FLTK 1.4.0: Fl_Preferences Class Reference

Fl_Preferences store user settings between application starts. More...

#include <Fl_Preferences.H>

Inheritance diagram for Fl_Preferences:

Classes
struct	Entry

class	Name
	'Name' provides a simple method to create numerical or more complex procedural names for entries and groups on the fly. More...

class	Node

class	RootNode

Public Types
typedef void *	ID
	Every Fl_Preferences-Group has a unique ID. More...

enum	Root { UNKNOWN_ROOT_TYPE = -1 , SYSTEM = 0 , USER , MEMORY , ROOT_MASK = 0x00FF , CORE = 0x0100 , C_LOCALE = 0x1000 , CLEAR = 0x2000 , SYSTEM_L = SYSTEM \| C_LOCALE , USER_L = USER \| C_LOCALE , CORE_SYSTEM_L = CORE \| SYSTEM_L , CORE_USER_L = CORE \| USER_L , CORE_SYSTEM = CORE \| SYSTEM , CORE_USER = CORE \| USER }
	Define the scope of the preferences. More...

Public Member Functions
char	clear ()
	Delete all groups and all entries.

char	delete_all_entries ()
	Delete all entries.

char	delete_all_groups ()
	Delete all groups.

char	delete_entry (const char *entry)
	Deletes a single name/value pair. More...

char	delete_group (const char *group)
	Deletes a group. More...

int	dirty ()
	Check if there were changes to the database that need to be written to disk. More...

int	entries ()
	Returns the number of entries (name/value pairs) in a group. More...

const char *	entry (int index)
	Returns the name of an entry. More...

char	entry_exists (const char *key)
	Returns non-zero if an entry with this name exists. More...

Root	filename (char *buffer, size_t buffer_size)
	Return the file name and path to the preference file. More...

	Fl_Preferences (const char path, const char vendor, const char *application)
	Deprecated: Use this constructor to create or read a preference file at an arbitrary position in the file system. More...

	Fl_Preferences (const char path, const char vendor, const char *application, Root flags)
	Use this constructor to create or read a preference file at an arbitrary position in the file system. More...

	Fl_Preferences (const Fl_Preferences &)
	Create another reference to a Preferences group.

	Fl_Preferences (Fl_Preferences &parent, const char *group)
	Generate or read a new group of entries within another group. More...

	Fl_Preferences (Fl_Preferences &parent, int groupIndex)
	Open a child group using a given index. More...

	Fl_Preferences (Fl_Preferences parent, const char group)
	Create or access a group of preferences using a name. More...

	Fl_Preferences (Fl_Preferences *parent, int groupIndex)

	Fl_Preferences (ID id)
	Create a new dataset access point using a dataset ID. More...

	Fl_Preferences (Root root, const char vendor, const char application)
	The constructor creates a group that manages key/value pairs and child groups. More...

int	flush ()
	Writes preferences to disk if they were modified. More...

char	get (const char entry, char &value, const char *defaultValue)
	Reads an entry from the group. More...

char	get (const char entry, char value, const char *defaultValue, int maxSize)
	Reads an entry from the group. More...

char	get (const char *entry, double &value, double defaultValue)
	Reads an entry from the group. More...

char	get (const char *entry, float &value, float defaultValue)
	Reads an entry from the group. More...

char	get (const char *entry, int &value, int defaultValue)
	Reads an entry from the group. More...

char	get (const char entry, void &value, const void *defaultValue, int defaultSize)
	Reads an entry from the group. More...

char	get (const char entry, void value, const void defaultValue, int defaultSize, int size)
	Reads a binary entry from the group, encoded in hexadecimal blocks. More...

char	get (const char entry, void value, const void *defaultValue, int defaultSize, int maxSize)
	Reads a binary entry from the group, encoded in hexadecimal blocks. More...

char	get_userdata_path (char *path, int pathlen)
	Creates a path that is related to the preference file and that is usable for additional application data. More...

const char *	group (int num_group)
	Returns the name of the Nth (`num_group`) group. More...

char	group_exists (const char *key)
	Returns non-zero if a group with this name exists. More...

int	groups ()
	Returns the number of groups that are contained within a group. More...

ID	id ()
	Return an ID that can later be reused to open more references to this dataset.

const char *	name ()
	Return the name of this entry.

const char *	path ()
	Return the full path to this entry.

char	set (const char entry, const char value)
	Sets an entry (name/value pair). More...

char	set (const char entry, const void value, int size)
	Sets an entry (name/value pair). More...

char	set (const char *entry, double value)
	Sets an entry (name/value pair). More...

char	set (const char *entry, double value, int precision)
	Sets an entry (name/value pair). More...

char	set (const char *entry, float value)
	Sets an entry (name/value pair). More...

char	set (const char *entry, float value, int precision)
	Sets an entry (name/value pair). More...

char	set (const char *entry, int value)
	Sets an entry (name/value pair). More...

int	size (const char *entry)
	Returns the size of the value part of an entry. More...

virtual	~Fl_Preferences ()
	The destructor removes allocated resources. More...

