GestureProtocol

public protocol GestureProtocol : EventControllerProtocol

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 nil GdkEventSequence value for these).

The number of touches that a GtkGesture need to be recognized is controlled by the [propertyGtk.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:

[signalGtk.Gesture::begin] when the gesture is recognized.
[signalGtk.Gesture::update], whenever an input event is processed.
[signalGtk.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 [methodGtk.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 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 [methodGtk.Gesture.group]. Grouped gestures synchronize the state of sequences, so calling [methodGtk.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 [signalGtk.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 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 [methodGtk.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

The GestureProtocol protocol exposes the methods and properties of an underlying GtkGesture instance. The default implementation of these can be found in the protocol extension below. For a concrete class that implements these methods and properties, see Gesture. Alternatively, use GestureRef as a lighweight, unowned reference if you already have an instance you just want to use.

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ptr
Untyped pointer to the underlying GtkGesture instance.
Declaration
Swift

var ptr: UnsafeMutableRawPointer! { get }
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gesture_ptr Default implementation
Typed pointer to the underlying GtkGesture instance.

Default Implementation

Return the stored, untyped pointer as a typed pointer to the GtkGesture instance.
Declaration
Swift

var gesture_ptr: UnsafeMutablePointer<GtkGesture>! { get }
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init(raw:)
Required Initialiser for types conforming to GestureProtocol
Declaration
Swift

init(raw: UnsafeMutableRawPointer)
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Gesture Class


                    
                    
                    bind(property:to:_:flags:transformFrom:transformTo:)

Extension method

Bind a GesturePropertyName source property to a given target object.

Declaration

Swift

@discardableResult
@inlinable
func bind<Q, T>(property source_property: GesturePropertyName, to target: T, _ target_property: Q, flags f: BindingFlags = .default, transformFrom transform_from: @escaping GLibObject.ValueTransformer = { $0.transform(destValue: $1) }, transformTo transform_to: @escaping GLibObject.ValueTransformer = { $0.transform(destValue: $1) }) -> BindingRef! where Q : PropertyNameProtocol, T : ObjectProtocol

Parameters

`source_property`	the source property to bind
`target`	the target object to bind to
`target_property`	the target property to bind to
`flags`	the flags to pass to the `Binding`
`transform_from`	`ValueTransformer` to use for forward transformation
`transform_to`	`ValueTransformer` to use for backwards transformation

Return Value

binding reference or nil in case of an error

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                    get(property:)

Extension method

Get the value of a Gesture property

Declaration

Swift

@inlinable
func get(property: GesturePropertyName) -> GLibObject.Value

Parameters


                                property

the property to get the value for

Return Value

the value of the named property

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                    set(property:value:)

Extension method

Set the value of a Gesture property. Note that this will only have an effect on properties that are writable and not construct-only!

Declaration

Swift

@inlinable
func set(property: GesturePropertyName, value v: GLibObject.Value)

Parameters


                                property

the property to get the value for

Return Value

the value of the named property

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Gesture signals


                    
                    
                    connect(signal:flags:handler:)

Extension method

Connect a Swift signal handler to the given, typed GestureSignalName signal

Declaration

Swift

@discardableResult
@inlinable
func connect(signal s: GestureSignalName, flags f: ConnectFlags = ConnectFlags(0), handler h: @escaping SignalHandler) -> Int

Parameters

`signal`	The signal to connect
`flags`	The connection flags to use
`data`	A pointer to user data to provide to the callback
`destroyData`	A `GClosureNotify` C function to destroy the data pointed to by `userData`
`handler`	The Swift signal handler (function or callback) to invoke on the given signal

Return Value

The signal handler ID (always greater than 0 for successful connections)

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                    connect(signal:flags:data:destroyData:signalHandler:)

Extension method

Connect a C signal handler to the given, typed GestureSignalName signal

Declaration

Swift

@discardableResult
@inlinable
func connect(signal s: GestureSignalName, flags f: ConnectFlags = ConnectFlags(0), data userData: gpointer!, destroyData destructor: GClosureNotify? = nil, signalHandler h: @escaping GCallback) -> Int

Parameters

`signal`	The signal to connect
`flags`	The connection flags to use
`data`	A pointer to user data to provide to the callback
`destroyData`	A `GClosureNotify` C function to destroy the data pointed to by `userData`
`signalHandler`	The C function to be called on the given signal

Return Value

The signal handler ID (always greater than 0 for successful connections)

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                    onBegin(flags:handler:)

Extension method

Emitted when the gesture is recognized.

