docs/reference/gobject/tmpl/objects.sgml

   1 <!-- ##### SECTION Title ##### -->
   2 GObject
   3
   4 <!-- ##### SECTION Short_Description ##### -->
   5 The base object type
   6
   7 <!-- ##### SECTION Long_Description ##### -->
   8 <para>
   9
  10 </para>
  11
  12 <!-- ##### SECTION See_Also ##### -->
  13 <para>
  14
  15 </para>
  16
  17 <!-- ##### STRUCT GObject ##### -->
  18 <para>
  19 All the fields in the <structname>GObject</structname> structure are private
  20 to the #GObject implementation and should never be accessed directly.
  21 </para>
  22
  23
  24 <!-- ##### SIGNAL GObject::notify ##### -->
  25 <para>
  26 The notify signal is emitted on an object when one of its properties
  27 has been changed. Note that getting this signal doesn't guarantee that the
  28 value of the property has actually changed, it may also be emitted when
  29 the setter for the property is called to reinstate the previous value.
  30 </para>
  31
  32 @gobject: the object which received the signal.
  33 @pspec: the #GParamSpec of the property which changed
  34
  35 <!-- ##### STRUCT GObjectClass ##### -->
  36 <para>
  37 The class structure for the <structname>GObject</structname> type.
  38 </para>
  39
  40 @g_type_class: the parent class
  41 @constructor:  the @constructor function is called by g_object_new () to
  42   complete the object initialization after all the construction properties are
  43   set. The first thing a @constructor implementation must do is chain up to the
  44   @constructor of the parent class. Overriding @constructor should be rarely
  45   needed.
  46 @set_property: the generic setter for all properties of this type. Should be
  47   overridden for every type with properties. Implementations of @set_property
  48   don't need to emit property change notification explicitly, this is handled
  49   by the type system.
  50 @get_property: the generic getter for all properties of this type. Should be
  51   overridden for every type with properties.
  52 @dispose: the @dispose function is supposed to drop all references to other
  53   objects, but keep the instance otherwise intact, so that client method
  54   invocations still work. It may be run multiple times (due to reference
  55   loops). Before returning, @dispose should chain up to the @dispose method
  56   of the parent class.
  57 @finalize: instance finalization function, should finish the finalization of
  58   the instance begun in @dispose and chain up to the @finalize method of the
  59   parent class.
  60 @dispatch_properties_changed: emits property change notification for a bunch
  61   of properties. Overriding @dispatch_properties_changed should be rarely
  62   needed.
  63 @notify: the class closure for the notify signal
  64
  65 <!-- ##### STRUCT GObjectConstructParam ##### -->
  66 <para>
  67 The <structname>GObjectConstructParam</structname> struct is an auxiliary
  68 structure used to hand #GParamSpec/#GValue pairs to the @constructor of
  69 a #GObjectClass.
  70 </para>
  71
  72 @pspec: the #GParamSpec of the construct parameter
  73 @value: the value to set the parameter to
  74
  75 <!-- ##### USER_FUNCTION GObjectGetPropertyFunc ##### -->
  76 <para>
  77 The type of the @get_property function of #GObjectClass.
  78 </para>
  79
  80 @object: a #GObject
  81 @property_id: the numeric id under which the property was registered with
  82    g_object_class_install_property().
  83 @value: a #GValue to return the property value in
  84 @pspec: the #GParamSpec describing the property
  85
  86
  87 <!-- ##### USER_FUNCTION GObjectSetPropertyFunc ##### -->
  88 <para>
  89 The type of the @set_property function of #GObjectClass.
  90 </para>
  91
  92 @object: a #GObject
  93 @property_id: the numeric id under which the property was registered with
  94    g_object_class_install_property().
