GI.Gtk.Objects.Gesture

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 Nothing GdkEventSequence value for these).

The number of touches that a GtkGesture need to be recognized is controlled by the Gesture:nPoints 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:

• Gesture::begin when the gesture is recognized.
• Gesture::update, whenever an input event is processed.
• 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 eventControllerSetPropagationPhase.

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 gestureGroup. Grouped gestures synchronize the state of sequences, so calling gestureSetState on one will effectively propagate the state throughout the group.

By default, all sequences start out in the EventSequenceStateNone state, sequences in this state trigger the gesture event handler, but event propagation will continue unstopped by gestures.

If a sequence enters into the EventSequenceStateDenied 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 EventSequenceStateClaimed state, the gesture group will grab all interaction on the sequence, by:

• Setting the same sequence to EventSequenceStateDenied on every other gesture group within the widget, and every gesture on parent widgets in the propagation chain.
• Emitting 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 EventSequenceStateClaimed on EventTypeTouchBegin/EventTypeButtonPress (so those events are captured before reaching the event widget, this implies PropagationPhaseCapture), one similar event will be emulated if the sequence changes to EventSequenceStateDenied. This way event coherence is preserved before event propagation is unstopped again.

Sequence states can't be changed freely. See gestureSetState 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 PropagationPhaseNone, ensuring events of type EventTypeTouchpadSwipe and EventTypeTouchpadPinch are handled by the GtkGesture

Exported types

newtype Gesture

Memory-managed wrapper type.

Constructors

Gesture (ManagedPtr Gesture)

Instances

Eq Gesture

Defined in GI.Gtk.Objects.Gesture

Methods

(==) :: Gesture -> Gesture -> Bool

(/=) :: Gesture -> Gesture -> Bool

GObject Gesture

Defined in GI.Gtk.Objects.Gesture

ManagedPtrNewtype Gesture

Defined in GI.Gtk.Objects.Gesture

Methods

toManagedPtr :: Gesture -> ManagedPtr Gesture

TypedObject Gesture

Defined in GI.Gtk.Objects.Gesture

Methods

glibType :: IO GType

HasParentTypes Gesture

Defined in GI.Gtk.Objects.Gesture

IsGValue (Maybe Gesture)

Convert Gesture to and from GValue. See toGValue and fromGValue.

Defined in GI.Gtk.Objects.Gesture

Methods

gvalueGType_ :: IO GType

gvalueSet_ :: Ptr GValue -> Maybe Gesture -> IO ()

gvalueGet_ :: Ptr GValue -> IO (Maybe Gesture)

type ParentTypes Gesture

Defined in GI.Gtk.Objects.Gesture

type ParentTypes Gesture = '[EventController, Object]

class (GObject o, IsDescendantOf Gesture o) => IsGesture o

Type class for types which can be safely cast to Gesture, for instance with toGesture.

Instances

(GObject o, IsDescendantOf Gesture o) => IsGesture o

Defined in GI.Gtk.Objects.Gesture

toGesture :: (MonadIO m, IsGesture o) => o -> m Gesture

Cast to Gesture, for types for which this is known to be safe. For general casts, use castTo.

Methods

Click to display all available methods, including inherited ones

Methods

bindProperty, bindPropertyFull, forceFloating, freezeNotify, getv, group, handlesSequence, isActive, isFloating, isGroupedWith, isRecognized, notify, notifyByPspec, ref, refSink, reset, runDispose, stealData, stealQdata, thawNotify, ungroup, unref, watchClosure.

Getters

getBoundingBox, getBoundingBoxCenter, getCurrentEvent, getCurrentEventDevice, getCurrentEventState, getCurrentEventTime, getData, getDevice, getGroup, getLastEvent, getLastUpdatedSequence, getName, getPoint, getPropagationLimit, getPropagationPhase, getProperty, getQdata, getSequenceState, getSequences, getWidget.

Setters

setData, setDataFull, setName, setPropagationLimit, setPropagationPhase, setProperty, setSequenceState, setState, setStaticName.

getBoundingBox

gestureGetBoundingBox

Arguments

:: (HasCallStack, MonadIO m, IsGesture a)

=> a

gesture: a GtkGesture

-> m (Bool, Rectangle)

Returns: True if there are active touches, False otherwise

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.

getBoundingBoxCenter

gestureGetBoundingBoxCenter

Arguments

:: (HasCallStack, MonadIO m, IsGesture a)

=> a

gesture: a GtkGesture

-> m (Bool, Double, Double)

Returns: False if no active touches are present, True otherwise

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.

getDevice

gestureGetDevice

Arguments

:: (HasCallStack, MonadIO m, IsGesture a)

=> a

gesture: a GtkGesture

-> m (Maybe Device)

Returns: a GdkDevice

Returns the logical GdkDevice that is currently operating on gesture.

