Gtk.Gesture¶

Subclasses:: Gtk.GestureRotate, Gtk.GestureSingle, Gtk.GestureZoom

Methods¶

Inherited:: Gtk.EventController (13), GObject.Object (37)
Structs:: GObject.ObjectClass (5)

	`get_bounding_box` ()
	`get_bounding_box_center` ()
	`get_device` ()
	`get_group` ()
	`get_last_event` (sequence)
	`get_last_updated_sequence` ()
	`get_point` (sequence)
	`get_sequence_state` (sequence)
	`get_sequences` ()
	`group` (gesture)
	`handles_sequence` (sequence)
	`is_active` ()
	`is_grouped_with` (other)
	`is_recognized` ()
	`set_sequence_state` (sequence, state)
	`set_state` (state)
	`ungroup` ()

Virtual Methods¶

Inherited:: GObject.Object (7)

Properties¶

Inherited:: Gtk.EventController (4)

Name	Type	Flags	Short Description
`n-points`	`int`	r/w/co

Signals¶

Inherited:: GObject.Object (1)

Name	Short Description
`begin`	Emitted when the gesture is recognized.
`cancel`	Emitted whenever a sequence is cancelled.
`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 [property`Gtk`.Gesture:n-points].
`sequence-state-changed`	Emitted whenever a sequence state changes.
`update`	Emitted whenever an event is handled while the gesture is recognized.

Fields¶

Inherited:: GObject.Object (1)

Class Details¶

class Gtk.Gesture(**kwargs)¶

Bases:: Gtk.EventController
Abstract:: Yes
Structure:: Gtk.GestureClass

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 None GdkEventSequence value for these).

The number of touches that a GtkGesture 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 GtkGesture subclasses.

A recognized gesture will then emit the following signals:

[signal`Gtk`.Gesture::begin] when the gesture is recognized.
[signal`Gtk`.Gesture::update], whenever an input event is processed.
[signal`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 [method`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 [method`Gtk`.Gesture.group]. Grouped gestures synchronize the state of sequences, so calling [method`Gtk`.Gesture.set_state] on one will effectively propagate the state throughout the group.

By default, all sequences start out in the 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 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 Gtk.EventSequenceState.CLAIMED state, the gesture group will grab all interaction on the sequence, by:

Setting the same sequence to Gtk.EventSequenceState.DENIED on every other gesture group within the widget, and every gesture on parent widgets in the propagation chain.
Emitting [signal`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.EventSequenceState.CLAIMED on Gdk.EventType.TOUCH_BEGIN/Gdk.EventType.BUTTON_PRESS (so those events are captured before reaching the event widget, this implies Gtk.PropagationPhase.CAPTURE), one similar event will be emulated if the sequence changes to Gtk.EventSequenceState.DENIED. This way event coherence is preserved before event propagation is unstopped again.

Sequence states can’t be changed freely. See [method`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 Gtk.PropagationPhase.NONE, ensuring events of type Gdk.EventType.TOUCHPAD_SWIPE and Gdk.EventType.TOUCHPAD_PINCH are handled by the GtkGesture

get_bounding_box()[source]¶

Returns:

True if there are active touches, False otherwise

rect:: bounding box containing all active touches.

Return type:

(bool, rect: Gdk.Rectangle)

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

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.

get_bounding_box_center()[source]¶

Returns:

False if no active touches are present, True otherwise

x:: X coordinate for the bounding box center
y:: Y coordinate for the bounding box center

Return type:

(bool, x: float, y: float)

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

Otherwise, False will be returned.

get_device()[source]¶

Returns:: a GdkDevice
Return type:: Gdk.Device or None

Returns the logical GdkDevice that is currently operating on self.

This returns None if the gesture is not being interacted.

get_group()[source]¶

Returns:: The list of ``GtkGesture``s, free with g_list_free()
Return type:: [Gtk.Gesture]

Returns all gestures in the group of self

get_last_event(sequence)[source]¶

Parameters:: sequence (Gdk.EventSequence or None) – a GdkEventSequence
Returns:: The last event from sequence
Return type:: Gdk.Event or 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 self. If in doubt, you should make a copy of the event.

get_last_updated_sequence()[source]¶

Returns:: The last updated sequence
Return type:: Gdk.EventSequence or None

Returns the GdkEventSequence that was last updated on self.

get_point(sequence)[source]¶

Parameters:

sequence (Gdk.EventSequence or None) – a GdkEventSequence, or None for pointer events

Returns:

True if sequence is currently interpreted

x:: return location for X axis of the sequence coordinates
y:: return location for Y axis of the sequence coordinates

Return type:

(bool, x: float, y: float)

If sequence is currently being interpreted by self, 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.

get_sequence_state(sequence)[source]¶

Parameters:: sequence (Gdk.EventSequence) – a GdkEventSequence
Returns:: The sequence state in self
Return type:: Gtk.EventSequenceState

Returns the sequence state, as seen by self.

get_sequences()[source]¶

Returns:: A list of GdkEventSequence, the list elements are owned by GTK and must not be freed or modified, the list itself must be deleted through g_list_free()
Return type:: [Gdk.EventSequence]

Returns the list of GdkEventSequences currently being interpreted by self.

group(gesture)[source]¶

Parameters:: gesture (Gtk.Gesture) – a GtkGesture

Adds gesture to the same group than self.

