Package org.gnome.gtk

Class Gesture

java.lang.Object

org.javagi.base.ProxyInstance

org.gnome.gobject.TypeInstance

org.gnome.gobject.GObject

org.gnome.gtk.EventController

org.gnome.gtk.Gesture

All Implemented Interfaces:

Proxy

Direct Known Subclasses:

Gesture.Gesture$Impl, GestureRotate, GestureSingle, GestureZoom

@Generated("io.github.jwharm.JavaGI")
public abstract class Gesture
extends EventController

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 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:

• 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 EventController.setPropagationPhase(org.gnome.gtk.PropagationPhase).

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 group(org.gnome.gtk.Gesture). Grouped gestures synchronize the state of sequences, so calling setState(org.gnome.gtk.EventSequenceState) on one will effectively propagate the state throughout the group.

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

• Setting the same sequence to EventSequenceState.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 EventSequenceState.CLAIMED on EventType.TOUCH_BEGIN/EventType.BUTTON_PRESS (so those events are captured before reaching the event widget, this implies PropagationPhase.CAPTURE), one similar event will be emulated if the sequence changes to EventSequenceState.DENIED. This way event coherence is preserved before event propagation is unstopped again.

Sequence states can't be changed freely. See setState(org.gnome.gtk.EventSequenceState) 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 PropagationPhase.NONE, ensuring events of type EventType.TOUCHPAD_SWIPE and EventType.TOUCHPAD_PINCH are handled by the GtkGesture

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	Gesture.BeginCallback	Functional interface declaration of the BeginCallback callback.
static class	Gesture.Builder<B extends Gesture.Builder<B>>	Inner class implementing a builder pattern to construct a GObject with properties.
static interface	Gesture.CancelCallback	Functional interface declaration of the CancelCallback callback.
static interface	Gesture.EndCallback	Functional interface declaration of the EndCallback callback.
static class	Gesture.Gesture$Impl	The Gesture$Impl type represents a native instance of the abstract Gesture class.
static class	Gesture.GestureClass
static interface	Gesture.SequenceStateChangedCallback	Functional interface declaration of the SequenceStateChangedCallback callback.
static interface	Gesture.UpdateCallback	Functional interface declaration of the UpdateCallback callback.

Nested classes/interfaces inherited from class org.gnome.gtk.EventController

EventController.EventController$Impl, EventController.EventControllerClass

Nested classes/interfaces inherited from class org.gnome.gobject.GObject

GObject.NotifyCallback, GObject.ObjectClass

Constructor Summary

Constructors

Constructor	Description
Gesture()	Creates a new Gesture.
Gesture(MemorySegment address)	Create a Gesture proxy instance for the provided memory address.

Method Summary

Modifier and Type	Method	Description
protected Gesture	asParent()	Returns this instance as if it were its parent type.
void	emitBegin(@Nullable EventSequence sequence)	Emits the "begin" signal.
void	emitCancel(@Nullable EventSequence sequence)	Emits the "cancel" signal.
void	emitEnd(@Nullable EventSequence sequence)	Emits the "end" signal.
void	emitSequenceStateChanged(@Nullable EventSequence sequence, EventSequenceState state)	Emits the "sequence-state-changed" signal.
void	emitUpdate(@Nullable EventSequence sequence)	Emits the "update" signal.
boolean	getBoundingBox(Rectangle rect)	If there are touch sequences being currently handled by gesture, returns true and fills in rect with the bounding box containing all active touches.
boolean	getBoundingBoxCenter(Out<Double> x, Out<Double> y)	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.
@Nullable Device	getDevice()	Returns the logical GdkDevice that is currently operating on gesture.
List<Gesture>	getGroup()	Returns all gestures in the group of this Gesture
@Nullable Event	getLastEvent(@Nullable EventSequence sequence)	Returns the last event that was processed for sequence.
@Nullable EventSequence	getLastUpdatedSequence()	Returns the GdkEventSequence that was last updated on gesture.
boolean	getPoint(@Nullable EventSequence sequence, @Nullable Out<Double> x, @Nullable Out<Double> y)	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.
List<EventSequence>	getSequences()	Returns the list of GdkEventSequences currently being interpreted by gesture.
EventSequenceState	getSequenceState(EventSequence sequence)	Returns the sequence state, as seen by gesture.
static @Nullable Type	getType()	Get the GType of the Gesture class
void	group(Gesture gesture)	Adds gesture to the same group than groupGesture.
boolean	handlesSequence(@Nullable EventSequence sequence)	Returns true if this Gesture is currently handling events corresponding to sequence.
boolean	isActive()	Returns true if the gesture is currently active.
boolean	isGroupedWith(Gesture other)	Returns true if both gestures pertain to the same group.
boolean	isRecognized()	Returns true if the gesture is currently recognized.
SignalConnection<Gesture.BeginCallback>	onBegin(Gesture.BeginCallback handler)	Emitted when the gesture is recognized.
SignalConnection<Gesture.CancelCallback>	onCancel(Gesture.CancelCallback handler)	Emitted whenever a sequence is cancelled.
SignalConnection<Gesture.EndCallback>	onEnd(Gesture.EndCallback handler)	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 Gtk.Gesture:n-points.
SignalConnection<Gesture.SequenceStateChangedCallback>	onSequenceStateChanged(Gesture.SequenceStateChangedCallback handler)	Emitted whenever a sequence state changes.
SignalConnection<Gesture.UpdateCallback>	onUpdate(Gesture.UpdateCallback handler)	Emitted whenever an event is handled while the gesture is recognized.
boolean	setSequenceState(EventSequence sequence, EventSequenceState state)	Deprecated. Use setState(org.gnome.gtk.EventSequenceState)
boolean	setState(EventSequenceState state)	Sets the state of all sequences that this Gesture is currently interacting with.
void	ungroup()	Separates this Gesture into an isolated group.