This means the number of touch sequences matches [propertyGtk.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.

Note

This represents the underlying begin signal

Declaration

Swift

@discardableResult
@inlinable
func onBegin(flags: ConnectFlags = ConnectFlags(0), handler: @escaping (_ unownedSelf: GestureRef, _ sequence: Gdk.EventSequenceRef?) -> Void) -> Int

Parameters

`flags`	Flags
`unownedSelf`	Reference to instance of self
`sequence`	the `GdkEventSequence` that made the gesture to be recognized
`handler`	The signal handler to call Run the given callback whenever the `begin` signal is emitted

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beginSignal Extension method
Typed begin signal for using the connect(signal:) methods
Declaration
Swift

static var beginSignal: GestureSignalName { get }
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                    onCancel(flags:handler:)

Extension method

Emitted whenever a sequence is cancelled.

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

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

Note

This represents the underlying cancel signal

Declaration

Swift

@discardableResult
@inlinable
func onCancel(flags: ConnectFlags = ConnectFlags(0), handler: @escaping (_ unownedSelf: GestureRef, _ sequence: Gdk.EventSequenceRef?) -> Void) -> Int

Parameters

`flags`	Flags
`unownedSelf`	Reference to instance of self
`sequence`	the `GdkEventSequence` that was cancelled
`handler`	The signal handler to call Run the given callback whenever the `cancel` signal is emitted

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cancelSignal Extension method
Typed cancel signal for using the connect(signal:) methods
Declaration
Swift

static var cancelSignal: GestureSignalName { get }
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                    onEnd(flags:handler:)

Extension method

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 [propertyGtk.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 [propertyGtk.Gesture:n-points]). This situation may be detected by checking through [methodGtk.Gesture.handles_sequence].

Note

This represents the underlying end signal

Declaration

Swift

@discardableResult
@inlinable
func onEnd(flags: ConnectFlags = ConnectFlags(0), handler: @escaping (_ unownedSelf: GestureRef, _ sequence: Gdk.EventSequenceRef?) -> Void) -> Int

Parameters

`flags`	Flags
`unownedSelf`	Reference to instance of self
`sequence`	the `GdkEventSequence` that made gesture recognition to finish
`handler`	The signal handler to call Run the given callback whenever the `end` signal is emitted

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endSignal Extension method
Typed end signal for using the connect(signal:) methods
Declaration
Swift

static var endSignal: GestureSignalName { get }
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                    onSequenceStateChanged(flags:handler:)

Extension method

Emitted whenever a sequence state changes.

See [methodGtk.Gesture.set_sequence_state] to know more about the expectable sequence lifetimes.

Note

This represents the underlying sequence-state-changed signal

Declaration

Swift

@discardableResult
@inlinable
func onSequenceStateChanged(flags: ConnectFlags = ConnectFlags(0), handler: @escaping (_ unownedSelf: GestureRef, _ sequence: Gdk.EventSequenceRef?, _ state: EventSequenceState) -> Void) -> Int

Parameters

`flags`	Flags
`unownedSelf`	Reference to instance of self
`sequence`	the `GdkEventSequence` that was cancelled
`state`	the new sequence state
`handler`	The signal handler to call Run the given callback whenever the `sequenceStateChanged` signal is emitted

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sequenceStateChangedSignal Extension method
Typed sequence-state-changed signal for using the connect(signal:) methods
Declaration
Swift

static var sequenceStateChangedSignal: GestureSignalName { get }
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                    onUpdate(flags:handler:)