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 [method`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 Gtk.EventSequenceState.CLAIMED on one group, every other gesture group attached to the same GtkWidget will switch the state for that sequence to Gtk.EventSequenceState.DENIED.

handles_sequence(sequence)[source]¶

Parameters:: sequence (Gdk.EventSequence or None) – a GdkEventSequence
Returns:: True if self is handling sequence, False otherwise
Return type:: bool

Returns True if self is currently handling events corresponding to sequence.

is_active()[source]¶

Returns:: True if gesture is active
Return type:: bool

Returns True if the gesture is currently active.

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

is_grouped_with(other)[source]¶

Parameters:: other (Gtk.Gesture) – another GtkGesture
Returns:: whether the gestures are grouped
Return type:: bool

Returns True if both gestures pertain to the same group.

is_recognized()[source]¶

Returns:: True if gesture is recognized
Return type:: bool

Returns True if the gesture is currently recognized.

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

set_sequence_state(sequence, state)[source]¶

Parameters:

sequence (Gdk.EventSequence) – a GdkEventSequence
state (Gtk.EventSequenceState) – the sequence state

Returns:

True if sequence is handled by self, and the state is changed successfully

Return type:

bool

Sets the state of sequence in self.

Sequences start in state Gtk.EventSequenceState.NONE, and whenever they change state, they can never go back to that state. Likewise, sequences in state 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 [signal`Gtk`.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:

```c static void first_gesture_begin_cb (Gtk.Gesture *first_gesture, Gdk.EventSequence *sequence, object user_data) { Gtk.Gesture.set_sequence_state (first_gesture, sequence, Gtk.EventSequenceState.CLAIMED); Gtk.Gesture.set_sequence_state (second_gesture, sequence, Gtk.EventSequenceState.DENIED); }

static void second_gesture_begin_cb (Gtk.Gesture *second_gesture, Gdk.EventSequence *sequence, object user_data) { if (Gtk.Gesture.get_sequence_state (first_gesture, sequence) == Gtk.EventSequenceState.CLAIMED) Gtk.Gesture.set_sequence_state (second_gesture, sequence, Gtk.EventSequenceState.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 since version 4.10.: Use [method`Gtk`.Gesture.set_state]

set_state(state)[source]¶

Parameters:: state (Gtk.EventSequenceState) – the sequence state
Returns:: True if the state of at least one sequence was changed successfully
Return type:: bool

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

Sequences start in state Gtk.EventSequenceState.NONE, and whenever they change state, they can never go back to that state. Likewise, sequences in state 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 [signal`Gtk`.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:

```c static void first_gesture_begin_cb (Gtk.Gesture *first_gesture, Gdk.EventSequence *sequence, object user_data) { Gtk.Gesture.set_state (first_gesture, Gtk.EventSequenceState.CLAIMED); Gtk.Gesture.set_state (second_gesture, Gtk.EventSequenceState.DENIED); }

static void second_gesture_begin_cb (Gtk.Gesture *second_gesture, Gdk.EventSequence *sequence, object user_data) { if (Gtk.Gesture.get_sequence_state (first_gesture, sequence) == Gtk.EventSequenceState.CLAIMED) Gtk.Gesture.set_state (second_gesture, Gtk.EventSequenceState.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.

ungroup()[source]¶: Separates self into an isolated group.

Signal Details¶

Gtk.Gesture.signals.begin(gesture, sequence)¶

Signal Name:

begin

Flags:

RUN_LAST

Parameters:

gesture (Gtk.Gesture) – The object which received the signal
sequence (Gdk.EventSequence or None) – the GdkEventSequence that made the gesture to be recognized

Emitted when the gesture is recognized.

This means the number of touch sequences matches [property`Gtk`.Gesture: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.

Gtk.Gesture.signals.cancel(gesture, sequence)¶

Signal Name:

cancel

Flags:

RUN_LAST

Parameters:

gesture (Gtk.Gesture) – The object which received the signal
sequence (Gdk.EventSequence or None) – the GdkEventSequence that was cancelled

Emitted whenever a sequence is cancelled.

This usually happens on active touches when [method`Gtk`.EventController.reset] is called on gesture (manually, due to grabs…), or the individual sequence was claimed by parent widgets’ controllers (see [method`Gtk`.Gesture.set_sequence_state]).

gesture must forget everything about sequence as in response to this signal.

Gtk.Gesture.signals.end(gesture, sequence)¶

Signal Name:

end

Flags:

RUN_LAST

Parameters:

gesture (Gtk.Gesture) – The object which received the signal
sequence (Gdk.EventSequence or None) – the GdkEventSequence that made gesture recognition to finish

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 [property`Gtk`.Gesture: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 [property`Gtk`.Gesture:n-points]). This situation may be detected by checking through [method`Gtk`.Gesture.handles_sequence].

Gtk.Gesture.signals.sequence_state_changed(gesture, sequence, state)¶

Signal Name:

sequence-state-changed

Flags:

RUN_LAST

Parameters:

gesture (Gtk.Gesture) – The object which received the signal
sequence (Gdk.EventSequence or None) – the GdkEventSequence that was cancelled
state (Gtk.EventSequenceState) – the new sequence state

Emitted whenever a sequence state changes.

See [method`Gtk`.Gesture.set_sequence_state] to know more about the expectable sequence lifetimes.

Gtk.Gesture.signals.update(gesture, sequence)¶

Signal Name:

update

Flags:

RUN_LAST

Parameters:

gesture (Gtk.Gesture) – The object which received the signal
sequence (Gdk.EventSequence or None) – the GdkEventSequence that was updated

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

sequence is guaranteed to pertain to the set of active touches.

Property Details¶

Gtk.Gesture.props.n_points¶

Name:: n-points
Type:: int
Default Value:: 1
Flags:: READABLE, WRITABLE, CONSTRUCT_ONLY

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