glib/docs/reference/gobject/tmpl/gparamspec.sgml

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

<!-- ##### SECTION Short_Description ##### -->
Metadata for parameter specifications

<!-- ##### SECTION Long_Description ##### -->
<para>
#GParamSpec is an object structure that encapsulates the metadata
required to specify parameters, such as e.g. #GObject properties.
</para>

<!-- ##### SECTION See_Also ##### -->
<para>
g_object_class_install_property(), g_object_set(), g_object_get(),
g_object_set_property(), g_object_get_property(), g_value_register_transform_func()
</para>

<!-- ##### MACRO G_TYPE_IS_PARAM ##### -->
<para>
Returns whether @type "is a" %G_TYPE_PARAM.
</para>

@type: a #GType ID


<!-- ##### MACRO G_PARAM_SPEC ##### -->
<para>
Cast a derived #GParamSpec object (e.g. of type #GParamSpecInt) into
a #GParamSpec object.
</para>

@pspec: a valid #GParamSpec


<!-- ##### MACRO G_IS_PARAM_SPEC ##### -->
<para>
Check whether @pspec "is a" valid #GParamSpec structure of type %G_TYPE_PARAM
or derived.
</para>

@pspec: a #GParamSpec


<!-- ##### MACRO G_PARAM_SPEC_CLASS ##### -->
<para>
Cast a derived #GParamSpecClass structure into a #GParamSpecClass structure.
</para>

@pclass: a valid #GParamSpecClass


<!-- ##### MACRO G_IS_PARAM_SPEC_CLASS ##### -->
<para>
Check whether @pclass "is a" valid #GParamSpecClass structure of type %G_TYPE_PARAM
or derived.
</para>

@pclass: a #GParamSpecClass


<!-- ##### MACRO G_PARAM_SPEC_GET_CLASS ##### -->
<para>
Retrieve the #GParamSpecClass of a #GParamSpec.
</para>

@pspec: a valid #GParamSpec


<!-- ##### MACRO G_PARAM_SPEC_TYPE ##### -->
<para>
Retrieve the #GType of this @pspec.
</para>

@pspec: a valid #GParamSpec


<!-- ##### MACRO G_PARAM_SPEC_TYPE_NAME ##### -->
<para>
Retrieve the #GType name of this @pspec.
</para>

@pspec: a valid #GParamSpec


<!-- ##### MACRO G_PARAM_SPEC_VALUE_TYPE ##### -->
<para>
Retrieve the #GType to intiialize a #GValue for this parameter.
</para>

@pspec: a valid #GParamSpec


<!-- ##### STRUCT GParamSpec ##### -->
<para>

</para>

@g_type_instance: private #GTypeInstance portion
@name:            name of this parameter
@flags:           #GParamFlags flags for this parameter
@value_type:      the #GValue type for this parameter
@owner_type:      #GType type that uses (introduces) this paremeter

<!-- ##### STRUCT GParamSpecClass ##### -->
<para>

</para>

@g_type_class: 
@value_type: 
@finalize: 
@value_set_default: 
@value_validate: 
@values_cmp: 
@dummy: 

<!-- ##### ENUM GParamFlags ##### -->
<para>
Through the #GParamFlags flag values, certain aspects of parameters
can be configured.
</para>

@G_PARAM_READABLE:       the parameter is readable
@G_PARAM_WRITABLE:       the parameter is writable
@G_PARAM_CONSTRUCT:      the parameter will be set upon object construction
@G_PARAM_CONSTRUCT_ONLY: the parameter will only be set upon object construction
@G_PARAM_LAX_VALIDATION: upon parameter conversion (see g_param_value_convert())
                         strict validation is not required
@G_PARAM_PRIVATE: 

<!-- ##### MACRO G_PARAM_READWRITE ##### -->
<para>
#GParamFlags value alias for %G_PARAM_READABLE | %G_PARAM_WRITABLE.
</para>



<!-- ##### MACRO G_PARAM_MASK ##### -->
<para>
Mask containing the bits of #GParamSpec.flags which are reserved for GLib.
</para>