Extension method

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

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

Note

This represents the underlying update signal

Declaration

Swift

@discardableResult
@inlinable
func onUpdate(flags: ConnectFlags = ConnectFlags(0), handler: @escaping (_ unownedSelf: GestureRef, _ sequence: Gdk.EventSequenceRef?) -> Void) -> Int

Parameters

`flags`	Flags
`unownedSelf`	Reference to instance of self
`sequence`	the `GdkEventSequence` that was updated
`handler`	The signal handler to call Run the given callback whenever the `update` signal is emitted

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updateSignal Extension method
Typed update signal for using the connect(signal:) methods
Declaration
Swift

static var updateSignal: GestureSignalName { get }
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                    onNotifyNPoints(flags:handler:)

Extension method

The notify signal is emitted on an object when one of its properties has its value set through g_object_set_property(), g_object_set(), et al.

Note that getting this signal doesn’t itself guarantee that the value of the property has actually changed. When it is emitted is determined by the derived GObject class. If the implementor did not create the property with G_PARAM_EXPLICIT_NOTIFY, then any call to g_object_set_property() results in notify being emitted, even if the new value is the same as the old. If they did pass G_PARAM_EXPLICIT_NOTIFY, then this signal is emitted only when they explicitly call g_object_notify() or g_object_notify_by_pspec(), and common practice is to do that only when the value has actually changed.

This signal is typically used to obtain change notification for a single property, by specifying the property name as a detail in the g_signal_connect() call, like this:

(C Language Example):

g_signal_connect (text_view->buffer, "notify::paste-target-list",
                  G_CALLBACK (gtk_text_view_target_list_notify),
                  text_view)

It is important to note that you must use canonical parameter names as detail strings for the notify signal.

Note

This represents the underlying notify::n-points signal

Declaration

Swift

@discardableResult
@inlinable
func onNotifyNPoints(flags: ConnectFlags = ConnectFlags(0), handler: @escaping (_ unownedSelf: GestureRef, _ pspec: ParamSpecRef) -> Void) -> Int

Parameters

`flags`	Flags
`unownedSelf`	Reference to instance of self
`pspec`	the `GParamSpec` of the property which changed.
`handler`	The signal handler to call Run the given callback whenever the `notifyNPoints` signal is emitted

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notifyNPointsSignal Extension method
Typed notify::n-points signal for using the connect(signal:) methods
Declaration
Swift

static var notifyNPointsSignal: GestureSignalName { get }
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Gesture Class: GestureProtocol extension (methods and fields)

getBoundingBox(rect:) Extension method
If there are touch sequences being currently handled by gesture, 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.
Declaration
Swift

@inlinable func getBoundingBox<RectangleT>(rect: RectangleT) -> Bool where RectangleT : RectangleProtocol
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getBoundingBoxCenter(x:y:) Extension method
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.

Otherwise, false will be returned.
Declaration
Swift

@inlinable func getBoundingBoxCenter(x: UnsafeMutablePointer<CDouble>!, y: UnsafeMutablePointer<CDouble>!) -> Bool
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getDevice() Extension method
Returns the logical GdkDevice that is currently operating on gesture.

This returns nil if the gesture is not being interacted.
Declaration
Swift

@inlinable func getDevice() -> Gdk.DeviceRef!
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getGroup() Extension method
Returns all gestures in the group of gesture
Declaration
Swift

@inlinable func getGroup() -> GLib.ListRef!
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getLastEvent(sequence:) Extension method
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.
Declaration
Swift

@inlinable func getLastEvent(sequence: Gdk.EventSequenceRef? = nil) -> Gdk.EventRef!
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getLastEvent(sequence:) Extension method
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.
Declaration
Swift

@inlinable func getLastEvent<EventSequenceT>(sequence: EventSequenceT?) -> Gdk.EventRef! where EventSequenceT : EventSequenceProtocol
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getLastUpdatedSequence() Extension method
Returns the GdkEventSequence that was last updated on gesture.
Declaration
Swift

@inlinable func getLastUpdatedSequence() -> Gdk.EventSequenceRef!
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getPoint(sequence:x:y:) Extension method
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.

