path: root/doc/gconf/tmpl/gconf.sgml

<!-- ##### SECTION Title ##### -->

GConf Core Interfaces

<!-- ##### SECTION Short_Description ##### -->

Basic functions to initialize GConf and get/set values

<!-- ##### SECTION Long_Description ##### -->
<para>
These functions initialize GConf, and communicate with the
<application>gconfd</application> server via a
#GConfEngine object. You can install a notification
request on the server, get values, set values, list directories, and associate
schema names with keys.
</para>

<para>
Most of this interface is replicated in the #GtkObject wrapper
(#GConfClient object); an alternative to the value-setting functions
is the #GConfChangeSet interface.
</para>

<!-- ##### SECTION See_Also ##### -->
<para>

</para>

<!-- ##### FUNCTION gconf_init ##### -->
<para>
Initializes the GConf library. Creates a connection to a CORBA ORB, and
initializes OAF (the object activation framework) if it isn't already
initialized.
</para>

@argc: 
@argv: 
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: <symbol>TRUE</symbol> on success, <symbol>FALSE</symbol> otherwise.


<!-- ##### FUNCTION gconf_preinit ##### -->
<para>

</para>

@app: 
@mod_info: 


<!-- ##### FUNCTION gconf_postinit ##### -->
<para>

</para>

@app: 
@mod_info: 


<!-- ##### FUNCTION gconf_is_initialized ##### -->
<para>
Asks whether the library has been initialized.
</para>

@Returns: <symbol>TRUE</symbol> if the library has been initialized.


<!-- ##### USER_FUNCTION GConfNotifyFunc ##### -->
<para>
A callback function invoked when a key's value changes. The @cnxn_id parameter
will be the connection ID returned from gconf_engine_notify_add(). @key will be the
full path of the changed key, @value will be the new value if the key is set.
If the key is unset, @value will be the default value if one exists, or
<symbol>NULL</symbol> otherwise. @is_default indicates whether a value is a
default setting or a user setting. If @value is <symbol>NULL</symbol>,
@is_default will be <symbol>TRUE</symbol>. @user_data is the data passed to
gconf_engine_notify_add().
</para>

@conf: the #GConfEngine passed to gconf_engine_notify_add().
@cnxn_id: the ID returned from gconf_engine_notify_add().
@key: the full path of the changed key.
@value: the new value, or <symbol>NULL</symbol> if the key was unset.
@is_default: if <symbol>TRUE</symbol>, the key is unset but this is the default value for it.
@user_data: the user data passed to gconf_engine_notify_add().


<!-- ##### FUNCTION gconf_engine_notify_add ##### -->
<para>
Registers a notification request with the <application>gconfd</application>
server.  The server will notify the client when any key at or below
@namespace_section is set or unset. Try to watch the smallest possible part of
the namespace; otherwise you will slow down the server and your application with
unnecessary notifications. Note that you should prefer gconf_client_notify_add()
if you're using the #GtkObject wrapper library, because
gconf_client_notify_add() does not require a client-server conversation for
every callback. gconf_engine_notify_add() requests a different server notification for
every callback. The function returns an ID you can use to remove the
notification request; 0 is an invalid ID, and is returned if an error occurs.
</para>

@conf: a #GConfEngine to monitor for changes.
@namespace_section: the directory or key to watch; you will be notified of changes at or below this point.
@func: the callback to invoke when a notification is received from the server.
@user_data: the data to pass to the callback.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: an ID for the notification request, or 0 on error.


<!-- ##### FUNCTION gconf_engine_notify_remove ##### -->
<para>
Removes a notification request.
</para>

@conf: the #GConfEngine you were monitoring for changes.
@cnxn: The ID returned by gconf_engine_notify_add().


<!-- ##### FUNCTION gconf_engine_get ##### -->
<para>
Returns the #GConfValue stored at @key, or <symbol>NULL</symbol> if no value is
set. You must call gconf_value_free() to free the returned value. If you know
the expected type of the value, you probably want to use the type-specific
convenience wrappers (gconf_engine_get_int(), etc.)  because they will do the
type-checking for you and return the appropriate type. Automatically returns the
default value for a key, if the key is unset and a default exists.
</para>

@conf: a #GConfEngine to get the value from.
@key: the key to get.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: newly-allocated #GConfValue, or <symbol>NULL</symbol> if unset and no default exists.


