Qt 4.8
|
The QSettings class provides persistent platform-independent application settings. More...
#include <qsettings.h>
Public Types | |
enum | Format { NativeFormat, IniFormat, InvalidFormat = 16, CustomFormat1, CustomFormat2, CustomFormat3, CustomFormat4, CustomFormat5, CustomFormat6, CustomFormat7, CustomFormat8, CustomFormat9, CustomFormat10, CustomFormat11, CustomFormat12, CustomFormat13, CustomFormat14, CustomFormat15, CustomFormat16 } |
This enum type specifies the storage format used by QSettings. More... | |
typedef bool(* | ReadFunc) (QIODevice &device, SettingsMap &map) |
Typedef for a pointer to a function with the following signature: More... | |
enum | Scope { UserScope, SystemScope } |
) in file paths: More... | |
typedef QMap< QString, QVariant > | SettingsMap |
Typedef for QMap<QString, QVariant>. More... | |
enum | Status { NoError = 0, AccessError, FormatError } |
The following status values are possible: More... | |
typedef bool(* | WriteFunc) (QIODevice &device, const SettingsMap &map) |
Typedef for a pointer to a function with the following signature: More... | |
Public Functions | |
QStringList | allKeys () const |
Returns a list of all keys, including subkeys, that can be read using the QSettings object. More... | |
QString | applicationName () const |
Returns the application name used for storing the settings. More... | |
void | beginGroup (const QString &prefix) |
Appends prefix to the current group. More... | |
int | beginReadArray (const QString &prefix) |
Adds prefix to the current group and starts reading from an array. More... | |
void | beginWriteArray (const QString &prefix, int size=-1) |
Adds prefix to the current group and starts writing an array of size size. More... | |
QStringList | childGroups () const |
Returns a list of all key top-level groups that contain keys that can be read using the QSettings object. More... | |
QStringList | childKeys () const |
Returns a list of all top-level keys that can be read using the QSettings object. More... | |
void | clear () |
Removes all entries in the primary location associated to this QSettings object. More... | |
bool | contains (const QString &key) const |
Returns true if there exists a setting called key; returns false otherwise. More... | |
void | endArray () |
Closes the array that was started using beginReadArray() or beginWriteArray(). More... | |
void | endGroup () |
Resets the group to what it was before the corresponding beginGroup() call. More... | |
bool | fallbacksEnabled () const |
Returns true if fallbacks are enabled; returns false otherwise. More... | |
QString | fileName () const |
Returns the path where settings written using this QSettings object are stored. More... | |
Format | format () const |
Returns the format used for storing the settings. More... | |
QString | group () const |
Returns the current group. More... | |
QTextCodec * | iniCodec () const |
Returns the codec that is used for accessing INI files. More... | |
bool | isWritable () const |
Returns true if settings can be written using this QSettings object; returns false otherwise. More... | |
QString | organizationName () const |
Returns the organization name used for storing the settings. More... | |
QSettings (const QString &organization, const QString &application=QString(), QObject *parent=0) | |
Constructs a QSettings object for accessing settings of the application called application from the organization called organization, and with parent parent. More... | |
QSettings (Scope scope, const QString &organization, const QString &application=QString(), QObject *parent=0) | |
Constructs a QSettings object for accessing settings of the application called application from the organization called organization, and with parent parent. More... | |
QSettings (Format format, Scope scope, const QString &organization, const QString &application=QString(), QObject *parent=0) | |
Constructs a QSettings object for accessing settings of the application called application from the organization called organization, and with parent parent. More... | |
QSettings (const QString &fileName, Format format, QObject *parent=0) | |
Constructs a QSettings object for accessing the settings stored in the file called fileName, with parent parent. More... | |
QSettings (QObject *parent=0) | |
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(). More... | |
void | remove (const QString &key) |
Removes the setting key and any sub-settings of key. More... | |
Scope | scope () const |
Returns the scope used for storing the settings. More... | |
void | setArrayIndex (int i) |
Sets the current array index to i. More... | |
void | setFallbacksEnabled (bool b) |
Sets whether fallbacks are enabled to b. More... | |
void | setIniCodec (QTextCodec *codec) |
Sets the codec for accessing INI files (including . More... | |
void | setIniCodec (const char *codecName) |
Sets the codec for accessing INI files (including . More... | |
void | setValue (const QString &key, const QVariant &value) |
Sets the value of setting key to value. More... | |
Status | status () const |
Returns a status code indicating the first error that was met by QSettings, or QSettings::NoError if no error occurred. More... | |
void | sync () |
