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RedHat 9 (Linux i386) - man page for qsettings (redhat section 3qt)

QSettings(3qt)									   QSettings(3qt)

NAME
       QSettings - Persistent platform-independent application settings

SYNOPSIS
       #include <qsettings.h>

   Public Members
       enum Format { Native = 0, Ini }
       enum System { Unix = 0, Windows, Mac }
       enum Scope { User, Global }
       QSettings ()
       QSettings ( Format format )
       ~QSettings ()
       bool writeEntry ( const QString & key, bool value )
       bool writeEntry ( const QString & key, double value )
       bool writeEntry ( const QString & key, int value )
       bool writeEntry ( const QString & key, const QString & value )
       bool writeEntry ( const QString & key, const QStringList & value )
       bool writeEntry ( const QString & key, const QStringList & value, const QChar & separator
	   )
       QStringList entryList ( const QString & key ) const
       QStringList subkeyList ( const QString & key ) const
       QStringList readListEntry ( const QString & key, bool * ok = 0 ) const
       QStringList readListEntry ( const QString & key, const QChar & separator, bool * ok = 0 )
	   const
       QString readEntry ( const QString & key, const QString & def = QString::null, bool * ok =
	   0 ) const
       int readNumEntry ( const QString & key, int def = 0, bool * ok = 0 ) const
       double readDoubleEntry ( const QString & key, double def = 0, bool * ok = 0 ) const
       bool readBoolEntry ( const QString & key, bool def = 0, bool * ok = 0 ) const
       bool removeEntry ( const QString & key )
       void insertSearchPath ( System s, const QString & path )
       void removeSearchPath ( System s, const QString & path )
       void setPath ( const QString & domain, const QString & product, Scope scope = Global )
       void beginGroup ( const QString & group )
       void endGroup ()
       void resetGroup ()
       QString group () const

DESCRIPTION
       The QSettings class provides persistent platform-independent application settings.

       On Unix systems, QSettings uses text files to store settings. On Windows systems,
       QSettings uses the system registry. On Mac OS X, QSettings uses the Carbon preferences
       API.

       Each setting comprises an identifying key and the data associated with the key. A key is a
       unicode string which consists of two or more subkeys. A subkey is a slash, '/', followed
       by one or more unicode characters (excluding slashes, newlines, carriage returns and
       equals, '=', signs). The associated data, called the entry or value, may be a boolean, an
       integer, a double, a string or a list of strings. Entry strings may contain any unicode
       characters.

       If you want to save and restore the entire desktop's settings, i.e. which applications are
       running, use QSettings to save the settings for each individual application and
       QSessionManager to save the desktop's session.

       Example settings:

	   /MyCompany/MyApplication/background color
	   /MyCompany/MyApplication/foreground color
	   /MyCompany/MyApplication/geometry/x
	   /MyCompany/MyApplication/geometry/y
	   /MyCompany/MyApplication/geometry/width
	   /MyCompany/MyApplication/geometry/height
	   /MyCompany/MyApplication/recent files/1
	   /MyCompany/MyApplication/recent files/2
	   /MyCompany/MyApplication/recent files/3
       Each line above is a complete key, made up of subkeys.

       A typical usage pattern for reading application startup:

	   QSettings settings;
	   settings.setPath( "MyCompany.com", "MyApplication" );
	   QString bgColor = settings.readEntry( "/background color", "white" );
	   int width = settings.readNumEntry( "/geometry/width", 640 );
	   // ...

       A typical usage pattern for application exit or 'save preferences':

	   QSettings settings;
	   settings.setPath( "MyCompany.com", "MyApplication" );
	   settings.writeEntry( "/background color", bgColor );
	   settings.writeEntry( "/geometry/width", width );
	   // ...

       QSettings can build a key prefix that is prepended to all keys. To build the key prefix,
       use beginGroup() and endGroup().

	   QSettings settings;
	   settings.beginGroup( "/MainWindow" );
	       settings.beginGroup( "/Geometry" );
		   int x = settings.readEntry( "/x" );
		   // ...
	       settings.endGroup();
	       settings.beginGroup( "/Toolbars" );
		   // ...
	       settings.endGroup();
	   settings.endGroup();

       You can get a list of entry-holding keys by calling entryList(), and a list of key-holding
       keys using subkeyList().