  95 @value: the new value for the property
  96 @pspec: the #GParamSpec describing the property
  97
  98
  99 <!-- ##### USER_FUNCTION GObjectFinalizeFunc ##### -->
 100 <para>
 101 The type of the @finalize function of #GObjectClass.
 102 </para>
 103
 104 @object: the #GObject being finalized
 105
 106
 107 <!-- ##### MACRO G_TYPE_IS_OBJECT ##### -->
 108 <para>
 109 Returns a boolean value of %FALSE or %TRUE indicating whether
 110 the passed in type id is a %G_TYPE_OBJECT or derived from it.
 111 </para>
 112
 113 @type: Type id to check for is a %G_TYPE_OBJECT relationship.
 114 @Returns: %FALSE or %TRUE, indicating whether @type is a %G_TYPE_OBJECT.
 115
 116
 117 <!-- ##### MACRO G_OBJECT ##### -->
 118 <para>
 119 Casts a #GObject or derived pointer into a (GObject*) pointer.
 120 Depending on the current debugging level, this function may invoke
 121 certain runtime checks to identify invalid casts.
 122 </para>
 123
 124 @object: Object which is subject to casting.
 125
 126
 127 <!-- ##### MACRO G_IS_OBJECT ##### -->
 128 <para>
 129 Checks whether a valid #GTypeInstance pointer is of type %G_TYPE_OBJECT.
 130 </para>
 131
 132 @object: Instance to check for being a %G_TYPE_OBJECT.
 133
 134
 135 <!-- ##### MACRO G_OBJECT_CLASS ##### -->
 136 <para>
 137 Casts a derived #GObjectClass structure into a #GObjectClass structure.
 138 </para>
 139
 140 @class: a valid #GObjectClass
 141
 142
 143 <!-- ##### MACRO G_IS_OBJECT_CLASS ##### -->
 144 <para>
 145 Checks whether @class "is a" valid #GObjectClass structure of type
 146 %G_TYPE_OBJECT or derived.
 147 </para>
 148
 149 @class: a #GObjectClass
 150
 151
 152 <!-- ##### MACRO G_OBJECT_GET_CLASS ##### -->
 153 <para>
 154 Returns the class structure associated to a #GObject instance.
 155 </para>
 156
 157 @object: a #GObject instance.
 158
 159
 160 <!-- ##### MACRO G_OBJECT_TYPE ##### -->
 161 <para>
 162 Return the type id of an object.
 163 </para>
 164
 165 @object: Object to return the type id for.
 166 @Returns: Type id of @object.
 167
 168
 169 <!-- ##### MACRO G_OBJECT_TYPE_NAME ##### -->
 170 <para>
 171 Returns the name of an object's type.
 172 </para>
 173
 174 @object: Object to return the type name for.
 175 @Returns: Type name of @object. The string is owned by the type system and
 176 should not be freed.
 177
 178
 179 <!-- ##### MACRO G_OBJECT_CLASS_TYPE ##### -->
 180 <para>
 181 Return the type id of a class structure.
 182 </para>
 183
 184 @class: a valid #GObjectClass
 185 @Returns: Type id of @class.
 186
 187
 188 <!-- ##### MACRO G_OBJECT_CLASS_NAME ##### -->
 189 <para>
 190 Return the name of a class structure's type.
 191 </para>
 192
 193 @class: a valid #GObjectClass
 194 @Returns: Type name of @class. The string is owned by the type system and
 195 should not be freed.
 196
 197
 198 <!-- ##### FUNCTION g_object_class_install_property ##### -->
 199 <para>
 200 Installs a new property. This is usually done in the class initializer.
 201 </para>
 202
 203 @oclass: a #GObjectClass
 204 @property_id: the id for the new property
 205 @pspec: the #GParamSpec for the new property
 206
 207
 208 <!-- ##### FUNCTION g_object_class_find_property ##### -->
 209 <para>
 210 Looks up the #GParamSpec for a property of a class.
 211 </para>
 212
 213 @oclass: a #GObjectClass
 214 @property_name: the name of the property to look up
 215 @Returns: the #GParamSpec for the property, or %NULL if the class doesn't have
 216 a property of that name
 217
 218
 219 <!-- ##### FUNCTION g_object_class_list_properties ##### -->
 220 <para>
 221 Returns an array of #GParamSpec* for all properties of a class.
 222 </para>
 223
 224 @oclass: a #GObjectClass
 225 @n_properties: return location for the length of the returned array
 226 @Returns: an array of #GParamSpec* which should be freed after use
 227
 228
 229 <!-- ##### FUNCTION g_object_class_override_property ##### -->
 230 <para>
 231 Registers @property_id as referring to a property with the
 232 name @name in a parent class or in an interface implemented
 233 by @oclass. This allows this class to <firstterm>override</firstterm>
 234 a property implementation in a parent class or to provide
 235 the implementation of a property from an interface.
