Gtk.Gesture.Gtk_Gesture is the base object for gesture recognition, although this object 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 Gdk.Event.Gdk_Event_Sequence value for these).
The number of touches that a Gtk.Gesture.Gtk_Gesture need to be recognized is controlled by the Gtk.Gesture.Gtk_Gesture:n-points property, if a gesture is keeping track of less or more than that number of sequences, it won't check wether the gesture is recognized.
As soon as the gesture has the expected number of touches, the gesture will run the Gtk.Gesture.Gtk_Gesture::check signal regularly on input events until the gesture is recognized, the criteria to consider a gesture as "recognized" is left to Gtk.Gesture.Gtk_Gesture subclasses.
A recognized gesture will then emit the following signals: - Gtk.Gesture.Gtk_Gesture::begin when the gesture is recognized. - A number of Gtk.Gesture.Gtk_Gesture::update, whenever an input event is processed. - Gtk.Gesture.Gtk_Gesture::end when the gesture is no longer recognized.
## Event propagation
In order to receive events, a gesture needs to either set a propagation phase through Gtk.Event_Controller.Set_Propagation_Phase, or feed those manually through Gtk.Event_Controller.Handle_Event.
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.
After the capture phase, GTK+ emits the traditional Gtk.Widget.Gtk_Widget::button-press-event, Gtk.Widget.Gtk_Widget::button-release-event, Gtk.Widget.Gtk_Widget::touch-event, etc signals. Gestures with the Gtk.Enums.Phase_Target phase are fed events from the default Gtk.Widget.Gtk_Widget::event handlers.
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 # {touch-sequence-states}
Whenever input interaction happens, a single event may trigger a cascade of Gtk_Gestures, 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 Gdk_Event_Sequences triggering those.
Within a widget, gestures can be grouped through Gtk.Gesture.Group, grouped gestures synchronize the state of sequences, so calling Gtk.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. - calling Gtk.Gesture.Gtk_Gesture::cancel on every gesture in widgets underneath in the propagation chain. - Stopping event propagation after the gesture group handles the event.
Note: if a sequence is set early to GTK_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 Gtk.Gesture.Set_Sequence_State to know about the possible lifetimes of a Gdk.Event.Gdk_Event_Sequence.
## Touchpad gestures
On the platforms that support it, Gtk.Gesture.Gtk_Gesture will handle transparently touchpad gesture events. The only precautions users of Gtk.Gesture.Gtk_Gesture should do to enable this support are: - Enabling Gdk.Event.Touchpad_Gesture_Mask on their Gdk_Windows - If the gesture has Gtk.Enums.Phase_None, ensuring events of type Gdk.Event.Touchpad_Swipe and Gdk.Event.Touchpad_Pinch are handled by the Gtk.Gesture.Gtk_Gesture
GtkAda
Gesture events are meant to replace low-level handling in most cases. For instance, you should move away from direct use of "button_press" event, and instead use a Gtk.Gesture.Multi_Press gesture. They give you more control (on the area for which a double click is valid for instance), work with touchpad in addition to mouse events, and you can have multiple gestures associated with the same widget, and that won't compete with each other.
For instance, having drag-and-drop on a widget which also manipulates low-level "button_press" events is hard to get rid, since the latter callback will often consume the events needed by gtk+ to detect that a drag operation is about to take place.
Gestures are objects in their full rights, and therefore needs to be Unref-ed to free memory. GtkAda provides a convenient function for this, so that the typical workflow is:
Gesture : Gtk_Gesture_Multi_Press;
Gtk_New (Gesture, Widget); Gesture.Watch (Widget); -- Destroy Gesture when Widget is destroyed Gesture.On_Pressed (On_Pressed'Access, Slot => Widget);
Without the call to Watch, Gesture would be kept in memory for ever, ready to be attached to some other widget.