	   QStringList keys = entryList( "/MyApplication" );
	   // keys contains 'background color' and 'foreground color'.
	   QStringList keys = entryList( "/MyApplication/recent files" );
	   // keys contains '1', '2' and '3'.
	   QStringList subkeys = subkeyList( "/MyApplication" );
	   // subkeys contains 'geometry' and 'recent files'
	   QStringList subkeys = subkeyList( "/MyApplication/recent files" );
	   // subkeys is empty.

       Since settings for Windows are stored in the registry there are size limits as follows:

       A subkey may not exceed 255 characters.

       An entry's value may not exceed 16,300 characters.

       All the values of a key (for example, all the 'recent files' subkeys values), may not
       exceed 65,535 characters.

       These limitations are not enforced on Unix or Mac OS X.

       If you wish to use a different search path call insertSearchPath() as often as necessary
       to add your preferred paths. Call removeSearchPath() to remove any unwanted paths.

Notes for Mac OS X Applications
       Internal to the CFPreferences API it is not defined (for Mac OS 9 support) where the
       settings will ultimitely be stored. However, at the time of this writing the settings will
       be stored (either on a global or user basis, preferring locally) into a plist file in
       $ROOT/System/Library/Preferences (in XML format). QSettings will create an appropriate
       plist file (com.<first group name>.plist) out of the full path to a key.

       For further information on CFPreferences see also Apple's Specifications

Notes for Unix Applications
       There is no universally accepted place for storing application settings under Unix. In the
       examples the settings file will be searched for in the following directories: <ol type=1>

       INSTALL/etc/settings

       /opt/MyCompany/share/etc

       /opt/MyCompany/share/MyApplication/etc

       $HOME/.qt When reading settings the files are searched in the order shown above, with
       later settings overriding earlier settings. Files for which the user doesn't have read
       permission are ignored. When saving settings QSettings works in the order shown above,
       writing to the first settings file for which the user has write permission. (INSTALL is
       the directory where Qt was installed. This can be modified by using the configure script's
       -prefix argument )

       If you want to put the settings in a particular place in the filesystem you could do this:

	   settings.insertSearchPath( QSettings::Unix, "/opt/MyCompany/share" );

       But in practice you may prefer not to use a search path for Unix. For example the
       following code:

	   settings.writeEntry( "/MyApplication/geometry/width", width );
       will end up writing the "geometry/width" setting to the file $HOME/.qt/myapplicationrc
       (assuming that the application is being run by an ordinary user, i.e. not by root).

       For cross-platform applications you should ensure that the Windows size limitations are
       not exceeded.

       See also Input/Output and Networking and Miscellaneous Classes.

   Member Type Documentation
QSettings::Format
       QSettings::Native - Store the settings in a platform dependent location

       QSettings::Ini - Store the settings in a text file

QSettings::Scope
       QSettings::Global - Save settings as global as possible

       QSettings::User - Save settings in user space

QSettings::System
       QSettings::Mac - Macintosh execution environments

       QSettings::Unix - Mac OS X, Unix, Linux and Unix-like execution environments

       QSettings::Windows - Windows execution environments

MEMBER FUNCTION DOCUMENTATION
QSettings::QSettings ()
       Creates a settings object.

QSettings::QSettings ( Format format )
       Creates a settings object. If format is 'Ini' the settings will be stored in a text file,
       using the Unix strategy (see above). If format is 'Native', the settings will be stored in
       a platform specific way (ie. the Windows registry).

QSettings::~QSettings ()
       Destroys the settings object. All modifications made to the settings will automatically be
       saved.

void QSettings::beginGroup ( const QString & group )
       Appends group to the current key prefix.

	   QSettings settings;
	   settings.beginGroup( "/MainWindow" );
	   // read values
	   settings.endGroup();

void QSettings::endGroup ()
       Undo previous calls to beginGroup(). Note that a single beginGroup("a/b/c") is undone by a
       single call to endGroup().

	   QSettings settings;
	   settings.beginGroup( "/MainWindow/Geometry" );
	   // read values
	   settings.endGroup();

QStringList QSettings::entryList ( const QString & key ) const
       Returns a list of the keys which contain entries under key. Does not return any keys that
       contain keys.

