current version of devel/gettext.
A rather common case is a port using gettext and configure. Generally, GNU configure should be able to locate gettext automatically. If it ever fails to, hints at the location of gettext can be passed in CPPFLAGS and LDFLAGS as follows:
USE_GETTEXT= yes
CPPFLAGS+= -I${LOCALBASE}/include
LDFLAGS+= -L${LOCALBASE}/lib
GNU_CONFIGURE= yes
CONFIGURE_ENV= CPPFLAGS="${CPPFLAGS}" \
LDFLAGS="${LDFLAGS}"
Of course, the code can be more compact if there are no more flags to pass to configure:
USE_GETTEXT= yes
GNU_CONFIGURE= yes
CONFIGURE_ENV= CPPFLAGS="-I${LOCALBASE}/include" \
LDFLAGS="-L${LOCALBASE}/lib"
Some software products allow for disabling NLS, e.g., through passing --disable-nls to configure. In that case,
your port should use gettext conditionally, depending on the
status of WITHOUT_NLS. For ports of low to medium complexity, you can rely
on the following idiom:
GNU_CONFIGURE= yes .if !defined(WITHOUT_NLS) USE_GETTEXT= yes PLIST_SUB+= NLS="" .else CONFIGURE_ARGS+= --disable-nls PLIST_SUB+= NLS="@comment " .endif
The next item on your to-do list is to arrange so that the message catalog files are included in the packing list conditionally. The Makefile part of this task is already provided by the idiom. It is explained in the section on advanced pkg-plist practices. In a nutshell, each occurrence of %%NLS%% in pkg-plist will be replaced by ``@comment '' if NLS is disabled, or by a null string if NLS is enabled. Consequently, the lines prefixed by %%NLS%% will become mere comments in the final packing list if NLS is off; otherwise the prefix will be just left out. All you need to do now is insert %%NLS%% before each path to a message catalog file in pkg-plist. For example:
%%NLS%%share/locale/fr/LC_MESSAGES/foobar.mo %%NLS%%share/locale/no/LC_MESSAGES/foobar.mo
In high complexity cases, you may need to use more advanced techniques than the recipe given here, such as dynamic packing list generation.
There is a point to note about installing message catalog files. The target directories for them, which reside under LOCALBASE/share/locale, should rarely be created and removed by your port. The most popular languages have their respective directories listed in /etc/mtree/BSD.local.dist; that is, they are a part of the base system. The directories for many other languages are governed by the devel/gettext port. You may want to consult its pkg-plist and see whether your port is going to install a message catalog file for a unique language.