Writes any unsaved changes to permanent storage, and reloads any settings that have been changed in the meantime by another application. More... | |
QVariant | value (const QString &key, const QVariant &defaultValue=QVariant()) const |
Returns the value for setting key. More... | |
~QSettings () | |
Destroys the QSettings object. More... | |
Public Functions inherited from QObject | |
bool | blockSignals (bool b) |
If block is true, signals emitted by this object are blocked (i.e., emitting a signal will not invoke anything connected to it). More... | |
const QObjectList & | children () const |
Returns a list of child objects. More... | |
bool | connect (const QObject *sender, const char *signal, const char *member, Qt::ConnectionType type=Qt::AutoConnection) const |
bool | disconnect (const char *signal=0, const QObject *receiver=0, const char *member=0) |
bool | disconnect (const QObject *receiver, const char *member=0) |
void | dumpObjectInfo () |
Dumps information about signal connections, etc. More... | |
void | dumpObjectTree () |
Dumps a tree of children to the debug output. More... | |
QList< QByteArray > | dynamicPropertyNames () const |
Returns the names of all properties that were dynamically added to the object using setProperty(). More... | |
virtual bool | eventFilter (QObject *, QEvent *) |
Filters events if this object has been installed as an event filter for the watched object. More... | |
template<typename T > | |
T | findChild (const QString &aName=QString()) const |
Returns the child of this object that can be cast into type T and that is called name, or 0 if there is no such object. More... | |
template<typename T > | |
QList< T > | findChildren (const QString &aName=QString()) const |
Returns all children of this object with the given name that can be cast to type T, or an empty list if there are no such objects. More... | |
template<typename T > | |
QList< T > | findChildren (const QRegExp &re) const |
bool | inherits (const char *classname) const |
Returns true if this object is an instance of a class that inherits className or a QObject subclass that inherits className; otherwise returns false. More... | |
void | installEventFilter (QObject *) |
Installs an event filter filterObj on this object. More... | |
bool | isWidgetType () const |
Returns true if the object is a widget; otherwise returns false. More... | |
void | killTimer (int id) |
Kills the timer with timer identifier, id. More... | |
virtual const QMetaObject * | metaObject () const |
Returns a pointer to the meta-object of this object. More... | |
void | moveToThread (QThread *thread) |
Changes the thread affinity for this object and its children. More... | |
QString | objectName () const |
QObject * | parent () const |
Returns a pointer to the parent object. More... | |
QVariant | property (const char *name) const |
Returns the value of the object's name property. More... | |
Q_INVOKABLE | QObject (QObject *parent=0) |
Constructs an object with parent object parent. More... | |
void | removeEventFilter (QObject *) |
Removes an event filter object obj from this object. More... | |
void | setObjectName (const QString &name) |
void | setParent (QObject *) |
Makes the object a child of parent. More... | |
bool | setProperty (const char *name, const QVariant &value) |
Sets the value of the object's name property to value. More... | |
void | setUserData (uint id, QObjectUserData *data) |
bool | signalsBlocked () const |
Returns true if signals are blocked; otherwise returns false. More... | |
int | startTimer (int interval) |
Starts a timer and returns a timer identifier, or returns zero if it could not start a timer. More... | |
QThread * | thread () const |
Returns the thread in which the object lives. More... | |
QObjectUserData * | userData (uint id) const |
virtual | ~QObject () |
Destroys the object, deleting all its child objects. More... | |
Static Public Functions | |
static Format | defaultFormat () |
static Format | registerFormat (const QString &extension, ReadFunc readFunc, WriteFunc writeFunc, Qt::CaseSensitivity caseSensitivity=Qt::CaseSensitive) |
Registers a custom storage format. More... | |
static void | setDefaultFormat (Format format) |
static void | setPath (Format format, Scope scope, const QString &path) |
Sets the path used for storing settings for the given format and scope, to path. More... | |
static void | setSystemIniPath (const QString &dir) |
Use setPath() instead. More... | |
static void | setUserIniPath (const QString &dir) |
Use setPath() instead. More... | |
Static Public Functions inherited from QObject | |
static bool | connect (const QObject *sender, const char *signal, const QObject *receiver, const char *member, Qt::ConnectionType=Qt::AutoConnection) |
Creates a connection of the given type from the signal in the sender object to the method in the receiver object. More... | |
static bool | connect (const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &method, Qt::ConnectionType type=Qt::AutoConnection) |
static bool | disconnect (const QObject *sender, const char *signal, const QObject *receiver, const char *member) |
Disconnects signal in object sender from method in object receiver. More... | |