Static Public Member Functions
static unsigned int	file_access ()
	Return the current file access permissions for the FLTK preferences system. More...

static void	file_access (unsigned int flags)
	Tell the FLTK preferences system which files in the file system it may read, create, or write. More...

static Root	filename (char buffer, size_t buffer_size, Root root, const char vendor, const char *application)
	Determine the file name and path to preferences that would be openend with these parameters. More...

static const char *	new_UUID ()
	Returns a UUID as generated by the system. More...

static char	remove (ID id_)
	Remove the group with this ID from a database.

Static Public Attributes
static const unsigned int	ALL = ALL_READ_OK \| ALL_WRITE_OK
	Set this to give FLTK and applications permission to read, write, and create preference files.

static const unsigned int	ALL_READ_OK = USER_READ_OK \| SYSTEM_READ_OK \| CORE_READ_OK
	Set this to allow FLTK and applications to read preference files.

static const unsigned int	ALL_WRITE_OK = USER_WRITE_OK \| SYSTEM_WRITE_OK \| CORE_WRITE_OK
	Set this to allow FLTK and applications to create and write preference files.

static const unsigned int	APP_OK = SYSTEM_OK \| USER_OK
	Set this if it is OK for applications to read, create, and write any kind of preference files.

static const unsigned int	CORE_OK = CORE_READ_OK \| CORE_WRITE_OK
	Set this if it is OK for FLTK to read, create, or write preference files.

static const unsigned int	CORE_READ_OK = 0x0010
	Set this if it is OK for FLTK to read preference files. More...

static const unsigned int	CORE_WRITE_OK = 0x0020
	Set this if it is OK for FLTK to create or write preference files. More...

static const unsigned int	NONE = 0x0000
	Set this if no call to Fl_Preferences shall access the file system. More...

static const unsigned int	SYSTEM_OK = SYSTEM_READ_OK \| SYSTEM_WRITE_OK
	Set this if it is OK for applications to read, create, and write system wide preference files.

static const unsigned int	SYSTEM_READ_OK = 0x0004
	Set this if it is OK for applications to read system wide preference files.

static const unsigned int	SYSTEM_WRITE_OK = 0x0008
	Set this if it is OK for applications to create and write system wide preference files.

static const unsigned int	USER_OK = USER_READ_OK \| USER_WRITE_OK
	Set this if it is OK for applications to read, create, and write user preference files.

static const unsigned int	USER_READ_OK = 0x0001
	Set this if it is OK for applications to read user preference files.

static const unsigned int	USER_WRITE_OK = 0x0002
	Set this if it is OK for applications to create and write user preference files.

Protected Attributes
Node *	node

RootNode *	rootNode

Friends
class	Node

class	RootNode

Detailed Description

Fl_Preferences store user settings between application starts.

Fl_Preferences are similar to the Registry on Windows and Preferences on MacOS, providing a simple method to store customizable user settings between app launches, for instance the previous window position or a history of previously used documents.

Preferences are organized in a hierarchy of groups. Every group can contain more groups and any number of key/value pairs. Keys can be text strings containing ASCII letters, digits, periods, and underscores. Forward slashes in a key name are treated as subgroups, i.e. the key 'window/width' would actually refer to the key 'width' inside the group 'window'.

Keys usually have a unique name within their group. Duplicate keys are possible though and can be accessed using the index based functions.

A value can be an UTF-8 string. Control characters and UTF-8 sequences are stored as octal values. Long strings are wrapped at the line ending and will be reassembled when reading the file back.

Several methods allow setting and getting numerical values and binary data.

Preferences are stored in text files that can be edited manually if needed. The file format is easy to read and relatively forgiving. Preference files are the same on all platforms. User comments in preference files are preserved. Filenames are unique for each application by using a vendor/application naming scheme. The user must provide default values for all entries to ensure proper operation should preferences be corrupted or not yet exist.

FLTK preferences are not meant to replace a fully features database. No merging of data takes place. If several instances of an app access the same database at the same time, only the most recent changes will persist.

Preferences should no be used to store document data. The .prefs file should be kept small for performance reasons. One application can have multiple preference files. Extensive binary data however should be stored in separate files: see Fl_Preferences::get_userdata_path() .

Fl_Preferences are not thread-safe. They can temporarily change the locale on some platforms during read and write access, which also changes it temporarily in other threads of the same app.

