:right-sidebar: True Gesture =================================================================== .. currentmodule:: gi.repository.Gtk .. class:: Gesture(**properties: ~typing.Any) :no-contents-entry: Superclasses: :class:`~gi.repository.Gtk.EventController`, :class:`~gi.repository.GObject.Object` Subclasses: :class:`~gi.repository.Gtk.GestureRotate`, :class:`~gi.repository.Gtk.GestureSingle`, :class:`~gi.repository.Gtk.GestureZoom` ``GtkGesture`` is the base class for gesture recognition. Although ``GtkGesture`` is quite generalized to serve as a base for multi-touch gestures, it is suitable to implement single-touch and pointer-based gestures (using the special :const:`None` ``GdkEventSequence`` value for these). The number of touches that a ``GtkGesture`` need to be recognized is controlled by the :obj:`~gi.repository.Gtk.Gesture.props.n_points` property, if a gesture is keeping track of less or more than that number of sequences, it won't check whether the gesture is recognized. As soon as the gesture has the expected number of touches, it will check regularly if it is recognized, the criteria to consider a gesture as "recognized" is left to ``GtkGesture`` subclasses. A recognized gesture will then emit the following signals: - :obj:`~gi.repository.Gtk.Gesture.signals.begin` when the gesture is recognized. - :obj:`~gi.repository.Gtk.Gesture.signals.update`, whenever an input event is processed. - :obj:`~gi.repository.Gtk.Gesture.signals.end` when the gesture is no longer recognized. Event propagation ----------------- In order to receive events, a gesture needs to set a propagation phase through :obj:`~gi.repository.Gtk.EventController.set_propagation_phase`. In the capture phase, events are propagated from the toplevel down to the target widget, and gestures that are attached to containers above the widget get a chance to interact with the event before it reaches the target. In the bubble phase, events are propagated up from the target widget to the toplevel, and gestures that are attached to containers above the widget get a chance to interact with events that have not been handled yet. States of a sequence -------------------- Whenever input interaction happens, a single event may trigger a cascade of ``GtkGesture``'s, both across the parents of the widget receiving the event and in parallel within an individual widget. It is a responsibility of the widgets using those gestures to set the state of touch sequences accordingly in order to enable cooperation of gestures around the ``GdkEventSequence``'s triggering those. Within a widget, gestures can be grouped through :obj:`~gi.repository.Gtk.Gesture.group`. Grouped gestures synchronize the state of sequences, so calling :obj:`~gi.repository.Gtk.Gesture.set_state` on one will effectively propagate the state throughout the group. By default, all sequences start out in the :const:`~gi.repository.Gtk.EventSequenceState.NONE` state, sequences in this state trigger the gesture event handler, but event propagation will continue unstopped by gestures. If a sequence enters into the :const:`~gi.repository.Gtk.EventSequenceState.DENIED` state, the gesture group will effectively ignore the sequence, letting events go unstopped through the gesture, but the "slot" will still remain occupied while the touch is active. If a sequence enters in the :const:`~gi.repository.Gtk.EventSequenceState.CLAIMED` state, the gesture group will grab all interaction on the sequence, by: - Setting the same sequence to :const:`~gi.repository.Gtk.EventSequenceState.DENIED` on every other gesture group within the widget, and every gesture on parent widgets in the propagation chain. - Emitting :obj:`~gi.repository.Gtk.Gesture.signals.cancel` on every gesture in widgets underneath in the propagation chain. - Stopping event propagation after the gesture group handles the event. Note: if a sequence is set early to :const:`~gi.repository.Gtk.EventSequenceState.CLAIMED` on ``%GDK_TOUCH_BEGIN``/``%GDK_BUTTON_PRESS`` (so those events are captured before reaching the event widget, this implies :const:`~gi.repository.Gtk.PropagationPhase.CAPTURE`), one similar event will be emulated if the sequence changes to :const:`~gi.repository.Gtk.EventSequenceState.DENIED`. This way event coherence is preserved before event