This returns Nothing if the gesture is not being interacted.

getGroup

gestureGetGroup

Arguments

:: (HasCallStack, MonadIO m, IsGesture a)

=> a

gesture: a GtkGesture

-> m [Gesture]

Returns: The list of GtkGestures, free with g_list_free()

Returns all gestures in the group of gesture

getLastEvent

gestureGetLastEvent

Arguments

:: (HasCallStack, MonadIO m, IsGesture a)

=> a

gesture: a GtkGesture

-> Maybe EventSequence

sequence: a GdkEventSequence

-> m (Maybe Event)

Returns: The last event from 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.

getLastUpdatedSequence

gestureGetLastUpdatedSequence

Arguments

:: (HasCallStack, MonadIO m, IsGesture a)

=> a

gesture: a GtkGesture

-> m (Maybe EventSequence)

Returns: The last updated sequence

Returns the GdkEventSequence that was last updated on gesture.

getPoint

gestureGetPoint

Arguments

:: (HasCallStack, MonadIO m, IsGesture a)

=> a

gesture: a GtkGesture

-> Maybe EventSequence

sequence: a GdkEventSequence, or Nothing for pointer events

-> m (Bool, Double, Double)

Returns: True if sequence is currently interpreted

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.

getSequenceState

gestureGetSequenceState

Arguments

:: (HasCallStack, MonadIO m, IsGesture a)

=> a

gesture: a GtkGesture

-> EventSequence

sequence: a GdkEventSequence

-> m EventSequenceState

Returns: The sequence state in gesture

Returns the sequence state, as seen by gesture.

getSequences

gestureGetSequences

Arguments

:: (HasCallStack, MonadIO m, IsGesture a)

=> a

gesture: a GtkGesture

-> m [EventSequence]

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()

Returns the list of GdkEventSequences currently being interpreted by gesture.

group

gestureGroup

Arguments

:: (HasCallStack, MonadIO m, IsGesture a, IsGesture b)

=> a

groupGesture: GtkGesture to group gesture with

-> b

gesture: a GtkGesture

-> m ()

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 gestureSetSequenceState, 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 EventSequenceStateClaimed on one group, every other gesture group attached to the same GtkWidget will switch the state for that sequence to EventSequenceStateDenied.

handlesSequence

gestureHandlesSequence

Arguments

:: (HasCallStack, MonadIO m, IsGesture a)

=> a

gesture: a GtkGesture

-> Maybe EventSequence

sequence: a GdkEventSequence

-> m Bool

Returns: True if gesture is handling sequence, False otherwise

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

isActive

gestureIsActive

Arguments

:: (HasCallStack, MonadIO m, IsGesture a)

=> a

gesture: a GtkGesture

-> m Bool

Returns: True if gesture is active

Returns True if the gesture is currently active.

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

isGroupedWith

gestureIsGroupedWith

Arguments

:: (HasCallStack, MonadIO m, IsGesture a, IsGesture b)

=> a

gesture: a GtkGesture

-> b

other: another GtkGesture

-> m Bool

Returns: whether the gestures are grouped

Returns True if both gestures pertain to the same group.

isRecognized

gestureIsRecognized

Arguments

:: (HasCallStack, MonadIO m, IsGesture a)

=> a

gesture: a GtkGesture

-> m Bool

Returns: True if gesture is recognized

Returns True if the gesture is currently recognized.

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

setSequenceState

gestureSetSequenceState

Arguments

:: (HasCallStack, MonadIO m, IsGesture a)

=> a

gesture: a GtkGesture

-> EventSequence

sequence: a GdkEventSequence

-> EventSequenceState

state: the sequence state

-> m Bool

Returns: True if sequence is handled by gesture, and the state is changed successfully

Deprecated: (Since version 4.10.)Use gestureSetState

Sets the state of sequence in gesture.

Sequences start in state EventSequenceStateNone, and whenever they change state, they can never go back to that state. Likewise, sequences in state EventSequenceStateDenied 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 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 code

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.

setState

gestureSetState

Arguments

:: (HasCallStack, MonadIO m, IsGesture a)

=> a

gesture: a GtkGesture

-> EventSequenceState

state: the sequence state

-> m Bool

Returns: True if the state of at least one sequence was changed successfully

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

Sequences start in state EventSequenceStateNone, and whenever they change state, they can never go back to that state. Likewise, sequences in state EventSequenceStateDenied 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 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 code

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.

ungroup

gestureUngroup

Arguments

:: (HasCallStack, MonadIO m, IsGesture a)

=> a

gesture: a GtkGesture

-> m ()

Separates gesture into an isolated group.

Properties

nPoints

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

constructGestureNPoints :: (IsGesture o, MonadIO m) => Word32 -> m (GValueConstruct o)

Construct a GValueConstruct with valid value for the “n-points” property. This is rarely needed directly, but it is used by new.

getGestureNPoints :: (MonadIO m, IsGesture o) => o -> m Word32

Get the value of the “n-points” property. When overloading is enabled, this is equivalent to

get gesture #nPoints

Signals

begin

type GestureBeginCallback

Arguments

 = Maybe EventSequence

sequence: the GdkEventSequence that made the gesture to be recognized

-> IO ()

Emitted when the gesture is recognized.

