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

Inheritance diagram for QtCore.QSettings:

Collaboration diagram for QtCore.QSettings:

Public Types
enum	Format { CustomFormat1 = 17, CustomFormat10 = 26, CustomFormat11 = 27, CustomFormat12 = 28, CustomFormat13 = 29, CustomFormat14 = 30, CustomFormat15 = 31, CustomFormat16 = 32, CustomFormat2 = 18, CustomFormat3 = 19, CustomFormat4 = 20, CustomFormat5 = 21, CustomFormat6 = 22, CustomFormat7 = 23, CustomFormat8 = 24, CustomFormat9 = 25, IniFormat = 1, InvalidFormat = 16, NativeFormat = 0 }
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enum	Scope { SystemScope = 1, UserScope = 0 }
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enum	Status { AccessError = 1, FormatError = 2, NoError = 0 }
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Public Member Functions
	QSettings (QObject parent=null)


	QSettings (string organization, string application="", QObject parent=null)


	QSettings (string fileName, QSettings.Format format, QObject parent=null)


	QSettings (QSettings.Scope scope, string organization, string application="", QObject parent=null)


	QSettings (QSettings.Format format, QSettings.Scope scope, string organization, string application="", QObject parent=null)


override void	CreateProxy ()

new System.Collections.Generic.List < string >	AllKeys ()


new string	ApplicationName ()


new void	BeginGroup (string prefix)


new int	BeginReadArray (string prefix)


new void	BeginWriteArray (string prefix, int size=-1)


new System.Collections.Generic.List < string >	ChildGroups ()


new System.Collections.Generic.List < string >	ChildKeys ()


new void	Clear ()


new bool	Contains (string key)


new void	EndArray ()


new void	EndGroup ()


override bool	OnEvent (QEvent @event)


new string	FileName ()


new QSettings.Format	format ()


new string	Group ()


new bool	IsWritable ()


new string	OrganizationName ()


new void	Remove (string key)


new QSettings.Scope	scope ()


new void	SetArrayIndex (int i)


new void	SetIniCodec (string codecName)


new void	SetValue (string key, object value)


new QSettings.Status	status ()


new void	Sync ()


new object	Value (string key)


new object	Value (string key, object defaultValue)


new void	Dispose ()

Public Member Functions inherited from QtCore.QObject
	QObject (QObject parent=null)


new bool	BlockSignals (bool b)


new System.Collections.Generic.List < QObject >	Children ()


new bool	Connect (QObject sender, string signal, string member, Qt.ConnectionType type=Qt.ConnectionType.AutoConnection)


new void	DeleteLater ()


new bool	Disconnect (QObject receiver, string member=null)


new bool	Disconnect (string signal=null, QObject receiver=null, string member=null)


new void	DumpObjectInfo ()


new void	DumpObjectTree ()


new System.Collections.Generic.List < QByteArray >	DynamicPropertyNames ()


virtual bool	OnEvent (QEvent arg1)


virtual bool	EventFilter (QObject arg1, QEvent arg2)


new bool	Inherits (string classname)


new void	InstallEventFilter (QObject arg1)


new bool	IsWidgetType ()


new void	KillTimer (int id)


new object	Property (string name)


new void	RemoveEventFilter (QObject arg1)


new bool	SetProperty (string name, object value)


new void	SetUserData (uint id, QObjectUserData data)

new bool	SignalsBlocked ()


new int	StartTimer (int interval)


new QObjectUserData	UserData (uint id)

new void	Dispose ()

Public Member Functions inherited from QtCore.Qt
delegate QTextStream	FuncQTextStreamQTextStream (QTextStream qTextStream)

delegate string	FuncStringQByteArray (QByteArray qByteArray)

delegate QByteArray	FuncQByteArrayString (string @string)

delegate void	ActionQtMsgTypeString (QtMsgType qtMsgType, string @string)

delegate QObject	FuncQObject ()

Static Public Member Functions
static QSettings.Format	RegisterFormat (string extension, bool readFunc, bool writeFunc, Qt.CaseSensitivity caseSensitivity=Qt.CaseSensitivity.CaseSensitive)


static void	SetPath (QSettings.Format format, QSettings.Scope scope, string path)


static void	SetSystemIniPath (string dir)


static void	SetUserIniPath (string dir)


static string	Tr (string s, string c=null)

static string	Tr (string s, string c, int n)

static string	TrUtf8 (string s, string c=null)

static string	TrUtf8 (string s, string c, int n)

Static Public Member Functions inherited from QtCore.QObject
static bool	Connect (QObject sender, QMetaMethod signal, QObject receiver, QMetaMethod method, Qt.ConnectionType type=Qt.ConnectionType.AutoConnection)


static bool	Connect (QObject sender, string signal, QObject receiver, string member, Qt.ConnectionType arg5=Qt.ConnectionType.AutoConnection)


static bool	Disconnect (QObject sender, QMetaMethod signal, QObject receiver, QMetaMethod member)


static bool	Disconnect (QObject sender, string signal, QObject receiver, string member)


static uint	RegisterUserData ()

static string	Tr (string s, string c=null)


static string	Tr (string s, string c, int n)


static string	TrUtf8 (string s, string c=null)


static string	TrUtf8 (string s, string c, int n)