type Cb_GObject_Gdk_Event_Sequence_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_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_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_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 : access Gdk.Rectangle.Gdk_Rectangle) return Boolean
If there are touch sequences being currently handled by Gesture, this function 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. Since: gtk+ 3.14
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 : access Gdouble;
Y : access Gdouble) return Boolean
If there are touch sequences being currently handled by Gesture, this function returns True and fills in X and Y with the center of the bounding box containing all active touches. Otherwise, False will be returned. Since: gtk+ 3.14
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.Device.Gdk_Device
Returns the master Gdk.Device.Gdk_Device that is currently operating on Gesture, or null if the gesture is not being interacted. Since: gtk+ 3.14
a Gdk.Device.Gdk_Device, or null
function Get_Group
(Self : not null access Gtk_Gesture_Record) return Gesture_List.Glist
Returns all gestures in the group of Gesture Since: gtk+ 3.14
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 Gdk.Event.Gdk_Event_Sequence
The last event from Sequence
function Get_Last_Updated_Sequence
(Self : not null access Gtk_Gesture_Record)
return Gdk.Event.Gdk_Event_Sequence
Returns the Gdk.Event.Gdk_Event_Sequence that was last updated on Gesture. Since: gtk+ 3.14
The last updated sequence
function Get_Point
(Self : not null access Gtk_Gesture_Record;
Sequence : Gdk.Event.Gdk_Event_Sequence;
X : access Gdouble;
Y : access Gdouble) return Boolean
If Sequence is currently being interpreted by Gesture, this function 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. Since: gtk+ 3.14
a Gdk.Event.Gdk_Event_Sequence, 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. Since: gtk+ 3.14
a Gdk.Event.Gdk_Event_Sequence
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 Gdk_Event_Sequences currently being interpreted by Gesture. Since: gtk+ 3.14
function Get_Type return Glib.GType
function Get_Window
(Self : not null access Gtk_Gesture_Record) return Gdk.Gdk_Window
Returns the user-defined window that receives the events handled by Gesture. See Gtk.Gesture.Set_Window for more information. Since: gtk+ 3.14
the user defined window, or null if none
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. When gestures are grouped, the state of Gdk_Event_Sequences is kept in sync for all of those, so calling Gtk.Gesture.Set_Sequence_State, on one will transfer the same value to the others. Groups also perform an "implicit grabbing" of sequences, if a Gdk.Event.Gdk_Event_Sequence state is set to GTK_EVENT_SEQUENCE_CLAIMED on one group, every other gesture group attached to the same Gtk.Widget.Gtk_Widget will switch the state for that sequence to GTK_EVENT_SEQUENCE_DENIED. Since: gtk+ 3.14
a Gtk.Gesture.Gtk_Gesture
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. Since: gtk+ 3.14
a Gdk.Event.Gdk_Event_Sequence or null
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 meanwhile there are touch sequences interacting with it. Since: gtk+ 3.14
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. Since: gtk+ 3.14
another Gtk.Gesture.Gtk_Gesture
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, and Gtk.Gesture.Gtk_Gesture::check returned True for the sequences being currently interpreted. Since: gtk+ 3.14
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_Void;
Slot : not null access Glib.Object.GObject_Record'Class;
After : Boolean := False)
This signal is emitted when the gesture is recognized. This means the number of touch sequences matches Gtk.Gesture.Gtk_Gesture:n-points, and the Gtk.Gesture.Gtk_Gesture::check handler(s) returned TRUE.
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_Void;
After : Boolean := False)
This signal is emitted when the gesture is recognized. This means the number of touch sequences matches Gtk.Gesture.Gtk_Gesture:n-points, and the Gtk.Gesture.Gtk_Gesture::check handler(s) returned TRUE.
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_Void;
Slot : not null access Glib.Object.GObject_Record'Class;
After : Boolean := False)
This signal is emitted whenever a sequence is cancelled. This usually happens on active touches when Gtk.Event_Controller.Reset is called on Gesture (manually, due to grabs...), or the individual Sequence was claimed by parent widgets' controllers (see Gtk.Gesture.Set_Sequence_State).
Gesture must forget everything about Sequence as a reaction to this signal.
procedure On_Cancel
(Self : not null access Gtk_Gesture_Record;
Call : Cb_Gtk_Gesture_Gdk_Event_Sequence_Void;
After : Boolean := False)
This signal is emitted whenever a sequence is cancelled. This usually happens on active touches when Gtk.Event_Controller.Reset is called on Gesture (manually, due to grabs...), or the individual Sequence was claimed by parent widgets' controllers (see Gtk.Gesture.Set_Sequence_State).
Gesture must forget everything about Sequence as a reaction to this signal.
procedure On_End
(Self : not null access Gtk_Gesture_Record;
Call : Cb_GObject_Gdk_Event_Sequence_Void;
Slot : not null access Glib.Object.GObject_Record'Class;
After : Boolean := False)
This signal is emitted when Gesture either stopped recognizing the event sequences as something to be handled (the Gtk.Gesture.Gtk_Gesture::check handler returned False), or the number of touch sequences became higher or lower than Gtk.Gesture.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.Gtk_Gesture:n-points). This situation may be detected by checking through Gtk.Gesture.Handles_Sequence.
