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 [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_state] on one will effectively propagate the state throughout the group.
By default, all sequences start out in the Gtk.Enums.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.Enums.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.Enums.Event_Sequence_Claimed state, the gesture group will grab all interaction on the sequence, by:
Setting the same sequence to Gtk.Enums.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.Enums.Event_Sequence_Claimed on GDK_TOUCH_BEGIN/GDK_BUTTON_PRESS (so those events are captured before reaching the event widget, this implies Gtk.Enums.Phase_Capture), one similar event will be emulated if the sequence changes to Gtk.Enums.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_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.Enums.Phase_None, ensuring events of type
GDK_TOUCHPAD_SWIPE and GDK_TOUCHPAD_PINCH are handled by the GtkGesture
<gtkada_demo>create_gestures.adb</gtkada_demo>
type Cb_GObject_Gdk_Event_Sequence_Or_Null_Gtk_Event_Sequence_State_Void is not null access procedure
(Self : access Glib.Object.GObject_Record'Class;
Sequence : Gdk.Event.Gdk_Event_Sequence;
State : Gtk.Enums.Gtk_Event_Sequence_State);
type Cb_GObject_Gdk_Event_Sequence_Or_Null_Void is not null access procedure
(Self : access Glib.Object.GObject_Record'Class;
Sequence : Gdk.Event.Gdk_Event_Sequence);
type Cb_Gtk_Gesture_Gdk_Event_Sequence_Or_Null_Gtk_Event_Sequence_State_Void is not null access procedure
(Self : access Gtk_Gesture_Record'Class;
Sequence : Gdk.Event.Gdk_Event_Sequence;
State : Gtk.Enums.Gtk_Event_Sequence_State);
type Cb_Gtk_Gesture_Gdk_Event_Sequence_Or_Null_Void is not null access procedure
(Self : access Gtk_Gesture_Record'Class;
Sequence : Gdk.Event.Gdk_Event_Sequence);
function Convert (R : Gdk.Event.Gdk_Event_Sequence) return System.Address
function Convert (R : Gtk.Gesture.Gtk_Gesture) return System.Address
function Convert (R : System.Address) return Gdk.Event.Gdk_Event_Sequence
function Convert (R : System.Address) return Gtk.Gesture.Gtk_Gesture
package Gdk_Event_Sequence_List is new Generic_List (Gdk.Event.Gdk_Event_Sequence);
package Gesture_List is new Generic_List (Gtk.Gesture.Gtk_Gesture);
function Get_Bounding_Box
(Self : not null access Gtk_Gesture_Record;
Rect : out Gdk.Rectangle.Gdk_Rectangle) return Boolean
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.
bounding box containing all active touches.
True if there are active touches, False otherwise
function Get_Bounding_Box_Center
(Self : not null access Gtk_Gesture_Record;
X : out Gdouble;
Y : out Gdouble) return Boolean
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.
X coordinate for the bounding box center
Y coordinate for the bounding box center
False if no active touches are present, True otherwise
function Get_Device
(Self : not null access Gtk_Gesture_Record) return Gdk.Gdk_Device
Returns the logical GdkDevice that is currently operating on Gesture. This returns null if the gesture is not being interacted.
a GdkDevice. Has transfer-ownership='none'.
function Get_Group
(Self : not null access Gtk_Gesture_Record) return Gesture_List.Glist
Returns all gestures in the group of Gesture
The list of GtkGestures, free with g_list_free
function Get_Last_Event
(Self : not null access Gtk_Gesture_Record;
Sequence : Gdk.Event.Gdk_Event_Sequence) return Gdk.Event.Gdk_Event
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.
a GdkEventSequence
The last event from Sequence. Has transfer-ownership='none'.
function Get_Last_Updated_Sequence
(Self : not null access Gtk_Gesture_Record)
return Gdk.Event.Gdk_Event_Sequence
Returns the GdkEventSequence that was last updated on Gesture.
The last updated sequence
function Get_Point
(Self : not null access Gtk_Gesture_Record;
Sequence : Gdk.Event.Gdk_Event_Sequence;
X : access Gdouble := null;
Y : access Gdouble := null) return Boolean
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.
a GdkEventSequence, or null for pointer events
return location for X axis of the sequence coordinates
return location for Y axis of the sequence coordinates
True if Sequence is currently interpreted
function Get_Sequence_State
(Self : not null access Gtk_Gesture_Record;
Sequence : Gdk.Event.Gdk_Event_Sequence)
return Gtk.Enums.Gtk_Event_Sequence_State
Returns the Sequence state, as seen by Gesture.
a GdkEventSequence
The sequence state in Gesture
function Get_Sequences
(Self : not null access Gtk_Gesture_Record)
return Gdk_Event_Sequence_List.Glist
Returns the list of GdkEventSequences currently being interpreted by Gesture.
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
function Get_Type return Glib.GType
procedure Group
(Self : not null access Gtk_Gesture_Record;
Gesture : not null access Gtk_Gesture_Record'Class)
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.Enums.Event_Sequence_Claimed on one group, every other gesture group attached to the same GtkWidget will switch the state for that sequence to Gtk.Enums.Event_Sequence_Denied.
a GtkGesture
type Gtk_Gesture is access all Gtk_Gesture_Record'Class;
type Gtk_Gesture_Record is new Gtk_Event_Controller_Record with null record;
function Handles_Sequence
(Self : not null access Gtk_Gesture_Record;
Sequence : Gdk.Event.Gdk_Event_Sequence) return Boolean
Returns True if Gesture is currently handling events corresponding to Sequence.
a GdkEventSequence
True if Gesture is handling Sequence, False otherwise
function Is_Active
(Self : not null access Gtk_Gesture_Record) return Boolean
Returns True if the gesture is currently active. A gesture is active while there are touch sequences interacting with it.