Static Public Member Functions inherited from QtCore.Qt
static QDataStream	Write (QDataStream s, object p)

static QDataStream	Write (QDataStream arg1, QSizeF arg2)

static QTextStream	Write (QTextStream s, Qt.FuncQTextStreamQTextStream f)

static QDataStream	Write (QDataStream arg1, QPoint arg2)

static QDataStream	Write (QDataStream arg1, QLineF arg2)

static QDataStream	Write (QDataStream arg1, QPointF arg2)

static QDataStream	Write (QDataStream arg1, QChar arg2)

static QDataStream	Write (QDataStream arg1, QByteArray arg2)

static QDataStream	Write (QDataStream arg1, QEasingCurve arg2)

static QDataStream	Write (QDataStream arg1, QRectF arg2)

static QDataStream	Write (QDataStream arg1, QDateTime arg2)

static QDataStream	Write (QDataStream arg1, QUrl arg2)

static QDataStream	Write (QDataStream arg1, QTime arg2)

static QDataStream	Write (QDataStream arg1, QLocale arg2)

static QDataStream	Write (QDataStream arg1, QBitArray arg2)

static QDataStream	Write (QDataStream arg1, QUuid arg2)

static QDataStream	Write (QDataStream arg1, QLine arg2)

static QDataStream	Write (QDataStream arg1, QDate arg2)

static QDataStream	Write (QDataStream @out, QRegExp regExp)

static QDataStream	Write (QDataStream arg1, QRect arg2)

static QDataStream	Write (QDataStream arg1, QSize arg2)

static QDataStream	Write (QDataStream s, QVariant.Type p)

static QDataStream	Write (QDataStream arg1, string arg2)

static QDataStream	Write (QDataStream @out, System.Collections.Generic.List< string > list)

static QDataStream	Read (QDataStream arg1, QChar arg2)

static QDataStream	Read (QDataStream arg1, QLocale arg2)

static QDataStream	Read (QDataStream arg1, QRect arg2)

static QDataStream	Read (QDataStream arg1, QEasingCurve arg2)

static QDataStream	Read (QDataStream arg1, QDate arg2)

static QDataStream	Read (QDataStream arg1, QUrl arg2)

static QDataStream	Read (QDataStream arg1, QUuid arg2)

static QTextStream	Read (QTextStream s, Qt.FuncQTextStreamQTextStream f)

static QDataStream	Read (QDataStream arg1, QLineF arg2)

static QDataStream	Read (QDataStream arg1, QRectF arg2)

static QDataStream	Read (QDataStream arg1, QPointF arg2)

static QDataStream	Read (QDataStream arg1, QLine arg2)

static QDataStream	Read (QDataStream arg1, QBitArray arg2)

static QDataStream	Read (QDataStream arg1, QSize arg2)

static QDataStream	Read (QDataStream arg1, QDateTime arg2)

static QDataStream	Read (QDataStream arg1, QTime arg2)

static QDataStream	Read (QDataStream arg1, QPoint arg2)

static QDataStream	Read (QDataStream @in, QRegExp regExp)

static QDataStream	Read (QDataStream s, object p)

static QDataStream	Read (QDataStream arg1, QByteArray arg2)

static QDataStream	Read (QDataStream arg1, QSizeF arg2)

static QDataStream	Read (QDataStream arg1, string arg2)

static QDataStream	Read (QDataStream s, QVariant.Type p)

static QDataStream	Read (QDataStream @in, System.Collections.Generic.List< string > list)

static double	qAcos (double v)

static void	qAddPostRoutine (System.Action arg1)

static string	qAppName ()

static double	qAsin (double v)

static double	qAtan (double v)

static double	qAtan2 (double x, double y)

static void	qBadAlloc ()

static int	qCeil (double v)

static ushort	qChecksum (string s, uint len)

static QByteArray	qCompress (QByteArray data)

static QByteArray	qCompress (QByteArray data, int compressionLevel=-1)

static QByteArray	qCompress (Pointer< byte > data, int nbytes)

static QByteArray	qCompress (Pointer< byte > data, int nbytes, int compressionLevel=-1)

static double	qCos (double v)

static double	qExp (double v)

static double	qFabs (double v)

static double	qFastCos (double x)

static double	qFastSin (double x)

static string	qFlagLocation (string method)

static int	qFloor (double v)

static bool	qFuzzyCompare (double p1, double p2)

static bool	qFuzzyCompare (float p1, float p2)

static bool	qFuzzyIsNull (double d)

static bool	qFuzzyIsNull (float f)

static uint	qHash (QBitArray key)

static uint	qHash (QChar key)

static uint	qHash (QStringRef key)

static uint	qHash (QUrl url)

static uint	qHash (QPersistentModelIndex index)

static uint	qHash (QByteArray key)

static uint	qHash (QModelIndex index)