<!-- ##### FUNCTION gconf_engine_get_with_locale ##### -->
<para>
Requests the value appropriate for a particular locale. Right now,
only values of type %GCONF_VALUE_SCHEMA are localized; the locale is
meaningless for other value types. Also, gconf_engine_get () automatically
requests the value in the user's current locale. So this function is
only useful if you want a schema for some locale other than the user's
current locale. Except for the additional argument, this function is
identical to gconf_engine_get () in all respects.
</para>

@conf: a #GConfEngine to get the value from.
@key: the key to get.
@locale: preferred locale (as in the locale-related environment variables).
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: newly-allocated #GConfValue, or <symbol>NULL</symbol> if unset.


<!-- ##### FUNCTION gconf_engine_get_without_default ##### -->
<para>
Identical to gconf_engine_get (), except that it will return <symbol>NULL</symbol> in
place of the default value if the key is unset. Note that gconf_engine_get () can also
return <symbol>NULL</symbol> if no default exists or an error occurs.
</para>

@conf: a #GConfEngine to get the value from.
@key: the key to get.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: newly-allocated #GConfValue, or <symbol>NULL</symbol> if unset.


<!-- ##### FUNCTION gconf_engine_get_full ##### -->
<para>
This function is basically for internal use.
</para>

@conf: 
@key: 
@locale: 
@use_schema_default: 
@value_is_default: 
@err: 
@Returns: 


<!-- ##### FUNCTION gconf_engine_get_default_from_schema ##### -->
<para>
Returns the default value stored in the key's schema, if the key has a schema
associated and the schema exists and the schema contains a default value.  Note
that gconf_engine_get (), gconf_engine_get_string(), and so on already return the default value
if no other value is found, so normally you do not need this function. This
function is just for convenience; you could also get the #GConfMetaInfo for the
key, read the schema name from there, then look up the schema by name and
extract the default value.
</para>

@conf: a #GConfEngine to get the value from.
@key: the key to get the default value for.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: newly-allocated #GConfValue, or <symbol>NULL</symbol> if unset.


<!-- ##### FUNCTION gconf_engine_set ##### -->
<para>
Sets the value of @key to @value. Does not modify the passed-in
#GConfValue, you must free it yourself. You may prefer a type-specific
convenience wrapper, such as gconf_engine_set_int().
</para>

<para>
 An error of note is %GCONF_OVERRIDDEN, indicating that the system
administrator has "forced" a value for this key. If no writable
configuration sources exist, it is not an error, but GConf will just
forget all your values; this allows users to have a configuration-free
setup without a constant barrage of error messages.
</para>

@conf: a #GConfEngine to set the value in.
@key: the key to set.
@value: the new value of @key.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: <symbol>TRUE</symbol> on success, <symbol>FALSE</symbol> on error.


<!-- ##### FUNCTION gconf_engine_unset ##### -->
<para>
Unsets the value of @key; if @key is already unset, has no effect.  An
error of note is %GCONF_OVERRIDDEN, indicating that the system
administrator has "forced" a value for this key.
</para>

@conf: a #GConfEngine to affect.
@key: the key to unset.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: <symbol>TRUE</symbol> on success, <symbol>FALSE</symbol> on error.


<!-- ##### FUNCTION gconf_engine_associate_schema ##### -->
<para>
Directs GConf to find the schema for @key at location
@schema_key. That is, the value stored at @schema_key should have type
#GCONF_VALUE_SCHEMA, and be descriptive of @key. Normally you don't
call this function from C code; you can ship a special file with your
application and ask <application>gconftool</application> to install
schema associations into the database during "make install."
</para>

@conf: a #GConfEngine to affect.
@key: the key to associate the schema with.
@schema_key: the key where the schema will be stored.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: <symbol>TRUE</symbol> on success, <symbol>FALSE</symbol> on error.


<!-- ##### FUNCTION gconf_engine_all_entries ##### -->
<para>
Lists the key-value pairs in @dir. Does not list subdirectories; for
that use gconf_engine_all_dirs(). The returned list contains #GConfEntry
objects. A #GConfEntry contains a <emphasis>relative</emphasis> key
and a value. The list is not recursive, it contains only the immediate
children of @dir.  To free the returned list, gconf_entry_free()
each list element, then g_slist_free() the list itself.
</para>

@conf: a #GConfEngine.
@dir: Directory to list.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: List of #GConfEntry.


<!-- ##### FUNCTION gconf_engine_all_dirs ##### -->
<para>
Lists the subdirectories in @dir. The returned list contains allocated
strings; you should g_free() each string in the list, then
g_slist_free() the list itself.
</para>

@conf: a #GConfEngine.
@dir: Directory to get subdirectories from.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: List of allocated subdirectory names.


