/////////////////////////////////////////////////////////////////////////////
-// Name: unicode
+// Name: unicode.h
// Purpose: topic overview
// Author: wxWidgets team
// RCS-ID: $Id$
// Licence: wxWindows license
/////////////////////////////////////////////////////////////////////////////
-/*!
-
- @page unicode_overview 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.
- @ref whatisunicode_overview
- @ref unicodeandansi_overview
- @ref unicodeinsidewxw_overview
- @ref unicodeoutsidewxw_overview
- @ref unicodesettings_overview
- @ref topic8_overview
-
-
- @section 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 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 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 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 mbconvclasses_overview.
-
- @section unicodesettings Unicode-related compilation settings
-
- You should define @c wxUSE_UNICODE to 1 to compile your program in
- Unicode mode. This currently works for wxMSW, wxGTK, wxMac and wxX11. If you
- compile your program in ANSI mode you can still define @c wxUSE_WCHAR_T
- to get some limited support for @c wchar_t type.
- This will allow your program to perform conversions between Unicode strings and
- ANSI ones (using @ref mbconvclasses_overview)
- and construct wxString objects from Unicode strings (presumably read
- from some external file or elsewhere).
-
- @section topic8 Traps for the unwary
-
-
-
- Casting c_str() to void* is now char*, not wxChar*
- Passing c_str(), mb_str() or wc_str() to variadic functions
- doesn't work
-
- */
-
+/**
+
+@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_unicode_what
+@li @ref overview_unicode_ansi
+@li @ref overview_unicode_supportin
+@li @ref overview_unicode_supportout
+@li @ref overview_unicode_settings
+
+<hr>
+
+
+@section overview_unicode_what 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. A different approach is to encode all
+strings in UTF8 which does not require the use of wide characters and
+additionally is backwards compatible with 7-bit ASCII. The solution to
+use UTF8 is prefered under Linux and partially OS X.
+
+More details about Unicode may be found at <http://www.unicode.org/>.
+
+Writing internationalized programs is much easier with Unicode. Moreover
+even a program which uses only standard ASCII can benefit from using Unicode
+for string representation because there will be no need to convert all
+strings the program uses to/from Unicode each time a system call is made.
+
+@section overview_unicode_ansi Unicode and ANSI Modes
+
+Until wxWidgets 3.0 it was possible to compile the library both in
+ANSI (=8-bit) mode as well as in wide char mode (16-bit per character
+on Windows and 32-but on most Unix versions, Linux and OS X). This
+has been changed in wxWidget with the removal of the ANSI mode,
+but much effort has been made so that most of the previous ANSI
+code should still compile and work as before.
+
+@section overview_unicode_supportin Unicode Support in wxWidgets
+
+Since wxWidgets 3.0 Unicode support is always enabled meaning
+that the wxString class always uses Unicode to encode its content.
+Under Windows wxString uses UCS-2 (basically an array of 16-bit
+wchar_t). Under Unix, Linux and OS X however, wxString uses UTF8
+to encode its content.
+
+For the programmer, the biggest change is that iterating over
+a string can be slower than before since wxString has to parse
+the entire string in order to find the n-th character in a
+string, meaning that iterating over a string should no longer
+be done by index but using iterators. Old code will still work
+but might be less efficient.
+
+Old code like this:
+
+@code
+wxString s = wxT("hello");
+size_t i;
+for (i = 0; i < s.Len(); i++)
+{
+ wxChar ch = s[i];
+
+ // do something with it
+}
+@endcode
+
+should be replaced (especially in time critical places) with:
+
+@code
+wxString s = "hello";
+wxString::iterator i;
+for (i = s.begin(); i != s.end(); ++i)
+{
+ wxUniChar uni_ch = *i;
+ wxChar ch = uni_ch;
+ // same as: wxChar ch = *i
+
+ // do something with it
+}
+@endcode
+
+If you want to replace individual characters in the string you
+need to get a reference to that character:
+
+@code
+wxString s = "hello";
+wxString::iterator i;
+for (i = s.begin(); i != s.end(); ++i)
+{
+ wxUniCharRef ch = *i;
+ ch = 'a';
+ // same as: *i = 'a';
+}
+@endcode
+
+which will change the content of the wxString s from "hello" to "aaaaa".
+
+String literals are translated to Unicode when they are assigned to
+a wxString object so code can be written like this:
+
+@code
+wxString s = "Hello, world!";
+int len = s.Len();
+@endcode
+
+wxWidgets provides wrappers around most Posix C functions (like printf(..))
+and the syntax has been adapted to support input with wxString, normal
+C-style strings and wchar_t strings:
+
+@code
+wxString s;
+s.Printf( "%s %s %s", "hello1", L"hello2", wxString("hello3") );
+wxPrintf( "Three times hello %s\n", s );
+@endcode
+
+@section overview_unicode_supportout 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
+
+For more information about converters and Unicode see the @ref overview_mbconv.
+
+
+@section overview_unicode_settings Unicode Related Compilation Settings
+
+You should define @c wxUSE_UNICODE to 1 to compile your program in Unicode
+mode. Since wxWidgets 3.0 this is always the case. When compiled in UTF8
+mode @c wxUSE_UNICODE_UTF8 is also defined.
+
+*/
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