-/*!
-
- @page overview_unicode Unicode support in wxWidgets
-
- 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.
-
- @li @ref overview_whatisunicode
- @li @ref overview_unicodeandansi
- @li @ref overview_unicodeinsidewxw
- @li @ref overview_unicodeoutsidewxw
- @li @ref overview_unicodesettings
- @li @ref overview_topic8
-
-
- @section overview_whatisunicode What is Unicode?
-
- wxWidgets 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 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 #http://www.unicode.org.
-
- 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 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 the program uses to/from Unicode
- each time a system call is made.
-
- @section overview_unicodeandansi Unicode and ANSI modes
-
- 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 wxWidgets.
- Basically, there are only a few things to watch out for:
-
-
- - Character type (@c char or @c wchar_t)
- - Literal strings (i.e. @c "Hello, world!" or @c '*')
- - String functions (@c strlen(), @c strcpy(), ...)
- - Special preprocessor tokens (@c __FILE__, @c __DATE__
- and @c __TIME__)
-
-
- Let's look at them in order. First of all, each character in an Unicode
- program takes 2 bytes instead of usual one, so another type should be used to
- store the characters (@c char only holds 1 byte usually). This type is
- called @c wchar_t which stands for @e wide-character type.
-
- Also, the string and character constants should be encoded using wide
- characters (@c wchar_t type) which typically take 2 or 4 bytes instead
- of @c char which only takes one. This is achieved by using the standard C
- (and C++) way: just put the letter @c 'L' after any string constant and it
- becomes a @e long constant, i.e. a wide character one. To make things a bit
- more readable, you are also allowed to prefix the constant with @c 'L'
- instead of putting it after it.
-
- Of course, the usual standard C functions don't work with @c wchar_t
- strings, so another set of functions exists which do the same thing but accept
- @c wchar_t * instead of @c char *. For example, a function to get the
- length of a wide-character string is called @c wcslen() (compare with
- @c 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").
-
- 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 @c __TFILE__, @c __TDATE__
- and @c __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:
-
- @code
- #ifdef __UNICODE__
- 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
- @endcode
-
- 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 @c #ifdef UNICODE an average
- program would have had!). Luckily, there is another way - see the next
- section.
-
- @section overview_unicodeinsidewxw Unicode support in wxWidgets
-
- In wxWidgets, the code fragment from above should be written instead:
-
- @code
- wxChar ch = wxT('*');
- wxString s = wxT("Hello, world!");
- int len = s.Len();
- @endcode
-
- What happens here? First of all, you see that there are no more @c #ifdefs
- at all. Instead, we define some types and macros which behave differently in
- the Unicode and ANSI builds and allow us to avoid using conditional
- compilation in the program itself.
-
- We have a @c wxChar type which maps either on @c char or @c 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
- #wxString supports Unicode, i.e. it stores either ANSI or
- Unicode strings depending on the compile mode.
-
- Finally, there is a special #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 @c 'L' to its argument in the Unicode mode.
-
- The important conclusion is that if you use @c wxChar instead of
- @c char, avoid using C style strings and use @c wxString instead and
- don't forget to enclose all string literals inside #wxT() macro, your
- program automatically becomes (almost) Unicode compliant!
-
- Just let us state once again the rules:
-
- - Always use @c wxChar instead of @c char
- - Always enclose literal string constants in #wxT() macro
- unless they're already converted to the right representation (another standard
- wxWidgets macro #_() does it, for example, so there is no
- need for @c wxT() in this case) or you intend to pass the constant directly
- to an external function which doesn't accept wide-character strings.
- - Use @c wxString instead of C style strings.
-
- @section overview_unicodeoutsidewxw Unicode and the outside world
-
- 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 conversions in the program). GTK 2.0 only accepts UTF-8 strings.
-
- 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
- #c_str() returns a pointer to the internal
- representation which is either ASCII or Unicode). More rarely used, but still
- 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:
-
-
- @code
- const char* ascii_str = "Some text";
- wxString str(ascii_str, wxConvUTF8);
- @endcode
-
- 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 @ref overview_mbconvclasses.
-
- @section overview_unicodesettings Unicode-related compilation settings
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