Class

GtkGesture

Description [src]

abstract class Gtk.Gesture : Gtk.EventController {
  /* No available fields */
}

GtkGesture is the base object for gesture recognition, although this object 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 NULL GdkEventSequence value for these).

The number of touches that a GtkGesture need to be recognized is controlled by the GtkGesture:n-points property, if a gesture is keeping track of less or more than that number of sequences, it won’t check wether the gesture is recognized.

As soon as the gesture has the expected number of touches, the gesture will run the GtkGesture::check signal regularly on input events until the gesture is recognized, the criteria to consider a gesture as “recognized” is left to GtkGesture subclasses.

A recognized gesture will then emit the following signals: - GtkGesture::begin when the gesture is recognized. - A number of GtkGesture::update, whenever an input event is processed. - GtkGesture::end when the gesture is no longer recognized.

Event propagation

In order to receive events, a gesture needs to either set a propagation phase through gtk_event_controller_set_propagation_phase(), or feed those manually through gtk_event_controller_handle_event().

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.

After the capture phase, GTK+ emits the traditional GtkWidget::button-press-event, GtkWidget::button-release-event, GtkWidget::touch-event, etc signals. Gestures with the GTK_PHASE_TARGET phase are fed events from the default GtkWidget::event handlers.

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 # {#touch-sequence-states}

Whenever input interaction happens, a single event may trigger a cascade of GtkGestures, 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 GdkEventSequences triggering those.

Within a widget, gestures can be grouped through gtk_gesture_group(), grouped gestures synchronize the state of sequences, so calling gtk_gesture_set_sequence_state() on one will effectively propagate the state throughout the group.

By default, all sequences start out in the #GTK_EVENT_SEQUENCE_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 #GTK_EVENT_SEQUENCE_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 #GTK_EVENT_SEQUENCE_CLAIMED state, the gesture group will grab all interaction on the sequence, by: - Setting the same sequence to #GTK_EVENT_SEQUENCE_DENIED on every other gesture group within the widget, and every gesture on parent widgets in the propagation chain. - calling GtkGesture::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 #GTK_EVENT_SEQUENCE_CLAIMED on

GDK_TOUCH_BEGIN/#GDK_BUTTON_PRESS (so those events are captured before

reaching the event widget, this implies #GTK_PHASE_CAPTURE), one similar event will emulated if the sequence changes to #GTK_EVENT_SEQUENCE_DENIED. This way event coherence is preserved before event propagation is unstopped again.

Sequence states can’t be changed freely, see gtk_gesture_set_sequence_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: - Enabling GDK_TOUCHPAD_GESTURE_MASK on their GdkWindows - If the gesture has GTK_PHASE_NONE, ensuring events of type GDK_TOUCHPAD_SWIPE and GDK_TOUCHPAD_PINCH are handled by the GtkGesture.

Hierarchy

hierarchy this GtkGesture ancestor_0 GtkEventController ancestor_0--this ancestor_1 GObject ancestor_1--ancestor_0

Instance methods

gtk_gesture_get_bounding_box

If there are touch sequences being currently handled by gesture, this function returns TRUE and fills in rect with the bounding box containing all active touches. Otherwise, FALSE will be returned.

Available since: 3.14

gtk_gesture_get_bounding_box_center

If there are touch sequences being currently handled by gesture, this function returns TRUE and fills in x and y with the center of the bounding box containing all active touches. Otherwise, FALSE will be returned.

Available since: 3.14

gtk_gesture_get_device

Returns the master GdkDevice that is currently operating on gesture, or NULL if the gesture is not being interacted.

Available since: 3.14

gtk_gesture_get_group

Returns all gestures in the group of gesture.

Available since: 3.14

gtk_gesture_get_last_event

Returns the last event that was processed for sequence.

gtk_gesture_get_last_updated_sequence

Returns the GdkEventSequence that was last updated on gesture.

Available since: 3.14

gtk_gesture_get_point

If sequence is currently being interpreted by gesture, this function returns 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.

Available since: 3.14

gtk_gesture_get_sequence_state

Returns the sequence state, as seen by gesture.

