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 addresses 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}.
+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, ...
\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}
\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 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.
+Finally, there is a special \helpref{wxT()}{wxt} macro which should enclose all
+literal 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.
The important conclusion is that if you use {\tt wxChar} instead of
{\tt char}, avoid using C style strings and use {\tt wxString} instead and
-don't forget to enclose all string literals inside {\tt wxT()} macro, your
+don't forget to enclose all string literals inside \helpref{wxT()}{wxt} macro, your
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
-they're already converted to the right representation (another standard
-wxWindows macro {\tt \_()} does it, so there is no need for {\tt wxT()} in this
-case) or you intend to pass the constant directly to an external function
-which doesn't accept wide-character strings.
+\item Always enclose literal string constants in \helpref{wxT()}{wxt} macro
+unless they're already converted to the right representation (another standard
+wxWindows macro \helpref{\_()}{underscore} does it, for example, so there is no
+need for {\tt wxT()} in this case) or you intend to pass the constant directly
+to an external function which doesn't accept wide-character strings.
\item Use {\tt wxString} instead of C style strings.
\end{itemize}
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 conversions in the program).
+any conversions in the program). GTK 2.0 only accepts UTF-8 strings.
To get a ANSI string from a wxString, you may use the
mb\_str() function which always returns an ANSI
\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
+Unicode mode. Note that it currently only works in Win32 and GTK 2.0 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
+ANSI ones (using \helpref{wxMBConv classes}{mbconvclasses})
+and construct wxString objects from Unicode strings (presumably read
from some external file or elsewhere).
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