Disable the use of UTF-8 by default in Unix builds.

Add up-to-date description of UTF-8 support to the Unicode overview.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71424 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

configure

@@ -3038,17 +3038,16 @@ DEFAULT_wxUSE_LIBSDL=no
 DEFAULT_wxUSE_ACCESSIBILITY=no
 DEFAULT_wxUSE_IPV6=no
 DEFAULT_wxUSE_GSTREAMER8=no
+DEFAULT_wxUSE_UNICODE_UTF8=no
+DEFAULT_wxUSE_UNICODE_UTF8_LOCALE=no
 
 DEFAULT_wxUSE_ARTPROVIDER_TANGO=auto
-DEFAULT_wxUSE_UNICODE_UTF8=auto
 DEFAULT_wxUSE_OPENGL=auto
 DEFAULT_wxUSE_MEDIACTRL=auto
 DEFAULT_wxUSE_COMPILER_TLS=auto
 DEFAULT_wxUSE_HOTKEY=auto
 DEFAULT_wxUSE_METAFILE=auto
 
-DEFAULT_wxUSE_UNICODE_UTF8_LOCALE=no
-
 DEFAULT_wxUSE_UNIVERSAL_BINARY=no
 DEFAULT_wxUSE_MAC_ARCH=no
 
@@ -34345,17 +34344,6 @@ fi
 
 
 
-if test "$wxUSE_UNICODE" = "yes" -a "$wxUSE_UNICODE_UTF8" = "auto" ; then
-    if test "$USE_UNIX" = 1 -a "$wxUSE_DARWIN" != 1 ; then
-        wxUSE_UNICODE_UTF8=yes
-    elif test "$USE_OS2" = 1 ; then
-                                wxUSE_UNICODE_UTF8=yes
-    else
-        wxUSE_UNICODE_UTF8=no
-    fi
-fi
-
-
 if test "$wxUSE_GUI" = "yes"; then
     if test "$wxUSE_UNIX" = "yes" -a "$wxUSE_PM" != 1; then
 

configure.in

@@ -385,18 +385,17 @@ dnl features disabled by default
 DEFAULT_wxUSE_ACCESSIBILITY=no
 DEFAULT_wxUSE_IPV6=no
 DEFAULT_wxUSE_GSTREAMER8=no
+DEFAULT_wxUSE_UNICODE_UTF8=no
+DEFAULT_wxUSE_UNICODE_UTF8_LOCALE=no
 
 dnl automatic features
 DEFAULT_wxUSE_ARTPROVIDER_TANGO=auto
-DEFAULT_wxUSE_UNICODE_UTF8=auto
 DEFAULT_wxUSE_OPENGL=auto
 DEFAULT_wxUSE_MEDIACTRL=auto
 DEFAULT_wxUSE_COMPILER_TLS=auto
 DEFAULT_wxUSE_HOTKEY=auto
 DEFAULT_wxUSE_METAFILE=auto
 
-DEFAULT_wxUSE_UNICODE_UTF8_LOCALE=no
-
 dnl Mac/Cocoa users need to enable building universal binaries explicitly
 DEFAULT_wxUSE_UNIVERSAL_BINARY=no
 DEFAULT_wxUSE_MAC_ARCH=no
@@ -3610,25 +3609,6 @@ else
 fi
 
 
-dnl ---------------------------------------------------------------------------
-dnl UTF-8 support
-dnl ---------------------------------------------------------------------------
-
-dnl If UTF-8 support wasn't explicitly enabled or disabled, enable it only
-dnl for ports where it makes sense by default (GTK+, DirectFB):
-if test "$wxUSE_UNICODE" = "yes" -a "$wxUSE_UNICODE_UTF8" = "auto" ; then
-    if test "$USE_UNIX" = 1 -a "$wxUSE_DARWIN" != 1 ; then
-        wxUSE_UNICODE_UTF8=yes
-    elif test "$USE_OS2" = 1 ; then
-        dnl wide char support is quite incomplete in libc;
-        dnl UTF-8 might actually work when evaluating/setting
-        dnl code pages correctly, even for ports other than GTK20.
-        wxUSE_UNICODE_UTF8=yes
-    else
-        wxUSE_UNICODE_UTF8=no
-    fi
-fi
-
 dnl ---------------------------------------------------------------------------
 dnl Optional libraries included when system library is not used
 dnl ---------------------------------------------------------------------------

docs/doxygen/overviews/unicode.h

@@ -126,11 +126,14 @@ terms reported above.
 
 @section overview_unicode_supportin Unicode Support in wxWidgets
 
-Since wxWidgets 3.0 Unicode support is always enabled and building the library
+@subsection overview_unicode_support_default Unicode is Always Used by Default
-without it is not recommended any longer and will cease to be supported in the
+
-near future. This means that internally only Unicode strings are used and that,
+Since wxWidgets 3.0 Unicode support is always enabled and while building the
-under Microsoft Windows, Unicode system API is used which means that wxWidgets
+library without it is still possible, it is not recommended any longer and will
-programs require the Microsoft Layer for Unicode to run on Windows 95/98/ME.
+cease to be supported in the near future. This means that internally only
+Unicode strings are used and that, under Microsoft Windows, Unicode system API
+is used which means that wxWidgets programs require the Microsoft Layer for
+Unicode to run on Windows 95/98/ME.
 
