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/*!
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@page mbconvclasses_overview wxMBConv classes overview
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- Classes: #wxMBConv, wxMBConvLibc,
- #wxMBConvUTF7, #wxMBConvUTF8,
- #wxCSConv,
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+ Classes: #wxMBConv, wxMBConvLibc,
+ #wxMBConvUTF7, #wxMBConvUTF8,
+ #wxCSConv,
#wxMBConvUTF16, #wxMBConvUTF32
The wxMBConv classes in wxWidgets enable an Unicode-aware application to
easily convert between Unicode and the variety of 8-bit encoding systems still
#wxCSConv
@ref convertingstrings_overview
@ref convertingbuffers_overview
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@section needforconversion Background: The need for conversion
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As programs are becoming more and more globalized, and users exchange documents
across country boundaries as never before, applications increasingly need to
take into account all the different character sets in use around the world. It
Unicode data from one Unicode-aware system to another may need encoding to an
8-bit multibyte encoding (UTF-7 or UTF-8 is typically used for this purpose), to
pass unhindered through any traditional transport channels.
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@section conversionandwxstring Background: The wxString class
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If you have compiled wxWidgets in Unicode mode, the wxChar type will become
identical to wchar_t rather than char, and a wxString stores wxChars. Hence,
all wxString manipulation in your application will then operate on Unicode
data over a network, or processing a text file for some other application. You
need a way to quickly convert your easily-handled Unicode data to and from a
traditional 8-bit encoding. And this is what the wxMBConv classes do.
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@section wxmbconvclasses wxMBConv classes
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The base class for all these conversions is the wxMBConv class (which itself
implements standard libc locale conversion). Derived classes include
wxMBConvLibc, several different wxMBConvUTFxxx classes, and wxCSConv, which
implement different kinds of conversions. You can also derive your own class
for your own custom encoding and use it, should you need it. All you need to do
is override the MB2WC and WC2MB methods.
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@section wxmbconvobjects wxMBConv objects
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Several of the wxWidgets-provided wxMBConv classes have predefined instances
(wxConvLibc, wxConvFileName, wxConvUTF7, wxConvUTF8, wxConvLocal). You can use
these predefined objects directly, or you can instantiate your own objects.
interface is supposed to use, in the case that the user interface is not
Unicode-based (like with GTK+ 1.2). By default, it points to wxConvLibc or
wxConvLocal, depending on which works best on the current platform.
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@section wxcsconvclass wxCSConv
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The wxCSConv class is special because when it is instantiated, you can tell it
which character set it should use, which makes it meaningful to keep many
instances of them around, each with a different character set (or you can
The predefined wxCSConv instance, wxConvLocal, is preset to use the
default user character set, but you should rarely need to use it directly,
it is better to go through wxConvCurrent.
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@section convertingstrings Converting strings
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Once you have chosen which object you want to use to convert your text,
here is how you would use them with wxString. These examples all assume
that you are using a Unicode build of wxWidgets, although they will still
compile in a non-Unicode build (they just won't convert anything).
Example 1: Constructing a wxString from input in current encoding.
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@code
wxString str(input_data, *wxConvCurrent);
@endcode
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Example 2: Input in UTF-8 encoding.
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@code
wxString str(input_data, wxConvUTF8);
@endcode
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Example 3: Input in KOI8-R. Construction of wxCSConv instance on the fly.
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@code
wxString str(input_data, wxCSConv(wxT("koi8-r")));
@endcode
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Example 4: Printing a wxString to stdout in UTF-8 encoding.
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@code
puts(str.mb_str(wxConvUTF8));
@endcode
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Example 5: Printing a wxString to stdout in custom encoding.
Using preconstructed wxCSConv instance.
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@code
wxCSConv cust(user_encoding);
printf("Data: %s\n", (const char*) str.mb_str(cust));
@endcode
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Note: Since mb_str() returns a temporary wxCharBuffer to hold the result
of the conversion, you need to explicitly cast it to const char* if you use
it in a vararg context (like with printf).
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@section convertingbuffers Converting buffers
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If you have specialized needs, or just don't want to use wxString, you
can also use the conversion methods of the conversion objects directly.
This can even be useful if you need to do conversion in a non-Unicode
build of wxWidgets; converting a string from UTF-8 to the current
encoding should be possible by doing this:
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@code
wxString str(wxConvUTF8.cMB2WC(input_data), *wxConvCurrent);
@endcode
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Here, cMB2WC of the UTF8 object returns a wxWCharBuffer containing a Unicode
string. The wxString constructor then converts it back to an 8-bit character
set using the passed conversion object, *wxConvCurrent. (In a Unicode build
of wxWidgets, the constructor ignores the passed conversion object and
retains the Unicode data.)
This could also be done by first making a wxString of the original data:
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@code
wxString input_str(input_data);
wxString str(input_str.wc_str(wxConvUTF8), *wxConvCurrent);
@endcode
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To print a wxChar buffer to a non-Unicode stdout:
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@code
printf("Data: %s\n", (const char*) wxConvCurrent-cWX2MB(unicode_data));
@endcode
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If you need to do more complex processing on the converted data, you
may want to store the temporary buffer in a local variable:
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@code
const wxWX2MBbuf tmp_buf = wxConvCurrent-cWX2MB(unicode_data);
const char *tmp_str = (const char*) tmp_buf;
printf("Data: %s\n", tmp_str);
process_data(tmp_str);
@endcode
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If a conversion had taken place in cWX2MB (i.e. in a Unicode build),
the buffer will be deallocated as soon as tmp_buf goes out of scope.
(The macro wxWX2MBbuf reflects the correct return value of cWX2MB
(either char* or wxCharBuffer), except for the const.)
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*/
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projects / wxWidgets.git / blobdiff