static bool | disconnect (const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &member) |
static uint | registerUserData () |
static QString | tr (const char *sourceText, const char *comment=0, int n=-1) |
static QString | trUtf8 (const char *sourceText, const char *comment=0, int n=-1) |
Protected Functions | |
bool | event (QEvent *event) |
Reimplemented Function More... | |
Protected Functions inherited from QObject | |
virtual void | childEvent (QChildEvent *) |
This event handler can be reimplemented in a subclass to receive child events. More... | |
virtual void | connectNotify (const char *signal) |
This virtual function is called when something has been connected to signal in this object. More... | |
virtual void | customEvent (QEvent *) |
This event handler can be reimplemented in a subclass to receive custom events. More... | |
virtual void | disconnectNotify (const char *signal) |
This virtual function is called when something has been disconnected from signal in this object. More... | |
QObject (QObjectPrivate &dd, QObject *parent=0) | |
int | receivers (const char *signal) const |
Returns the number of receivers connected to the signal. More... | |
QObject * | sender () const |
Returns a pointer to the object that sent the signal, if called in a slot activated by a signal; otherwise it returns 0. More... | |
int | senderSignalIndex () const |
virtual void | timerEvent (QTimerEvent *) |
This event handler can be reimplemented in a subclass to receive timer events for the object. More... | |
Additional Inherited Members | |
Public Slots inherited from QObject | |
void | deleteLater () |
Schedules this object for deletion. More... | |
Signals inherited from QObject | |
void | destroyed (QObject *=0) |
This signal is emitted immediately before the object obj is destroyed, and can not be blocked. More... | |
Static Public Variables inherited from QObject | |
static const QMetaObject | staticMetaObject |
This variable stores the meta-object for the class. More... | |
Protected Variables inherited from QObject | |
QScopedPointer< QObjectData > | d_ptr |
Static Protected Variables inherited from QObject | |
static const QMetaObject | staticQtMetaObject |
Related Functions inherited from QObject | |
T | qFindChildqFindChildren (const QObject *obj, const QString &name)() |
QList< T > | qFindChildrenqFindChildren (const QObject *obj, const QString &name)() |
QList< T > | qFindChildrenqFindChildren (const QObject *obj, const QRegExp ®Exp)() |
T * | qobject_cast (QObject *object) |
QObjectList | |
void * | qt_find_obj_child (QObject *parent, const char *type, const QString &name) |
Returns a pointer to the object named name that inherits type and with a given parent. More... | |
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.
section1
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 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:
...
(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:
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():
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():
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().
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:
The inverse conversion (e.g., from QColor to QVariant) is automatic for all data types supported by QVariant, including GUI-related types:
Custom types registered using qRegisterMetaType() and qRegisterMetaTypeStreamOperators() can be stored using QSettings.
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".
You can form hierarchical keys using the '/' character as a separator, similar to Unix file paths. For example:
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:
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.
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:
(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:
The table below summarizes which QSettings objects access which location. "<b>X</b>" 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.
Locations | obj1 | obj2 | obj3 | obj4 |
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:
The Settings Editor example lets you experiment with different settings location and with fallbacks turned on or off.
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.
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:
...
See the Application example for a self-contained example that uses QSettings.
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).
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
HKEY_LOCAL_MACHINE\Software\WOW6432node
.On BlackBerry only a single file is used (see Platform Limitations). If the file format is NativeFormat, this is "Settings/MySoft/Star Runner.conf" in the application's home directory.
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 BlackBerry only a single file is used (see Platform Limitations). If the file format is IniFormat, this is "Settings/MySoft/Star Runner.ini" in the application's home directory.
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:/data/.config/MySoft/Star Runner.conf
c:/data/.config/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:
.
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 setting the
XDG_CONFIG_HOME
environment variable; see setPath() for details.
