Starting with release 2.1 wxWindows has support for compiling in Unicode mode
on the platforms which support it. Unicode is a standard for character
-encoding which addreses the shortcomings of the previous, 8 bit standards, by
-using 16 bit for encoding each character. This allows to have 65536 characters
-instead of the usual 256 and is sufficient to encode all of the world
-languages at once. More details about Unicode may be found at {\tt www.unicode.org}.
+encoding which addresses the shortcomings of the previous, 8 bit standards, by
+using at least 16 (and possibly 32) bits for encoding each character. This
+allows to have at least 65536 characters (what is called the BMP, or basic
+multilingual plane) and possible $2^{32}$ of them instead of the usual 256 and
+is sufficient to encode all of the world languages at once. More details about
+Unicode may be found at {\tt www.unicode.org}.
% TODO expand on it, say that Unicode extends ASCII, mention ISO8859, ...
As this solution is obviously preferable to the previous ones (think of
incompatible encodings for the same language, locale chaos and so on), many
-modern ooperating systems support it. The probably first example is Windows NT
+modern operating systems support it. The probably first example is Windows NT
which uses only Unicode internally since its very first version.
Writing internationalized programs is much easier with Unicode and, as the
support for it improves, it should become more and more so. Moreover, in the
Windows NT/2000 case, even the program which uses only standard ASCII can profit
from using Unicode because they will work more efficiently - there will be no
-need for the system to convert all strings hte program uses to/from Unicode
+need for the system to convert all strings the program uses to/from Unicode
each time a system call is made.
\subsection{Unicode and ANSI modes}
be compiled either in ANSI (traditional) mode or in the Unicode one.
This can be achieved quite simply by using the means provided by wxWindows.
-Basicly, there are only a few things to watch out for:
+Basically, there are only a few things to watch out for:
+
\begin{itemize}
\item Character type ({\tt char} or {\tt wchar\_t})
\item Literal strings (i.e. {\tt "Hello, world!"} or {\tt '*'})
\item String functions ({\tt strlen()}, {\tt strcpy()}, ...)
+\item Special preprocessor tokens ({\tt \_\_FILE\_\_}, {\tt \_\_DATE\_\_}
+and {\tt \_\_TIME\_\_})
\end{itemize}
Let's look at them in order. First of all, each character in an Unicode
store the characters ({\tt char} only holds 1 byte usually). This type is
called {\tt wchar\_t} which stands for {\it wide-character type}.
-Also, the string and character constants should be encoded on 2 bytes instead
-of one. This is achieved by using the standard C (and C++) way: just put the
-letter {\tt 'L'} after any string constant and it becomes a {\it long}
-constant, i.e. a wide character one. To make things a bit more readable, you
-are also allowed to prefix the constant with {\tt 'L'} instead of putting it
-after it.
+Also, the string and character constants should be encoded using wide
+characters ({\tt wchar\_t} type) which typically take $2$ or $4$ bytes instead
+of {\tt char} which only takes one. This is achieved by using the standard C
+(and C++) way: just put the letter {\tt 'L'} after any string constant and it
+becomes a {\it long} constant, i.e. a wide character one. To make things a bit
+more readable, you are also allowed to prefix the constant with {\tt 'L'}
+instead of putting it after it.
-Finally, the standard C functions don't work with {\tt wchar\_t} strings, so
-another set of functions exists which do the same thing but accept
+Of course, the usual standard C functions don't work with {\tt wchar\_t}
+strings, so another set of functions exists which do the same thing but accept
{\tt wchar\_t *} instead of {\tt char *}. For example, a function to get the
length of a wide-character string is called {\tt wcslen()} (compare with
{\tt strlen()} - you see that the only difference is that the "str" prefix
-standing for "string" has been replaced with "wcs" standing for
-"wide-character string").
+standing for "string" has been replaced with "wcs" standing for "wide-character
+string").