 236 </para>
 237 <note>
 238 <para>
 239 Internally, overriding is implemented by creating a property of type
 240 #GParamSpecOverride; generally operations that query the properties of
 241 the object class, such as g_object_class_find_property() or
 242 g_object_class_list_properties() will return the overridden
 243 property. However, in one case, the @construct_properties argument of
 244 the @constructor virtual function, the #GParamSpecOverride is passed
 245 instead, so that the @param_id field of the #GParamSpec will be
 246 correct.  For virtually all uses, this makes no difference. If you
 247 need to get the overridden property, you can call
 248 g_param_spec_get_redirect_target().
 249 </para>
 250 </note>
 251
 252 @oclass: a #GObjectClass
 253 @property_id: the new property ID
 254 @name: the name of a property registered in a parent class or
 255        in an interface of this class.
 256
 257
 258 <!-- ##### FUNCTION g_object_interface_install_property ##### -->
 259 <para>
 260 Add a property to an interface; this is only useful for interfaces
 261 that are added to GObject-derived types. Adding a property to an
 262 interface forces all objects classes with that interface to have a
 263 compatible property. The compatible property could be a newly
 264 created #GParamSpec, but normally
 265 g_object_class_override_property() will be used so that the object
 266 class only needs to provide an implementation and inherits the
 267 property description, default value, bounds, and so forth from the
 268 interface property.
 269 </para>
 270 <para>
 271 This function is meant to be called from the interface's default
 272 vtable initialization function (the @class_init member of
 273 #GTypeInfo.) It must not be called after after @class_init has
 274 been called for any object types implementing this interface.
 275 </para>
 276
 277 @g_iface: any interface vtable for the interface, or the default
 278  vtable for the interface.
 279 @pspec: the #GParamSpec for the new property
 280 @Since: 2.4
 281
 282
 283 <!-- ##### FUNCTION g_object_interface_find_property ##### -->
 284 <para>
 285 Find the #GParamSpec with the given name for an
 286 interface. Generally, the interface vtable passed in as @g_iface
 287 will be the default vtable from g_type_default_interface_ref(), or,
 288 if you know the interface has already been loaded,
 289 g_type_default_interface_peek().
 290 </para>
 291
 292 @g_iface: any interface vtable for the interface, or the default
 293   vtable for the interface
 294 @property_name: name of a property to lookup.
 295 @Returns: the #GParamSpec for the property of the
 296   interface with the name @property_name, or %NULL
 297   if no such property exists.
 298 @Since: 2.4
 299
 300
 301 <!-- ##### FUNCTION g_object_interface_list_properties ##### -->
 302 <para>
 303 Lists the properties of an interface.Generally, the interface
 304 vtable passed in as @g_iface will be the default vtable from
 305 g_type_default_interface_ref(), or, if you know the interface has
 306 already been loaded, g_type_default_interface_peek().
 307 </para>
 308
 309 @g_iface: any interface vtable for the interface, or the default
 310  vtable for the interface
 311 @n_properties_p: location to store number of properties returned.
 312 @Returns: a pointer to an array of pointers to #GParamSpec structures.
 313   The paramspecs are owned by GLib, but the array should
 314   be freed with g_free() when you are done with it.
 315 @Since: 2.4
 316
 317
 318 <!-- ##### FUNCTION g_object_new ##### -->
 319 <para>
 320 Creates a new instance of a #GObject subtype and sets its properties.
 321 </para>
 322 <para>
 323 Construction parameters (see #G_PARAM_CONSTRUCT, #G_PARAM_CONSTRUCT_ONLY)
 324 which are not explicitly specified are set to their default values.