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:
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:
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:
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:
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.
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:
On other platforms than Windows, "Default" and "." would be treated as regular subkeys.
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
:
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:
Note that this may affect framework libraries' functionality if they expect the settings to be shared between applications.
On Mac OS X, the global Qt settings (stored in com.trolltech.plist
) are stored in the application settings file in two situations:
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.
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:
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.
On the BlackBerry platform, applications run in a sandbox. They are not allowed to read or write outside of this sandbox. This involves the following limitations:
Definition at line 73 of file qsettings.h.
QSettings::ReadFunc |
Typedef for a pointer to a function with the following signature:
ReadFunc
is used in registerFormat()
as a pointer to a function that reads a set of key/value pairs. ReadFunc
should read all the options in one pass, and return all the settings in the SettingsMap
container, which is initially empty.
Definition at line 191 of file qsettings.h.
Typedef for QMap<QString, QVariant>.
Definition at line 190 of file qsettings.h.
QSettings::WriteFunc |
Typedef for a pointer to a function with the following signature:
WriteFunc
is used in registerFormat()
as a pointer to a function that writes a set of key/value pairs. WriteFunc
is only called once, so you need to output the settings in one go.
Definition at line 192 of file qsettings.h.
enum 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 </tt>-based syntax to encode the type. For example:
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 (
{
Definition at line 92 of file qsettings.h.
enum QSettings::Scope |
) in file paths:
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().
This enum specifies whether settings are user-specific or shared by all users of the same system.
Enumerator | |
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UserScope | |
SystemScope |
Definition at line 115 of file qsettings.h.
enum QSettings::Status |
The following status values are possible:
Enumerator | |
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NoError | |
AccessError | |
FormatError |
Definition at line 86 of file qsettings.h.
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explicit |
Constructs a QSettings object for accessing settings of the application called application from the organization called organization, and with parent parent.
Example:
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).
Definition at line 2666 of file qsettings.cpp.
Referenced by QSettings().
QSettings::QSettings | ( | Scope | scope, |
const QString & | organization, | ||
const QString & | application = QString() , |
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QObject * | parent = 0 |
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) |
Constructs a QSettings object for accessing settings of the application called application from the organization called organization, and with parent parent.
If scope is QSettings::UserScope, the QSettings object searches user-specific settings first, before it searches system-wide settings as a fallback. If scope is QSettings::SystemScope, the QSettings object ignores user-specific settings and provides access to system-wide settings.
The storage format is set to QSettings::NativeFormat (i.e. calling setDefaultFormat() before calling this constructor has no effect).
If no application name is given, the QSettings object will only access the organization-wide Fallback Mechanism{locations}.
Definition at line 2691 of file qsettings.cpp.
QSettings::QSettings | ( | Format | format, |
Scope | scope, | ||
const QString & | organization, | ||
const QString & | application = QString() , |
||
QObject * | parent = 0 |
||
) |
Constructs a QSettings object for accessing settings of the application called application from the organization called organization, and with parent parent.
If scope is QSettings::UserScope, the QSettings object searches user-specific settings first, before it searches system-wide settings as a fallback. If scope is QSettings::SystemScope, the QSettings object ignores user-specific settings and provides access to system-wide settings.
If format is QSettings::NativeFormat, the native API is used for storing settings. If format is QSettings::IniFormat, the INI format is used.
If no application name is given, the QSettings object will only access the organization-wide Fallback Mechanism{locations}.
Definition at line 2715 of file qsettings.cpp.
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.
.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:@
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. Definition at line 2751 of file qsettings.cpp.
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explicit |
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
is equivalent to
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.
Definition at line 2790 of file qsettings.cpp.
QSettings::~QSettings | ( | ) |
Destroys the QSettings object.
Any unsaved changes will eventually be written to permanent storage.
Definition at line 2841 of file qsettings.cpp.
QStringList QSettings::allKeys | ( | ) | const |
Returns a list of all keys, including subkeys, that can be read using the QSettings object.
Example:
If a group is set using beginGroup(), only the keys in the group are returned, without the group prefix:
Definition at line 3240 of file qsettings.cpp.
QString QSettings::applicationName | ( | ) | const |
Returns the application name used for storing the settings.
