Update Unicode overview to 3.0

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@53092 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

diff --git a/docs/doxygen/overviews/unicode.h b/docs/doxygen/overviews/unicode.h
index 657368058172d3ef0c6de9bdad6ab639eaf3bb41..0913bfbfb1807e302e671a536c6c22bf347f1889 100644 (file)
--- a/docs/doxygen/overviews/unicode.h
+++ b/docs/doxygen/overviews/unicode.h
@@ -19,8 +19,6 @@ characters from languages other than English.
 @li @ref overview_unicode_supportin
 @li @ref overview_unicode_supportout
 @li @ref overview_unicode_settings
 @li @ref overview_unicode_supportin
 @li @ref overview_unicode_supportout
 @li @ref overview_unicode_settings

-@li @ref overview_unicode_traps
-

 
 <hr>
 
 
 <hr>
 


@@ -33,127 +31,101 @@ 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
 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.
+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.

 
 

-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.
+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
 
 
 @section overview_unicode_ansi 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:
+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.

 
 

-@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
+@section overview_unicode_supportin Unicode Support in wxWidgets

 
 

-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 UNICODE checkes an average
-program would have had!). Luckily, there is another way - see the next section.
+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 the standard Windows encoding UCS-2
+(basically an array of 16-bit wchar_t). Under Unix 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.

 
 

-@section overview_unicode_supportin Unicode Support in wxWidgets
+Old code like this:

 
 

-In wxWidgets, the code fragment from above should be written instead:
+@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
 
 @code

-wxChar ch = wxT('*');
-wxString s = wxT("Hello, world!");
-int len = s.Len();
+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
 
 @endcode
 

-What happens here? First of all, you see that there are no more UNICODE checks
-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.
+If you want to replace individual characters in the string you
+need to get a reference to that character:

 
 

-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.
+@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

 
 

-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.
+which will change the content of the wxString s from "hello" to "aaaaa".

 
 

-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!
+String literals are translated to Unicode when they are assigned to
+a wxString object so code can be written like this:

 
 

-Just let us state once again the rules:
+@code
+wxString s = "Hello, world!";
+int len = s.Len();
+@endcode

 
 

-@li Always use wxChar instead of @c char
-@li 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 wxT() in this case)
-    or you intend to pass the constant directly to an external function which
-    doesn't accept wide-character strings.
-@li Use wxString instead of C style strings.
+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
 
 
 @section overview_unicode_supportout Unicode and the Outside World
 


@@ -179,29 +151,14 @@ const char* ascii_str = "Some text";
 wxString str(ascii_str, wxConvUTF8);
 @endcode
 
 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_mbconv.
 
 
 @section overview_unicode_settings Unicode Related Compilation Settings
 
 You should define @c wxUSE_UNICODE to 1 to compile your program in Unicode
 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. 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 overview_mbconv "wxMBConv") and construct wxString
-objects from Unicode strings (presumably read from some external file or
-elsewhere).
-
-
-@section overview_unicode_traps Traps for the Unwary
-
-@li Casting c_str() to void* is now char*, not wxChar*
-@li Passing c_str(), mb_str() or wc_str() to variadic functions doesn't work.
+mode. Since wxWidgets 3.0 this is always the case. When compiled in UTF8
+mode @c wxUSE_UNICODE_UTF8 is also defined.

 
 */
 
 
 */