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The TQSettings class provides persistent platform-independent application settings. More...
#include <qsettings.h>
On Unix systems, TQSettings uses text files to store settings. On Windows systems, TQSettings uses the system registry. On Mac OS X, TQSettings uses the Carbon preferences API.
Each setting comprises an identifying key and the data associated with the key. A key is a unicode string which consists of two or more subkeys. A subkey is a slash, '/', followed by one or more unicode characters (excluding slashes, newlines, carriage returns and equals, '=', signs). The associated data, called the entry or value, may be a boolean, an integer, a double, a string or a list of strings. Entry strings may contain any unicode characters.
If you want to save and restore the entire desktop's settings, i.e. which applications are running, use TQSettings to save the settings for each individual application and TQSessionManager to save the desktop's session.
Example settings:
/MyCompany/MyApplication/background color
/MyCompany/MyApplication/foreground color
/MyCompany/MyApplication/geometry/x
/MyCompany/MyApplication/geometry/y
/MyCompany/MyApplication/geometry/width
/MyCompany/MyApplication/geometry/height
/MyCompany/MyApplication/recent files/1
/MyCompany/MyApplication/recent files/2
/MyCompany/MyApplication/recent files/3
Each line above is a complete key, made up of subkeys.
A typical usage pattern for reading settings at application startup:
TQSettings settings;
settings.setPath( "MyCompany.com", "MyApplication" );
TQString bgColor = settings.readEntry( "/colors/background", "white" );
int width = settings.readNumEntry( "/geometry/width", 640 );
// ...
A typical usage pattern for saving settings at application exit or 'save preferences':
TQSettings settings;
settings.setPath( "MyCompany.com", "MyApplication" );
settings.writeEntry( "/colors/background", bgColor );
settings.writeEntry( "/geometry/width", width );
// ...
A key prefix can be prepended to all keys using beginGroup(). The application of the prefix is stopped using endGroup(). For example:
TQSettings settings;
settings.beginGroup( "/MainWindow" );
settings.beginGroup( "/Geometry" );
int x = settings.readEntry( "/x" );
// ...
settings.endGroup();
settings.beginGroup( "/Toolbars" );
// ...
settings.endGroup();
settings.endGroup();
You can get a list of entry-holding keys by calling entryList(), and a list of key-holding keys using subkeyList().
TQStringList keys = settings.entryList( "/MyApplication" );
// keys contains 'background color' and 'foreground color'.
TQStringList keys = settings.entryList( "/MyApplication/recent files" );
// keys contains '1', '2' and '3'.
TQStringList subkeys = settings.subkeyList( "/MyApplication" );
// subkeys contains 'geometry' and 'recent files'
TQStringList subkeys = settings.subkeyList( "/MyApplication/recent files" );
// subkeys is empty.
Since settings for Windows are stored in the registry there are some size limitations as follows:
These limitations are not enforced on Unix or Mac OS X.
Warning: Creating multiple, simultaneous instances of TQSettings writing to a text file may lead to data loss! This is a known issue which will be fixed in a future release of TQt.
The location where settings are stored is not formally defined by the CFPreferences API.
At the time of writing settings are stored (either on a global or user basis, preferring locally) into a plist file in $ROOT/System/Library/Preferences (in XML format). TQSettings will create an appropriate plist file (com.<first group name>.plist) out of the full path to a key.
For further information on CFPreferences see Apple's Specifications
There is no universally accepted place for storing application settings under Unix. In the examples the settings file will be searched for in the following directories:
If you want to put the settings in a particular place in the filesystem you could do this:
settings.insertSearchPath( TQSettings::Unix, "/opt/MyCompany/share" );
But in practice you may prefer not to use a search path for Unix. For example the following code:
settings.writeEntry( "/MyApplication/geometry/width", width );
will end up writing the "geometry/width" setting to the file
$HOME/.qt/myapplicationrc (assuming that the application is
being run by an ordinary user, i.e. not by root).
For cross-platform applications you should ensure that the Windows size limitations are not exceeded.
Warning: TQSettings doesn't write the settings until it is destroyed so you should construct the TQSettings object on the stack.
See also Input/Output and Networking and Miscellaneous Classes.
Be aware that you must call setPath() or insertSearchPath() before you can use the TQSettings object.
Be aware that you must call setPath() or insertSearchPath() before you can use the TQSettings object.