Definition at line 2961 of file qsettings.cpp.
void QSettings::beginGroup | ( | const QString & | prefix | ) |
Appends prefix to the current group.
The current group is automatically prepended to all keys specified to QSettings. In addition, query functions such as childGroups(), childKeys(), and allKeys() are based on the group. By default, no group is set.
Groups are useful to avoid typing in the same setting paths over and over. For example:
This will set the value of three settings:
mainwindow/size
mainwindow/fullScreen
outputpanel/visible
Call endGroup() to reset the current group to what it was before the corresponding beginGroup() call. Groups can be nested.
Definition at line 3073 of file qsettings.cpp.
Referenced by fontPath(), QFileDialogPrivate::init(), QKde::kdeToolBarIconSize(), QKde::kdeToolButtonStyle(), QLibraryInfo::location(), QMultiInputContext::QMultiInputContext(), QPSPrintEnginePrivate::QPSPrintEnginePrivate(), QApplicationPrivate::qt_mac_apply_settings(), MetaObjectGenerator::readClassInfo(), QAxBase::setControl(), QGuiPlatformPlugin::systemIconThemeName(), QApplicationPrivate::x11_apply_settings(), and QFileDialog::~QFileDialog().
int QSettings::beginReadArray | ( | const QString & | prefix | ) |
Adds prefix to the current group and starts reading from an array.
Returns the size of the array.
Example:
Use beginWriteArray() to write the array in the first place.
Definition at line 3129 of file qsettings.cpp.
void QSettings::beginWriteArray | ( | const QString & | prefix, |
int | size = -1 |
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) |
Adds prefix to the current group and starts writing an array of size size.
If size is -1 (the default), it is automatically determined based on the indexes of the entries written.
If you have many occurrences of a certain set of keys, you can use arrays to make your life easier. For example, let's suppose that you want to save a variable-length list of user names and passwords. You could then write:
The generated keys will have the form
logins/size
logins/1/userName
logins/1/password
logins/2/userName
logins/2/password
logins/3/userName
logins/3/password
To read back an array, use beginReadArray().
Definition at line 3165 of file qsettings.cpp.
QStringList QSettings::childGroups | ( | ) | const |
Returns a list of all key top-level groups that contain keys that can be read using the QSettings object.
Example:
If a group is set using beginGroup(), the first-level keys in that group are returned, without the group prefix.
You can navigate through the entire setting hierarchy using childKeys() and childGroups() recursively.
Definition at line 3288 of file qsettings.cpp.
Referenced by QLibraryInfo::location(), MetaObjectGenerator::readClassInfo(), and QAxBase::setControl().
QStringList QSettings::childKeys | ( | ) | const |
Returns a list of all top-level keys that can be read using the QSettings object.
Example:
If a group is set using beginGroup(), the top-level keys in that group are returned, without the group prefix:
You can navigate through the entire setting hierarchy using childKeys() and childGroups() recursively.
Definition at line 3264 of file qsettings.cpp.
Referenced by QApplicationPrivate::qt_mac_apply_settings(), and QApplicationPrivate::x11_apply_settings().
void QSettings::clear | ( | ) |
Removes all entries in the primary location associated to this QSettings object.
Entries in fallback locations are not removed.
If you only want to remove the entries in the current group(), use remove("") instead.
Definition at line 2864 of file qsettings.cpp.
bool QSettings::contains | ( | const QString & | key | ) | const |
Returns true if there exists a setting called key; returns false otherwise.
If a group is set using beginGroup(), key is taken to be relative to that group.
Note that 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, see the Section and Key Syntax rules.
Definition at line 3394 of file qsettings.cpp.
Referenced by QLocalServerPrivate::listen(), QLibraryInfo::location(), qt_applyFontDatabaseSettings(), and QLocalServerPrivate::removeServer().
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static |
Returns default file format used for storing settings for the QSettings(QObject *) constructor. If no default format is set, QSettings::NativeFormat is used.
Definition at line 3494 of file qsettings.cpp.
void QSettings::endArray | ( | ) |
Closes the array that was started using beginReadArray() or beginWriteArray().
Definition at line 3182 of file qsettings.cpp.
void QSettings::endGroup | ( | ) |
Resets the group to what it was before the corresponding beginGroup() call.
Example:
Definition at line 3089 of file qsettings.cpp.