<!-- ##### MACRO G_PARAM_USER_SHIFT ##### -->
<para>
Minimum shift count to be used for user defined flags, to be stored in
#GParamSpec.flags.
</para>



<!-- ##### FUNCTION g_param_spec_ref ##### -->
<para>
Increment the reference count of @pspec.
</para>

@pspec:   a valid #GParamSpec
@Returns: the #GParamSpec that was passed into this function


<!-- ##### FUNCTION g_param_spec_unref ##### -->
<para>
Decrement the reference count of a @pspec.
</para>

@pspec: a valid #GParamSpec


<!-- ##### FUNCTION g_param_spec_sink ##### -->
<para>
The initial reference count of a newly created #GParamSpec is 1,
even though no one has explicitly called g_param_spec_ref() on it yet.
So the inital reference count is flagged as "floating", until someone
calls g_param_spec_ref (@pspec); g_param_spec_sink (@pspec);
in sequence on it, taking over the initial reference count (thus
ending up with a @pspec that has a reference count of 1 still, but is
not flagged "floating" anymore).
</para>

@pspec: a valid #GParamSpec


<!-- ##### FUNCTION g_param_value_set_default ##### -->
<para>
Set @value to its default value as specified in @pspec.
</para>

@pspec: a valid #GParamSpec
@value: a #GValue of correct type for @pspec


<!-- ##### FUNCTION g_param_value_defaults ##### -->
<para>
Check whether @value contains the default value as specified in @pspec.
</para>

@pspec:   a valid #GParamSpec
@value:   a #GValue of correct type for @pspec
@Returns: whether @value contains the canonical defualt for this @pspec


<!-- ##### FUNCTION g_param_value_validate ##### -->
<para>
Ensure that the contents of @value comply with the specifications
set out by @pspec. For example, a #GParamSpecInt might require
that integers stored in @value may not be smaller than -42 and not be
greater than +42. If @value contains an integer outside of this range,
it is modified accordingly, so the resulting value will fit into the
range -42 .. +42.
</para>

@pspec:   a valid #GParamSpec
@value:   a #GValue of correct type for @pspec
@Returns: whether modifying @value was necessary to ensure validity


<!-- ##### FUNCTION g_param_value_convert ##### -->
<para>
This function transforms @src_value into @dest_value if possible,
and then validates @dest_value, in order for it to conform to
@pspec.
If @strict_validation is %TRUE this function will only suceed if
the transformed @dest_value complied to @pspec without modifications.

See also g_value_type_transformable(), g_value_transform() and
g_param_value_validate().
</para>

@pspec:             a valid #GParamSpec
@src_value:         souce #GValue
@dest_value:        destination #GValue of correct type for @pspec
@strict_validation: %TRUE requires @dest_value to conform to @pspec without modifications
@Returns:           %TRUE if transformation and validation were successfull,
                    %FALSE otherwise and @dest_value is left untouched.


<!-- ##### FUNCTION g_param_values_cmp ##### -->
<para>
Compare @value1 with @value2 according to @pspec, and return -1, 0 or +1,
if @value1 is found to be less than, equal to or greater than @value2, respectively.
</para>

@pspec:   a valid #GParamSpec
@value1:  a #GValue of correct type for @pspec
@value2:  a #GValue of correct type for @pspec
@Returns: -1, 0 or +1, for a less than, equal to or greater than result


<!-- ##### FUNCTION g_param_spec_get_name ##### -->
<para>
Returns the name of a #GParamSpec.
</para>

@pspec: a valid #GParamSpec
@Returns: the name of @pspec.


<!-- ##### FUNCTION g_param_spec_get_nick ##### -->
<para>
Returns the nickname of a #GParamSpec.
</para>

@pspec: a valid #GParamSpec
@Returns: the nickname of @pspec.


<!-- ##### FUNCTION g_param_spec_get_blurb ##### -->
<para>
Returns the short description of a #GParamSpec.
</para>

@pspec: a valid #GParamSpec
@Returns: the short description of @pspec.