 325 </para>
 326
 327 @object_type: the type id of the #GObject subtype to instantiate
 328 @first_property_name: the name of the first property
 329 @Varargs: the value of the first property, followed optionally by more
 330      name/value pairs, followed by %NULL
 331 @Returns: a new instance of @object_type
 332
 333
 334 <!-- ##### FUNCTION g_object_newv ##### -->
 335 <para>
 336 Creates a new instance of a #GObject subtype and sets its properties.
 337 </para>
 338 <para>
 339 Construction parameters (see #G_PARAM_CONSTRUCT, #G_PARAM_CONSTRUCT_ONLY)
 340 which are not explicitly specified are set to their default values.
 341 </para>
 342
 343 @object_type: the type id of the #GObject subtype to instantiate
 344 @n_parameters: the length of the @parameters array
 345 @parameters: an array of #GParameter
 346 @Returns: a new instance of @object_type
 347
 348
 349 <!-- ##### STRUCT GParameter ##### -->
 350 <para>
 351 The <structname>GParameter</structname> struct is an auxiliary structure used
 352 to hand parameter name/value pairs to g_object_newv().
 353 </para>
 354
 355 @name: the parameter name
 356 @value: the parameter value
 357
 358 <!-- ##### FUNCTION g_object_ref ##### -->
 359 <para>
 360 Increases the reference count of @object.
 361 </para>
 362
 363 @object: a #GObject
 364 @Returns: @object
 365
 366
 367 <!-- ##### FUNCTION g_object_unref ##### -->
 368 <para>
 369 Decreases the reference count if @object.
 370 When its reference count drops to 0, the object is finalized (i.e. its memory is freed).
 371 </para>
 372
 373 @object: a #GObject
 374
 375
 376 <!-- ##### USER_FUNCTION GWeakNotify ##### -->
 377 <para>
 378 A #GWeakNotify function can be added to an object as a callback that gets
 379 triggered when the object is finalized. Since the object is already being
 380 finalized when the #GWeakNotify is called, there's not much you could do
 381 with the object, apart from e.g. using its adress as hash-index or the like.
 382 </para>
 383
 384 @data: data that was provided when the weak reference was established
 385 @where_the_object_was: the object being finalized
 386
 387
 388 <!-- ##### FUNCTION g_object_weak_ref ##### -->
 389 <para>
 390 Adds a weak reference callback to an object. Weak references are used for
 391 notification when an object is finalized. They are called "weak references"
 392 because they allow you to safely hold a pointer to an object without calling
 393 g_object_ref() (g_object_ref() adds a strong reference, that is, forces the
 394 object to stay alive).
 395 </para>
 396
 397 @object: #GObject to reference weakly
 398 @notify: callback to invoke before the object is freed
 399 @data: extra data to pass to notify
 400
 401
 402 <!-- ##### FUNCTION g_object_weak_unref ##### -->
 403 <para>
 404 Removes a weak reference callback to an object.
 405 </para>
 406
 407 @object: #GObject to remove a weak reference from
 408 @notify: callback to search for
 409 @data: data to search for
 410
 411
 412 <!-- ##### FUNCTION g_object_add_weak_pointer ##### -->
 413 <para>
 414 Adds a weak reference from weak_pointer to @object to indicate that
 415 the pointer located at @weak_pointer_location is only valid during the
 416 lifetime of @object. When the @object is finalized, @weak_pointer will
 417 be set to %NULL.
 418 </para>
 419
 420 @object: The object that should be weak referenced.
 421 @weak_pointer_location: The memory address of a pointer.
 422
 423
 424 <!-- ##### FUNCTION g_object_remove_weak_pointer ##### -->
 425 <para>
 426 Removes a weak reference from @object that was previously added
 427 using g_object_add_weak_pointer(). The @weak_pointer_location has
 428 to match the one used with g_object_add_weak_pointer().
