%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Name: tunicode.tex
-%% Purpose: Overview of the Unicode support in wxWindows
+%% Purpose: Overview of the Unicode support in wxWidgets
%% Author: Vadim Zeitlin
%% Modified by:
%% Created: 22.09.99
%% Licence: wxWindows license
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-\section{Unicode support in wxWindows}\label{unicode}
+\section{Unicode support in wxWidgets}\label{unicode}
-This section briefly describes the state of the Unicode support in wxWindows.
+This section briefly describes the state of the Unicode support in wxWidgets.
Read it if you want to know more about how to write programs able to work with
characters from languages other than English.
-\subsection{What is Unicode?}
+\subsection{What is Unicode?}\label{whatisunicode}
-Starting with release 2.1 wxWindows has support for compiling in Unicode mode
+Starting with release 2.1 wxWidgets 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}
+\subsection{Unicode and ANSI modes}\label{unicodeandansi}
-As not all platforms supported by wxWindows support Unicode (fully) yet, in
+As not all platforms supported by wxWidgets support Unicode (fully) yet, in
many cases it is unwise to write a program which can only work in Unicode
environment. A better solution is to write programs in such way that they may
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:
+This can be achieved quite simply by using the means provided by wxWidgets.
+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. wxWidgets 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}
program would have had!). Luckily, there is another way - see the next
section.
-\subsection{Unicode support in wxWindows}
+\subsection{Unicode support in wxWidgets}\label{unicodeinsidewxw}
-In wxWindows, the code fragment froim above should be written instead:
+In wxWidgets, the code fragment from above should be written instead:
\begin{verbatim}
wxChar ch = wxT('*');
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
+the Unicode and ANSI builds and allow 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}
\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
-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
+wxWidgets 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}
-\subsection{Unicode and the outside world}
+\subsection{Unicode and the outside world}\label{unicodeoutsidewxw}
-We have seen that it was easy to write Unicode programs using wxWindows types
+We have seen that it was easy to write Unicode programs using wxWidgets types
and macros, but it has been also mentioned that it isn't quite enough.
Although everything works fine inside the program, things can get nasty when
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). GTK 2.0 only accepts UTF-8 strings.
-To get a ANSI string from a wxString, you may use the
+To get an 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
useful, is wc\_str() function which always returns
the Unicode string.
+Sometimes it is also necessary to go from ANSI strings to wxStrings.
+In this case, you can use the converter-constructor, as follows:
+
+\begin{verbatim}
+ const char* ascii_str = "Some text";
+ wxString str(ascii_str, wxConvUTF8);
+\end{verbatim}
+
+This code also compiles fine under a non-Unicode build of wxWidgets,
+but in that case the converter is ignored.
+
+For more information about converters and Unicode see
+the \helpref{wxMBConv classes overview}{mbconvclasses}.
+
% TODO describe fn_str(), wx_str(), wxCharBuf classes, ...
-% Please remember to put a blank line at the end of each file! (Tex2RTF 'issue')
+
+\subsection{Unicode-related compilation settings}\label{unicodesettings}
+
+You should define {\tt wxUSE\_UNICODE} to $1$ to compile your program in
+Unicode mode. Note that it currently only works in Win32 and GTK 2.0 and
+that some parts of
+wxWidgets are not Unicode-compliant yet. 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 (using \helpref{wxMBConv classes}{mbconvclasses})
+and construct wxString objects from Unicode strings (presumably read
+from some external file or elsewhere).
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