True if gesture is active
function Is_Grouped_With
(Self : not null access Gtk_Gesture_Record;
Other : not null access Gtk_Gesture_Record'Class) return Boolean
Returns True if both gestures pertain to the same group.
another GtkGesture
whether the gestures are grouped
function Is_Recognized
(Self : not null access Gtk_Gesture_Record) return Boolean
Returns True if the gesture is currently recognized. A gesture is recognized if there are as many interacting touch sequences as required by Gesture.
True if gesture is recognized
N_Points_Property : constant Glib.Properties.Property_Uint;
The number of touch points that trigger recognition on this gesture.
procedure On_Begin
(Self : not null access Gtk_Gesture_Record;
Call : Cb_GObject_Gdk_Event_Sequence_Or_Null_Void;
Slot : not null access Glib.Object.GObject_Record'Class;
After : Boolean := False)
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.
procedure On_Begin
(Self : not null access Gtk_Gesture_Record;
Call : Cb_Gtk_Gesture_Gdk_Event_Sequence_Or_Null_Void;
After : Boolean := False)
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.
procedure On_Cancel
(Self : not null access Gtk_Gesture_Record;
Call : Cb_GObject_Gdk_Event_Sequence_Or_Null_Void;
Slot : not null access Glib.Object.GObject_Record'Class;
After : Boolean := False)
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.
procedure On_Cancel
(Self : not null access Gtk_Gesture_Record;
Call : Cb_Gtk_Gesture_Gdk_Event_Sequence_Or_Null_Void;
After : Boolean := False)
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.
procedure On_End
(Self : not null access Gtk_Gesture_Record;
Call : Cb_GObject_Gdk_Event_Sequence_Or_Null_Void;
Slot : not null access Glib.Object.GObject_Record'Class;
After : Boolean := False)
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].
procedure On_End
(Self : not null access Gtk_Gesture_Record;
Call : Cb_Gtk_Gesture_Gdk_Event_Sequence_Or_Null_Void;
After : Boolean := False)
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].
procedure On_Sequence_State_Changed
(Self : not null access Gtk_Gesture_Record;
Call : Cb_GObject_Gdk_Event_Sequence_Or_Null_Gtk_Event_Sequence_State_Void;
Slot : not null access Glib.Object.GObject_Record'Class;
After : Boolean := False)
Emitted whenever a sequence state changes.
See [methodGtk.Gesture.set_sequence_state] to know more about the expectable sequence lifetimes.
Callback parameters: -- @param Sequence the GdkEventSequence that was cancelled -- @param State the new sequence state
procedure On_Sequence_State_Changed
(Self : not null access Gtk_Gesture_Record;
Call : Cb_Gtk_Gesture_Gdk_Event_Sequence_Or_Null_Gtk_Event_Sequence_State_Void;
After : Boolean := False)
Emitted whenever a sequence state changes.
See [methodGtk.Gesture.set_sequence_state] to know more about the expectable sequence lifetimes.
Callback parameters: -- @param Sequence the GdkEventSequence that was cancelled -- @param State the new sequence state
procedure On_Update
(Self : not null access Gtk_Gesture_Record;
Call : Cb_GObject_Gdk_Event_Sequence_Or_Null_Void;
Slot : not null access Glib.Object.GObject_Record'Class;
After : Boolean := False)
Emitted whenever an event is handled while the gesture is recognized.
Sequence is guaranteed to pertain to the set of active touches.
procedure On_Update
(Self : not null access Gtk_Gesture_Record;
Call : Cb_Gtk_Gesture_Gdk_Event_Sequence_Or_Null_Void;
After : Boolean := False)
Emitted whenever an event is handled while the gesture is recognized.
Sequence is guaranteed to pertain to the set of active touches.
function Set_Sequence_State
(Self : not null access Gtk_Gesture_Record;
Sequence : Gdk.Event.Gdk_Event_Sequence;
State : Gtk.Enums.Gtk_Event_Sequence_State) return Boolean
Sets the state of Sequence in Gesture. Sequences start in state Gtk.Enums.Event_Sequence_None, and whenever they change state, they can never go back to that state. Likewise, sequences in state Gtk.Enums.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 â Denied * None â Claimed * None â Claimed â 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:
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.
Deprecated since 4.10., 1
a GdkEventSequence
the sequence state
True if Sequence is handled by Gesture, and the state is changed successfully
function Set_State
(Self : not null access Gtk_Gesture_Record;
State : Gtk.Enums.Gtk_Event_Sequence_State) return Boolean
Sets the state of all sequences that Gesture is currently interacting with. Sequences start in state Gtk.Enums.Event_Sequence_None, and whenever they change state, they can never go back to that state. Likewise, sequences in state Gtk.Enums.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 â Denied * None â Claimed * None â Claimed â 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:
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.
the sequence state
True if the state of at least one sequence was changed successfully
Signal_Begin : constant Glib.Signal_Name := "begin";
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.
Signal_Cancel : constant Glib.Signal_Name := "cancel";
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.
Signal_End : constant Glib.Signal_Name := "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 [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].
Signal_Sequence_State_Changed : constant Glib.Signal_Name := "sequence-state-changed";
Emitted whenever a sequence state changes.
See [methodGtk.Gesture.set_sequence_state] to know more about the expectable sequence lifetimes.
Callback parameters: -- @param Sequence the GdkEventSequence that was cancelled -- @param State the new sequence state
Signal_Update : constant Glib.Signal_Name := "update";
Emitted whenever an event is handled while the gesture is recognized.
Sequence is guaranteed to pertain to the set of active touches.
procedure Ungroup (Self : not null access Gtk_Gesture_Record)
Separates Gesture into an isolated group.