Typically a preferences database is read at startup, and then reopened and written at app shutdown:

int appWindowWidth, appWindowHeight;
 
void launch() {
  Fl_Preferences app(Fl_Preferences::USER_L, "matthiasm.com", "hello");
  // 'app' constructor will be called, reading data from .prefs file
  Fl_Preferences window(app, "window");
  window.get("width", appWindowWidth, 800);
  window.get("height", appWindowHeight, 600);
  // 'app' destructor will be called. This will write data to the
  // .prefs file if any preferences were changed or added
}
 
void quit() {
  Fl_Preferences app(Fl_Preferences::USER_L, "matthiasm.com", "hello");
  Fl_Preferences window(app, "window");
  window.set("width", appWindowWidth);
  window.set("height", appWindowHeight);
}

See also: Fl_Preferences::Fl_Preferences(Root root, const char *vendor, const char *application)

As a special case, Fl_Preferences can be memory mapped and not be associated with a file on disk.

See also: Fl_Preferences::Fl_Preferences(Fl_Preferences *parent, const char *group) for more details on memory mapped preferences.

Note: Starting with FLTK 1.3, preference databases are expected to be in UTF-8 encoding. Previous databases were stored in the current character set or code page which renders them incompatible for text entries using international characters.; Starting with FLTK 1.4, searching a valid path to store the preference files has changed slightly. Please see Fl_Preferences::Fl_Preferences(Root, const char*, const char*) for details.; Starting with FLTK 1.4, preference files should be created with SYSTEM_L or USER_L to be interchangeable between computers with differing locale settings. The legacy modes, LOCAL and SYSTEM, will read and write floating point values using the decimal point of the current locale. As a result, a fp-value would be written '3,1415' on a German machine, and would be read back as '3.0' on a US machine because the comma would not be recognized as an alternative decimal point.

Member Typedef Documentation

◆ ID

typedef void* Fl_Preferences::ID

Every Fl_Preferences-Group has a unique ID.

ID's can be retrieved from an Fl_Preferences-Group and can then be used to create more Fl_Preference references to the same data set, as long as the database remains open.

Member Enumeration Documentation

◆ Root

enum Fl_Preferences::Root

Define the scope of the preferences.

Enumerator
UNKNOWN_ROOT_TYPE	Returned if storage could not be determined.
SYSTEM	Preferences are used system-wide. Deprecated, see SYSTEM_L.
USER	Preferences apply only to the current user. Deprecated, see USER_L.
MEMORY	Returned if querying memory mapped preferences.
ROOT_MASK	Mask for the values above.
CORE	OR'd by FLTK to read and write core library preferences and options.
C_LOCALE	This flag should always be set, it makes sure that floating point.
CLEAR	Don't read a possibly existing database. Instead, start with an empty set of preferences. values are written correctly independently of the current locale
SYSTEM_L	Preferences are used system-wide, locale independent.
USER_L	Preferences apply only to the current user, locale independent.
CORE_SYSTEM_L	Same as CORE \| SYSTEM \| C_LOCALE.
CORE_USER_L	Same as CORE \| USER \| C_LOCALE.
CORE_SYSTEM	Deprecated, same as CORE \| SYSTEM. Use CORE_SYSTEM_L instead.
CORE_USER	Deprecated, same as CORE \| USER. Use CORE_USER_L instead.

Constructor & Destructor Documentation

◆ Fl_Preferences() [1/8]

Fl_Preferences::Fl_Preferences	(	Root	root,
		const char *	vendor,
		const char *	application
	)

The constructor creates a group that manages key/value pairs and child groups.

Preferences can be stored per user using the root type Fl_Preferences::USER_L, or stored system-wide using Fl_Preferences::SYSTEM_L.

Groups and key/value pairs can be read and written randomly. Reading undefined values will return the default value. Writing undefined values will create all required groups and key/vlaue pairs.

This constructor creates the base instance for all following entries and reads the database from disk into memory if it exists. The vendor argument is a unique text string identifying the development team or vendor of an application. A domain name or an EMail address (replacing the '@' with a '.') are great unique names, e.g. "research.matthiasm.com" or "fluid.fltk.org". The application argument can be the working title or final name of your application. Both vendor and application must be valid UNIX path segments as they become parts of the preference file path and may contain forward slashes to create deeper file structures.

Note: On Windows, the directory is constructed by querying the Common AppData or AppData key of the Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders registry entry. The filename and path is then constructed as $(query)/$(vendor)/$(application).prefs . If the query call fails, data will be stored in RAM only. It will be lost when the app exits.

In FLTK versions before 1.4.0, if querying the registry failed,: preferences would be written to C:\FLTK\$(vendor)\$(application).prefs .

Note: On Linux, the USER directory is constructed by reading $HOME . If $HOME is not set or not pointing to an existing directory, FLTK will check the path member of the passwd struct returned by getpwuid(getuid()) . If all attempts fail, data will be stored in RAM only and be lost when the app exits.

The SYSTEM preference filename is hardcoded as /etc/fltk/$(vendor)/$(application).prefs .