<!-- ##### FUNCTION g_param_spec_get_qdata ##### -->
<para>
This function gets back user data pointers stored via
g_param_spec_set_qdata().
</para>

@pspec: a valid #GParamSpec
@quark: a #GQuark, naming the user data pointer
@Returns: the user data pointer set, or %NULL


<!-- ##### FUNCTION g_param_spec_set_qdata ##### -->
<para>
This sets an opaque, named pointer on a #GParamSpec.
The name is specified through a #GQuark (retrived e.g. via
g_quark_from_static_string()), and the pointer
can be gotten back from the @pspec with g_param_spec_get_qdata().
Setting a previously set user data pointer, overrides (frees)
the old pointer set, using #NULL as pointer essentially
removes the data stored.
</para>

@pspec: the #GParamSpec to set store a user data pointer
@quark: a #GQuark, naming the user data pointer
@data: an opaque user data pointer


<!-- ##### FUNCTION g_param_spec_set_qdata_full ##### -->
<para>
This function works like g_param_spec_set_qdata(), but in addition,
a <literal>void (*destroy) (gpointer)</literal> function may be 
specified which is called with @data as argument when the @pspec is 
finalized, or
the data is being overwritten by a call to g_param_spec_set_qdata()
with the same @quark.
</para>

@pspec:   the #GParamSpec to set store a user data pointer
@quark:   a #GQuark, naming the user data pointer
@data:    an opaque user data pointer
@destroy: function to invoke with @data as argument, when @data needs to
          be freed


<!-- ##### FUNCTION g_param_spec_steal_qdata ##### -->
<para>
This function gets back user data pointers stored via
g_param_spec_set_qdata() and removes the @data from @pspec
without invoking it's destroy() function (if any was
set).
Usually, calling this function is only required to update
user data pointers with a destroy notifier.
</para>

@pspec: the #GParamSpec to get a stored user data pointer from
@quark: a #GQuark, naming the user data pointer
@Returns: the user data pointer set, or %NULL


<!-- ##### FUNCTION g_param_spec_internal ##### -->
<para>
Creates a new #GParamSpec instance.
</para>
<para>
A property name consists of segments consisting of ASCII letters and
digits, separated by either the '-' or '_' character. The first
character of a property name must be a letter. Names which violate these
rules lead to undefined behaviour. 
</para>
<para>
When creating and looking up a #GParamSpec, either separator can be used, 
but they cannot be mixed. Using '-' is considerably more efficient and in 
fact required when using property names as detail strings for signals.
</para>

@param_type: the #GType for the property; must be derived from #G_TYPE_PARAM
@name: the canonical name of the property
@nick: the nickname of the property
@blurb: a short description of the property
@flags: a combination of #GParamFlags
@Returns: a newly allocated #GParamSpec instance


<!-- ##### STRUCT GParamSpecTypeInfo ##### -->
<para>

</para>

@instance_size: 
@n_preallocs: 
@instance_init: 
@value_type: 
@finalize: 
@value_set_default: 
@value_validate: 
@values_cmp: 

<!-- ##### FUNCTION g_param_type_register_static ##### -->
<para>

</para>

@name: 
@pspec_info: 
@Returns: 


<!-- ##### STRUCT GParamSpecPool ##### -->
<para>

</para>


<!-- ##### FUNCTION g_param_spec_pool_new ##### -->
<para>

</para>

@type_prefixing: 
@Returns: 


<!-- ##### FUNCTION g_param_spec_pool_insert ##### -->
<para>

</para>

@pool: 
@pspec: 
@owner_type: 


<!-- ##### FUNCTION g_param_spec_pool_remove ##### -->
<para>

</para>

@pool: 
@pspec: 


<!-- ##### FUNCTION g_param_spec_pool_lookup ##### -->
<para>

</para>

@pool: 
@param_name: 
@owner_type: 
@walk_ancestors: 
@Returns: 
<!-- # Unused Parameters # -->
@trailer_p: 


<!-- ##### FUNCTION g_param_spec_pool_list ##### -->
<para>

</para>

@pool: 
@owner_type: 
@n_pspecs_p: 
@Returns: 


<!-- ##### FUNCTION g_param_spec_pool_list_owned ##### -->
<para>

</para>

@pool: 
@owner_type: 
@Returns: