wxGetTranslation() wxTRANSLATE() wxT() _() _T()
我的结论，wxT() == _T() 只是为了让代码在Unicode和ANSI模式都可以方便的编译。
_T() 和 _wxTRANSLATE() 宏 是为了翻译需要。平时使用 _T() 就可以，但是某些特殊的初始化无法使用 _T() 就需要用到 _wxTRANSLATE() 。
::wxGetTranslation()
const wxChar * wxGetTranslation(const wxChar* str,
const wxChar* domain = NULL)
const wxChar * wxGetTranslation(const wxChar* str, const wxChar* strPlural, size_t n,
const wxChar* domain = NULL)
This function returns the translation of string str in the current
locale. If the string is not found in any of the loaded
message catalogs (see internationalization overview), the
original string is returned. In debug build, an error message is logged -- this
should help to find the strings which were not yet translated. If
domain is specified then only that domain/catalog is searched
for a matching string. As this function
is used very often, an alternative (and also common in Unix world) syntax is
provided: the _() macro is defined to do the same thing
as wxGetTranslation.
The second form is used when retrieving translation of string that has
different singular and plural form in English or different plural forms in some
other language. It takes two extra arguments: as above, str
parameter must contain the singular form of the string to be converted and
is used as the key for the search in the catalog. The strPlural parameter
is the plural form (in English). The parameter n is used to determine the
plural form. If no message catalog is found str is returned if 'n == 1',
otherwise strPlural.
See GNU gettext manual
for additional information on plural forms handling. For a shorter alternative
see the wxPLURAL() macro.
Both versions call wxLocale::GetString.
Note that this function is not suitable for literal strings in Unicode
builds, since the literal strings must be enclosed into
_T() or wxT macro which makes them
unrecognised by xgettext, and so they are not extracted to the message
catalog. Instead, use the _() and
wxPLURAL macro for all literal strings.
wxT()
wxChar wxT(char ch)
const wxChar * wxT(const char *s)
wxT() is a macro which can be used with character and string literals (in other
words, 'x' or "foo") to automatically convert them to Unicode in
Unicode build configuration. Please see the
Unicode overview for more information.
This macro is simply returns the value passed to it without changes in ASCII
build. In fact, its definition is:
#ifdef UNICODE
#define wxT(x) L ## x
#else // !Unicode
#define wxT(x) x
#endif
wxTRANSLATE()
const wxChar * wxTRANSLATE(const char *s)
This macro doesn't do anything in the program code -- it simply expands to the
value of its argument (except in Unicode build where it is equivalent to
wxT which makes it unnecessary to use both wxTRANSLATE and wxT
with the same string which would be really unreadable).
However it does have a purpose and it is to mark the literal strings for the
extraction into the message catalog created by xgettext program. Usually
this is achieved using _() but that macro not only marks
the string for extraction but also expands into a
wxGetTranslation function call which means that it
cannot be used in some situations, notably for static array
initialization.
Here is an example which should make it more clear: suppose that you have a
static array of strings containing the weekday names and which have to be
translated (note that it is a bad example, really, as
wxDateTime already can be used to get the localized week
day names already). If you write
static const wxChar * const weekdays[] = { _("Mon"), ..., _("Sun") };
...
// use weekdays[n] as usual
the code wouldn't compile because the function calls are forbidden in the array
initializer. So instead you should do
static const wxChar * const weekdays[] = { wxTRANSLATE("Mon"), ..., wxTRANSLATE("Sun") };
...
// use wxGetTranslation(weekdays[n])
here.
Note that although the code would compile if you simply omit
wxTRANSLATE() in the above, it wouldn't work as expected because there would be
no translations for the weekday names in the program message catalog and
wxGetTranslation wouldn't find them.
_()
const wxChar * _(const char *s)
This macro expands into a call to wxGetTranslation
function, so it marks the message for the extraction by xgettext just as
wxTRANSLATE does, but also returns the translation of
the string for the current locale during execution.
Don't confuse this macro with _T()!
_T()
wxChar _T(char ch)
const wxChar * _T(const wxChar ch)
This macro is exactly the same as wxT and is defined in
wxWidgets simply because it may be more intuitive for Windows programmers as
the standard Win32 headers also define it (as well as yet another name for the
same macro which is _TEXT()).
Don't confuse this macro with _()!