For backward compatibility, the old USER .prefs file naming scheme $(directory)/.fltk/$(vendor)/$(application).prefs is checked first. If that file does not exist, the environment variable $XDG_CONFIG_HOME is read as a base directory. If $XDG_CONFIG_HOME not set, the base directory defaults to $HOME/.config/.

The user preferences will be stored in $(directory)/$(vendor)/$(application).prefs. The user data path will be $(directory)/$(vendor)/$(application)/.

In FLTK versions before 1.4.0, if $HOME was not set, the USER path would be empty, generating $(vendor)/$(application).prefs, which was used relative to the current working directory.

Note: On macOS, the USER directory is constructed by reading $HOME . If $HOME is not set or not pointing to an existing directory, we check the path returned by NSHomeDirectory() , and finally checking the path member of the passwd struct returned by getpwuid(getuid()) . If all attempts fail, data will be stored in RAM only and be lost when the app exits. The filename and path is then constructed as $(directory)/Library/Preferences/$(vendor)/$(application).prefs . The SYSTEM directory is hardcoded as /Library/Preferences/$(vendor)/$(application).prefs .

In FLTK versions before 1.4.0, if $HOME was not set, the USER path: would be NULL , generating <null>/Library/Preferences/$(vendor)/$(application).prefs, which would silently fail to create a preference file.

Parameters

[in]	root	can be `USER_L` or `SYSTEM_L` for user specific or system wide preferences, add the `CLEAR` flag to start with a clean set of preferences instead of reading them from a preexisting database
[in]	vendor	unique text describing the company or author of this file, must be a valid filepath segment
[in]	application	unique text describing the application, must be a valid filepath segment

See also: Fl_Preferences(Fl_Preferences *parent, const char *group) with parent set to NULL

◆ Fl_Preferences() [2/8]

Fl_Preferences::Fl_Preferences	(	const char *	path,
		const char *	vendor,
		const char *	application,
		Root	flags
	)

Use this constructor to create or read a preference file at an arbitrary position in the file system.

The file name is generated in the form $(path)/$(application).prefs. If application is NULL, path is taken literally as the file path and name.

// Example: read from an existing database and write modifications when flushed
// or destructor is called
Fl_Preferences database("/user/matt/test.prefs", "org.fltk.test", NULL,
                        Fl_Preferences::C_LOCALE);
 
// Example: create a new preferences file with an empty data set
Fl_Preferences database("/user/matt/test.prefs", "org.fltk.test", NULL,
     (Fl_Preferences::Root)(Fl_Preferences::C_LOCALE|Fl_Preferences::CLEAR));

Note: the C_LOCALE flag is is not set by default for backward compatibility, but it is highly recommended to set it when opening a database.

Parameters

[in]	path	path to the directory that contains the preference file
[in]	vendor	unique text describing the company or author of this file, must be a valid file path segment
[in]	application	unique text describing the application, must be a valid filename or NULL
[in]	flags	C_LOCALE to make the preferences file independent of the current locale, add the CLEAR flag to start with a clean set of preferences instead of reading from the database

◆ Fl_Preferences() [3/8]

Fl_Preferences::Fl_Preferences	(	Fl_Preferences &	parent,
		const char *	group
	)

Generate or read a new group of entries within another group.

Use the group argument to name the group that you would like to access. Group can also contain a path to a group further down the hierarchy by separating group names with a forward slash '/'.

Parameters

[in]	parent	reference object for the new group
[in]	group	name of the group to access (may contain '/'s)

◆ Fl_Preferences() [4/8]

Fl_Preferences::Fl_Preferences	(	Fl_Preferences *	parent,
		const char *	group
	)

Create or access a group of preferences using a name.

Parent should point to a previously created parent preferences group to create a preferences hierarchy.

If parent is set to NULL, an unnamed database will be accessed that exists only in local memory and is not associated with a file on disk. The root type of this database is set to Fl_Preferences::MEMORY.

the memory database is not shared among multiple instances of the same app
memory databases are not thread safe
all data will be lost when the app quits

void some_function() {
  Fl_Preferences guide( NULL, "Guide" );
  guide.set("answer", 42);
}
void other_function() {
  int x;
  Fl_Preferences guide( NULL, "Guide" );
  guide.get("answer", x, -1);
}

FLTK uses the memory database to manage plugins. See Fl_Plugin.

Parameters

[in]	parent	the parameter parent is a pointer to the parent group. If `parent` is `NULL`, the new preferences item refers to an application internal database ("runtime prefs") which exists only once, and remains in RAM only until the application quits. This database is used to manage plugins and other data indexes by strings. Runtime prefs are not thread-safe.
[in]	group	a group name that is used as a key into the database

See also: Fl_Preferences( Fl_Preferences&, const char *group )

◆ Fl_Preferences() [5/8]

Fl_Preferences::Fl_Preferences	(	Fl_Preferences &	parent,
		int	groupIndex
	)

Open a child group using a given index.