 429 </para>
 430
 431 @object: The object that is weak referenced.
 432 @weak_pointer_location: The memory address of a pointer.
 433
 434
 435 <!-- ##### FUNCTION g_object_connect ##### -->
 436 <para>
 437 A convenience function to connect multiple signals at once.
 438 </para>
 439 <para>
 440 The signal specs expected by this function have the form
 441 "modifier::signal_name", where modifier can be one of the following:
 442 <variablelist>
 443 <varlistentry>
 444 <term>signal</term>
 445 <listitem><para>
 446 equivalent to <literal>g_signal_connect_data (...)</literal>
 447 </para></listitem>
 448 </varlistentry>
 449 <varlistentry>
 450 <term>object_signal</term>
 451 <term>object-signal</term>
 452 <listitem><para>
 453 equivalent to <literal>g_signal_connect_object (...)</literal>
 454 </para></listitem>
 455 </varlistentry>
 456 <varlistentry>
 457 <term>swapped_signal</term>
 458 <term>swapped-signal</term>
 459 <listitem><para>
 460 equivalent to <literal>g_signal_connect_data (..., G_CONNECT_SWAPPED)</literal>
 461 </para></listitem>
 462 </varlistentry>
 463 <varlistentry>
 464 <term>swapped_object_signal</term>
 465 <term>swapped-object-signal</term>
 466 <listitem><para>
 467 equivalent to <literal>g_signal_connect_object (..., G_CONNECT_SWAPPED)</literal>
 468 </para></listitem>
 469 </varlistentry>
 470 <varlistentry>
 471 <term>signal_after</term>
 472 <term>signal-after</term>
 473 <listitem><para>
 474 equivalent to <literal>g_signal_connect_data (..., G_CONNECT_AFTER)</literal>
 475 </para></listitem>
 476 </varlistentry>
 477 <varlistentry>
 478 <term>object_signal_after</term>
 479 <term>object-signal-after</term>
 480 <listitem><para>
 481 equivalent to <literal>g_signal_connect_object (..., G_CONNECT_AFTER)</literal>
 482 </para></listitem>
 483 </varlistentry>
 484 <varlistentry>
 485 <term>swapped_signal_after</term>
 486 <term>swapped-signal-after</term>
 487 <listitem><para>
 488 equivalent to <literal>g_signal_connect_data (..., G_CONNECT_SWAPPED | G_CONNECT_AFTER)</literal>
 489 </para></listitem>
 490 </varlistentry>
 491 <varlistentry>
 492 <term>swapped_object_signal_after</term>
 493 <term>swapped-object-signal-after</term>
 494 <listitem><para>
 495 equivalent to <literal>g_signal_connect_object (..., G_CONNECT_SWAPPED | G_CONNECT_AFTER)</literal>
 496 </para></listitem>
 497 </varlistentry>
 498 </variablelist>
 499 </para>
 500 <informalexample>
 501 <programlisting>
 502   menu->toplevel = g_object_connect (g_object_new (GTK_TYPE_WINDOW,
 503                                                    "type", GTK_WINDOW_POPUP,
 504                                                    "child", menu,
 505                                                    NULL),
 506                                      "signal::event", gtk_menu_window_event, menu,
 507                                      "signal::size_request", gtk_menu_window_size_request, menu,
 508                                      "signal::destroy", gtk_widget_destroyed, &amp;menu-&gt;toplevel,
 509                                      NULL);
 510 </programlisting>
 511 </informalexample>
 512
 513 @object: a #GObject
 514 @signal_spec: the spec for the first signal
 515 @Varargs: #GCallback for the first signal, followed by data for the first signal,
 516           followed optionally by more signal spec/callback/data triples,
 517           followed by %NULL
 518 @Returns: @object
 519
 520
 521 <!-- ##### FUNCTION g_object_disconnect ##### -->
 522 <para>
 523 A convenience function to disconnect multiple signals at once.
 524 </para>
 525 <para>
 526 The signal specs expected by this function have the form "any_signal", which
 527 means to disconnect any signal with matching callback and data, or
 528 "any_signal::signal_name", which only disconnects the signal named "signal_name".