static uint	qHash (uint key)

static uint	qHash (sbyte key)

static uint	qHash (byte key)

static uint	qHash (short key)

static uint	qHash (NativeLong key)

static uint	qHash (ushort key)

static uint	qHash (long key)

static uint	qHash (ulong key)

static uint	qHash (int key)

static uint	qHash (string key)

static uint	qHash (NativeULong key)

static double	qInf ()

static Qt.ActionQtMsgTypeString	qInstallMsgHandler (Qt.ActionQtMsgTypeString arg1)

static int	qIntCast (float f)

static int	qIntCast (double f)

static bool	qIsFinite (double d)

static bool	qIsFinite (float f)

static bool	qIsInf (float f)

static bool	qIsInf (double d)

static bool	qIsNaN (float f)

static bool	qIsNaN (double d)

static bool	qIsNull (float f)

static bool	qIsNull (double d)

static double	qLn (double v)

static double	qPow (double x, double y)

static double	qQNaN ()

static void	qRegisterStaticPluginInstanceFunction (Qt.FuncQObject function)

static void	qRemovePostRoutine (System.Action arg1)

static int	qRound (double d)

static long	qRound64 (double d)

static double	qSNaN ()

static bool	qSharedBuild ()

static double	qSin (double v)

static double	qSqrt (double v)

static bool	qStringComparisonHelper (QStringRef s1, string s2)

static double	qTan (double v)

static QByteArray	qUncompress (QByteArray data)

static QByteArray	qUncompress (Pointer< byte > data, int nbytes)

static string	qVersion ()

static void	Qbswap_helper (Pointer< byte > src, Pointer< byte > dest, int size)

static QByteArray	Qgetenv (string varName)

static bool	Qputenv (string varName, QByteArray value)

static int	Qrand ()

static void	Qsrand (uint seed)

static int	Qstrcmp (QByteArray str1, QByteArray str2)

static int	Qstrcmp (QByteArray str1, string str2)

static int	Qstrcmp (string str1, QByteArray str2)

static int	Qstrcmp (string str1, string str2)

static Pointer< sbyte >	Qstrcpy (Pointer< sbyte > dst, string src)

static Pointer< sbyte >	Qstrdup (string arg1)

static int	Qstricmp (string arg1, string arg2)

static uint	Qstrlen (string str)

static int	Qstrncmp (string str1, string str2, uint len)

static Pointer< sbyte >	Qstrncpy (Pointer< sbyte > dst, string src, uint len)

static int	Qstrnicmp (string arg1, string arg2, uint len)

static uint	Qstrnlen (string str, uint maxlen)

static string	QtTrId (string id, int n=-1)

Protected Member Functions
	QSettings (System.Type dummy)

Protected Member Functions inherited from QtCore.QObject
	QObject (System.Type dummy)

virtual void	OnChildEvent (QChildEvent arg1)


virtual void	ConnectNotify (string signal)


virtual void	OnCustomEvent (QEvent arg1)


new void	OnDestroyed (QObject arg1=null)


virtual void	DisconnectNotify (string signal)


new int	Receivers (string signal)


new QObject	Sender ()


new int	SenderSignalIndex ()


virtual void	OnTimerEvent (QTimerEvent arg1)

Properties
static QSettings.Format	DefaultFormat `[get, set]`


new bool	FallbacksEnabled `[get, set]`


new QTextCodec	IniCodec `[get, set]`


static new QMetaObject	StaticMetaObject `[get]`

new IQSettingsSignals	Emit `[get]`

Properties inherited from QtCore.QObject
virtual EventHandler < QEventArgs< QChildEvent > >	ChildEvent


virtual EventHandler < QEventArgs< QEvent > >	CustomEvent


virtual EventHandler < QEventArgs< QEvent > >	Event


virtual EventHandler < QEventArgs< QTimerEvent > >	TimerEvent


Slot< QObject >	DestroyedQObject

Slot	Destroyed


new QObject	Parent `[get, set]`


virtual System.IntPtr	SmokeObject `[get, set]`

new string	ObjectName `[get, set]`


static new QMetaObject	StaticMetaObject `[get]`


static new QMetaObject	StaticQtMetaObject `[get]`

new IQObjectSignals	Emit `[get]`

Additional Inherited Members
Protected Attributes inherited from QtCore.QObject
object	Q_EMIT = null

SmokeInvocation	interceptor

readonly List< QEventHandler >	eventFilters = new List<QEventHandler>()

Detailed Description

The QSettings class provides persistent platform-independent application settings.

Users normally expect an application to remember its settings (window sizes and positions, options, etc.) across sessions. This information is often stored in the system registry on Windows, and in XML preferences files on Mac OS X. On Unix systems, in the absence of a standard, many applications (including the KDE applications) use INI text files.

QSettings is an abstraction around these technologies, enabling you to save and restore application settings in a portable manner. It also supports custom storage formats.

QSettings's API is based on QVariant, allowing you to save most value-based types, such as QString, QRect, and QImage, with the minimum of effort.