Use the groupIndex argument to find the group that you would like to access. If the given index is invalid (negative or too high), a new group is created with a UUID as a name.

The index needs to be fixed. It is currently backward. Index 0 points to the last member in the 'list' of preferences.

Parameters

[in]	parent	reference object for the new group
[in]	groupIndex	zero based index into child groups

◆ Fl_Preferences() [6/8]

Fl_Preferences::Fl_Preferences	(	Fl_Preferences *	parent,
		int	groupIndex
	)

See also: Fl_Preferences( Fl_Preferences&, int groupIndex )

◆ Fl_Preferences() [7/8]

Fl_Preferences::Fl_Preferences ( Fl_Preferences::ID id )

Create a new dataset access point using a dataset ID.

ID's are a great way to remember shortcuts to database entries that are deeply nested in a preferences database, as long as the database root is not deleted. An ID can be retrieved from any Fl_Preferences dataset, and can then be used to create multiple new references to the same dataset.

ID's can be very helpful when put into the user_data() field of widget callbacks.

◆ ~Fl_Preferences()

Fl_Preferences::~Fl_Preferences ( )

virtual

The destructor removes allocated resources.

When used on the base preferences group, the destructor flushes all changes to the preference file and deletes all internal databases.

The destructor does not remove any data from the database. It merely deletes your reference to the database.

◆ Fl_Preferences() [8/8]

Fl_Preferences::Fl_Preferences	(	const char *	path,
		const char *	vendor,
		const char *	application
	)

Deprecated: Use this constructor to create or read a preference file at an arbitrary position in the file system.

Deprecated:: "in 1.4.0 - use Fl_Preferences(path, vendor, application, flags) instead"

This constructor should no longer be used because the generated database uses the current locale, making it impossible to exchange floating point settings between machines with different language settings.

Use Fl_Preferences(path, vendor, application, Fl_Preferences::C_LOCALE) in new projects and Fl_Preferences(path, vendor, application, 0) if you must keep backward compatibility.

See also: Fl_Preferences( const char *path, const char *vendor, const char *application, Root flags )

Member Function Documentation

◆ delete_entry()

char Fl_Preferences::delete_entry ( const char * key )

Deletes a single name/value pair.

This function removes the entry key from the database.

Parameters

[in] key name of entry to delete

Returns: 0 if deleting the entry failed

◆ delete_group()

char Fl_Preferences::delete_group ( const char * group )

Deletes a group.

Removes a group and all keys and groups within that group from the database.

Parameters

[in] group name of the group to delete

Returns: 0 if call failed

◆ dirty()

int Fl_Preferences::dirty ( )

Check if there were changes to the database that need to be written to disk.

Returns: 1 if the database will be written to disk by flush or destructor.; 0 if the database is unchanged since the last write operation.; -1 f there is an internal database error.

◆ entries()

int Fl_Preferences::entries ( )

Returns the number of entries (name/value pairs) in a group.

Returns: number of entries

◆ entry()

const char * Fl_Preferences::entry ( int index )

Returns the name of an entry.

There is no guaranteed order of entry names. The index must be within the range given by entries().

Parameters

[in] index number indexing the requested entry

Returns: pointer to value cstring

◆ entry_exists()

char Fl_Preferences::entry_exists ( const char * key )

Returns non-zero if an entry with this name exists.

Parameters

[in] key name of entry that is searched for

Returns: 0 if entry was not found

◆ file_access() [1/2]

unsigned int Fl_Preferences::file_access ( )

static

Return the current file access permissions for the FLTK preferences system.

See also: Fl_Preferences::file_access(unsigned int)

◆ file_access() [2/2]

void Fl_Preferences::file_access ( unsigned int flags )

static

Tell the FLTK preferences system which files in the file system it may read, create, or write.

The FLTK core library will try to read or even create or write preference files when calling Fl::option(), Fl_File_Chooser, the printing panel, and possibly some other internal functions. If your application wants to keep FLTK from touching the file system, call this function before making any other FLTK calls:

// neither FLTK nor the app may read, create, or write preference files

Fl_Preferences::file_access( Fl_Preferences::NONE );

Fl_Preferences::NONE

static const unsigned int NONE

Set this if no call to Fl_Preferences shall access the file system.

Definition: Fl_Preferences.H:163

Fl_Preferences::file_access

static unsigned int file_access()

Return the current file access permissions for the FLTK preferences system.

Definition: Fl_Preferences.cxx:119

// FLTK may not read, create, or write preference files, but the application may

Fl_Preferences::file_access( Fl_Preferences::APP_OK );

Fl_Preferences::APP_OK

static const unsigned int APP_OK

Set this if it is OK for applications to read, create, and write any kind of preference files.