propagation is unstopped again. Sequence states can't be changed freely. See :obj:`~gi.repository.Gtk.Gesture.set_state` to know about the possible lifetimes of a ``GdkEventSequence``. Touchpad gestures ----------------- On the platforms that support it, ``GtkGesture`` will handle transparently touchpad gesture events. The only precautions users of ``GtkGesture`` should do to enable this support are: - If the gesture has :const:`~gi.repository.Gtk.PropagationPhase.NONE`, ensuring events of type ``%GDK_TOUCHPAD_SWIPE`` and ``%GDK_TOUCHPAD_PINCH`` are handled by the ``GtkGesture`` Methods ------- .. rst-class:: interim-class .. class:: Gesture :no-index: .. method:: get_bounding_box() -> tuple[bool, ~gi.repository.Gdk.Rectangle] If there are touch sequences being currently handled by ``gesture``, returns :const:`True` and fills in ``rect`` with the bounding box containing all active touches. Otherwise, :const:`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. .. method:: get_bounding_box_center() -> tuple[bool, float, float] If there are touch sequences being currently handled by ``gesture``, returns :const:`True` and fills in ``x`` and ``y`` with the center of the bounding box containing all active touches. Otherwise, :const:`False` will be returned. .. method:: get_device() -> ~gi.repository.Gdk.Device | None Returns the logical ``GdkDevice`` that is currently operating on ``gesture``. This returns :const:`None` if the gesture is not being interacted. .. method:: get_group() -> list[~gi.repository.Gtk.Gesture] Returns all gestures in the group of ``gesture`` .. method:: get_last_event(sequence: ~gi.repository.Gdk.EventSequence | None = None) -> ~gi.repository.Gdk.Event | None Returns the last event that was processed for ``sequence``. 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. :param sequence: a ``GdkEventSequence`` .. method:: get_last_updated_sequence() -> ~gi.repository.Gdk.EventSequence | None Returns the ``GdkEventSequence`` that was last updated on ``gesture``. .. method:: get_point(sequence: ~gi.repository.Gdk.EventSequence | None = None) -> tuple[bool, float, float] If ``sequence`` is currently being interpreted by ``gesture``, returns :const:`True` and fills in ``x`` and ``y`` with the last coordinates stored for that event sequence. The coordinates are always relative to the widget allocation. :param sequence: a ``GdkEventSequence``, or :const:`None` for pointer events .. method:: get_sequence_state(sequence: ~gi.repository.Gdk.EventSequence) -> ~gi.repository.Gtk.EventSequenceState Returns the ``sequence`` state, as seen by ``gesture``. :param sequence: a ``GdkEventSequence`` .. method:: get_sequences() -> list[~gi.repository.Gdk.EventSequence] Returns the list of ``GdkEventSequences`` currently being interpreted by ``gesture``. .. method:: group(gesture: ~gi.repository.Gtk.Gesture) -> None Adds ``gesture`` to the same group than ``group_gesture``. 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 :obj:`~gi.repository.Gtk.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 :const:`~gi.repository.Gtk.EventSequenceState.CLAIMED` on one group, every other gesture group attached to the same ``GtkWidget`` will switch the state for that sequence to :const:`~gi.repository.Gtk.EventSequenceState.DENIED`. :param gesture: a ``GtkGesture`` .. method:: handles_sequence(sequence: ~gi.repository.Gdk.EventSequence | None = None) -> bool Returns :const:`True` if ``gesture`` is currently handling events corresponding to ``sequence``. :param sequence: a ``GdkEventSequence`` .. method:: is_active() -> bool Returns :const:`True` if the gesture is currently active. A gesture is active while there are touch sequences interacting with it. .. method:: is_grouped_with(other: ~gi.repository.Gtk.Gesture) -> bool Returns :const:`True` if both gestures pertain to the same group. :param other: another ``GtkGesture`` .. method:: is_recognized() -> bool Returns :const:`True` if the gesture is currently recognized. A gesture is recognized if there are as many interacting touch sequences as required by ``gesture``. .. method:: set_sequence_state(sequence: ~gi.repository.Gdk.EventSequence, state: ~gi.repository.Gtk.EventSequenceState) -> bool Sets the state of ``sequence`` in ``gesture``. Sequences start in state :const:`~gi.repository.Gtk.EventSequenceState.NONE`, and whenever they change state, they can never go back to that state. Likewise, sequences in state :const:`~gi.repository.Gtk.EventSequenceState.