Methods inherited from class org.gnome.gtk.EventController

getCurrentEvent, getCurrentEventDevice, getCurrentEventState, getCurrentEventTime, getName, getPropagationLimit, getPropagationPhase, getWidget, reset, setName, setPropagationLimit, setPropagationPhase, setStaticName

Methods inherited from class org.gnome.gobject.GObject

addToggleRef, addWeakPointer, bindProperty, bindProperty, bindProperty, bindPropertyFull, bindPropertyFull, bindPropertyWithClosures, bindPropertyWithClosures, builder, compatControl, connect, connect, connect, constructed, disconnect, dispatchPropertiesChanged, dispose, dupData, dupQdata, emit, emitNotify, finalize_, forceFloating, freezeNotify, get, getData, getMemoryLayout, getProperty, getProperty, getProperty, getQdata, getv, interfaceFindProperty, interfaceInstallProperty, interfaceListProperties, isFloating, newInstance, newInstance, newv, notify, notify, notifyByPspec, onNotify, ref, refSink, removeToggleRef, removeWeakPointer, replaceData, replaceQdata, runDispose, set, setData, setDataFull, setProperty, setProperty, setProperty, setQdata, setQdataFull, setv, stealData, stealQdata, takeRef, thawNotify, unref, watchClosure, weakRef, weakUnref, withProperties

Methods inherited from class org.gnome.gobject.TypeInstance

callParent, callParent, cast, getPrivate, readGClass, writeGClass

Methods inherited from class org.javagi.base.ProxyInstance

equals, handle, hashCode

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Details

Gesture

public Gesture(MemorySegment address)

Create a Gesture proxy instance for the provided memory address.

Parameters:

address - the memory address of the native object

Gesture

public Gesture()

Creates a new Gesture.

Method Details

getType

public static @Nullable Type getType()

Get the GType of the Gesture class

Returns:

the GType

asParent

protected Gesture asParent()

Returns this instance as if it were its parent type. This is mostly synonymous to the Java super keyword, but will set the native typeclass function pointers to the parent type. When overriding a native virtual method in Java, "chaining up" with super.methodName() doesn't work, because it invokes the overridden function pointer again. To chain up, call asParent().methodName(). This will call the native function pointer of this virtual method in the typeclass of the parent type.

Overrides:

asParent in class EventController

getBoundingBox

public boolean getBoundingBox(Rectangle rect)

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.

Parameters:

rect - bounding box containing all active touches.

Returns:

true if there are active touches, false otherwise

getBoundingBoxCenter

public boolean getBoundingBoxCenter(Out<Double> x,
 Out<Double> y)

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.

Parameters:

x - X coordinate for the bounding box center

y - Y coordinate for the bounding box center

Returns:

false if no active touches are present, true otherwise

getDevice

public @Nullable Device getDevice()

Returns the logical GdkDevice that is currently operating on gesture.

This returns null if the gesture is not being interacted.

Returns:

a GdkDevice

getGroup

public List<Gesture> getGroup()

Returns all gestures in the group of this Gesture

Returns:

The list of GtkGestures, free with g_list_free()

getLastEvent

public @Nullable Event getLastEvent(@Nullable EventSequence sequence)

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.

Parameters:

sequence - a GdkEventSequence

Returns:

The last event from sequence

getLastUpdatedSequence

public @Nullable EventSequence getLastUpdatedSequence()

Returns the GdkEventSequence that was last updated on gesture.

Returns:

The last updated sequence

getPoint

public boolean getPoint(@Nullable EventSequence sequence,
 @Nullable Out<Double> x,
 @Nullable Out<Double> y)

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.

Parameters:

sequence - a GdkEventSequence, or null for pointer events

x - return location for X axis of the sequence coordinates

y - return location for Y axis of the sequence coordinates

Returns:

true if sequence is currently interpreted

getSequenceState

public EventSequenceState getSequenceState(EventSequence sequence)

Returns the sequence state, as seen by gesture.

Parameters:

sequence - a GdkEventSequence

Returns:

The sequence state in this Gesture

getSequences

public List<EventSequence> getSequences()

Returns the list of GdkEventSequences currently being interpreted by gesture.

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()

group

public void group(Gesture gesture)

Adds gesture to the same group than groupGesture.

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 setSequenceState(org.gnome.gdk.EventSequence, org.gnome.gtk.EventSequenceState), 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 EventSequenceState.CLAIMED on one group, every other gesture group attached to the same GtkWidget will switch the state for that sequence to EventSequenceState.DENIED.