Definition: Fl_Preferences.H:177

All flags can be combined using an OR operator. If flags are not set, that specific access to the file system will not be allowed. By default, all access is granted. To clear one or more flags from the default setting, use:

Fl_Preferences::file_access( Fl_Preferences::file_access()

&~ Fl_Preferences::SYSTEM_WRITE );

If preferences are created using a filename (instead of Fl_Preferences::USER or Fl_Preferences::SYSTEM), file access is handled as if the Fl_Preferences::USER flag was set.

See also: Fl_Preferences::NONE and others for a list of flags.; Fl_Preferences::file_access()

◆ filename() [1/2]

Fl_Preferences::Root Fl_Preferences::filename	(	char *	buffer,
		size_t	buffer_size
	)

Return the file name and path to the preference file.

If the preferences have not changed or have not been flushed, the file or directory may not have been created yet.

Parameters

[out]	buffer	write the resulting path into this buffer
[in]	buffer_size	size of the `buffer` in bytes

Returns: the root type at creation type, or MEMORY for runtime prefs, it does not return CORE or LOCALE flags.

◆ filename() [2/2]

Fl_Preferences::Root Fl_Preferences::filename	(	char *	buffer,
		size_t	buffer_size,
		Root	root,
		const char *	vendor,
		const char *	application
	)

static

Determine the file name and path to preferences that would be openend with these parameters.

Find the possible location of a preference file on disk without touching any of the pathname components. This can be used to check if a preference file already exists.

Parameters

[out]	buffer	write the resulting path into this buffer
[in]	buffer_size	size of the `buffer` in bytes
[in]	root	can be `USER_L` or `SYSTEM_L` for user specific or system wide preferences
[in]	vendor	unique text describing the company or author of this file, must be a valid filepath segment
[in]	application	unique text describing the application, must be a valid filepath segment

Returns: the input root value, or Fl_Preferences::UNKNOWN_ROOT_TYPE if the path could not be determined.

See also: Fl_Preferences( Root root, const char *vendor, const char *application )

◆ flush()

int Fl_Preferences::flush ( )

Writes preferences to disk if they were modified.

This method can be used to verify that writing a preference file went well. Deleting the base preferences object will also write the contents of the database to disk.

Returns: -1 if anything went wrong, i.e. file could not be opened, permissions blocked writing, etc.; 0 if the file was written to disk. This does not check if the disk ran out of space and the file is truncated.; 1 if no data was written to the database and no write attempt to disk was made.

◆ get() [1/8]

char Fl_Preferences::get	(	const char *	key,
		char *&	text,
		const char *	defaultValue
	)

Reads an entry from the group.

A default value must be supplied. The return value indicates if the value was available (non-zero) or the default was used (0). get() allocates memory of sufficient size to hold the value. The buffer must be free'd by the developer using 'free(value)'.

Parameters

[in]	key	name of entry
[out]	text	returned from preferences or default value if none was set
[in]	defaultValue	default value to be used if no preference was set

Returns: 0 if the default value was used

◆ get() [2/8]

char Fl_Preferences::get	(	const char *	key,
		char *	text,
		const char *	defaultValue,
		int	maxSize
	)

Reads an entry from the group.

A default value must be supplied. The return value indicates if the value was available (non-zero) or the default was used (0). 'maxSize' is the maximum length of text that will be read. The text buffer must allow for one additional byte for a trailing zero.

Parameters

[in]	key	name of entry
[out]	text	returned from preferences or default value if none was set
[in]	defaultValue	default value to be used if no preference was set
[in]	maxSize	maximum length of value plus one byte for a trailing zero

Returns: 0 if the default value was used

◆ get() [3/8]

char Fl_Preferences::get	(	const char *	key,
		double &	value,
		double	defaultValue
	)

Reads an entry from the group.

A default value must be supplied. The return value indicates if the value was available (non-zero) or the default was used (0).

Parameters

[in]	key	name of entry
[out]	value	returned from preferences or default value if none was set
[in]	defaultValue	default value to be used if no preference was set

Returns: 0 if the default value was used

◆ get() [4/8]

char Fl_Preferences::get	(	const char *	key,
		float &	value,
		float	defaultValue
	)

Reads an entry from the group.

A default value must be supplied. The return value indicates if the value was available (non-zero) or the default was used (0).

Parameters

[in]	key	name of entry
[out]	value	returned from preferences or default value if none was set
[in]	defaultValue	default value to be used if no preference was set

Returns: 0 if the default value was used

◆ get() [5/8]

char Fl_Preferences::get	(	const char *	key,
		int &	value,
		int	defaultValue
	)

Reads an entry from the group.

A default value must be supplied. The return value indicates if the value was available (non-zero) or the default was used (0).

Parameters

[in]	key	name of entry
[out]	value	returned from preferences or default value if none was set
[in]	defaultValue	default value to be used if no preference was set

Returns: 0 if the default value was used

◆ get() [6/8]

char Fl_Preferences::get	(	const char *	key,
		void *&	data,
		const void *	defaultValue,
		int	defaultSize
	)

Reads an entry from the group.

