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authorTimothy Pearson <kb9vqf@pearsoncomputing.net>2011-11-08 12:31:36 -0600
committerTimothy Pearson <kb9vqf@pearsoncomputing.net>2011-11-08 12:31:36 -0600
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+/****************************************************************************
+**
+** Documentation of Unicode support in Qt.
+**
+** Copyright (C) 1992-2008 Trolltech ASA. All rights reserved.
+**
+** This file is part of the Qt GUI Toolkit.
+**
+** This file may be used under the terms of the GNU General
+** Public License versions 2.0 or 3.0 as published by the Free
+** Software Foundation and appearing in the files LICENSE.GPL2
+** and LICENSE.GPL3 included in the packaging of this file.
+** Alternatively you may (at your option) use any later version
+** of the GNU General Public License if such license has been
+** publicly approved by Trolltech ASA (or its successors, if any)
+** and the KDE Free Qt Foundation.
+**
+** Please review the following information to ensure GNU General
+** Public Licensing retquirements will be met:
+** http://trolltech.com/products/qt/licenses/licensing/opensource/.
+** If you are unsure which license is appropriate for your use, please
+** review the following information:
+** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
+** or contact the sales department at sales@trolltech.com.
+**
+** This file may be used under the terms of the Q Public License as
+** defined by Trolltech ASA and appearing in the file LICENSE.QPL
+** included in the packaging of this file. Licensees holding valid Qt
+** Commercial licenses may use this file in accordance with the Qt
+** Commercial License Agreement provided with the Software.
+**
+** This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
+** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted
+** herein.
+**
+**********************************************************************/
+
+/*! \page unicode.html
+
+\title About Unicode
+
+Unicode is a multi-byte character set, portable across all major
+computing platforms and with decent coverage over most of the world.
+It is also single-locale; it includes no code pages or other
+complexities that make software harder to write and test. There is no
+competing character set that's reasonably multiplatform. For these
+reasons, Trolltech uses Unicode as the native character set for Qt
+(since version 2.0).
+
+
+\section1 Information about Unicode on the web.
+
+The \link http://www.unicode.org Unicode Consortium\endlink
+has a number of documents available, including
+
+\list
+
+\i \link http://www.unicode.org/unicode/standard/principles.html
+A technical introduction to Unicode\endlink
+\i \link http://www.unicode.org/unicode/standard/standard.html
+The home page for the standard\endlink
+
+\endlist
+
+
+\section1 The Standard
+
+The current version of the standard is 3.2
+
+\list
+
+\i \link http://www.amazon.com/exec/obidos/ASIN/0201616335/trolltech/t
+The Unicode Standard, version 3.2.\endlink See also
+\link http://www.unicode.org/unicode/standard/versions/
+its home page.\endlink
+\i \link http://www.amazon.com/exec/obidos/ASIN/0201473459/trolltech/t
+The Unicode Standard, version 2.0.\endlink See also the
+\link http://www.unicode.org/unicode/reports/tr8.html 2.1
+update\endlink and
+\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.
+
+\endlist
+
+\section1 Unicode in Qt
+
+In Qt, and in most applications that use Qt, most or all user-visible
+strings are stored using Unicode. Qt provides:
+
+\list
+
+\i Translation to/from legacy encodings for file I/O: see \l
+QTextCodec and \l QTextStream.
+\i Translation from Input Methods and 8-bit keyboard input.
+\i Translation to legacy character sets for on-screen display.
+\i A string class, \l QString, that stores Unicode characters, with
+support for migrating from C strings including fast (cached)
+translation to and from US-ASCII, and all the usual string
+operations.
+\i Unicode-aware widgets where appropriate.
+\i Unicode support detection on Windows, so that Qt provides Unicode
+even on Windows platforms that do not support it natively.
+
+\endlist
+
+To fully benefit from Unicode, we recommend using QString for storing
+all user-visible strings, and performing all text file I/O using
+QTextStream. Use \l QKeyEvent::text() for keyboard input in any custom
+widgets you write; it does not make much difference for slow typists
+in Western Europe or North America, but for fast typists or people
+using special input methods using text() is beneficial.
+
+All the function arguments in Qt that may be user-visible strings, \l
+QLabel::setText() and a many others, take \c{const QString &}s.
+\l QString provides implicit casting from \c{const char *}
+so that things like
+\code
+ myLabel->setText( "Hello, Dolly!" );
+\endcode
+will work. There is also a function, \l QObject::tr(), that provides
+translation support, like this:
+\code
+ myLabel->setText( tr("Hello, Dolly!") );
+\endcode
+
+tr() (simplifying somewhat) maps from \c{const char *} to a
+Unicode string, and uses installable \l QTranslator objects to do the
+mapping.
+
+Qt provides a number of built-in \l QTextCodec classes, that is,
+classes that know how to translate between Unicode and legacy
+encodings to support programs that must talk to other programs or
+read/write files in legacy file formats.
+
+By default, conversion to/from \c{const char *} uses a
+locale-dependent codec. However, applications can easily find codecs
+for other locales, and set any open file or network connection to use
+a special codec. It is also possible to install new codecs, for
+encodings that the built-in ones do not support. (At the time of
+writing, Vietnamese/VISCII is one such example.)
+
+Since US-ASCII and ISO-8859-1 are so common, there are also especially
+fast functions for mapping to and from them. For example, to open an
+application's icon one might do this:
+\code
+ QFile f( QString::fromLatin1("appicon.png") );
+\endcode
+
+Regarding output, Qt will do a best-effort conversion from
+Unicode to whatever encoding the system and fonts provide.
+Depending on operating system, locale, font availability and Qt's
+support for the characters used, this conversion may be good or bad.
+We will extend this in upcoming versions, with emphasis on the most
+common locales first.
+
+*/