If all you need is a non-persistent memory-based structure, consider using QMap<QString, QVariant> instead.

Basic Usage

When creating a QSettings object, you must pass the name of your company or organization as well as the name of your application. For example, if your product is called Star Runner and your company is called MySoft, you would construct the QSettings object as follows:

QSettings settings("MySoft", "Star Runner");

QSettings objects can be created either on the stack or on the heap (i.e. using new). Constructing and destroying a QSettings object is very fast.

If you use QSettings from many places in your application, you might want to specify the organization name and the application name using QCoreApplication::setOrganizationName() and QCoreApplication::setApplicationName(), and then use the default QSettings constructor:

QCoreApplication::setOrganizationName("MySoft");

QCoreApplication::setOrganizationDomain("mysoft.com");

QCoreApplication::setApplicationName("Star Runner");

...

QSettings settings;

(Here, we also specify the organization's Internet domain. When the Internet domain is set, it is used on Mac OS X instead of the organization name, since Mac OS X applications conventionally use Internet domains to identify themselves. If no domain is set, a fake domain is derived from the organization name. See the Platform-Specific Notes below for details.)

QSettings stores settings. Each setting consists of a QString that specifies the setting's name (the key) and a QVariant that stores the data associated with the key. To write a setting, use setValue(). For example:

settings.setValue("editor/wrapMargin", 68);

If there already exists a setting with the same key, the existing value is overwritten by the new value. For efficiency, the changes may not be saved to permanent storage immediately. (You can always call sync() to commit your changes.)

You can get a setting's value back using value():

int margin = settings.value("editor/wrapMargin").toInt();

If there is no setting with the specified name, QSettings returns a null QVariant (which can be converted to the integer 0). You can specify another default value by passing a second argument to value():

int margin = settings.value("editor/wrapMargin", 80).toInt();

To test whether a given key exists, call contains(). To remove the setting associated with a key, call remove(). To obtain the list of all keys, call allKeys(). To remove all keys, call clear().

QVariant and GUI Types

Because QVariant is part of the QtCore library, it cannot provide conversion functions to data types such as QColor, QImage, and QPixmap, which are part of QtGui. In other words, there is no toColor(), toImage(), or toPixmap() functions in QVariant.

Instead, you can use the QVariant::value() or the qVariantValue() template function. For example:

QSettings settings("MySoft", "Star Runner");

QColor color = settings.value("DataPump/bgcolor").value<QColor>();

The inverse conversion (e.g., from QColor to QVariant) is automatic for all data types supported by QVariant, including GUI-related types:

QSettings settings("MySoft", "Star Runner");

QColor color = palette().background().color();

settings.setValue("DataPump/bgcolor", color);

Custom types registered using qRegisterMetaType() and qRegisterMetaTypeStreamOperators() can be stored using QSettings.

Section and Key Syntax

Setting keys can contain any Unicode characters. The Windows registry and INI files use case-insensitive keys, whereas the Carbon Preferences API on Mac OS X uses case-sensitive keys. To avoid portability problems, follow these simple rules:

Always refer to the same key using the same case. For example, if you refer to a key as "text fonts" in one place in your code, don't refer to it as "Text Fonts" somewhere else.

Avoid key names that are identical except for the case. For example, if you have a key called "MainWindow", don't try to save another key as "mainwindow".

Do not use slashes ('/' and '\') in section or key names; the backslash character is used to separate sub keys (see below). On windows '\' are converted by QSettings to '/', which makes them identical.

You can form hierarchical keys using the '/' character as a separator, similar to Unix file paths. For example:

settings.setValue("mainwindow/size", win->size());

settings.setValue("mainwindow/fullScreen", win->isFullScreen());

settings.setValue("outputpanel/visible", panel->isVisible());

If you want to save or restore many settings with the same prefix, you can specify the prefix using beginGroup() and call endGroup() at the end. Here's the same example again, but this time using the group mechanism:

settings.beginGroup("mainwindow");

settings.setValue("size", win->size());

settings.setValue("fullScreen", win->isFullScreen());

settings.endGroup();

settings.beginGroup("outputpanel");

settings.setValue("visible", panel->isVisible());

settings.endGroup();

If a group is set using beginGroup(), the behavior of most functions changes consequently. Groups can be set recursively.

In addition to groups, QSettings also supports an "array" concept. See beginReadArray() and beginWriteArray() for details.

Fallback Mechanism

Let's assume that you have created a QSettings object with the organization name MySoft and the application name Star Runner. When you look up a value, up to four locations are searched in that order:

a user-specific location for the Star Runner application

a user-specific location for all applications by MySoft

a system-wide location for the Star Runner application

a system-wide location for all applications by MySoft

(See Platform-Specific Notes below for information on what these locations are on the different platforms supported by Qt.)

If a key cannot be found in the first location, the search goes on in the second location, and so on. This enables you to store system-wide or organization-wide settings and to override them on a per-user or per-application basis. To turn off this mechanism, call setFallbacksEnabled(false).