Parameters

[in]	key	name of entry
[out]	data	returned from preferences or default value if none was set
[in]	defaultValue	default value to be used if no preference was set
[in]	defaultSize	size of default value array

Returns: 0 if the default value was used

◆ get() [7/8]

char Fl_Preferences::get	(	const char *	key,
		void *	data,
		const void *	defaultValue,
		int	defaultSize,
		int *	maxSize
	)

Reads a binary entry from the group, encoded in hexadecimal blocks.

A binary (not hex) default value can be supplied. The return value indicates if the value was available (non-zero) or the default was used (0). maxSize is the maximum length of text that will be read and returns the actual number of bytes read.

Parameters

[in]	key	name of entry
[out]	data	value returned from preferences or default value if none was set
[in]	defaultValue	default value to be used if no preference was set
[in]	defaultSize	size of default value array
[in,out]	maxSize	maximum length of value and actual number of bytes set

Returns: 0 if the default value was used

◆ get() [8/8]

char Fl_Preferences::get	(	const char *	key,
		void *	data,
		const void *	defaultValue,
		int	defaultSize,
		int	maxSize
	)

Reads a binary entry from the group, encoded in hexadecimal blocks.

Parameters

[in]	key	name of entry
[out]	data	value returned from preferences or default value if none was set
[in]	defaultValue	default value
[in]	defaultSize	size of default value array
[in]	maxSize	maximum length of value, to receive the number of bytes read, use the function below instead.

Returns: 0 if the default value was used

See also: Fl_Preferences::get( const char *key, void *data, const void *defaultValue, int defaultSize, int *maxSize )

◆ get_userdata_path()

char Fl_Preferences::get_userdata_path	(	char *	path,
		int	pathlen
	)

Creates a path that is related to the preference file and that is usable for additional application data.

This function creates a directory that is named after the preferences database without the .prefs extension and located in the same directory. It then fills the given buffer with the complete path name.

There is no way to verify that the path name fit into the buffer. If the name is too long, it will be clipped.

This function can be used with direct paths that don't end in .prefs . getUserDataPath() will remove any extension and end the path with a / . If the file name has no extension, getUserDataPath() will append .data/ to the path name.

Example:

Fl_Preferences prefs( USER, "matthiasm.com", "test" );
char path[FL_PATH_MAX];
prefs.getUserdataPath( path, FL_PATH_MAX );

creates the preferences database in the directory (User 'matt' on Linux):

/Users/matt/.fltk/matthiasm.com/test.prefs

..and returns the userdata path:

/Users/matt/.fltk/matthiasm.com/test/

Parameters

[out]	path	buffer for user data path
[in]	pathlen	size of path buffer (should be at least `FL_PATH_MAX` )

Returns: 1 if there is no filename (path will be unmodified); 1 if pathlen is 0 (path will be unmodified); 1 if a path was created successfully, path will contain the path name ending in a '/'; 0 if path was not created for some reason; path will contain the pathname that could not be created

See also: Fl_Preferences::Fl_Preferences(Root, const char*, const char*)

◆ group()

const char * Fl_Preferences::group ( int num_group )

Returns the name of the Nth (num_group) group.

There is no guaranteed order of group names. The index must be within the range given by groups().

Parameters

[in] num_group number indexing the requested group

Returns: 'C' string pointer to the group name

◆ group_exists()

char Fl_Preferences::group_exists ( const char * key )

Returns non-zero if a group with this name exists.

Group names are relative to the Fl_Preferences node and can contain a path. "." describes the current node, "./" describes the topmost node. By preceding a groupname with a "./" its path becomes relative to the topmost node.

Parameters

[in] key name of group that is searched for

Returns: 0 if no group by that name was found

◆ groups()

int Fl_Preferences::groups ( )

Returns the number of groups that are contained within a group.

Returns: 0 for no groups at all

◆ new_UUID()

const char * Fl_Preferences::new_UUID ( )

static

Returns a UUID as generated by the system.

A UUID is a "universally unique identifier" which is commonly used in configuration files to create identities. A UUID in ASCII looks like this: 937C4900-51AA-4C11-8DD3-7AB59944F03E. It has always 36 bytes plus a trailing zero.

Returns: a pointer to a static buffer containing the new UUID in ASCII format. The buffer is overwritten during every call to this function!

◆ set() [1/7]

char Fl_Preferences::set	(	const char *	key,
		const char *	text
	)

Sets an entry (name/value pair).

The return value indicates if there was a problem storing the data in memory. However it does not reflect if the value was actually stored in the preference file.

Parameters

[in]	key	name of entry
[in]	text	set this entry to `value`

Returns: 0 if setting the value failed

◆ set() [2/7]

char Fl_Preferences::set	(	const char *	key,
		const void *	data,
		int	dsize
	)

Sets an entry (name/value pair).