The coordinates are always relative to the widget allocation.
Declaration
Swift

@inlinable func getPoint(sequence: Gdk.EventSequenceRef? = nil, x: UnsafeMutablePointer<CDouble>! = nil, y: UnsafeMutablePointer<CDouble>! = nil) -> Bool
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getPoint(sequence:x:y:) Extension method
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.

The coordinates are always relative to the widget allocation.
Declaration
Swift

@inlinable func getPoint<EventSequenceT>(sequence: EventSequenceT?, x: UnsafeMutablePointer<CDouble>! = nil, y: UnsafeMutablePointer<CDouble>! = nil) -> Bool where EventSequenceT : EventSequenceProtocol
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                    getSequenceState(sequence:)

Extension method

Returns the sequence state, as seen by gesture.

Declaration

Swift

@inlinable
func getSequenceState<EventSequenceT>(sequence: EventSequenceT) -> GtkEventSequenceState where EventSequenceT : EventSequenceProtocol

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getSequences() Extension method
Returns the list of GdkEventSequences currently being interpreted by gesture.
Declaration
Swift

@inlinable func getSequences() -> GLib.ListRef!
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getGroup(gesture:) Extension method
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 [methodGtk.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_EVENT_SEQUENCE_CLAIMED on one group, every other gesture group attached to the same GtkWidget will switch the state for that sequence to GTK_EVENT_SEQUENCE_DENIED.
Declaration
Swift

@inlinable func getGroup<GestureT>(gesture: GestureT) where GestureT : GestureProtocol
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handles(sequence:) Extension method
Returns true if gesture is currently handling events corresponding to sequence.
Declaration
Swift

@inlinable func handles(sequence: Gdk.EventSequenceRef? = nil) -> Bool
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handles(sequence:) Extension method
Returns true if gesture is currently handling events corresponding to sequence.
Declaration
Swift

@inlinable func handles<EventSequenceT>(sequence: EventSequenceT?) -> Bool where EventSequenceT : EventSequenceProtocol
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isGroupedWith(other:) Extension method
Returns true if both gestures pertain to the same group.
Declaration
Swift

@inlinable func isGroupedWith<GestureT>(other: GestureT) -> Bool where GestureT : GestureProtocol
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                    setSequenceState(sequence:state:)

Extension method

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:

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 [signalGtk.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:

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.

Declaration

Swift

@inlinable
func setSequenceState<EventSequenceT>(sequence: EventSequenceT, state: GtkEventSequenceState) -> Bool where EventSequenceT : EventSequenceProtocol

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set(state:) Extension method
Sets the state of all sequences that gesture is currently interacting with.

See [methodGtk.Gesture.set_sequence_state] for more details on sequence states.
Declaration
Swift

@inlinable func set(state: GtkEventSequenceState) -> Bool
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ungroup() Extension method
Separates gesture into an isolated group.
Declaration
Swift

@inlinable func ungroup()
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device Extension method
Returns the logical GdkDevice that is currently operating on gesture.

This returns nil if the gesture is not being interacted.
Declaration
Swift

@inlinable var device: Gdk.DeviceRef! { get }
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group Extension method
Returns all gestures in the group of gesture
Declaration
Swift

@inlinable var group: GLib.ListRef! { get }
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isActive Extension method
Returns true if the gesture is currently active.

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

@inlinable var isActive: Bool { get }
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isRecognized Extension method
Returns true if the gesture is currently recognized.

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

@inlinable var isRecognized: Bool { get }
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lastUpdatedSequence Extension method
Returns the GdkEventSequence that was last updated on gesture.
Declaration
Swift

@inlinable var lastUpdatedSequence: Gdk.EventSequenceRef! { get }
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sequences Extension method
Returns the list of GdkEventSequences currently being interpreted by gesture.
Declaration
Swift

@inlinable var sequences: GLib.ListRef! { get }
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GestureProtocol

Event propagation

States of a sequence

Touchpad gestures

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Default Implementation

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Gesture Class

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Gesture signals

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Gesture Class: GestureProtocol extension (methods and fields)

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