Available since: 3.14

gtk_gesture_get_sequences

Returns the list of GdkEventSequences currently being interpreted by gesture.

Available since: 3.14

gtk_gesture_get_window

Returns the user-defined window that receives the events handled by gesture. See gtk_gesture_set_window() for more information.

Available since: 3.14

gtk_gesture_group

Adds gesture to the same group than group_gesture. Gestures are by default isolated in their own groups.

Available since: 3.14

gtk_gesture_handles_sequence

Returns TRUE if gesture is currently handling events corresponding to sequence.

Available since: 3.14

gtk_gesture_is_active

Returns TRUE if the gesture is currently active. A gesture is active meanwhile there are touch sequences interacting with it.

Available since: 3.14

gtk_gesture_is_grouped_with

Returns TRUE if both gestures pertain to the same group.

Available since: 3.14

gtk_gesture_is_recognized

Returns TRUE if the gesture is currently recognized. A gesture is recognized if there are as many interacting touch sequences as required by gesture, and GtkGesture::check returned TRUE for the sequences being currently interpreted.

Available since: 3.14

gtk_gesture_set_sequence_state

Sets the state of sequence in gesture. 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:

Available since: 3.14

gtk_gesture_set_state

Sets the state of all sequences that gesture is currently interacting with. See gtk_gesture_set_sequence_state() for more details on sequence states.

Available since: 3.14

gtk_gesture_set_window

Sets a specific window to receive events about, so gesture will effectively handle only events targeting window, or a child of it. window must pertain to gtk_event_controller_get_widget().

Available since: 3.14

gtk_gesture_ungroup

Separates gesture into an isolated group.

Available since: 3.14

Methods inherited from GtkEventController (5)
gtk_event_controller_get_propagation_phase

Gets the propagation phase at which controller handles events.

Available since: 3.14

gtk_event_controller_get_widget

Returns the GtkWidget this controller relates to.

Available since: 3.14

gtk_event_controller_handle_event

Feeds an events into controller, so it can be interpreted and the controller actions triggered.

Available since: 3.14

gtk_event_controller_reset

Resets the controller to a clean state. Every interaction the controller did through GtkEventController::handle-event will be dropped at this point.

Available since: 3.14

gtk_event_controller_set_propagation_phase

Sets the propagation phase at which a controller handles events.

Available since: 3.14

Methods inherited from GObject (42)

Properties

Gtk.Gesture:n-points

The number of touch points that trigger recognition on this gesture,

Available since: 3.14

Gtk.Gesture:window

If non-NULL, the gesture will only listen for events that happen on this GdkWindow, or a child of it.

Available since: 3.14

Properties inherited from GtkEventController (2)
Gtk.EventController:propagation-phase

The propagation phase at which this controller will handle events.

Available since: 3.14

Gtk.EventController:widget

The widget receiving the GdkEvents that the controller will handle.

Available since: 3.14

Signals

Gtk.Gesture::begin

This signal is emitted when the gesture is recognized. This means the number of touch sequences matches GtkGesture:n-points, and the GtkGesture::check handler(s) returned TRUE.

Available since: 3.14

Gtk.Gesture::cancel

This signal is emitted whenever a sequence is cancelled. This usually happens on active touches when gtk_event_controller_reset() is called on gesture (manually, due to grabs…), or the individual sequence was claimed by parent widgets’ controllers (see gtk_gesture_set_sequence_state()).

Available since: 3.14

Gtk.Gesture::end

This signal is emitted when gesture either stopped recognizing the event sequences as something to be handled (the GtkGesture::check handler returned FALSE), or the number of touch sequences became higher or lower than GtkGesture:n-points.

Available since: 3.14

Gtk.Gesture::sequence-state-changed

This signal is emitted whenever a sequence state changes. See gtk_gesture_set_sequence_state() to know more about the expectable sequence lifetimes.

Available since: 3.14

Gtk.Gesture::update

This signal is emitted whenever an event is handled while the gesture is recognized. sequence is guaranteed to pertain to the set of active touches.

Available since: 3.14

Signals inherited from GObject (1)

Class structure

struct GtkGestureClass {
  /* no available fields */
}