One place where the
gettext functions, if used normally, have big
problems is within programs with graphical user interfaces (GUIs). The
problem is that many of the strings which have to be translated are very
short. They have to appear in pull-down menus which restricts the
length. But strings which are not containing entire sentences or at
least large fragments of a sentence may appear in more than one
situation in the program but might have different translations. This is
especially true for the one-word strings which are frequently used in
As a consequence many people say that the
gettext approach is
wrong and instead
catgets should be used which indeed does not
have this problem. But there is a very simple and powerful method to
handle this kind of problems with the
Contexts can be added to strings to be translated. A context dependent translation lookup is when a translation for a given string is searched, that is limited to a given context. The translation for the same string in a different context can be different. The different translations of the same string in different contexts can be stored in the in the same MO file, and can be edited by the translator in the same PO file.
The gettext.h include file contains the lookup macros for strings
with contexts. They are implemented as thin macros and inline functions
over the functions from
const char *pgettext (const char *msgctxt, const char *msgid);
In a call of this macro, msgctxt and msgid must be string literals. The macro returns the translation of msgid, restricted to the context given by msgctxt.
The msgctxt string is visible in the PO file to the translator. You should try to make it somehow canonical and never changing. Because every time you change an msgctxt, the translator will have to review the translation of msgid.
Finding a canonical msgctxt string that doesn’t change over time can
be hard. But you shouldn’t use the file name or class name containing the
pgettext call – because it is a common development task to rename
a file or a class, and it shouldn’t cause translator work. Also you shouldn’t
use a comment in the form of a complete English sentence as msgctxt –
because orthography or grammar changes are often applied to such sentences,
and again, it shouldn’t force the translator to do a review.
The ‘p’ in ‘pgettext’ stands for “particular”:
fetches a particular translation of the msgid.
const char *dpgettext (const char *domain_name, const char *msgctxt, const char *msgid); const char *dcpgettext (const char *domain_name, const char *msgctxt, const char *msgid, int category);
These are generalizations of
pgettext. They behave similarly to
dcgettext, respectively. The domain_name
argument defines the translation domain. The category argument
allows to use another locale category than
As as example consider the following fictional situation. A GUI program has a menu bar with the following entries:
+------------+------------+--------------------------------------+ | File | Printer | | +------------+------------+--------------------------------------+ | Open | | Select | | New | | Open | +----------+ | Connect | +----------+
To have the strings
Connect translated there has to be
at some point in the code a call to a function of the
family. But in two places the string passed into the function would be
Open. The translations might not be the same and therefore we
are in the dilemma described above.
What distinguishes the two places is the menu path from the menu root to the particular menu entries:
Menu|File Menu|Printer Menu|File|Open Menu|File|New Menu|Printer|Select Menu|Printer|Open Menu|Printer|Connect
The context is thus the menu path without its last part. So, the calls look like this:
pgettext ("Menu|", "File") pgettext ("Menu|", "Printer") pgettext ("Menu|File|", "Open") pgettext ("Menu|File|", "New") pgettext ("Menu|Printer|", "Select") pgettext ("Menu|Printer|", "Open") pgettext ("Menu|Printer|", "Connect")
Whether or not to use the ‘|’ character at the end of the context is a matter of style.
For more complex cases, where the msgctxt or msgid are not string literals, more general macros are available:
const char *pgettext_expr (const char *msgctxt, const char *msgid); const char *dpgettext_expr (const char *domain_name, const char *msgctxt, const char *msgid); const char *dcpgettext_expr (const char *domain_name, const char *msgctxt, const char *msgid, int category);
Here msgctxt and msgid can be arbitrary string-valued expressions. These macros are more general. But in the case that both argument expressions are string literals, the macros without the ‘_expr’ suffix are more efficient.