Although keys from all four locations are available for reading, only the first file (the user-specific location for the application at hand) is accessible for writing. To write to any of the other files, omit the application name and/or specify QSettings::SystemScope (as opposed to QSettings::UserScope, the default).

Let's see with an example:

QSettings obj1("MySoft", "Star Runner");

QSettings obj2("MySoft");

QSettings obj3(QSettings::SystemScope, "MySoft", "Star Runner");

QSettings obj4(QSettings::SystemScope, "MySoft");

The table below summarizes which QSettings objects access which location. "X" means that the location is the main location associated to the QSettings object and is used both for reading and for writing; "o" means that the location is used as a fallback when reading.

Locationsobj1obj2obj3obj4

1. User, Application X

2. User, Organization o X

3. System, Application o X

4. System, Organization o o o X

The beauty of this mechanism is that it works on all platforms supported by Qt and that it still gives you a lot of flexibility, without requiring you to specify any file names or registry paths.

If you want to use INI files on all platforms instead of the native API, you can pass QSettings::IniFormat as the first argument to the QSettings constructor, followed by the scope, the organization name, and the application name:

QSettings settings(QSettings::IniFormat, QSettings::UserScope,

"MySoft", "Star Runner");

The Settings Editor example lets you experiment with different settings location and with fallbacks turned on or off.

Restoring the State of a GUI Application

QSettings is often used to store the state of a GUI application. The following example illustrates how to use QSettings to save and restore the geometry of an application's main window.

void MainWindow::writeSettings()

{

QSettings settings("Moose Soft", "Clipper");

settings.beginGroup("MainWindow");

settings.setValue("size", size());

settings.setValue("pos", pos());

settings.endGroup();

}

void MainWindow::readSettings()

{

QSettings settings("Moose Soft", "Clipper");

settings.beginGroup("MainWindow");

resize(settings.value("size", QSize(400, 400)).toSize());

move(settings.value("pos", QPoint(200, 200)).toPoint());

settings.endGroup();

}

See Window Geometry for a discussion on why it is better to call QWidget::resize() and QWidget::move() rather than QWidget::setGeometry() to restore a window's geometry.

The readSettings() and writeSettings() functions must be called from the main window's constructor and close event handler as follows:

MainWindow::MainWindow()

{

...

readSettings();

}

void MainWindow::closeEvent(QCloseEvent *event)

{

if (userReallyWantsToQuit()) {

writeSettings();

event->accept();

} else {

event->ignore();

}

See the Application example for a self-contained example that uses QSettings.

Accessing Settings from Multiple Threads or Processes Simultaneously

QSettings is reentrant. This means that you can use distinct QSettings object in different threads simultaneously. This guarantee stands even when the QSettings objects refer to the same files on disk (or to the same entries in the system registry). If a setting is modified through one QSettings object, the change will immediately be visible in any other QSettings objects that operate on the same location and that live in the same process.

QSettings can safely be used from different processes (which can be different instances of your application running at the same time or different applications altogether) to read and write to the same system locations. It uses advisory file locking and a smart merging algorithm to ensure data integrity. Note that sync() imports changes made by other processes (in addition to writing the changes from this QSettings).

Platform-Specific Notes

Locations Where Application Settings Are Stored

As mentioned in the Fallback Mechanism section, QSettings stores settings for an application in up to four locations, depending on whether the settings are user-specific or system-wide and whether the settings are application-specific or organization-wide. For simplicity, we're assuming the organization is called MySoft and the application is called Star Runner.

On Unix systems, if the file format is NativeFormat, the following files are used by default:

$HOME/.config/MySoft/Star Runner.conf (Qt for Embedded Linux: $HOME/Settings/MySoft/Star Runner.conf)

$HOME/.config/MySoft.conf (Qt for Embedded Linux: $HOME/Settings/MySoft.conf)

/etc/xdg/MySoft/Star Runner.conf

/etc/xdg/MySoft.conf

On Mac OS X versions 10.2 and 10.3, these files are used by default:

$HOME/Library/Preferences/com.MySoft.Star Runner.plist

$HOME/Library/Preferences/com.MySoft.plist

/Library/Preferences/com.MySoft.Star Runner.plist

/Library/Preferences/com.MySoft.plist

On Windows, NativeFormat settings are stored in the following registry paths:

HKEY_CURRENT_USER\Software\MySoft\Star Runner

HKEY_CURRENT_USER\Software\MySoft

HKEY_LOCAL_MACHINE\Software\MySoft\Star Runner

HKEY_LOCAL_MACHINE\Software\MySoft

Note: On Windows, for 32-bit programs running in WOW64 mode, settings are stored in the following registry path: HKEY_LOCAL_MACHINE\Software\WOW6432node.

