class Gtk::Gesture

• Gtk::Gesture
• Gtk::EventController
• GObject::Object
• Reference
• Object

Overview

Gtk::Gesture is the base class for gesture recognition.

Although Gtk::Gesture 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 nil Gdk::EventSequence value for these).

The number of touches that a Gtk::Gesture need to be recognized is controlled by the [property@Gtk.Gesture: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 Gtk::Gesture subclasses.

A recognized gesture will then emit the following signals:

• Gtk::Gesture::#begin when the gesture is recognized.
• Gtk::Gesture::#update, whenever an input event is processed.
• Gtk::Gesture::#end when the gesture is no longer recognized.

Event propagation

In order to receive events, a gesture needs to set a propagation phase through Gtk::EventController#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 Gtk::Gestures, 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 Gdk::EventSequences triggering those.

Within a widget, gestures can be grouped through Gtk::Gesture#group. Grouped gestures synchronize the state of sequences, so calling Gtk::Gesture#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 Gtk::Gesture::#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 be 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#sequence_state= to know about the possible lifetimes of a Gdk::EventSequence.

Touchpad gestures

On the platforms that support it, Gtk::Gesture will handle transparently touchpad gesture events. The only precautions users of Gtk::Gesture 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 Gtk::Gesture

Direct Known Subclasses

• Gtk::GestureRotate
• Gtk::GestureSingle
• Gtk::GestureZoom

Defined in:

Constructors

• .new

  Initialize a new Gesture.

• .new(*, n_points : UInt32 | Nil = nil, name : String | Nil = nil, propagation_limit : Gtk::PropagationLimit | Nil = nil, propagation_phase : Gtk::PropagationPhase | Nil = nil, widget : Gtk::Widget | Nil = nil)

Class Method Summary

• .g_type : UInt64

  Returns the type id (GType) registered in GLib type system.

Instance Method Summary

• #==(other : self)

  Returns true if this reference is the same as other.

• #begin_signal
• #bounding_box : Gdk::Rectangle

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

• #bounding_box_center(x : Float64, y : Float64) : Bool

  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.

• #cancel_signal
• #device : Gdk::Device | Nil

  Returns the logical Gdk::Device that is currently operating on gesture.

• #end_signal
• #group(gesture : Gtk::Gesture) : Nil

  Adds gesture to the same group than group_gesture.

• #group : GLib::List

  Returns all gestures in the group of gesture

• #handles_sequence(sequence : Gdk::EventSequence | Nil) : Bool

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

• #hash(hasher)

  See Object#hash(hasher)

• #is_active : Bool

  Returns true if the gesture is currently active.

• #is_grouped_with(other : Gtk::Gesture) : Bool

  Returns true if both gestures pertain to the same group.

• #is_recognized : Bool

  Returns true if the gesture is currently recognized.

• #last_event(sequence : Gdk::EventSequence | Nil) : Gdk::Event | Nil

  Returns the last event that was processed for sequence.

• #last_updated_sequence : Gdk::EventSequence | Nil

  Returns the Gdk::EventSequence that was last updated on gesture.

• #n_points : UInt32
• #n_points=(value : UInt32) : UInt32
• #point(sequence : Gdk::EventSequence | Nil) : Bool

  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.

• #sequence_state(sequence : Gdk::EventSequence) : Gtk::EventSequenceState

  Returns the sequence state, as seen by gesture.

• #sequence_state_changed_signal
• #sequences : GLib::List

  Returns the list of Gdk::EventSequences currently being interpreted by gesture.

• #set_sequence_state(sequence : Gdk::EventSequence, state : Gtk::EventSequenceState) : Bool

  Sets the state of sequence in gesture.

• #state=(state : Gtk::EventSequenceState) : Bool

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

• #ungroup : Nil

  Separates gesture into an isolated group.

• #update_signal

Constructor Detail

Class Method Detail

Instance Method Detail

static void
first_gesture_begin_cb (Gtk::Gesture       *first_gesture,
                        Gdk::EventSequence *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 (Gtk::Gesture       *second_gesture,
                         Gdk::EventSequence *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);
}