The return value indicates if there was a problem storing the data in memory. However it does not reflect if the value was actually stored in the preference file.

Parameters

[in]	key	name of entry
[in]	data	set this entry to `value`
[in]	dsize	size of data array

Returns: 0 if setting the value failed

◆ set() [3/7]

char Fl_Preferences::set	(	const char *	key,
		double	value
	)

Sets an entry (name/value pair).

The return value indicates if there was a problem storing the data in memory. However it does not reflect if the value was actually stored in the preference file.

Parameters

[in]	key	name of entry
[in]	value	set this entry to `value`

Returns: 0 if setting the value failed

◆ set() [4/7]

char Fl_Preferences::set	(	const char *	key,
		double	value,
		int	precision
	)

Sets an entry (name/value pair).

The return value indicates if there was a problem storing the data in memory. However it does not reflect if the value was actually stored in the preference file.

Parameters

[in]	key	name of entry
[in]	value	set this entry to `value`
[in]	precision	number of decimal digits to represent value

Returns: 0 if setting the value failed

◆ set() [5/7]

char Fl_Preferences::set	(	const char *	key,
		float	value
	)

Sets an entry (name/value pair).

The return value indicates if there was a problem storing the data in memory. However it does not reflect if the value was actually stored in the preference file.

Parameters

[in]	key	name of entry
[in]	value	set this entry to `value`

Returns: 0 if setting the value failed

◆ set() [6/7]

char Fl_Preferences::set	(	const char *	key,
		float	value,
		int	precision
	)

Sets an entry (name/value pair).

The return value indicates if there was a problem storing the data in memory. However it does not reflect if the value was actually stored in the preference file.

Parameters

[in]	key	name of entry
[in]	value	set this entry to `value`
[in]	precision	number of decimal digits to represent value

Returns: 0 if setting the value failed

◆ set() [7/7]

char Fl_Preferences::set	(	const char *	key,
		int	value
	)

Sets an entry (name/value pair).

The return value indicates if there was a problem storing the data in memory. However it does not reflect if the value was actually stored in the preference file.

Parameters

[in]	key	name of entry
[in]	value	set this entry to `value`

Returns: 0 if setting the value failed

◆ size()

int Fl_Preferences::size ( const char * key )

Returns the size of the value part of an entry.

Parameters

[in] key name of entry

Returns: size of value

Member Data Documentation

◆ CORE_READ_OK

const unsigned int Fl_Preferences::CORE_READ_OK = 0x0010

static

Set this if it is OK for FLTK to read preference files.

USER_READ_OK and/or SYSTEM_READ_OK must also be set.

◆ CORE_WRITE_OK

const unsigned int Fl_Preferences::CORE_WRITE_OK = 0x0020

static

Set this if it is OK for FLTK to create or write preference files.

USER_WRITE_OK and/or SYSTEM_WRITE_OK must also be set.

◆ NONE

const unsigned int Fl_Preferences::NONE = 0x0000

static

Set this if no call to Fl_Preferences shall access the file system.

See also: Fl_Preferences::file_access(unsigned int); Fl_Preferences::file_access()

The documentation for this class was generated from the following files:

Fl_Preferences.H
Fl_Preferences.cxx

Classes

Public Types

Public Member Functions

Static Public Member Functions

Static Public Attributes

Protected Attributes

Friends

Detailed Description

Member Typedef Documentation

◆ ID

Member Enumeration Documentation

◆ Root

Constructor & Destructor Documentation

◆ Fl_Preferences() [1/8]

◆ Fl_Preferences() [2/8]

◆ Fl_Preferences() [3/8]

◆ Fl_Preferences() [4/8]

◆ Fl_Preferences() [5/8]

◆ Fl_Preferences() [6/8]

◆ Fl_Preferences() [7/8]

◆ ~Fl_Preferences()

◆ Fl_Preferences() [8/8]

Member Function Documentation

◆ delete_entry()

◆ delete_group()

◆ dirty()

◆ entries()

◆ entry()

◆ entry_exists()

◆ file_access() [1/2]

◆ file_access() [2/2]

◆ filename() [1/2]

◆ filename() [2/2]

◆ flush()

◆ get() [1/8]

◆ get() [2/8]

◆ get() [3/8]

◆ get() [4/8]

◆ get() [5/8]

◆ get() [6/8]

◆ get() [7/8]

◆ get() [8/8]

◆ get_userdata_path()

◆ group()

◆ group_exists()

◆ groups()

◆ new_UUID()

◆ set() [1/7]

◆ set() [2/7]

◆ set() [3/7]

◆ set() [4/7]

◆ set() [5/7]

◆ set() [6/7]

◆ set() [7/7]

◆ size()

Member Data Documentation

◆ CORE_READ_OK

◆ CORE_WRITE_OK

◆ NONE