Parameters:

gesture - a GtkGesture

handlesSequence

public boolean handlesSequence(@Nullable EventSequence sequence)

Returns true if this Gesture is currently handling events corresponding to sequence.

Parameters:

sequence - a GdkEventSequence

Returns:

true if this Gesture is handling sequence, false otherwise

isActive

public boolean isActive()

Returns true if the gesture is currently active.

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

Returns:

true if gesture is active

isGroupedWith

public boolean isGroupedWith(Gesture other)

Returns true if both gestures pertain to the same group.

Parameters:

other - another GtkGesture

Returns:

whether the gestures are grouped

isRecognized

public boolean isRecognized()

Returns true if the gesture is currently recognized.

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

Returns:

true if gesture is recognized

setSequenceState

@Deprecated
public boolean setSequenceState(EventSequence sequence,
 EventSequenceState state)

Deprecated.

Use setState(org.gnome.gtk.EventSequenceState)

Sets the state of sequence in gesture.

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

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.

Parameters:

sequence - a GdkEventSequence

state - the sequence state

Returns:

true if sequence is handled by gesture, and the state is changed successfully

setState

public boolean setState(EventSequenceState state)

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

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

static void
 first_gesture_begin_cb (GtkGesture       *first_gesture,
                         GdkEventSequence *sequence,
                         gpointer          user_data)
 {
   gtk_gesture_set_state (first_gesture, GTK_EVENT_SEQUENCE_CLAIMED);
   gtk_gesture_set_state (second_gesture, 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_state (second_gesture, 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.

Parameters:

state - the sequence state

Returns:

true if the state of at least one sequence was changed successfully

ungroup

public void ungroup()

Separates this Gesture into an isolated group.

onBegin

public SignalConnection<Gesture.BeginCallback> onBegin(Gesture.BeginCallback handler)

Emitted when the gesture is recognized.

This means the number of touch sequences matches 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.

Parameters:

handler - the signal handler

Returns:

a signal handler ID to keep track of the signal connection

See Also:

• Gesture.BeginCallback.run(org.gnome.gdk.EventSequence)

emitBegin

public void emitBegin(@Nullable EventSequence sequence)

Emits the "begin" signal. See onBegin(org.gnome.gtk.Gesture.BeginCallback).

onCancel

public SignalConnection<Gesture.CancelCallback> onCancel(Gesture.CancelCallback handler)

Emitted whenever a sequence is cancelled.

This usually happens on active touches when EventController.reset() is called on gesture (manually, due to grabs...), or the individual sequence was claimed by parent widgets' controllers (see setSequenceState(org.gnome.gdk.EventSequence, org.gnome.gtk.EventSequenceState)).

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

Parameters:

handler - the signal handler

Returns:

a signal handler ID to keep track of the signal connection

See Also:

• Gesture.CancelCallback.run(org.gnome.gdk.EventSequence)

emitCancel

public void emitCancel(@Nullable EventSequence sequence)

Emits the "cancel" signal. See onCancel(org.gnome.gtk.Gesture.CancelCallback).

onEnd

public SignalConnection<Gesture.EndCallback> onEnd(Gesture.EndCallback handler)

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 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 Gtk.Gesture:n-points). This situation may be detected by checking through handlesSequence(org.gnome.gdk.EventSequence).

Parameters:

handler - the signal handler

Returns:

a signal handler ID to keep track of the signal connection

See Also:

• Gesture.EndCallback.run(org.gnome.gdk.EventSequence)

emitEnd

public void emitEnd(@Nullable EventSequence sequence)

Emits the "end" signal. See onEnd(org.gnome.gtk.Gesture.EndCallback).

onSequenceStateChanged

public SignalConnection<Gesture.SequenceStateChangedCallback> onSequenceStateChanged(Gesture.SequenceStateChangedCallback handler)

Emitted whenever a sequence state changes.

See setSequenceState(org.gnome.gdk.EventSequence, org.gnome.gtk.EventSequenceState) to know more about the expectable sequence lifetimes.

Parameters:

handler - the signal handler

Returns:

a signal handler ID to keep track of the signal connection

See Also:

• Gesture.SequenceStateChangedCallback.run(org.gnome.gdk.EventSequence, org.gnome.gtk.EventSequenceState)

emitSequenceStateChanged

public void emitSequenceStateChanged(@Nullable EventSequence sequence,
 EventSequenceState state)

Emits the "sequence-state-changed" signal. See onSequenceStateChanged(org.gnome.gtk.Gesture.SequenceStateChangedCallback).

onUpdate

public SignalConnection<Gesture.UpdateCallback> onUpdate(Gesture.UpdateCallback handler)

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

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

Parameters:

handler - the signal handler

Returns:

a signal handler ID to keep track of the signal connection

See Also:

• Gesture.UpdateCallback.run(org.gnome.gdk.EventSequence)

emitUpdate

public void emitUpdate(@Nullable EventSequence sequence)

Emits the "update" signal. See onUpdate(org.gnome.gtk.Gesture.UpdateCallback).