 529 </para>
 530
 531 @object: a #GObject
 532 @signal_spec: the spec for the first signal
 533 @Varargs: #GCallback for the first signal, followed by data for the first signal,
 534           followed optionally by more signal spec/callback/data triples,
 535           followed by %NULL
 536
 537
 538 <!-- ##### FUNCTION g_object_set ##### -->
 539 <para>
 540 Sets properties on an object.
 541 </para>
 542
 543 @object: a #GObject
 544 @first_property_name: name of the first property to set
 545 @Varargs: value for the first property, followed optionally by more
 546           name/value pairs, followed by %NULL
 547
 548
 549 <!-- ##### FUNCTION g_object_get ##### -->
 550 <para>
 551 Gets properties of an object.
 552 </para>
 553 <para>
 554 In general, a copy is made of the property contents and the caller is
 555 responsible for freeing the memory in the appropriate manner for the type,
 556 for instance by calling g_free() or g_object_unref().
 557 </para>
 558 <example>
 559 <title>Using g_object_get(<!-- -->)</title>
 560 <para>
 561 An example of using g_object_get() to get the contents
 562 of three properties - one of type #G_TYPE_INT,
 563 one of type #G_TYPE_STRING, and one of type #G_TYPE_OBJECT:
 564 </para>
 565 <programlisting>
 566  gint intval;
 567  gchar *strval;
 568  GObject *objval;
 569
 570  g_object_get (my_object,
 571                "intproperty", &amp;intval,
 572                "strproperty", &amp;strval,
 573                "objproperty", &amp;objval,
 574                NULL);
 575
 576  /* Do something with intval, strval, objval */
 577
 578  g_free (strval);
 579  g_object_unref (objval);
 580 </programlisting>
 581 </example>
 582
 583 @object: a #GObject
 584 @first_property_name: name of the first property to get
 585 @Varargs: return location for the first property, followed optionally by more
 586           name/return location pairs, followed by %NULL
 587
 588
 589 <!-- ##### FUNCTION g_object_notify ##### -->
 590 <para>
 591 Emits a "notify" signal for the property @property_name on @object.
 592 </para>
 593
 594 @object: a #GObject
 595 @property_name: the name of a property installed on the class of @object.
 596
 597
 598 <!-- ##### FUNCTION g_object_freeze_notify ##### -->
 599 <para>
 600 Stops emission of "notify" signals on @object. The signals are
 601 queued until g_object_thaw_notify() is called on @object.
 602 </para>
 603 <para>
 604 This is necessary for accessors that modify multiple properties to prevent
 605 premature notification while the object is still being modified.
 606 </para>
 607
 608 @object: a #GObject
 609
 610
 611 <!-- ##### FUNCTION g_object_thaw_notify ##### -->
 612 <para>
 613 Reverts the effect of a previous call to g_object_freeze_notify().
 614 This causes all queued "notify" signals on @object to be emitted.
 615 </para>
 616
 617 @object: a #GObject
 618
 619
 620 <!-- ##### FUNCTION g_object_get_data ##### -->
 621 <para>
 622 Gets a named field from the objects table of associations (see g_object_set_data()).
 623 </para>
 624
 625 @object: #GObject containing the associations
 626 @key: name of the key for that association
 627 @Returns: the data if found, or %NULL if no such data exists.
 628
 629
 630 <!-- ##### FUNCTION g_object_set_data ##### -->
 631 <para>
 632 Each object carries around a table of associations from
 633 strings to pointers.  This function lets you set an association.
 634 </para>
 635 <para>
 636 If the object already had an association with that name,
 637 the old association will be destroyed.
 638 </para>
 639
 640 @object: #GObject containing the associations.
 641 @key: name of the key
 642 @data: data to associate with that key
 643
 644
 645 <!-- ##### FUNCTION g_object_set_data_full ##### -->
 646 <para>
 647 Like g_object_set_data() except it adds notification
 648 for when the association is destroyed, either by setting it
 649 to a different value or when the object is destroyed.