<!-- ##### FUNCTION gconf_engine_suggest_sync ##### -->
<para>
Suggests to <application>gconfd</application> that you've just finished
a block of changes, and it would be an optimal time to sync to
permanent storage. This is only a suggestion; and
<application>gconfd</application> will eventually sync even if you
don't call gconf_engine_suggest_sync(). This function is just a "hint"
provided to <application>gconfd</application> to maximize efficiency
and minimize data loss.
</para>

@conf: the #GConfEngine to suggest syncing to.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.


<!-- ##### FUNCTION gconf_engine_dir_exists ##### -->
<para>
Queries whether the directory @dir exists in the GConf
database. Returns <symbol>TRUE</symbol> or <symbol>FALSE</symbol>.
</para>

@conf: a #GConfEngine.
@dir: Directory to check for.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: <symbol>TRUE</symbol> or <symbol>FALSE</symbol>.


<!-- ##### FUNCTION gconf_valid_key ##### -->
<para>
Asks whether a key is syntactically correct, that is, it ensures that
the key consists of slash-separated strings and contains only legal
characters. Normally you shouldn't need to call this function; the
GConf functions all check this for you and return an error if the key
is invalid. However, it may be useful to validate input to an entry
field or the like. If you pass a non-<symbol>NULL</symbol> address as
the @why_invalid argument, an allocated string is returned explaining
why the key is invalid, if it is. If the key is valid the @why_invalid
argument is unused.
</para>

@key: key to check.
@why_invalid: return location for an explanation of the problem, if any. g_free() the returned string.
@Returns: <symbol>TRUE</symbol> if the key is valid, or <symbol>FALSE</symbol> if not.


<!-- ##### FUNCTION gconf_key_is_below ##### -->
<para>
Asks whether the key @below would be found below the key @above, were
they both to exist in the database. For example, <symbol>/foo</symbol>
is always found below <symbol>/</symbol> and above
<symbol>/foo/bar</symbol>. This probably isn't useful but GConf uses
it internally so here it is if you need it.
</para>

@above: the key on the "left hand side" of the predicate.
@below: the key on the "right hand side."
@Returns: <symbol>TRUE</symbol> or <symbol>FALSE</symbol>.


<!-- ##### FUNCTION gconf_engine_get_float ##### -->
<para>
Requests the floating point number (%GCONF_VALUE_FLOAT) stored at
@key. Automatically performs type-checking, so if a non-float is
stored at @key, an error is returned. On error, or if @key is unset, 
0.0 is returned.
</para>

@conf: a #GConfEngine.
@key: key you want the value of.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: the value of @key, or 0.0 if no value is obtained.


<!-- ##### FUNCTION gconf_engine_get_int ##### -->
<para>
Requests the integer (%GCONF_VALUE_INT) stored at
@key. Automatically performs type-checking, so if a non-integer is
stored at @key, an error is returned. On error, or if @key is unset, 
0 is returned.
</para>

@conf: a #GConfEngine.
@key: key you want the value of.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: the value of @key, or 0 if no value is obtained.


<!-- ##### FUNCTION gconf_engine_get_string ##### -->
<para>
Requests the string (%GCONF_VALUE_STRING) stored at
@key. Automatically performs type-checking, so if a non-string is
stored at @key, an error is returned. On error, or if @key is unset, 
<symbol>NULL</symbol> is returned.
</para>

@conf: a #GConfEngine.
@key: key you want the value of.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: allocated string (value of @key), or <symbol>NULL</symbol> if no value is obtained.


<!-- ##### FUNCTION gconf_engine_get_bool ##### -->
<para>
Requests the boolean value (%GCONF_VALUE_BOOL) stored at
@key. Automatically performs type-checking, so if a non-bool is
stored at @key, an error is returned. On error, or if @key is unset, 
<symbol>FALSE</symbol> is returned.
</para>

@conf: a #GConfEngine.
@key: key you want the value of.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: the value of @key, or <symbol>FALSE</symbol> if no value is obtained.


<!-- ##### FUNCTION gconf_engine_get_schema ##### -->
<para>
Requests the schema (%GCONF_VALUE_SCHEMA) stored at @key.
Automatically performs type-checking, so if a non-schema is stored at
@key, an error is returned. If no value is set or an error occurs,
<symbol>NULL</symbol> is returned.
</para>

@conf: a #GConfEngine.
@key: key you want the value of.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: the value of @key as an allocated #GConfSchema, or <symbol>NULL</symbol> if no value was obtained.


