Class X11Screen

Whenever the source_property is changed the target_property is updated using the same value. For instance:

  g_object_bind_property (action, "active", widget, "sensitive", 0);

Will result in the "sensitive" property of the widget #GObject instance to be updated with the same value of the "active" property of the action #GObject instance.

If flags contains %G_BINDING_BIDIRECTIONAL then the binding will be mutual: if target_property on target changes then the source_property on source will be updated as well.

The binding will automatically be removed when either the source or the target instances are finalized. To remove the binding without affecting the source and the target you can just call g_object_unref() on the returned #GBinding instance.

Removing the binding by calling g_object_unref() on it must only be done if the binding, source and target are only used from a single thread and it is clear that both source and target outlive the binding. Especially it is not safe to rely on this if the binding, source or target can be finalized from different threads. Keep another reference to the binding and use g_binding_unbind() instead to be on the safe side.

A #GObject can have multiple bindings.

This function is the language bindings friendly version of g_object_bind_property_full(), using #GClosures instead of function pointers.

This is necessary for accessors that modify multiple properties to prevent premature notification while the object is still being modified.

On X11, this is done by inspecting the _NET_ACTIVE_WINDOW property on the root window, as described in the Extended Window Manager Hints. If there is no currently currently active window, or the window manager does not support the _NET_ACTIVE_WINDOW hint, this function returns %NULL.

On other platforms, this function may return %NULL, depending on whether it is implementable on that platform.

The returned window should be unrefed using g_object_unref() when no longer needed.

Note that this value is somewhat ill-defined when the screen has multiple monitors of different resolution. It is recommended to use the monitor dimensions instead.

Monitor numbers start at 0. To obtain the number of monitors of screen, use gdk_screen_get_n_monitors().

Note that the size of the entire screen area can be retrieved via gdk_screen_get_width() and gdk_screen_get_height().

This can be used if you want to create pixel based data for a particular monitor, but most of the time you’re drawing to a window where it is better to use gdk_window_get_scale_factor() instead.

The work area should be considered when positioning menus and similar popups, to avoid placing them below panels, docks or other desktop components.

Note that not all backends may have a concept of workarea. This function will return the monitor geometry if a workarea is not available, or does not apply.

Monitor numbers start at 0. To obtain the number of monitors of screen, use gdk_screen_get_n_monitors().

If no primary monitor is configured by the user, the return value will be 0, defaulting to the first monitor.

The value can be:

• an empty #GValue initialized by %G_VALUE_INIT, which will be automatically initialized with the expected type of the property (since GLib 2.60)
• a #GValue initialized with the expected type of the property
• a #GValue initialized with a type to which the expected type of the property can be transformed

In general, a copy is made of the property contents and the caller is responsible for freeing the memory by calling g_value_unset().

Note that g_object_get_property() is really intended for language bindings, g_object_get() is much more convenient for C programming.

This functionality is not implemented in the Windows backend.

For setting an overall opacity for a top-level window, see gdk_window_set_opacity().

FIXME needs a list of valid settings here, or a link to more information.

The returned list should be freed with g_list_free(), but its elements need not be freed.

Note that this value is somewhat ill-defined when the screen has multiple monitors of different resolution. It is recommended to use the monitor dimensions instead.

On X11, this is done by inspecting the _NET_CLIENT_LIST_STACKING property on the root window, as described in the Extended Window Manager Hints. If the window manager does not support the _NET_CLIENT_LIST_STACKING hint, this function returns %NULL.

On other platforms, this function may return %NULL, depending on whether it is implementable on that platform.

The returned list is newly allocated and owns references to the windows it contains, so it should be freed using g_list_free() and its windows unrefed using g_object_unref() when no longer needed.

On X11 this function returns whether a compositing manager is compositing screen.

Call g_list_free() on the return value when you’re finished with it.

When possible, eg. when signaling a property change from within the class that registered the property, you should use g_object_notify_by_pspec() instead.

Note that emission of the notify signal may be blocked with g_object_freeze_notify(). In this case, the signal emissions are queued and will be emitted (in reverse order) when g_object_thaw_notify() is called.

This function omits the property name lookup, hence it is faster than g_object_notify().

One way to avoid using g_object_notify() from within the class that registered the properties, and using g_object_notify_by_pspec() instead, is to store the GParamSpec used with g_object_class_install_property() inside a static array, e.g.:

  enum
  {
    PROP_0,
    PROP_FOO,
    PROP_LAST
  };

  static GParamSpec *properties[PROP_LAST];

  static void
  my_object_class_init (MyObjectClass *klass)
  {
    properties[PROP_FOO] = g_param_spec_int ("foo", "Foo", "The foo",
                                             0, 100,
                                             50,
                                             G_PARAM_READWRITE);
    g_object_class_install_property (gobject_class,
                                     PROP_FOO,
                                     properties[PROP_FOO]);
  }

and then notify a change on the "foo" property with:

  g_object_notify_by_pspec (self, properties[PROP_FOO]);

Since GLib 2.56, if GLIB_VERSION_MAX_ALLOWED is 2.56 or greater, the type of object will be propagated to the return type (using the GCC typeof() extension), so any casting the caller needs to do on the return type must be explicit.

In other words, if the object is floating, then this call "assumes ownership" of the floating reference, converting it to a normal reference by clearing the floating flag while leaving the reference count unchanged. If the object is not floating, then this call adds a new normal reference increasing the reference count by one.

Since GLib 2.56, the type of object will be propagated to the return type under the same conditions as for g_object_ref().

This function should only be called from object system implementations.

If the object already had an association with that name, the old association will be destroyed.

Internally, the key is converted to a #GQuark using g_quark_from_string(). This means a copy of key is kept permanently (even after object has been finalized) — so it is recommended to only use a small, bounded set of values for key in your program, to avoid the #GQuark storage growing unbounded.

void
object_add_to_user_list (GObject     *object,
                         const gchar *new_string)
{
  // the quark, naming the object data
  GQuark quark_string_list = g_quark_from_static_string ("my-string-list");
  // retrieve the old string list
  GList *list = g_object_steal_qdata (object, quark_string_list);

  // prepend new string
  list = g_list_prepend (list, g_strdup (new_string));
  // this changed 'list', so we need to set it again
  g_object_set_qdata_full (object, quark_string_list, list, free_string_list);
}
static void
free_string_list (gpointer data)
{
  GList *node, *list = data;

  for (node = list; node; node = node->next)
    g_free (node->data);
  g_list_free (list);
}

Using g_object_get_qdata() in the above example, instead of g_object_steal_qdata() would have left the destroy function set, and thus the partial string list would have been freed upon g_object_set_qdata_full().

Duplicate notifications for each property are squashed so that at most one #GObject::notify signal is emitted for each property, in the reverse order in which they have been queued.

It is an error to call this function when the freeze count is zero.

If the pointer to the #GObject may be reused in future (for example, if it is an instance variable of another object), it is recommended to clear the pointer to %NULL rather than retain a dangling pointer to a potentially invalid #GObject instance. Use g_clear_object() for this.