TQSettings settings;
settings.beginGroup( "/MainWindow" );
// read values
settings.endGroup();
TQSettings settings;
settings.beginGroup( "/MainWindow/Geometry" );
// read values
settings.endGroup();
Example settings:
/MyCompany/MyApplication/background color
/MyCompany/MyApplication/foreground color
/MyCompany/MyApplication/geometry/x
/MyCompany/MyApplication/geometry/y
/MyCompany/MyApplication/geometry/width
/MyCompany/MyApplication/geometry/height
TQStringList keys = settings.entryList( "/MyCompany/MyApplication" );
In the above example, keys will contain 'background color' and 'foreground color'. It will not contain 'geometry' because this key contains subkeys not entries.
To access the geometry values, you could either use subkeyList() to read the keys then read each entry, or simply read each entry directly by specifying its full key, e.g. "/MyCompany/MyApplication/geometry/y".
See also subkeyList().
See also beginGroup().
When s is Windows and the execution environment is not Windows the function does nothing. Similarly when s is Unix and the execution environment is not Unix the function does nothing.
When s is Windows, and the execution environment is Windows, the search path list will be used as the first subfolder of the "Software" folder in the registry.
When reading settings the folders are searched forwards from the first folder (listed below) to the last, returning the first settings found, and ignoring any folders for which the user doesn't have read permission.
TQSettings settings; settings.insertSearchPath( TQSettings::Windows, "/MyCompany" ); settings.writeEntry( "/MyApplication/Tip of the day", TRUE );The code above will write the subkey "Tip of the day" into the first of the registry folders listed below that is found and for which the user has write permission.
When s is Unix, and the execution environment is Unix, the search path list will be used when trying to determine a suitable filename for reading and writing settings files. By default, there are two entries in the search path:
All insertions into the search path will go before $HOME/.qt/. For example:
TQSettings settings; settings.insertSearchPath( TQSettings::Unix, "/opt/MyCompany/share/etc" ); settings.insertSearchPath( TQSettings::Unix, "/opt/MyCompany/share/MyApplication/etc" ); // ...Will result in a search path of:
Note that paths in the file system are not created by this function, so they must already exist to be useful.
Settings under Unix are stored in files whose names are based on the first subkey of the key (not including the search path). The algorithm for creating names is essentially: lowercase the first subkey, replace spaces with underscores and add 'rc', e.g. /MyCompany/MyApplication/background color will be stored in myapplicationrc (assuming that /MyCompany is part of the search path).
See also removeSearchPath().
Example: chart/chartform.cpp.
Reads the entry specified by key, and returns a bool, or the default value, def, if the entry couldn't be read. If ok is non-null, *ok is set to TRUE if the key was read, FALSE otherwise.
See also readEntry(), readNumEntry(), readDoubleEntry(), writeEntry(), and removeEntry().
Reads the entry specified by key, and returns a double, or the default value, def, if the entry couldn't be read. If ok is non-null, *ok is set to TRUE if the key was read, FALSE otherwise.
See also readEntry(), readNumEntry(), readBoolEntry(), writeEntry(), and removeEntry().
Reads the entry specified by key, and returns a TQString, or the default value, def, if the entry couldn't be read. If ok is non-null, *ok is set to TRUE if the key was read, FALSE otherwise.
See also readListEntry(), readNumEntry(), readDoubleEntry(), readBoolEntry(), writeEntry(), and removeEntry().
Note that if you want to iterate over the list, you should iterate over a copy, e.g.
TQStringList list = mySettings.readListEntry( "recentfiles" );
TQStringList::Iterator it = list.begin();
while( it != list.end() ) {
myProcessing( *it );
++it;
}
See also readEntry(), readDoubleEntry(), readBoolEntry(), writeEntry(), removeEntry(), and TQStringList::split().
This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.
Reads the entry specified by key as a string. The separator is used to create a TQStringList by calling TQStringList::split(separator, entry). If ok is not 0: *ok is set to TRUE if the key was read, otherwise *ok is set to FALSE.
Warning: As the documentation states, TQStringList::split() will omit empty strings from the list. Because of this, it is impossible to retrieve identical list data with this function. We recommend using the readListEntry() and writeEntry() overloads that do not take a separator argument.
Note that if you want to iterate over the list, you should iterate over a copy, e.g.
TQStringList list = mySettings.readListEntry( "size", " " );
TQStringList::Iterator it = list.begin();
while( it != list.end() ) {
myProcessing( *it );
++it;
}
See also readEntry(), readDoubleEntry(), readBoolEntry(), writeEntry(), removeEntry(), and TQStringList::split().