If the file format is IniFormat, the following files are used on Unix and Mac OS X:

$HOME/.config/MySoft/Star Runner.ini (Qt for Embedded Linux: $HOME/Settings/MySoft/Star Runner.ini)

$HOME/.config/MySoft.ini (Qt for Embedded Linux: $HOME/Settings/MySoft.ini)

/etc/xdg/MySoft/Star Runner.ini

/etc/xdg/MySoft.ini

On Windows, the following files are used:

APPDATA%\MySoft\Star Runner.ini

APPDATA%\MySoft.ini

COMMON_APPDATA%\MySoft\Star Runner.ini

COMMON_APPDATA%\MySoft.ini

The APPDATA% path is usually C:\Documents and Settings\User Name\Application Data; the COMMON_APPDATA% path is usually C:\Documents and Settings\All Users\Application Data.

On Symbian, the following files are used for both IniFormat and NativeFormat (in this example, we assume that the application is installed on the e-drive and its Secure ID is 0xECB00931):

c:\dataconfig\MySoft\Star Runner.conf

c:\dataconfig\MySoft.conf

e:\private\ecb00931\MySoft\Star Runner.conf

e:\private\ecb00931\MySoft.conf

The SystemScope settings location is determined from the installation drive and Secure ID (UID3) of the application. If the application is built-in on the ROM, the drive used for SystemScope is c:.

Note: Symbian SystemScope settings are by default private to the application and not shared between applications, unlike other environments.

The paths for the .ini and .conf files can be changed using setPath(). On Unix and Mac OS X, the user can override them by by setting the XDG_CONFIG_HOME environment variable; see setPath() for details.

Accessing INI and .plist Files Directly

Sometimes you do want to access settings stored in a specific file or registry path. On all platforms, if you want to read an INI file directly, you can use the QSettings constructor that takes a file name as first argument and pass QSettings::IniFormat as second argument. For example:

QSettings settings("/home/petra/misc/myapp.ini",

QSettings::IniFormat);

You can then use the QSettings object to read and write settings in the file.

On Mac OS X, you can access XML-based .plist files by passing QSettings::NativeFormat as second argument. For example:

QSettings settings("/Users/petra/misc/myapp.plist",

QSettings::NativeFormat);

Accessing the Windows Registry Directly

On Windows, QSettings lets you access settings that have been written with QSettings (or settings in a supported format, e.g., string data) in the system registry. This is done by constructing a QSettings object with a path in the registry and QSettings::NativeFormat.

For example:

QSettings settings("HKEY_CURRENT_USER\\Software\\Microsoft\\Office",

QSettings::NativeFormat);

All the registry entries that appear under the specified path can be read or written through the QSettings object as usual (using forward slashes instead of backslashes). For example:

settings.setValue("11.0/Outlook/Security/DontTrustInstalledFiles", 0);

Note that the backslash character is, as mentioned, used by QSettings to separate subkeys. As a result, you cannot read or write windows registry entries that contain slashes or backslashes; you should use a native windows API if you need to do so.

Accessing Common Registry Settings on Windows

On Windows, it is possible for a key to have both a value and subkeys. Its default value is accessed by using "Default" or "." in place of a subkey:

settings.setValue("HKEY_CURRENT_USER\\MySoft\\Star Runner\\Galaxy", "Milkyway");

settings.setValue("HKEY_CURRENT_USER\\MySoft\\Star Runner\\Galaxy\\Sun", "OurStar");

settings.value("HKEY_CURRENT_USER\\MySoft\\Star Runner\\Galaxy\\Default"); // returns "Milkyway"

On other platforms than Windows, "Default" and "." would be treated as regular subkeys.

Securing application settings in Symbian

UserScope settings in Symbian are writable by any application by default. To protect the application settings from access and tampering by other applications, the settings need to be placed in the private secure area of the application. This can be done by specifying the settings storage path directly to the private area. The following snippet changes the UserScope to c:/private/ecb00931/MySoft.conf (provided the application is installed on the c-drive and its Secure ID is 0xECB00931:

QSettings settings(QApplication::applicationDirPath() + "/MySoft.conf");

Framework libraries (like Qt itself) may store configuration and cache settings using UserScope, which is accessible and writable by other applications. If the application is very security sensitive or uses high platform security capabilities, it may be prudent to also force framework settings to be stored in the private directory of the application. This can be done by changing the default path of UserScope before QApplication is created:

#include <QSettings>

#include <QDesktopServices>

int main(int argc, char *argv[])

{

#ifdef Q_OS_SYMBIAN

// Use QDesktopServices:storageLocation as QApplication is not yet created

QSettings::setPath(

QSettings::NativeFormat, QSettings::UserScope,

QDesktopServices::storageLocation(QDesktopServices::DataLocation) + "/settings");

#endif

QApplication app(argc, argv);

...

}

Note that this may affect framework libraries' functionality if they expect the settings to be shared between applications.

Changing the location of global Qt settings on Mac OS X

On Mac OS X, the global Qt settings (stored in com.trolltech.plist) are stored in the application settings file in two situations:

If the application runs in a Mac OS X sandbox (on Mac OS X 10.7 or later) or

If the Info.plist file of the application contains the key "ForAppStore" with the value "yes"

In these situations, the application settings file is named using the bundle identifier of the application, which must consequently be set in the application's Info.plist file.