+
+And finally, the standard preprocessor tokens enumerated above expand to ANSI
+strings but it is more likely that Unicode strings are wanted in the Unicode
+build. wxWindows provides the macros {\tt \_\_TFILE\_\_}, {\tt \_\_TDATE\_\_}
+and {\tt \_\_TTIME\_\_} which behave exactly as the standard ones except that
+they produce ANSI strings in ANSI build and Unicode ones in the Unicode build.
To summarize, here is a brief example of how a program which can be compiled
in both ANSI and Unicode modes could look like:
wchar_t wch = L'*';
const wchar_t *ws = L"Hello, world!";
int len = wcslen(ws);
+
+ wprintf(L"Compiled at %s\n", __TDATE__);
#else // ANSI
char ch = '*';
const char *s = "Hello, world!";
int len = strlen(s);
+
+ printf("Compiled at %s\n", __DATE__);
#endif // Unicode/ANSI
\end{verbatim}
Of course, it would be nearly impossibly to write such programs if it had to
-be done this way (try to imagine the number of {\tt #ifdef UNICODE} an average
+be done this way (try to imagine the number of {\tt \#ifdef UNICODE} an average
program would have had!). Luckily, there is another way - see the next
section.
int len = s.Len();
\end{verbatim}
-What happens here? First of all, you see that there are no more {\tt #ifdef}s
+What happens here? First of all, you see that there are no more {\tt \#ifdef}s
at all. Instead, we define some types and macros which behave differently in
the Unicode and ANSI builds and allows us to avoid using conditional
compilation in the program itself.
We have a {\tt wxChar} type which maps either on {\tt char} or {\tt wchar\_t}
depending on the mode in which program is being compiled. There is no need for
a separate type for strings though, because the standard
-\helpref{wxString}{wxstring} supports Unicode, i.e. it stores iether ANSI or
-Unicode strings depending on the mode.
+\helpref{wxString}{wxstring} supports Unicode, i.e. it stores either ANSI or
+Unicode strings depending on the compile mode.
Finally, there is a special {\tt wxT()} macro which should enclose all literal
-strings in the program. As it's easy to see comparing the last fragment with
+strings in the program. As it is easy to see comparing the last fragment with
the one above, this macro expands to nothing in the (usual) ANSI mode and
prefixes {\tt 'L'} to its argument in the Unicode mode.
program automatically becomes (almost) Unicode compliant!
Just let us state once again the rules:
+
\begin{itemize}
\item Always use {\tt wxChar} instead of {\tt char}
\item Always enclose literal string constants in {\tt wxT()} macro unless
it tries to communicate with the outside world which, sadly, often expects
ANSI strings (a notable exception is the entire Win32 API which accepts either
Unicode or ANSI strings and which thus makes it unnecessary to ever perform
-any convertions in the program).
+any conversions in the program).
-To get a ANSI string from a wxString, you may use
-\helpref{mb\_str()}{wxstringmbstr} function which always returns an ANSI
+To get a ANSI string from a wxString, you may use the
+mb\_str() function which always returns an ANSI
string (independently of the mode - while the usual
\helpref{c\_str()}{wxstringcstr} returns a pointer to the internal
representation which is either ASCII or Unicode). More rarely used, but still
-useful, is \helpref{wc\_str()}{wxstringwcstr} function which always returns
+useful, is wc\_str() function which always returns
the Unicode string.
% TODO describe fn_str(), wx_str(), wxCharBuf classes, ...
+
+\subsection{Unicode-related compilation settings}
+
+You should define {\tt wxUSE\_UNICODE} to $1$ to compile your program in
+Unicode mode. Note that it currently only works in Win32 and that some parts of
+wxWindows are not Unicode-compliant yet (ODBC classes, for example). If you
+compile your program in ANSI mode you can still define {\tt wxUSE\_WCHAR\_T}
+to get some limited support for {\tt wchar\_t} type.
+
+This will allow your program to perform conversions between Unicode strings and
+ANSI ones (\helpref{wxEncodingConverter}{wxencodingconverter} depends on this
+partially) and construct wxString objects from Unicode strings (presumably read
+from some external file or elsewhere).
+
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