Reads the entry specified by key, and returns an integer, or the default value, def, if the entry couldn't be read. If ok is non-null, *ok is set to TRUE if the key was read, FALSE otherwise.
See also readEntry(), readDoubleEntry(), readBoolEntry(), writeEntry(), and removeEntry().
Returns true if the entry was successfully removed; otherwise returns false. Note that removing the last entry in any given folder, will also remove the folder.
See also readEntry() and writeEntry().
See also insertSearchPath().
The domain should be an Internet domain name controlled by the producer of the software, eg. Trolltech products use "trolltech.com".
The product should be the official name of the product.
The scope should be TQSettings::User for user-specific settings, or TQSettings::Global for system-wide settings (generally these will be read-only to many users).
Not all information is relevant on all systems.
Example settings:
/MyCompany/MyApplication/background color
/MyCompany/MyApplication/foreground color
/MyCompany/MyApplication/geometry/x
/MyCompany/MyApplication/geometry/y
/MyCompany/MyApplication/geometry/width
/MyCompany/MyApplication/geometry/height
/MyCompany/MyApplication/recent files/1
/MyCompany/MyApplication/recent files/2
/MyCompany/MyApplication/recent files/3
TQStringList keys = settings.subkeyList( "/MyCompany/MyApplication" );
In the above example, keys will contain 'geometry' and 'recent files'. It will not contain 'background color' or 'foreground color' because those keys contain entries not subkeys. To get a list of keys that contain entries rather than subkeys use entryList() instead.
Warning: In the above example, if TQSettings is writing to an Ini file, then a call to
subkeyList("/MyCompany")
will return an empty list. This happens because a key like
/MyCompany/MyApplication/background coloris written to the file "mycompanyrc", under the section [MyApplication]. This call is therefore a request to list the sections in an ini file, which is not supported in this version of TQSettings. This is a known issue which will be fixed in TQt-4.
See also entryList().
If an error occurs the settings are left unchanged and FALSE is returned; otherwise TRUE is returned.
Warning: On certain platforms, keys are required to contain at least two components (e.g., "/foo/bar"). This limitation does not apply to TQt 4.
See also readListEntry(), readNumEntry(), readDoubleEntry(), readBoolEntry(), and removeEntry().
Example: chart/chartform.cpp.
Writes the double entry value into key key. The key is created if it doesn't exist. Any previous value is overwritten by value.
If an error occurs the settings are left unchanged and FALSE is returned; otherwise TRUE is returned.
See also readListEntry(), readNumEntry(), readDoubleEntry(), readBoolEntry(), and removeEntry().
Writes the integer entry value into key key. The key is created if it doesn't exist. Any previous value is overwritten by value.
If an error occurs the settings are left unchanged and FALSE is returned; otherwise TRUE is returned.
See also readListEntry(), readNumEntry(), readDoubleEntry(), readBoolEntry(), and removeEntry().
Writes the string entry value into key key. The key is created if it doesn't exist. Any previous value is overwritten by value. If value is an empty string or a null string the key's value will be an empty string.
If an error occurs the settings are left unchanged and FALSE is returned; otherwise TRUE is returned.
See also readListEntry(), readNumEntry(), readDoubleEntry(), readBoolEntry(), and removeEntry().
Writes the string list entry value into key key. The key is created if it doesn't exist. Any previous value is overwritten by value.
If an error occurs the settings are left unchanged and FALSE is returned; otherwise returns TRUE.
See also readListEntry(), readNumEntry(), readDoubleEntry(), readBoolEntry(), and removeEntry().
This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.
Writes the string list entry value into key key. The key is created if it doesn't exist. Any previous value is overwritten by value. The list is stored as a sequence of strings separated by separator (using TQStringList::join()), so none of the strings in the list should contain the separator. If the list is empty or null the key's value will be an empty string.
Warning: The list should not contain empty or null strings, as readListEntry() will use TQStringList::split() to recreate the list. As the documentation states, TQStringList::split() will omit empty strings from the list. Because of this, it is impossible to retrieve identical list data that is stored with this function. We recommend using the writeEntry() and readListEntry() overloads that do not take a separator argument.
If an error occurs the settings are left unchanged and FALSE is returned; otherwise returns TRUE.
See also readListEntry(), readNumEntry(), readDoubleEntry(), readBoolEntry(), removeEntry(), and TQStringList::join().
This file is part of the TQt toolkit. Copyright © 1995-2007 Trolltech. All Rights Reserved.
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