This feature is provided to ease the acceptance of Qt applications into the Mac App Store, as the default behaviour of storing global Qt settings in the com.trolltech.plist file does not conform with Mac App Store file system usage requirements. For more information about submitting Qt applications to the Mac App Store, see Preparing a Qt application for Mac App Store submission.

Platform Limitations

While QSettings attempts to smooth over the differences between the different supported platforms, there are still a few differences that you should be aware of when porting your application:

The Windows system registry has the following limitations: A subkey may not exceed 255 characters, an entry's value may not exceed 16,383 characters, and all the values of a key may not exceed 65,535 characters. One way to work around these limitations is to store the settings using the IniFormat instead of the NativeFormat.

On Mac OS X, allKeys() will return some extra keys for global settings that apply to all applications. These keys can be read using value() but cannot be changed, only shadowed. Calling setFallbacksEnabled(false) will hide these global settings.

On Mac OS X, the CFPreferences API used by QSettings expects Internet domain names rather than organization names. To provide a uniform API, QSettings derives a fake domain name from the organization name (unless the organization name already is a domain name, e.g. OpenOffice.org). The algorithm appends ".com" to the company name and replaces spaces and other illegal characters with hyphens. If you want to specify a different domain name, call QCoreApplication::setOrganizationDomain(), QCoreApplication::setOrganizationName(), and QCoreApplication::setApplicationName() in your main() function and then use the default QSettings constructor. Another solution is to use preprocessor directives, for example: #ifdef Q_WS_MAC

QSettings settings("grenoullelogique.fr", "Squash");

#else

QSettings settings("Grenoulle Logique", "Squash");

#endif

On Unix and Mac OS X systems, the advisory file locking is disabled if NFS (or AutoFS or CacheFS) is detected to work around a bug in the NFS fcntl() implementation, which hangs forever if statd or lockd aren't running. Also, the locking isn't performed when accessing .plist files.

See also QVariant, QSessionManager, Settings Editor Example, and Application Example.

Member Enumeration Documentation

enum QtCore.QSettings.Format

This enum type specifies the storage format used by QSettings.

On Unix, NativeFormat and IniFormat mean the same thing, except that the file extension is different (.conf for NativeFormat, .ini for IniFormat).

The INI file format is a Windows file format that Qt supports on all platforms. In the absence of an INI standard, we try to follow what Microsoft does, with the following exceptions:

If you store types that QVariant can't convert to QString (e.g., QPoint, QRect, and QSize), Qt uses an @-based syntax to encode the type. For example: pos = (100 100)

To minimize compatibility issues, any @ that doesn't appear at the first position in the value or that isn't followed by a Qt type (Point, Rect, Size, etc.) is treated as a normal character.

Although backslash is a special character in INI files, most Windows applications don't escape backslashes (\) in file paths: windir = C:\Windows

QSettings always treats backslash as a special character and provides no API for reading or writing such entries.

The INI file format has severe restrictions on the syntax of a key. Qt works around this by using % as an escape character in keys. In addition, if you save a top-level setting (a key with no slashes in it, e.g., "someKey"), it will appear in the INI file's "General" section. To avoid overwriting other keys, if you save something using the a key such as "General/someKey", the key will be located in the "General" section, not in the "General" section.

Following the philosophy that we should be liberal in what we accept and conservative in what we generate, QSettings will accept Latin-1 encoded INI files, but generate pure ASCII files, where non-ASCII values are encoded using standard INI escape sequences. To make the INI files more readable (but potentially less compatible), call setIniCodec().

See also registerFormat() and setPath().

Enumerator:

CustomFormat1
CustomFormat10
CustomFormat11
CustomFormat12
CustomFormat13
CustomFormat14
CustomFormat15
CustomFormat16
CustomFormat2
CustomFormat3
CustomFormat4
CustomFormat5
CustomFormat6
CustomFormat7
CustomFormat8
CustomFormat9
IniFormat	Store the settings in INI files.
InvalidFormat	Special value returned by registerFormat().
NativeFormat	Store the settings using the most appropriate storage format for the platform. On Windows, this means the system registry; on Mac OS X, this means the CFPreferences API; on Unix, this means textual configuration files in INI format.

enum QtCore.QSettings.Scope

This enum specifies whether settings are user-specific or shared by all users of the same system.

Constructor & Destructor Documentation

QtCore.QSettings.QSettings ( System.Type dummy )

protected

QtCore.QSettings.QSettings ( QObject parent = null )

Constructs a QSettings object for accessing settings of the application and organization set previously with a call to QCoreApplication::setOrganizationName(), QCoreApplication::setOrganizationDomain(), and QCoreApplication::setApplicationName().

The scope is QSettings::UserScope and the format is defaultFormat() (QSettings::NativeFormat by default). Use setDefaultFormat() before calling this constructor to change the default format used by this constructor.

The code

QSettings settings("Moose Soft", "Facturo-Pro");

is equivalent to

QCoreApplication::setOrganizationName("Moose Soft");

QCoreApplication::setApplicationName("Facturo-Pro");

QSettings settings;

If QCoreApplication::setOrganizationName() and QCoreApplication::setApplicationName() has not been previously called, the QSettings object will not be able to read or write any settings, and status() will return AccessError.