       Example settings:

	   /MyCompany/MyApplication/background color
	   /MyCompany/MyApplication/foreground color
	   /MyCompany/MyApplication/geometry/x
	   /MyCompany/MyApplication/geometry/y
	   /MyCompany/MyApplication/geometry/width
	   /MyCompany/MyApplication/geometry/height

	   QStringList keys = entryList( "/MyCompany/MyApplication" );
       keys contains 'background color' and 'foreground color'. It does not contain 'geometry'
       because this key contains keys not entries.

       To access the geometry values could either use subkeyList() to read the keys and then read
       each entry, or simply read each entry directly by specifying its full key, e.g."
       /MyCompany/MyApplication/geometry/y".

       See also subkeyList().

QString QSettings::group () const
       Returns the current key prefix, or a null string if there is no key prefix set.

       See also beginGroup().

void QSettings::insertSearchPath ( System s, const QString & path )
       Inserts path into the settings search path. The semantics of path depends on the system s.

       When s is Windows and the execution environment is not Windows the function does nothing.
       Similarly when s is Unix and the execution environment is not Unix the function does
       nothing.

       When s is Windows, and the execution environment is Windows, the search path list will be
       used as the first subfolder of the "Software" folder in the registry.

       When reading settings the folders are searched forwards from the first folder (listed
       below) to the last, returning the first settings found, and ignoring any folders for which
       the user doesn't have read permission. <ol type=1>

       HKEY_CURRENT_USER/Software/MyCompany/MyApplication

       HKEY_LOCAL_MACHINE/Software/MyCompany/MyApplication

       HKEY_CURRENT_USER/Software/MyApplication

       HKEY_LOCAL_MACHINE/Software/MyApplication

	 QSettings settings;
	 settings.insertSearchPath( QSettings::Windows, "/MyCompany" );
	 settings.writeEntry( "/MyApplication/Tip of the day", TRUE );
       The code above will write the subkey "Tip of the day" into the first of the registry
       folders listed below that is found and for which the user has write permission. <ol
       type=1>

       HKEY_LOCAL_MACHINE/Software/MyCompany/MyApplication

       HKEY_CURRENT_USER/Software/MyCompany/MyApplication

       HKEY_LOCAL_MACHINE/Software/MyApplication

       HKEY_CURRENT_USER/Software/MyApplication If a setting is found in the HKEY_CURRENT_USER
       space, this setting is overwritten independently of write permissions in the
       HKEY_LOCAL_MACHINE space.

       When s is Unix, and the execution environment is Unix, the search path list will be used
       when trying to determine a suitable filename for reading and writing settings files. By
       default, there are two entries in the search path:

       <ol type=1>

       INSTALL/etc - where INSTALL is the directory where Qt was installed.

       $HOME/.qt/ - where $HOME is the user's home directory.

       All insertions into the search path will go before $HOME/.qt/. For example:

	 QSettings settings;
	 settings.insertSearchPath( QSettings::Unix, "/opt/MyCompany/share/etc" );
	 settings.insertSearchPath( QSettings::Unix, "/opt/MyCompany/share/MyApplication/etc" );
	 // ...
       Will result in a search path of: <ol type=1>

       INSTALL/etc

       /opt/MyCompany/share/etc

       /opt/MyCompany/share/MyApplication/etc

       $HOME/.qt When reading settings the files are searched in the order shown above, with
       later settings overriding earlier settings. Files for which the user doesn't have read
       permission are ignored. When saving settings QSettings works in the order shown above,
       writing to the first settings file for which the user has write permission.

       Settings under Unix are stored in files whose names are based on the first subkey of the
       key (not including the search path). The algorithm for creating names is essentially:
       lowercase the first subkey, replace spaces with underscores and add 'rc', e.g.
       /MyCompany/MyApplication/background color will be stored in myapplicationrc (assuming that
       /MyCompany is part of the search path).

       See also removeSearchPath().

       Example: chart/chartform.cpp.

bool QSettings::readBoolEntry ( const QString & key, bool def = 0, bool * ok = 0 ) const
       Reads the entry specified by key, and returns a bool, or the default value, def, if the
       entry couldn't be read. If ok is non-null, *ok is set to TRUE if the key was read, FALSE
       otherwise.

