Class DragSource

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.

Otherwise, %FALSE will be returned.

Note: This function will yield unexpected results on touchpad gestures. Since there is no correlation between physical and pixel distances, these will look as if constrained in an infinitely small area, rect width and height will thus be 0 regardless of the number of touchpoints.

Otherwise, %FALSE will be returned.

If this is 0, the gesture reacts to any button press.

At other times, %NULL is returned.

At other times, %NULL is returned.

At other times, 0 is returned.

At other times, 0 is returned.

This is only meaningful if [methodGtk.Gesture.is_active] returns %TRUE.

This returns %NULL if the gesture is not being interacted.

For more information, see [methodGtk.GestureSingle.set_exclusive].

Note that the returned pointer is only valid as long as the sequence is still interpreted by the gesture. If in doubt, you should make a copy of the event.

The coordinates are always relative to the widget allocation.

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.

Gestures are by default isolated in their own groups.

Both gestures must have been added to the same widget before they can be grouped.

When gestures are grouped, the state of GdkEventSequences is kept in sync for all of those, so calling [methodGtk.Gesture.set_sequence_state], on one will transfer the same value to the others.

Groups also perform an "implicit grabbing" of sequences, if a GdkEventSequence state is set to %GTK_EVENT_SEQUENCE_CLAIMED on one group, every other gesture group attached to the same GtkWidget will switch the state for that sequence to %GTK_EVENT_SEQUENCE_DENIED.

A gesture is active while there are touch sequences interacting with it.

A gesture is recognized if there are as many interacting touch sequences as required by gesture.

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 non-0, every button press from a different button number will be ignored. Touch events implicitly match with button 1.

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.

An exclusive gesture will only handle pointer and "pointer emulated" touch events, so at any given time, there is only one sequence able to interact with those.

If the limit is set to %GTK_LIMIT_SAME_NATIVE, the controller won't handle events that are targeted at widgets on a different surface, such as popovers.

If phase is %GTK_PHASE_NONE, no automatic event handling will be performed, but other additional gesture maintenance will.

Sequences start in state %GTK_EVENT_SEQUENCE_NONE, and whenever they change state, they can never go back to that state. Likewise, sequences in state %GTK_EVENT_SEQUENCE_DENIED cannot turn back to a not denied state. With these rules, the lifetime of an event sequence is constrained to the next four:

• None
• None → Denied
• None → Claimed
• None → Claimed → Denied

Note: Due to event handling ordering, it may be unsafe to set the state on another gesture within a [signalGtk.Gesture::begin] signal handler, as the callback might be executed before the other gesture knows about the sequence. A safe way to perform this could be:

static void
first_gesture_begin_cb (GtkGesture       *first_gesture,
                        GdkEventSequence *sequence,
                        gpointer          user_data)
{
  gtk_gesture_set_sequence_state (first_gesture, sequence, GTK_EVENT_SEQUENCE_CLAIMED);
  gtk_gesture_set_sequence_state (second_gesture, sequence, GTK_EVENT_SEQUENCE_DENIED);
}

static void
second_gesture_begin_cb (GtkGesture       *second_gesture,
                         GdkEventSequence *sequence,
                         gpointer          user_data)
{
  if (gtk_gesture_get_sequence_state (first_gesture, sequence) == GTK_EVENT_SEQUENCE_CLAIMED)
    gtk_gesture_set_sequence_state (second_gesture, sequence, GTK_EVENT_SEQUENCE_DENIED);
}

If both gestures are in the same group, just set the state on the gesture emitting the event, the sequence will be already be initialized to the group's global state when the second gesture processes the event.

See [methodGtk.Gesture.set_sequence_state] for more details on sequence states.

If touch_only is %TRUE, gesture will only handle events of type %GDK_TOUCH_BEGIN, %GDK_TOUCH_UPDATE or %GDK_TOUCH_END. If %FALSE, mouse events will be handled too.

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.

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.