procedure On_End
(Self : not null access Gtk_Gesture_Record;
Call : Cb_Gtk_Gesture_Gdk_Event_Sequence_Void;
After : Boolean := False)
This signal is emitted when Gesture either stopped recognizing the event sequences as something to be handled (the Gtk.Gesture.Gtk_Gesture::check handler returned False), or the number of touch sequences became higher or lower than Gtk.Gesture.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.Gtk_Gesture:n-points). This situation may be detected by checking through Gtk.Gesture.Handles_Sequence.
procedure On_Sequence_State_Changed
(Self : not null access Gtk_Gesture_Record;
Call : Cb_GObject_Gdk_Event_Sequence_Gtk_Event_Sequence_State_Void;
Slot : not null access Glib.Object.GObject_Record'Class;
After : Boolean := False)
This signal is emitted whenever a sequence state changes. See Gtk.Gesture.Set_Sequence_State to know more about the expectable sequence lifetimes.
Callback parameters: -- @param Sequence the Gdk.Event.Gdk_Event_Sequence 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_Gtk_Event_Sequence_State_Void;
After : Boolean := False)
This signal is emitted whenever a sequence state changes. See Gtk.Gesture.Set_Sequence_State to know more about the expectable sequence lifetimes.
Callback parameters: -- @param Sequence the Gdk.Event.Gdk_Event_Sequence 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_Void;
Slot : not null access Glib.Object.GObject_Record'Class;
After : Boolean := False)
This signal is 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_Void;
After : Boolean := False)
This signal is 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_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 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 Gtk.Gesture.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. Since: gtk+ 3.14
a Gdk.Event.Gdk_Event_Sequence
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. See Gtk.Gesture.Set_Sequence_State for more details on sequence states. Since: gtk+ 3.14
the sequence state
True if the state of at least one sequence was changed successfully
procedure Set_State
(Self : not null access Gtk_Gesture_Record'Class;
State : Gtk.Enums.Gtk_Event_Sequence_State := Event_Sequence_Denied)
Same as the function Set_State, but ignore the return value. This is in general call in a gesture callback to stop monitoring the current sequence of events. For instance, when you have a multipress gesture, you could call Set_State when the number of clicks is greater than 2 and you will never be interested in triple clicks or more.
procedure Set_Window
(Self : not null access Gtk_Gesture_Record;
Window : Gdk.Gdk_Window)
Sets a specific window to receive events about, so Gesture will effectively handle only events targeting Window, or a child of it. Window must pertain to Gtk.Event_Controller.Get_Widget. Since: gtk+ 3.14
a Gdk.Gdk_Window, or null
Signal_Begin : constant Glib.Signal_Name := "begin";
This signal is emitted when the gesture is recognized. This means the number of touch sequences matches Gtk.Gesture.Gtk_Gesture:n-points, and the Gtk.Gesture.Gtk_Gesture::check handler(s) returned TRUE.
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";
This signal is emitted whenever a sequence is cancelled. This usually happens on active touches when Gtk.Event_Controller.Reset is called on Gesture (manually, due to grabs...), or the individual Sequence was claimed by parent widgets' controllers (see Gtk.Gesture.Set_Sequence_State).
Gesture must forget everything about Sequence as a reaction to this signal.
Signal_End : constant Glib.Signal_Name := "end";
This signal is emitted when Gesture either stopped recognizing the event sequences as something to be handled (the Gtk.Gesture.Gtk_Gesture::check handler returned False), or the number of touch sequences became higher or lower than Gtk.Gesture.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.Gtk_Gesture:n-points). This situation may be detected by checking through Gtk.Gesture.Handles_Sequence.
Signal_Sequence_State_Changed : constant Glib.Signal_Name := "sequence-state-changed";
This signal is emitted whenever a sequence state changes. See Gtk.Gesture.Set_Sequence_State to know more about the expectable sequence lifetimes.
Callback parameters: -- @param Sequence the Gdk.Event.Gdk_Event_Sequence that was cancelled -- @param State the new sequence state
Signal_Update : constant Glib.Signal_Name := "update";
This signal is 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. Since: gtk+ 3.14
procedure Watch
(Self : not null access Gtk_Gesture_Record'Class;
Object : not null access GObject_Record'Class)
Automatically unref Self when Widget is destroyed. This is a convenience function, since attaching a gesture to a widget does not automatically free the gesture when the widget is destroyed (presumably so that you can reuse the gesture and its settings for another widget).
Window_Property : constant Glib.Properties.Property_Boxed;
Type: Gdk.Window If non-null, the gesture will only listen for events that happen on this Gdk.Gdk_Window, or a child of it.