       See also readEntry(), readNumEntry(), readDoubleEntry(), writeEntry(), and removeEntry().

double QSettings::readDoubleEntry ( const QString & key, double def = 0, bool * ok = 0 ) const
       Reads the entry specified by key, and returns a double, or the default value, def, if the
       entry couldn't be read. If ok is non-null, *ok is set to TRUE if the key was read, FALSE
       otherwise.

       See also readEntry(), readNumEntry(), readBoolEntry(), writeEntry(), and removeEntry().

QString QSettings::readEntry ( const QString & key, const QString & def = QString::null, bool *
       ok = 0 ) const
       Reads the entry specified by key, and returns a QString, or the default value, def, if the
       entry couldn't be read. If ok is non-null, *ok is set to TRUE if the key was read, FALSE
       otherwise.

       See also readListEntry(), readNumEntry(), readDoubleEntry(), readBoolEntry(),
       writeEntry(), and removeEntry().

QStringList QSettings::readListEntry ( const QString & key, bool * ok = 0 ) const
       Reads the entry specified by key as a string. If ok is not 0, *ok is set to TRUE if the
       key was read, otherwise *ok is set to FALSE.

       Note that if you want to iterate over the list, you should iterate over a copy, e.g.

	   QStringList list = mySettings.readListEntry( "recentfiles" );
	   QStringList::Iterator it = list.begin();
	   while( it != list.end() ) {
	       myProcessing( *it );
	       ++it;
	   }

       See also readEntry(), readDoubleEntry(), readBoolEntry(), writeEntry(), removeEntry(), and
       QStringList::split().

QStringList QSettings::readListEntry ( const QString & key, const QChar & separator, bool * ok =
       0 ) const
       This is an overloaded member function, provided for convenience. It behaves essentially
       like the above function.

       Reads the entry specified by key as a string. The separator is used to create a
       QStringList by calling QStringList::split(separator, entry). If ok is not 0: *ok is set to
       TRUE if the key was read, otherwise *ok is set to FALSE.

       Note that if you want to iterate over the list, you should iterate over a copy, e.g.

	   QStringList list = mySettings.readListEntry( "size", " " );
	   QStringList::Iterator it = list.begin();
	   while( it != list.end() ) {
	       myProcessing( *it );
	       ++it;
	   }

       See also readEntry(), readDoubleEntry(), readBoolEntry(), writeEntry(), removeEntry(), and
       QStringList::split().

int QSettings::readNumEntry ( const QString & key, int def = 0, bool * ok = 0 ) const
       Reads the entry specified by key, and returns an integer, or the default value, def, if
       the entry couldn't be read. If ok is non-null, *ok is set to TRUE if the key was read,
       FALSE otherwise.

       See also readEntry(), readDoubleEntry(), readBoolEntry(), writeEntry(), and removeEntry().

bool QSettings::removeEntry ( const QString & key )
       Removes the entry specified by key.

       Returns TRUE if the entry existed and was removed; otherwise returns FALSE.

       See also readEntry() and writeEntry().

void QSettings::removeSearchPath ( System s, const QString & path )
       Removes all occurrences of path (using exact matching) from the settings search path for
       system s. Note that the default search paths cannot be removed.

       See also insertSearchPath().

void QSettings::resetGroup ()
       Set the current key prefix to the empty string.

void QSettings::setPath ( const QString & domain, const QString & product, Scope scope = Global )

       Insert platform-dependent paths from platform-independent information.

       The domain should be an Internet domain name controlled by the producer of the software,
       eg. Trolltech products use "trolltech.com".

       The product should be the official name of the product.

       The scope should be QSettings::User for user-specific settings, or QSettings::Global for
       system-wide settings (generally these will be read-only to many users).

       Not all information is relevant on all systems (e.g. scoping is currently used only if
       QSettings accesses the Windows registry).

QStringList QSettings::subkeyList ( const QString & key ) const
       Returns a list of the keys which contain keys under key. Does not return any keys that
       contain entries.

       Example settings:

	   /MyCompany/MyApplication/background color
	   /MyCompany/MyApplication/foreground color
	   /MyCompany/MyApplication/geometry/x
	   /MyCompany/MyApplication/geometry/y
	   /MyCompany/MyApplication/geometry/width
	   /MyCompany/MyApplication/geometry/height
	   /MyCompany/MyApplication/recent files/1
	   /MyCompany/MyApplication/recent files/2
	   /MyCompany/MyApplication/recent files/3

	   QStringList keys = subkeyList( "/MyCompany/MyApplication" );
       keys contains 'geometry' and 'recent files'. It does not contain 'background color' or
       'foreground color' because they are keys which contain entries not keys. To get a list of
       keys that have values rather than subkeys use entryList().