This means the number of touch sequences matches Gesture:nPoints.

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.

afterGestureBegin :: (IsGesture a, MonadIO m) => a -> ((?self :: a) => GestureBeginCallback) -> m SignalHandlerId

Connect a signal handler for the begin signal, to be run after the default handler. When overloading is enabled, this is equivalent to

after gesture #begin callback

By default the object invoking the signal is not passed to the callback. If you need to access it, you can use the implit ?self parameter. Note that this requires activating the ImplicitParams GHC extension.

onGestureBegin :: (IsGesture a, MonadIO m) => a -> ((?self :: a) => GestureBeginCallback) -> m SignalHandlerId

Connect a signal handler for the begin signal, to be run before the default handler. When overloading is enabled, this is equivalent to

on gesture #begin callback

cancel

type GestureCancelCallback

Arguments

 = Maybe EventSequence

sequence: the GdkEventSequence that was cancelled

-> IO ()

Emitted whenever a sequence is cancelled.

This usually happens on active touches when eventControllerReset is called on gesture (manually, due to grabs...), or the individual sequence was claimed by parent widgets' controllers (see gestureSetSequenceState).

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

afterGestureCancel :: (IsGesture a, MonadIO m) => a -> ((?self :: a) => GestureCancelCallback) -> m SignalHandlerId

Connect a signal handler for the cancel signal, to be run after the default handler. When overloading is enabled, this is equivalent to

after gesture #cancel callback

By default the object invoking the signal is not passed to the callback. If you need to access it, you can use the implit ?self parameter. Note that this requires activating the ImplicitParams GHC extension.

onGestureCancel :: (IsGesture a, MonadIO m) => a -> ((?self :: a) => GestureCancelCallback) -> m SignalHandlerId

Connect a signal handler for the cancel signal, to be run before the default handler. When overloading is enabled, this is equivalent to

on gesture #cancel callback

end

type GestureEndCallback

Arguments

 = Maybe EventSequence

sequence: the GdkEventSequence that made gesture recognition to finish

-> IO ()

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 Gesture:nPoints.

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 Gesture:nPoints). This situation may be detected by checking through gestureHandlesSequence.

afterGestureEnd :: (IsGesture a, MonadIO m) => a -> ((?self :: a) => GestureEndCallback) -> m SignalHandlerId

Connect a signal handler for the end signal, to be run after the default handler. When overloading is enabled, this is equivalent to

after gesture #end callback

By default the object invoking the signal is not passed to the callback. If you need to access it, you can use the implit ?self parameter. Note that this requires activating the ImplicitParams GHC extension.

onGestureEnd :: (IsGesture a, MonadIO m) => a -> ((?self :: a) => GestureEndCallback) -> m SignalHandlerId

Connect a signal handler for the end signal, to be run before the default handler. When overloading is enabled, this is equivalent to

on gesture #end callback

sequenceStateChanged

type GestureSequenceStateChangedCallback

Arguments

 = Maybe EventSequence

sequence: the GdkEventSequence that was cancelled

-> EventSequenceState

state: the new sequence state

-> IO ()

Emitted whenever a sequence state changes.

See gestureSetSequenceState to know more about the expectable sequence lifetimes.

afterGestureSequenceStateChanged :: (IsGesture a, MonadIO m) => a -> ((?self :: a) => GestureSequenceStateChangedCallback) -> m SignalHandlerId

Connect a signal handler for the sequenceStateChanged signal, to be run after the default handler. When overloading is enabled, this is equivalent to

after gesture #sequenceStateChanged callback

By default the object invoking the signal is not passed to the callback. If you need to access it, you can use the implit ?self parameter. Note that this requires activating the ImplicitParams GHC extension.

onGestureSequenceStateChanged :: (IsGesture a, MonadIO m) => a -> ((?self :: a) => GestureSequenceStateChangedCallback) -> m SignalHandlerId

Connect a signal handler for the sequenceStateChanged signal, to be run before the default handler. When overloading is enabled, this is equivalent to

on gesture #sequenceStateChanged callback

update

type GestureUpdateCallback

Arguments

 = Maybe EventSequence

sequence: the GdkEventSequence that was updated

-> IO ()

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

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

afterGestureUpdate :: (IsGesture a, MonadIO m) => a -> ((?self :: a) => GestureUpdateCallback) -> m SignalHandlerId

Connect a signal handler for the update signal, to be run after the default handler. When overloading is enabled, this is equivalent to

after gesture #update callback

By default the object invoking the signal is not passed to the callback. If you need to access it, you can use the implit ?self parameter. Note that this requires activating the ImplicitParams GHC extension.

onGestureUpdate :: (IsGesture a, MonadIO m) => a -> ((?self :: a) => GestureUpdateCallback) -> m SignalHandlerId

Connect a signal handler for the update signal, to be run before the default handler. When overloading is enabled, this is equivalent to

on gesture #update callback