 However, unlike the Unicode build mode of the previous versions of wxWidgets, this
 support is mostly transparent: you can still continue to work with the @b narrow
@@ -181,6 +184,54 @@ in your program there is really nothing special to do. However you should be
 aware of the potential problems covered by the following section.
 
 
+@subsection overview_unicode_support_utf Choosing Unicode Representation
+
+wxWidgets uses the system @c wchar_t in wxString implementation by default
+under all systems. Thus, under Microsoft Windows, UCS-2 (simplified version of
+UTF-16 without support for surrogate characters) is used as @c wchar_t is 2
+bytes on this platform. Under Unix systems, including Mac OS X, UCS-4 (also
+known as UTF-32) is used by default, however it is also possible to build
+wxWidgets to use UTF-8 internally by passing @c --enable-utf8 option to
+configure.
+
+The interface provided by wxString is the same independently of the format used
+internally. However different formats have specific advantages and
+disadvantages. Notably, under Unix, the underlying graphical toolkit (e.g.
+GTK+) usually uses UTF-8 encoded strings and using the same representations for
+the strings in wxWidgets allows to avoid conversion from UTF-32 to UTF-8 and
+vice versa each time a string is shown in the UI or retrieved from it. The
+overhead of such conversions is usually negligible for small strings but may be
+important for some programs. If you believe that it would be advantageous to
+use UTF-8 for the strings in your particular application, you may rebuild
+wxWidgets to use UTF-8 as explained above (notice that this is currently not
+supported under Microsoft Windows and arguably doesn't make much sense there as
+Windows itself uses UTF-16 and not UTF-8) but be sure to be aware of the
+performance implications (see @ref overview_unicode_performance) of using UTF-8
+in wxString before doing this!
+
+Generally speaking you should only use non-default UTF-8 build in specific
+circumstances e.g. building for resource-constrained systems where the overhead
+of conversions (and also reduced memory usage of UTF-8 compared to UTF-32 for
+the European languages) can be important. If the environment in which your
+program is running is under your control -- as is quite often the case in such
+scenarios -- consider ensuring that the system always uses UTF-8 locale and
+use @c --enable-utf8only configure option to disable support for the other
+locales and consider all strings to be in UTF-8. This further reduces the code
+size and removes the need for conversions in more cases.
+
+
+@subsection overview_unicode_settings Unicode Related Preprocessor Symbols
+
+@c wxUSE_UNICODE is defined as 1 now to indicate Unicode support. It can be
+explicitly set to 0 in @c setup.h under MSW or you can use @c --disable-unicode
+under Unix but doing this is strongly discouraged. By default, @c
+wxUSE_UNICODE_WCHAR is also defined as 1, however in UTF-8 build (described in
+the previous section), it is set to 0 and @c wxUSE_UNICODE_UTF8, which is
+usually 0, is set to 1 instead. In the latter case, @c wxUSE_UTF8_LOCALE_ONLY
+can also be set to 1 to indicate that all strings are considered to be in UTF-8.
+
+
+
 @section overview_unicode_pitfalls Potential Unicode Pitfalls
 
 The problems can be separated into three broad classes:
@@ -280,17 +331,18 @@ wxWidgets 3.0 and the new code should be used with this in mind and ideally
 avoiding implicit conversions to @c char*.
 
 
-@subsection overview_unicode_performance Unicode Performance Implications
+@subsection overview_unicode_performance Performance Implications of Using UTF-8
 
-Under Unix systems wxString class uses variable-width UTF-8 encoding for
+As mentioned above, under Unix systems wxString class can use variable-width
-internal representation and this implies that it can't guarantee constant-time
+UTF-8 encoding for internal representation. In this case it can't guarantee
-access to N-th element of the string any longer as to find the position of this
+constant-time access to N-th element of the string any longer as to find the
-character in the string we have to examine all the preceding ones. Usually this
+position of this character in the string we have to examine all the preceding
-doesn't matter much because most algorithms used on the strings examine them
+ones. Usually this doesn't matter much because most algorithms used on the
-sequentially anyhow and because wxString implements a cache for iterating over
+strings examine them sequentially anyhow and because wxString implements a
-the string by index but it can have serious consequences for algorithms
+cache for iterating over the string by index but it can have serious
-using random access to string elements as they typically acquire O(N^2) time
+consequences for algorithms using random access to string elements as they
-complexity instead of O(N) where N is the length of the string.
+typically acquire O(N^2) time complexity instead of O(N) where N is the length
+of the string.
 
 Even despite caching the index, indexed access should be replaced with
 sequential access using string iterators. For example a typical loop:
@@ -384,15 +436,5 @@ But, once again, none of these cryptic types is really needed if you just pass
 the return value of any of the functions mentioned in this section to another
 function directly.
 
-@section overview_unicode_settings Unicode Related Compilation Settings
-
-@c wxUSE_UNICODE is now defined as @c 1 by default to indicate Unicode support.
-If UTF-8 is used for the internal storage in wxString, @c wxUSE_UNICODE_UTF8 is
-also defined, otherwise @c wxUSE_UNICODE_WCHAR is.
-
-You are encouraged to always use the default build settings of wxWidgets; this avoids
-the need of different builds of the same application/library because of different
-"build modes".
-
 */