On Mac OS X, if both a name and an Internet domain are specified for the organization, the domain is preferred over the name. On other platforms, the name is preferred over the domain.

See also QCoreApplication::setOrganizationName(), QCoreApplication::setOrganizationDomain(), QCoreApplication::setApplicationName(), and setDefaultFormat().

QtCore.QSettings.QSettings	(	string	organization,
		string	application = `""`,
		QObject	parent = `null`
	)

Constructs a QSettings object for accessing settings of the application called application from the organization called organization, and with parent parent.

Example:

QSettings settings("Moose Tech", "Facturo-Pro");

The scope is set to QSettings::UserScope, and the format is set to QSettings::NativeFormat (i.e. calling setDefaultFormat() before calling this constructor has no effect).

See also setDefaultFormat() and Fallback Mechanism.

QtCore.QSettings.QSettings	(	string	fileName,
		QSettings.Format	format,
		QObject	parent = `null`
	)

Constructs a QSettings object for accessing the settings stored in the file called fileName, with parent parent. If the file doesn't already exist, it is created.

If format is QSettings::NativeFormat, the meaning of fileName depends on the platform. On Unix, fileName is the name of an INI file. On Mac OS X, fileName is the name of a .plist file. On Windows, fileName is a path in the system registry.

If format is QSettings::IniFormat, fileName is the name of an INI file.

Warning: This function is provided for convenience. It works well for accessing INI or .plist files generated by Qt, but might fail on some syntaxes found in such files originated by other programs. In particular, be aware of the following limitations:

QSettings provides no way of reading INI "path" entries, i.e., entries with unescaped slash characters. (This is because these entries are ambiguous and cannot be resolved automatically.)

In INI files, QSettings uses the @ character as a metacharacter in some contexts, to encode Qt-specific data types (e.g., ), and might therefore misinterpret it when it occurs in pure INI files.

Member Function Documentation

new System.Collections.Generic.List<string> QtCore.QSettings.AllKeys ( )

Returns a list of all keys, including subkeys, that can be read using the QSettings object.

Example:

QSettings settings;

settings.setValue("fridge/color", Qt::white);

settings.setValue("fridge/size", QSize(32, 96));

settings.setValue("sofa", true);

settings.setValue("tv", false);

QStringList keys = settings.allKeys();

// keys: ["fridge/color", "fridge/size", "sofa", "tv"]

If a group is set using beginGroup(), only the keys in the group are returned, without the group prefix:

settings.beginGroup("fridge");

keys = settings.allKeys();

// keys: ["color", "size"]

Property Documentation

QSettings.Format QtCore.QSettings.DefaultFormat

staticgetset

Returns default file format used for storing settings for the QSettings(QObject *) constructor. If no default format is set, QSettings::NativeFormat is used.

This function was introduced in Qt 4.4.

Sets the default file format to the given format, which is used for storing settings for the QSettings(QObject *) constructor.

If no default format is set, QSettings::NativeFormat is used. See the documentation for the QSettings constructor you are using to see if that constructor will ignore this function.

This function was introduced in Qt 4.4.

new IQSettingsSignals QtCore.QSettings.Emit

getprotected

new bool QtCore.QSettings.FallbacksEnabled

getset

Returns true if fallbacks are enabled; returns false otherwise.

By default, fallbacks are enabled.

Sets whether fallbacks are enabled to b.

By default, fallbacks are enabled.

new QTextCodec QtCore.QSettings.IniCodec

getset

Returns the codec that is used for accessing INI files. By default, no codec is used, so a null pointer is returned.

This function was introduced in Qt 4.5.

Sets the codec for accessing INI files (including .conf files on Unix) to codec. The codec is used for decoding any data that is read from the INI file, and for encoding any data that is written to the file. By default, no codec is used, and non-ASCII characters are encoded using standard INI escape sequences.

Warning: The codec must be set immediately after creating the QSettings object, before accessing any data.

This function was introduced in Qt 4.5.

new QMetaObject QtCore.QSettings.StaticMetaObject

staticget

SystemScope	Store settings in a global location, so that all users on the same machine access the same set of settings.
UserScope	Store settings in a location specific to the current user (e.g., in the user's home directory).

AccessError	An access error occurred (e.g. trying to write to a read-only file).
FormatError	A format error occurred (e.g. loading a malformed INI file).
NoError	No error occurred.

new void QtCore.QSettings.BeginWriteArray	(	string	prefix,
		int	size = `-1`
	)

new void QtCore.QSettings.SetValue	(	string	key,
		object	value
	)

new object QtCore.QSettings.Value	(	string	key,
		object	defaultValue
	)

QtCore.QSettings.QSettings	(	QSettings.Scope	scope,
		string	organization,
		string	application = `""`,
		QObject	parent = `null`
	)

Public Types

Public Member Functions

Static Public Member Functions

Protected Member Functions

Properties

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

Property Documentation