 650 </para>
 651
 652 @object: #GObject containing the associations
 653 @key: name of the key
 654 @data: data to associate with that key
 655 @destroy: function to call when the association is destroyed
 656
 657
 658 <!-- ##### FUNCTION g_object_steal_data ##### -->
 659 <para>
 660 Remove a specified datum from the object's data associations,
 661 without invoking the association's destroy handler.
 662 </para>
 663
 664 @object: #GObject containing the associations
 665 @key: name of the key
 666 @Returns: the data if found, or %NULL if no such data exists.
 667
 668
 669 <!-- ##### FUNCTION g_object_get_qdata ##### -->
 670 <para>
 671 This function gets back user data pointers stored via
 672 g_object_set_qdata().
 673 </para>
 674
 675 @object:  The GObject to get a stored user data pointer from
 676 @quark:   A #GQuark, naming the user data pointer
 677 @Returns: The user data pointer set, or %NULL
 678
 679
 680 <!-- ##### FUNCTION g_object_set_qdata ##### -->
 681 <para>
 682 This sets an opaque, named pointer on an object.
 683 The name is specified through a #GQuark (retrived e.g. via
 684 g_quark_from_static_string()), and the pointer
 685 can be gotten back from the @object with g_object_get_qdata()
 686 until the @object is finalized.
 687 Setting a previously set user data pointer, overrides (frees)
 688 the old pointer set, using #NULL as pointer essentially
 689 removes the data stored.
 690 </para>
 691
 692 @object: The GObject to set store a user data pointer
 693 @quark:  A #GQuark, naming the user data pointer
 694 @data:   An opaque user data pointer
 695
 696
 697 <!-- ##### FUNCTION g_object_set_qdata_full ##### -->
 698 <para>
 699 This function works like g_object_set_qdata(), but in addition,
 700 a void (*destroy) (gpointer) function may be specified which is
 701 called with @data as argument when the @object is finalized, or
 702 the data is being overwritten by a call to g_object_set_qdata()
 703 with the same @quark.
 704 </para>
 705
 706 @object:  The GObject to set store a user data pointer
 707 @quark:   A #GQuark, naming the user data pointer
 708 @data:    An opaque user data pointer
 709 @destroy: Function to invoke with @data as argument, when @data needs to be freed
 710
 711
 712 <!-- ##### FUNCTION g_object_steal_qdata ##### -->
 713 <para>
 714 This function gets back user data pointers stored via
 715 g_object_set_qdata() and removes the @data from object
 716 without invoking it's destroy() function (if any was
 717 set).
 718 Usually, calling this function is only required to update
 719 user data pointers with a destroy notifier, for example:
 720 <programlisting>
 721 void
 722 object_add_to_user_list (GObject     *object,
 723                          const gchar *new_string)
 724 {
 725   /* the quark, naming the object data */
 726   GQuark quark_string_list = g_quark_from_static_string ("my-string-list");
 727   /* retrive the old string list */
 728   GList *list = g_object_steal_qdata (object, quark_string_list);
 729
 730   /* prepend new string */
 731   list = g_list_prepend (list, g_strdup (new_string));
 732   /* this changed 'list', so we need to set it again */
 733   g_object_set_qdata_full (object, quark_string_list, list, free_string_list);
 734 }
 735 static void
 736 free_string_list (gpointer data)
 737 {
 738   GList *node, *list = data;
 739
 740   for (node = list; node; node = node->next)
 741     g_free (node->data);
 742   g_list_free (list);
 743 }
 744 </programlisting>
 745 Using g_object_get_qdata() in the above example, instead of g_object_steal_qdata()
 746 would have left the destroy function set, and thus the partial string list would
 747 have been freed upon g_object_set_qdata_full().
