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157 lines
6.0 KiB
157 lines
6.0 KiB
/****************************************************************************
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**
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** Documentation of Unicode support in Qt.
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**
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** Copyright (C) 1992-2008 Trolltech ASA. All rights reserved.
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**
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** This file is part of the TQt GUI Toolkit.
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**
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** This file may be used under the terms of the GNU General
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** Public License versions 2.0 or 3.0 as published by the Free
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** Software Foundation and appearing in the files LICENSE.GPL2
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** and LICENSE.GPL3 included in the packaging of this file.
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** Alternatively you may (at your option) use any later version
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** of the GNU General Public License if such license has been
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** publicly approved by Trolltech ASA (or its successors, if any)
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** and the KDE Free TQt Foundation.
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**
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** Please review the following information to ensure GNU General
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** Public Licensing requirements will be met:
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** http://trolltech.com/products/qt/licenses/licensing/opensource/.
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** If you are unsure which license is appropriate for your use, please
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** review the following information:
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** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
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** or contact the sales department at sales@trolltech.com.
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**
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** This file may be used under the terms of the Q Public License as
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** defined by Trolltech ASA and appearing in the file LICENSE.QPL
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** included in the packaging of this file. Licensees holding valid Qt
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** Commercial licenses may use this file in accordance with the Qt
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** Commercial License Agreement provided with the Software.
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**
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** This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
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** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
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** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted
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** herein.
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**
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**********************************************************************/
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/*! \page unicode.html
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\title About Unicode
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Unicode is a multi-byte character set, portable across all major
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computing platforms and with decent coverage over most of the world.
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It is also single-locale; it includes no code pages or other
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complexities that make software harder to write and test. There is no
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competing character set that's reasonably multiplatform. For these
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reasons, Trolltech uses Unicode as the native character set for Qt
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(since version 2.0).
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\section1 Information about Unicode on the web.
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The \link http://www.unicode.org Unicode Consortium\endlink
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has a number of documents available, including
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\list
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\i \link http://www.unicode.org/unicode/standard/principles.html
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A technical introduction to Unicode\endlink
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\i \link http://www.unicode.org/unicode/standard/standard.html
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The home page for the standard\endlink
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\endlist
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\section1 The Standard
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The current version of the standard is 3.2
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\list
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\i \link http://www.amazon.com/exec/obidos/ASIN/0201616335/trolltech/t
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The Unicode Standard, version 3.2.\endlink See also
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\link http://www.unicode.org/unicode/standard/versions/
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its home page.\endlink
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\i \link http://www.amazon.com/exec/obidos/ASIN/0201473459/trolltech/t
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The Unicode Standard, version 2.0.\endlink See also the
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\link http://www.unicode.org/unicode/reports/tr8.html 2.1
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update\endlink and
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\link http://www.unicode.org/unicode/standard/versions/enumeratedversions.html#Unicode 2.1.9 the 2.1.9 data files\endlink at www.unicode.org.
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\endlist
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\section1 Unicode in Qt
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In Qt, and in most applications that use Qt, most or all user-visible
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strings are stored using Unicode. TQt provides:
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\list
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\i Translation to/from legacy encodings for file I/O: see \l
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QTextCodec and \l QTextStream.
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\i Translation from Input Methods and 8-bit keyboard input.
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\i Translation to legacy character sets for on-screen display.
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\i A string class, \l TQString, that stores Unicode characters, with
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support for migrating from C strings including fast (cached)
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translation to and from US-ASCII, and all the usual string
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operations.
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\i Unicode-aware widgets where appropriate.
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\i Unicode support detection on Windows, so that TQt provides Unicode
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even on Windows platforms that do not support it natively.
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\endlist
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To fully benefit from Unicode, we recommend using TQString for storing
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all user-visible strings, and performing all text file I/O using
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QTextStream. Use \l QKeyEvent::text() for keyboard input in any custom
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widgets you write; it does not make much difference for slow typists
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in Western Europe or North America, but for fast typists or people
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using special input methods using text() is beneficial.
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All the function arguments in TQt that may be user-visible strings, \l
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QLabel::setText() and a many others, take \c{const TQString &}s.
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\l TQString provides implicit casting from \c{const char *}
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so that things like
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\code
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myLabel->setText( "Hello, Dolly!" );
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\endcode
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will work. There is also a function, \l TQObject::tr(), that provides
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translation support, like this:
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\code
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myLabel->setText( tr("Hello, Dolly!") );
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\endcode
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tr() (simplifying somewhat) maps from \c{const char *} to a
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Unicode string, and uses installable \l QTranslator objects to do the
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mapping.
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Qt provides a number of built-in \l QTextCodec classes, that is,
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classes that know how to translate between Unicode and legacy
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encodings to support programs that must talk to other programs or
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read/write files in legacy file formats.
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By default, conversion to/from \c{const char *} uses a
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locale-dependent codec. However, applications can easily find codecs
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for other locales, and set any open file or network connection to use
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a special codec. It is also possible to install new codecs, for
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encodings that the built-in ones do not support. (At the time of
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writing, Vietnamese/VISCII is one such example.)
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Since US-ASCII and ISO-8859-1 are so common, there are also especially
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fast functions for mapping to and from them. For example, to open an
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application's icon one might do this:
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\code
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QFile f( TQString::fromLatin1("appicon.png") );
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\endcode
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Regarding output, TQt will do a best-effort conversion from
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Unicode to whatever encoding the system and fonts provide.
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Depending on operating system, locale, font availability and Qt's
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support for the characters used, this conversion may be good or bad.
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We will extend this in upcoming versions, with emphasis on the most
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common locales first.
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*/
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