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 :obj:`~gi.repository.Gtk.Gesture.signals.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: .. code-block:: :dedent: 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. .. deprecated:: 4.10. Use :obj:`~gi.repository.Gtk.Gesture.set_state` :param sequence: a ``GdkEventSequence`` :param state: the sequence state .. method:: set_state(state: ~gi.repository.Gtk.EventSequenceState) -> bool Sets the state of all sequences that ``gesture`` is currently interacting with. Sequences start in state :const:`~gi.repository.Gtk.EventSequenceState.NONE`, and whenever they change state, they can never go back to that state. Likewise, sequences in state :const:`~gi.repository.Gtk.EventSequenceState.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 :obj:`~gi.repository.Gtk.Gesture.signals.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: .. code-block:: :dedent: static void first_gesture_begin_cb (GtkGesture *first_gesture, GdkEventSequence *sequence, gpointer user_data) { gtk_gesture_set_state (first_gesture, GTK_EVENT_SEQUENCE_CLAIMED); gtk_gesture_set_state (second_gesture, 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_state (second_gesture, 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. :param state: the sequence state .. method:: ungroup() -> None Separates ``gesture`` into an isolated group. Properties ---------- .. rst-class:: interim-class .. class:: Gesture :no-index: .. attribute:: props.n_points :type: int The number of touch points that trigger recognition on this gesture. Signals ------- .. rst-class:: interim-class .. class:: Gesture.signals :no-index: .. method:: begin(sequence: ~gi.repository.Gdk.EventSequence | None = None) -> None Emitted when the gesture is recognized. This means the number of touch sequences matches :obj:`~gi.repository.Gtk.Gesture.props.n_points`. Note: These conditions may also happen when an extra touch (eg. a third touch on a 2-touches gesture) is lifted, in that situation ``sequence`` won't pertain to the current set of active touches, so don't rely on this being true. :param sequence: the ``GdkEventSequence`` that made the gesture to be recognized .. method:: cancel(sequence: ~gi.repository.Gdk.EventSequence | None = None) -> None Emitted whenever a sequence is cancelled. This usually happens on active touches when :obj:`~gi.repository.Gtk.EventController.reset` is called on ``gesture`` (manually, due to grabs...), or the individual ``sequence`` was claimed by parent widgets' controllers (see :obj:`~gi.repository.Gtk.Gesture.set_sequence_state`). ``gesture`` must forget everything about ``sequence`` as in response to this signal. :param sequence: the ``GdkEventSequence`` that was cancelled .. method:: end(sequence: ~gi.repository.Gdk.EventSequence | None = None) -> None Emitted when ``gesture`` either stopped recognizing the event sequences as something to be handled, or the number of touch sequences became higher or lower than :obj:`~gi.repository.Gtk.Gesture.props.n_points`. Note: ``sequence`` might not pertain to the group of sequences that were previously triggering recognition on ``gesture`` (ie. a just pressed touch sequence that exceeds :obj:`~gi.repository.Gtk.Gesture.props.n_points`). This situation may be detected by checking through :obj:`~gi.repository.Gtk.Gesture.handles_sequence`. :param sequence: the ``GdkEventSequence`` that made gesture recognition to finish .. method:: sequence_state_changed(sequence: ~gi.repository.Gdk.EventSequence | None, state: ~gi.repository.Gtk.EventSequenceState) -> None Emitted whenever a sequence state changes. See :obj:`~gi.repository.Gtk.Gesture.set_sequence_state` to know more about the expectable sequence lifetimes. :param sequence: the ``GdkEventSequence`` that was cancelled :param state: the new sequence state .. method:: update(sequence: ~gi.repository.Gdk.EventSequence | None = None) -> None Emitted whenever an event is handled while the gesture is recognized. ``sequence`` is guaranteed to pertain to the set of active touches. :param sequence: the ``GdkEventSequence`` that was updated