<!-- ##### FUNCTION gconf_engine_get_list ##### -->
<para>
Requests the list (%GCONF_VALUE_LIST) stored at @key.  Automatically
performs type-checking, so if a non-list is stored at @key, or the
list does not contain elements of type @list_type, an error is
returned. If no value is set or an error occurs, <symbol>NULL</symbol>
is returned. Note that <symbol>NULL</symbol> is also the empty list,
so if you need to distinguish the empty list from an unset value, you
must use gconf_engine_get () to obtain a raw #GConfValue.
</para>

<para>
<emphasis>Remember that GConf lists can only store primitive types:
%GCONF_VALUE_FLOAT, %GCONF_VALUE_INT, %GCONF_VALUE_BOOL,
%GCONF_VALUE_STRING, %GCONF_VALUE_SCHEMA.</emphasis> Also remember
that lists must be uniform, you may not mix types in the same list.
</para>

<para>
The type of the list elements depends on @list_type. A #GConfValue
with type %GCONF_VALUE_LIST normally stores a list of more #GConfValue
objects. gconf_engine_get_list() automatically converts to primitive C
types. Thus, the list-&gt;data fields in the returned list 
contain:
 
<informaltable pgwide=1 frame="none">
<tgroup cols="2"><colspec colwidth="2*"><colspec colwidth="8*">
<tbody>

<row>
<entry>%GCONF_VALUE_INT</entry>
<entry>The integer itself, converted with GINT_TO_POINTER()</entry>
</row>

<row>
<entry>%GCONF_VALUE_BOOL</entry>
<entry>The bool itself, converted with GINT_TO_POINTER()</entry>
</row>

<row>
<entry>%GCONF_VALUE_FLOAT</entry>
<entry>A pointer to #gdouble, which should be freed with g_free()</entry>
</row>

<row>
<entry>%GCONF_VALUE_STRING</entry>
<entry>A pointer to #gchar, which should be freed with g_free()</entry>
</row>

<row>
<entry>%GCONF_VALUE_SCHEMA</entry>
<entry>A pointer to #GConfSchema, which should be freed with gconf_schema_free()</entry>
</row>

</tbody></tgroup></informaltable>

In the %GCONF_VALUE_FLOAT and %GCONF_VALUE_STRING cases, you must
g_free() each list element. In the %GCONF_VALUE_SCHEMA case you must
gconf_schema_free() each element. In all cases you must free the
list itself with g_slist_free().
</para>

@conf: a #GConfEngine.
@key: key you want the value of.
@list_type: type of each list element.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: an allocated list, with elements as described above.


<!-- ##### FUNCTION gconf_engine_get_pair ##### -->
<para>
Requests the pair (%GCONF_VALUE_PAIR) stored at @key.  Automatically
performs type-checking, so if a non-pair is stored at @key, or the
pair does not have the right @car_type and @cdr_type, an error is
returned. Remember that the <firstterm>car</firstterm> of a pair is
its first value, and the <firstterm>cdr</firstterm> is its second
value, in the Lisp tradition. 
</para>

<para>
<emphasis>Remember that GConf pairs can only store primitive types:
%GCONF_VALUE_FLOAT, %GCONF_VALUE_INT, %GCONF_VALUE_BOOL,
%GCONF_VALUE_STRING, %GCONF_VALUE_SCHEMA.</emphasis>
</para>

<para>
gconf_engine_get_pair() stores the two fields of the pair in the locations
pointed to by @car_retloc and @cdr_retloc. The type of these pointers
depends on the corresponding @car_type and @cdr_type:
 
<informaltable pgwide=1 frame="none">
<tgroup cols="2"><colspec colwidth="2*"><colspec colwidth="8*">
<tbody>

<row>
<entry>%GCONF_VALUE_INT</entry>
<entry>pointer to #gint</entry>
</row>

<row>
<entry>%GCONF_VALUE_BOOL</entry>
<entry>pointer to #gboolean</entry>
</row>

<row>
<entry>%GCONF_VALUE_FLOAT</entry>
<entry>pointer to #gdouble</entry>
</row>

<row>
<entry>%GCONF_VALUE_STRING</entry>
<entry>pointer to #gchar*</entry>
</row>

<row>
<entry>%GCONF_VALUE_SCHEMA</entry>
<entry>pointer to #GConfSchema*</entry>
</row>

