Class

GtkGesture

Description [src]

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

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 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 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:

Event propagation

In order to receive events, a gesture needs to set a propagation phase through gtk_event_controller_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 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.
  • Emitting 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:

  • 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

Ancestors

Instance methods

gtk_gesture_get_bounding_box

If there are touch sequences being currently handled by gesture, returns TRUE and fills in rect with the bounding box containing all active touches.

gtk_gesture_get_bounding_box_center

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

gtk_gesture_get_device

Returns the logical GdkDevice that is currently operating on gesture.

gtk_gesture_get_group

Returns all gestures in the group of gesture.

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.

gtk_gesture_get_point

If sequence is currently being interpreted by gesture, returns TRUE and fills in x and y with the last coordinates stored for that event sequence.

gtk_gesture_get_sequence_state

Returns the sequence state, as seen by gesture.

gtk_gesture_get_sequences

Returns the list of GdkEventSequences currently being interpreted by gesture.

gtk_gesture_group

Adds gesture to the same group than group_gesture.

gtk_gesture_handles_sequence

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

gtk_gesture_is_active

Returns TRUE if the gesture is currently active.

gtk_gesture_is_grouped_with

Returns TRUE if both gestures pertain to the same group.

gtk_gesture_is_recognized

Returns TRUE if the gesture is currently recognized.

gtk_gesture_set_sequence_state

Sets the state of sequence in gesture.

gtk_gesture_set_state

Sets the state of all sequences that gesture is currently interacting with.

gtk_gesture_ungroup

Separates gesture into an isolated group.

Methods inherited from GtkEventController (12)
gtk_event_controller_get_current_event

Returns the event that is currently being handled by the controller.

gtk_event_controller_get_current_event_device

Returns the device of the event that is currently being handled by the controller.

gtk_event_controller_get_current_event_state

Returns the modifier state of the event that is currently being handled by the controller.

gtk_event_controller_get_current_event_time

Returns the timestamp of the event that is currently being handled by the controller.

gtk_event_controller_get_name

Gets the name of controller.

gtk_event_controller_get_propagation_limit

Gets the propagation limit of the event controller.

gtk_event_controller_get_propagation_phase

Gets the propagation phase at which controller handles events.

gtk_event_controller_get_widget

Returns the GtkWidget this controller relates to.

gtk_event_controller_reset

Resets the controller to a clean state.

gtk_event_controller_set_name

Sets a name on the controller that can be used for debugging.

gtk_event_controller_set_propagation_limit

Sets the event propagation limit on the event controller.

gtk_event_controller_set_propagation_phase

Sets the propagation phase at which a controller handles events.

Properties

Gtk.Gesture:n-points

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

Properties inherited from GtkEventController (4)
Gtk.EventController:name

The name for this controller, typically used for debugging purposes.

Gtk.EventController:propagation-limit

The limit for which events this controller will handle.

Gtk.EventController:propagation-phase

The propagation phase at which this controller will handle events.

Gtk.EventController:widget

The widget receiving the GdkEvents that the controller will handle.

Signals

Gtk.Gesture::begin

Emitted when the gesture is recognized.

Gtk.Gesture::cancel

Emitted whenever a sequence is cancelled.

Gtk.Gesture::end

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 GtkGesture:n-points.

Gtk.Gesture::sequence-state-changed

Emitted whenever a sequence state changes.

Gtk.Gesture::update

Emitted whenever an event is handled while the gesture is recognized.

Class structure

struct GtkGestureClass {
  /* no available fields */
}