       See also entryList().

bool QSettings::writeEntry ( const QString & key, bool value )
       Writes the boolean entry value into key key. The key is created if it doesn't exist. Any
       previous value is overwritten by value.

       If an error occurs the settings are left unchanged and FALSE is returned; otherwise TRUE
       is returned.

       See also readListEntry(), readNumEntry(), readDoubleEntry(), readBoolEntry(), and
       removeEntry().

       Example: chart/chartform.cpp.

bool QSettings::writeEntry ( const QString & key, double value )
       This is an overloaded member function, provided for convenience. It behaves essentially
       like the above function.

       Writes the double entry value into key key. The key is created if it doesn't exist. Any
       previous value is overwritten by value.

       If an error occurs the settings are left unchanged and FALSE is returned; otherwise TRUE
       is returned.

       See also readListEntry(), readNumEntry(), readDoubleEntry(), readBoolEntry(), and
       removeEntry().

bool QSettings::writeEntry ( const QString & key, int value )
       This is an overloaded member function, provided for convenience. It behaves essentially
       like the above function.

       Writes the integer entry value into key key. The key is created if it doesn't exist. Any
       previous value is overwritten by value.

       If an error occurs the settings are left unchanged and FALSE is returned; otherwise TRUE
       is returned.

       See also readListEntry(), readNumEntry(), readDoubleEntry(), readBoolEntry(), and
       removeEntry().

bool QSettings::writeEntry ( const QString & key, const QString & value )
       This is an overloaded member function, provided for convenience. It behaves essentially
       like the above function.

       Writes the string entry value into key key. The key is created if it doesn't exist. Any
       previous value is overwritten by value. If value is an empty string or a null string the
       key's value will be an empty string.

       If an error occurs the settings are left unchanged and FALSE is returned; otherwise TRUE
       is returned.

       See also readListEntry(), readNumEntry(), readDoubleEntry(), readBoolEntry(), and
       removeEntry().

bool QSettings::writeEntry ( const QString & key, const QStringList & value )
       This is an overloaded member function, provided for convenience. It behaves essentially
       like the above function.

       Writes the string list entry value into key key. The key is created if it doesn't exist.
       Any previous value is overwritten by value.

       If an error occurs the settings are left unchanged and FALSE is returned; otherwise
       returns TRUE.

       See also readListEntry(), readNumEntry(), readDoubleEntry(), readBoolEntry(), and
       removeEntry().

bool QSettings::writeEntry ( const QString & key, const QStringList & value, const QChar &
       separator )
       This is an overloaded member function, provided for convenience. It behaves essentially
       like the above function.

       Writes the string list entry value into key key. The key is created if it doesn't exist.
       Any previous value is overwritten by value. The list is stored as a sequence of strings
       separated by separator, so none of the strings in the list should contain the separator.
       If the list is empty or null the key's value will be an empty string.

       If an error occurs the settings are left unchanged and FALSE is returned; otherwise
       returns TRUE.

       See also readListEntry(), readNumEntry(), readDoubleEntry(), readBoolEntry(), and
       removeEntry().

SEE ALSO
       http://doc.trolltech.com/qsettings.html http://www.trolltech.com/faq/tech.html

COPYRIGHT
       Copyright 1992-2001 Trolltech AS, http://www.trolltech.com.  See the license file included
       in the distribution for a complete license statement.

AUTHOR
       Generated automatically from the source code.

BUGS
       If you find a bug in Qt, please report it as described in
       http://doc.trolltech.com/bughowto.html.	Good bug reports help us to help you. Thank you.

       The definitive Qt documentation is provided in HTML format; it is located at
       $QTDIR/doc/html and can be read using Qt Assistant or with a web browser. This man page is
       provided as a convenience for those users who prefer man pages, although this format is
       not officially supported by Trolltech.

       If you find errors in this manual page, please report them to qt-bugs@trolltech.com.
       Please include the name of the manual page (qsettings.3qt) and the Qt version (3.1.1).

Trolltech AS				 9 December 2002			   QSettings(3qt)


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