Referenced by QLibraryInfo::location(), QApplicationPrivate::qt_mac_apply_settings(), MetaObjectGenerator::readClassInfo(), QAxBase::setControl(), and QApplicationPrivate::x11_apply_settings().
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protectedvirtual |
Reimplemented Function
Reimplemented from QObject.
Definition at line 3431 of file qsettings.cpp.
bool QSettings::fallbacksEnabled | ( | ) | const |
Returns true if fallbacks are enabled; returns false otherwise.
By default, fallbacks are enabled.
Definition at line 3421 of file qsettings.cpp.
QString QSettings::fileName | ( | ) | const |
Returns the path where settings written using this QSettings object are stored.
On Windows, if the format is QSettings::NativeFormat, the return value is a system registry path, not a file path.
Definition at line 2897 of file qsettings.cpp.
QSettings::Format QSettings::format | ( | ) | const |
Returns the format used for storing the settings.
Definition at line 2913 of file qsettings.cpp.
Referenced by setDefaultFormat().
QString QSettings::group | ( | ) | const |
Returns the current group.
Definition at line 3111 of file qsettings.cpp.
Referenced by endArray(), endGroup(), and remove().
QTextCodec * QSettings::iniCodec | ( | ) | const |
Returns the codec that is used for accessing INI files.
By default, no codec is used, so a null pointer is returned.
Definition at line 3023 of file qsettings.cpp.
bool QSettings::isWritable | ( | ) | const |
Returns true if settings can be written using this QSettings object; returns false otherwise.
One reason why isWritable() might return false is if QSettings operates on a read-only file.
Definition at line 3306 of file qsettings.cpp.
Referenced by UpdateRegistry().
QString QSettings::organizationName | ( | ) | const |
Returns the organization name used for storing the settings.
Definition at line 2945 of file qsettings.cpp.
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static |
Registers a custom storage format.
On success, returns a special Format value that can then be passed to the QSettings constructor. On failure, returns InvalidFormat.
The extension is the file extension associated to the format (without the '.').
The readFunc and writeFunc parameters are pointers to functions that read and write a set of key/value pairs. The QIODevice parameter to the read and write functions is always opened in binary mode (i.e., without the QIODevice::Text flag).
The caseSensitivity parameter specifies whether keys are case sensitive or not. This makes a difference when looking up values using QSettings. The default is case sensitive.
By default, if you use one of the constructors that work in terms of an organization name and an application name, the file system locations used are the same as for IniFormat. Use setPath() to specify other locations.
Example:
Definition at line 3663 of file qsettings.cpp.
void QSettings::remove | ( | const QString & | key | ) |
Removes the setting key and any sub-settings of key.
Example:
Be aware that if one of the fallback locations contains a setting with the same key, that setting will be visible after calling remove().
If key is an empty string, all keys in the current group() are removed. For example:
Note that 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, see the Section and Key Syntax rules.
Definition at line 3359 of file qsettings.cpp.
Referenced by QLocalServerPrivate::closeServer(), and QLocalServerPrivate::removeServer().
QSettings::Scope QSettings::scope | ( | ) | const |
Returns the scope used for storing the settings.
Definition at line 2929 of file qsettings.cpp.
void QSettings::setArrayIndex | ( | int | i | ) |
Sets the current array index to i.
Calls to functions such as setValue(), value(), remove(), and contains() will operate on the array entry at that index.
You must call beginReadArray() or beginWriteArray() before you can call this function.
Definition at line 3211 of file qsettings.cpp.
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static |
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.
Definition at line 3481 of file qsettings.cpp.
void QSettings::setFallbacksEnabled | ( | bool | b | ) |
Sets whether fallbacks are enabled to b.
By default, fallbacks are enabled.
Definition at line 3408 of file qsettings.cpp.
void QSettings::setIniCodec | ( | QTextCodec * | codec | ) |
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.
Definition at line 2986 of file qsettings.cpp.
void QSettings::setIniCodec | ( | const char * | codecName | ) |
Sets the codec for accessing INI files (including .
conf files on Unix) to the QTextCodec for the encoding specified by codecName. Common values for codecName
include "ISO 8859-1", "UTF-8", and "UTF-16". If the encoding isn't recognized, nothing happens.
Definition at line 3006 of file qsettings.cpp.
Sets the path used for storing settings for the given format and scope, to path.