</tbody></tgroup></informaltable>

In the %GCONF_VALUE_STRING case, you must g_free() the string(s)
stored in the return location(s). In the %GCONF_VALUE_SCHEMA case you
must gconf_schema_free() the returned schema. If there's an error
or the value is unset, @car_retloc and @cdr_retloc are left unchanged.
</para>

<para>
gconf_engine_get_pair() returns <symbol>TRUE</symbol> on success.
</para>

<para>
An example of gconf_engine_get_pair() in action:
<programlisting>
gdouble car = 10.0;
gchar* cdr  = NULL; 
GError* error = NULL;

if (!gconf_engine_get_pair(conf, "/foo", 
                    GCONF_VALUE_FLOAT,
                    GCONF_VALUE_STRING, 
                    &amp;car, &amp;cdr, &amp;error))
  {
    /* Note: car/cdr should be untouched, because an error occurred */
    g_assert(error != NULL);
    fprintf(stderr, "Error: %s\n", error->message);
    g_error_free(error);
    error = NULL;
  }
else
  {
    /* Note: car/cdr may be untouched even though there was no error, 
       if no value was set for "/foo"
     */
    printf("Found pair (%g,%s)\n", car, cdr);
    if (cdr != NULL)
      g_free(cdr);
  }
</programlisting>
</para>

@conf: a #GConfEngine.
@key: key you want the value of.
@car_type: desired type of the pair's first field (car).
@cdr_type: desired type of the pair's second field (cdr).
@car_retloc: address of a return location for the car.
@cdr_retloc: address of a return location for the cdr.
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: <symbol>TRUE</symbol> on success, <symbol>FALSE</symbol> on error.


<!-- ##### FUNCTION gconf_engine_set_float ##### -->
<para>

</para>

@conf: a #GConfEngine.
@key: 
@val: 
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: 


<!-- ##### FUNCTION gconf_engine_set_int ##### -->
<para>

</para>

@conf: a #GConfEngine.
@key: 
@val: 
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: 


<!-- ##### FUNCTION gconf_engine_set_string ##### -->
<para>

</para>

@conf: a #GConfEngine.
@key: 
@val: 
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: 


<!-- ##### FUNCTION gconf_engine_set_bool ##### -->
<para>

</para>

@conf: a #GConfEngine.
@key: 
@val: 
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: 


<!-- ##### FUNCTION gconf_engine_set_schema ##### -->
<para>

</para>

@conf: a #GConfEngine.
@key: 
@val: 
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: 


<!-- ##### FUNCTION gconf_engine_set_list ##### -->
<para>

</para>

@conf: a #GConfEngine.
@key: 
@list_type: 
@list: 
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: 


<!-- ##### FUNCTION gconf_engine_set_pair ##### -->
<para>

</para>

@conf: a #GConfEngine.
@key: 
@car_type: 
@cdr_type: 
@address_of_car: 
@address_of_cdr: 
@err: the return location for an allocated #GError, or <symbol>NULL</symbol> to ignore errors.
@Returns: 


<!-- ##### STRUCT GConfEnumStringPair ##### -->
<para>

</para>

@enum_value: 
@str: 

<!-- ##### FUNCTION gconf_string_to_enum ##### -->
<para>
It's best to store enumeration values as strings rather than integers. This is
robust against changes in the enumeration, and also human-readable.
This function makes it more convenient to store enums as strings.
</para>

<para>
The first argument is a lookup table, typically declared statically as follows:
<programlisting>
static GConfEnumStringPair foo_enum_lookup_table[] = {
  { FOO_BLAH, "Blah" },
  { FOO_BAR,  "Bar"  },
  { 0, NULL }
};
</programlisting>
Note that the last element of the table is <literal>{ 0, NULL }</literal>.
Typically the strings you use should be semi-human-readable, for GTK+ and GNOME
stripping off the library prefix and converting to StudlyCaps is the recommended
convention.
</para>

<para>
The function returns <symbol>TRUE</symbol> if a match for the string is found,
and if a match is found the enum value is placed in @enum_value_retloc.
</para>

@lookup_table: a lookup table mapping enum values to strings.
@str: the string to convert to an enum value.
@enum_value_retloc: the address of an enum variable.
@Returns: <symbol>TRUE</symbol> if a match was found.


<!-- ##### FUNCTION gconf_enum_to_string ##### -->
<para>
See gconf_string_to_enum() for background information on this function.
</para>

@lookup_table: a lookup table mapping enum values to strings.
@enum_value: the enumeration value to convert to a string.
@Returns: a pointer to the proper string in the lookup table, or <symbol>NULL</symbol> if no match was found.