 748 </para>
 749
 750 @object:  The GObject to get a stored user data pointer from
 751 @quark:   A #GQuark, naming the user data pointer
 752 @Returns: The user data pointer set, or %NULL
 753
 754
 755 <!-- ##### FUNCTION g_object_set_property ##### -->
 756 <para>
 757 Sets a property on an object.
 758 </para>
 759
 760 @object: a #GObject
 761 @property_name: the name of the property to set
 762 @value: the value
 763
 764
 765 <!-- ##### FUNCTION g_object_get_property ##### -->
 766 <para>
 767 Gets a property of an object.
 768 </para>
 769 <para>
 770 In general, a copy is made of the property contents and the caller is
 771 responsible for freeing the memory in the appropriate manner for the type,
 772 for instance by calling g_free() or g_object_unref().
 773 </para>
 774 <para>
 775 See g_object_get().
 776 </para>
 777
 778 @object: a #GObject
 779 @property_name: the name of the property to get
 780 @value: return location for the property value
 781
 782
 783 <!-- ##### FUNCTION g_object_new_valist ##### -->
 784 <para>
 785 Creates a new instance of a #GObject subtype and sets its properties.
 786 </para>
 787 <para>
 788 Construction parameters (see #G_PARAM_CONSTRUCT, #G_PARAM_CONSTRUCT_ONLY)
 789 which are not explicitly specified are set to their default values.
 790 </para>
 791
 792 @object_type: the type id of the #GObject subtype to instantiate
 793 @first_property_name: the name of the first property
 794 @var_args: the value of the first property, followed optionally by more
 795      name/value pairs, followed by %NULL
 796 @Returns: a new instance of @object_type
 797
 798
 799 <!-- ##### FUNCTION g_object_set_valist ##### -->
 800 <para>
 801 Sets properties on an object.
 802 </para>
 803
 804 @object: a #GObject
 805 @first_property_name: name of the first property to set
 806 @var_args: value for the first property, followed optionally by more
 807            name/value pairs, followed by %NULL
 808
 809
 810 <!-- ##### FUNCTION g_object_get_valist ##### -->
 811 <para>
 812 Gets properties of an object.
 813 </para>
 814 <para>
 815 In general, a copy is made of the property contents and the caller is
 816 responsible for freeing the memory in the appropriate manner for the type,
 817 for instance by calling g_free() or g_object_unref().
 818 </para>
 819 <para>
 820 See g_object_get().
 821 </para>
 822
 823 @object: a #GObject
 824 @first_property_name: name of the first property to get
 825 @var_args: return location for the first property, followed optionally by more
 826            name/return location pairs, followed by %NULL
 827
 828
 829 <!-- ##### FUNCTION g_object_watch_closure ##### -->
 830 <para>
 831 This function essentially limits the life time of the @closure
 832 to the life time of the object. That is, when the object is finalized,
 833 the @closure is invalidated by calling g_closure_invalidate() on it,
 834 in order to prevent invocations of the closure with a finalized
 835 (nonexisting) object. Also, g_object_ref() and g_object_unref() are added
 836 as marshal guards to the @closure, to ensure that an extra reference
 837 count is held on @object during invocation of the @closure.
 838 Usually, this function will be called on closures that use this @object
 839 as closure data.
 840 </para>
 841
 842 @object:  GObject restricting lifetime of @closure
 843 @closure: GClosure to watch
 844
 845
 846 <!-- ##### FUNCTION g_object_run_dispose ##### -->
 847 <para>
 848 Releases all references to other objects. This can be used to break
 849 reference cycles.
 850 </para>
 851 <note><para>
 852 This functions should only be called from object system implementations.
 853 </para></note>
 854
 855 @object: a #GObject
 856
 857
 858 <!-- ##### MACRO G_OBJECT_WARN_INVALID_PROPERTY_ID ##### -->
 859 <para>
 860 This macros should be used to emit a standard warning about unexpected
 861 properties in set_property() and get_property() implementations.
 862 </para>
 863
 864 @object: the #GObject on which set_property() or get_property() was called
 865 @property_id: the numeric id of the property
 866 @pspec: the #GParamSpec of the property
 867
 868