The format can be a custom format.
The table below summarizes the default values:
Platform | Format | Scope | Path |
Windows | IniFormat | UserScope | APPDATA% |
SystemScope | COMMON_APPDATA% | ||
Unix | NativeFormat, IniFormat | UserScope | $HOME/ .config |
SystemScope | /etc/xdg | ||
Qt for Embedded Linux | NativeFormat, IniFormat | UserScope | $HOME/Settings |
SystemScope | /etc/xdg | ||
Mac OS X | IniFormat | UserScope | $HOME/ .config |
SystemScope | /etc/xdg | ||
Symbian | NativeFormat, IniFormat | UserScope | c:/data/ .config |
SystemScope | <drive>/private/<uid> |
The default UserScope paths on Unix and Mac OS X ($HOME/
.config or $HOME/Settings) can be overridden by the user by setting the XDG_CONFIG_HOME
environment variable. The default SystemScope paths on Unix and Mac OS X (/etc/xdg
) can be overridden when building the Qt library using the configure
script's –sysconfdir
flag (see QLibraryInfo for details).
Setting the NativeFormat paths on Windows and Mac OS X has no effect.
Definition at line 3578 of file qsettings.cpp.
Referenced by setSystemIniPath(), and setUserIniPath().
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static |
Use setPath() instead.
setSystemIniPath(path); setPath(QSettings::NativeFormat, QSettings::SystemScope, path); setPath(QSettings::IniFormat, QSettings::SystemScope, path);
Definition at line 3514 of file qsettings.cpp.
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static |
Use setPath() instead.
Definition at line 3531 of file qsettings.cpp.
Sets the value of setting key to value.
If the key already exists, the previous value is overwritten.
Note that 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, see the Section and Key Syntax rules.
Example:
Definition at line 3328 of file qsettings.cpp.
Referenced by beginWriteArray(), QLocalServerPrivate::closeServer(), endArray(), QLibraryPrivate::isPlugin(), QLocalServerPrivate::listen(), qmlsqldatabase_change_version(), qmlsqldatabase_open_sync(), QFactoryLoader::updateDir(), QColorDialog::~QColorDialog(), QFileDialog::~QFileDialog(), and QScriptEngineDebuggerPrivate::~QScriptEngineDebuggerPrivate().
QSettings::Status QSettings::status | ( | ) | const |
Returns a status code indicating the first error that was met by QSettings, or QSettings::NoError if no error occurred.
Be aware that QSettings delays performing some operations. For this reason, you might want to call sync() to ensure that the data stored in QSettings is written to disk before calling status().
Definition at line 3041 of file qsettings.cpp.
void QSettings::sync | ( | ) |
Writes any unsaved changes to permanent storage, and reloads any settings that have been changed in the meantime by another application.
This function is called automatically from QSettings's destructor and by the event loop at regular intervals, so you normally don't need to call it yourself.
Definition at line 2882 of file qsettings.cpp.
Returns the value for setting key.
If the setting doesn't exist, returns defaultValue.
If no default value is specified, a default QVariant is returned.
Note that 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, see the Section and Key Syntax rules.
Example:
Definition at line 3460 of file qsettings.cpp.
Referenced by allowsMessages(), beginReadArray(), QLocalSocket::connectToServer(), fontNameSubstitute(), fontPath(), QColorDialogPrivate::init(), QFileDialogPrivate::init(), QLibraryPrivate::isPlugin(), kdeColor(), QKde::kdeStyle(), QKde::kdeToolBarIconSize(), QKde::kdeToolButtonStyle(), QLibraryInfo::location(), qmlsqldatabase_open_sync(), QMultiInputContext::QMultiInputContext(), QPSPrintEnginePrivate::QPSPrintEnginePrivate(), qt_applyFontDatabaseSettings(), QApplicationPrivate::qt_mac_apply_settings(), qt_mac_update_os_settings(), MetaObjectGenerator::readClassInfo(), MetaObjectGenerator::readEventInfo(), MetaObjectGenerator::readInterfaceInfo(), QAxBase::setControl(), QApplication::setDoubleClickInterval(), QScriptEngineDebugger::standardWindow(), QGuiPlatformPlugin::systemIconThemeName(), QFactoryLoader::updateDir(), and QApplicationPrivate::x11_apply_settings().