Clutter Reference Manual: ClutterPanAction

## ClutterPanAction ClutterPanAction — Action for pan gestures |

## Synopsis

    struct              ClutterPanAction;
    struct              ClutterPanActionClass;
    ClutterAction *     clutter_pan_action_new              (void);
    enum                ClutterPanAxis;
    void                clutter_pan_action_set_pan_axis     (ClutterPanAction *self,
                                                             ClutterPanAxis axis);
    ClutterPanAxis      clutter_pan_action_get_pan_axis     (ClutterPanAction *self);
    void                clutter_pan_action_set_interpolate  (ClutterPanAction *self,
                                                             gboolean should_interpolate);
    gboolean            clutter_pan_action_get_interpolate  (ClutterPanAction *self);
    void                clutter_pan_action_set_deceleration (ClutterPanAction *self,
                                                             gdouble rate);
    gdouble             clutter_pan_action_get_deceleration (ClutterPanAction *self);
    void                clutter_pan_action_set_acceleration_factor
                                                            (ClutterPanAction *self,
                                                             gdouble factor);
    gdouble             clutter_pan_action_get_acceleration_factor
                                                            (ClutterPanAction *self);

    void                clutter_pan_action_get_interpolated_coords
                                                            (ClutterPanAction *self,
                                                             gfloat *interpolated_x,
                                                             gfloat *interpolated_y);
    gfloat              clutter_pan_action_get_interpolated_delta
                                                            (ClutterPanAction *self,
                                                             gfloat *delta_x,
                                                             gfloat *delta_y);
    void                clutter_pan_action_get_motion_coords
                                                            (ClutterPanAction *self,
                                                             guint point,
                                                             gfloat *motion_x,
                                                             gfloat *motion_y);
    gfloat              clutter_pan_action_get_motion_delta (ClutterPanAction *self,
                                                             guint point,
                                                             gfloat *delta_x,
                                                             gfloat *delta_y);

## Object Hierarchy

      GObject
       +----GInitiallyUnowned
             +----ClutterActorMeta
                   +----ClutterAction
                         +----ClutterGestureAction
                               +----ClutterPanAction

## Properties

      "acceleration-factor"      gdouble               : Read / Write
      "deceleration"             gdouble               : Read / Write
      "interpolate"              gboolean              : Read / Write
      "pan-axis"                 ClutterPanAxis        : Read / Write

## Signals

      "pan"                                            : Run Last
      "pan-stopped"                                    : Run Last

## Description

ClutterPanAction is a sub-class of ClutterGestureAction that implements the logic for recognizing pan gestures.

The simplest usage of ClutterPanAction consists in adding it to a ClutterActor with a child and setting it as reactive; for instance, the following code:

    1
    2
    clutter_actor_add_action (actor, clutter_pan_action_new ());
    clutter_actor_set_reactive (actor, TRUE);

will automatically result in the actor children to be moved when dragging.

## Details

### struct ClutterPanAction

    struct ClutterPanAction;

The ClutterPanAction structure contains only private data and should be accessed using the provided API

Since 1.12

### struct ClutterPanActionClass

    struct ClutterPanActionClass {
      gboolean (* pan)               (ClutterPanAction    *action,
                                      ClutterActor        *actor,
                                      gboolean             is_interpolated);
      void     (* pan_stopped)       (ClutterPanAction    *action,
                                      ClutterActor        *actor);
    };

The ClutterPanActionClass structure contains only private data.

`pan` () | class handler for the "pan" signal
`pan_stopped` () | class handler for the "pan-stopped" signal

Since 1.12

### clutter_pan_action_new ()

    ClutterAction *     clutter_pan_action_new              (void);

Creates a new ClutterPanAction instance

Returns : | the newly created ClutterPanAction

Since 1.12

### enum ClutterPanAxis

    typedef enum {
     /*< prefix=CLUTTER_PAN >*/
      CLUTTER_PAN_AXIS_NONE = 0,

      CLUTTER_PAN_X_AXIS,
      CLUTTER_PAN_Y_AXIS
    } ClutterPanAxis;

The axis of the constraint that should be applied on the panning action

`CLUTTER_PAN_AXIS_NONE` | No constraint
`CLUTTER_PAN_X_AXIS` | Set a constraint on the X axis
`CLUTTER_PAN_Y_AXIS` | Set a constraint on the Y axis

Since 1.12

### clutter_pan_action_set_pan_axis ()

    void                clutter_pan_action_set_pan_axis     (ClutterPanAction *self,
                                                             ClutterPanAxis axis);

Restricts the panning action to a specific axis

`self` : | a ClutterPanAction
`axis` : | the axis to constraint the panning to

Since 1.12

### clutter_pan_action_get_pan_axis ()

    ClutterPanAxis      clutter_pan_action_get_pan_axis     (ClutterPanAction *self);

Retrieves the axis constraint set by `clutter_pan_action_set_pan_axis()`

`self` : | a ClutterPanAction
Returns : | the axis constraint

Since 1.12

### clutter_pan_action_set_interpolate ()

    void                clutter_pan_action_set_interpolate  (ClutterPanAction *self,
                                                             gboolean should_interpolate);

Sets whether the action should emit interpolated ::pan events after the drag has ended, to emulate the gesture kinetic inertia.

`self` : | a ClutterPanAction
`should_interpolate` : | whether to enable interpolated pan events

Since 1.12

### clutter_pan_action_get_interpolate ()

    gboolean            clutter_pan_action_get_interpolate  (ClutterPanAction *self);

Checks if the action should emit ::pan events even after releasing the pointer during a panning gesture, to emulate some kind of kinetic inertia.

`self` : | a ClutterPanAction
Returns : | `TRUE` if interpolated events emission is active.

Since 1.12

### clutter_pan_action_set_deceleration ()

    void                clutter_pan_action_set_deceleration (ClutterPanAction *self,
                                                             gdouble rate);

Sets the deceleration rate of the interpolated ::pan events generated after a pan gesture. This is approximately the value that the momentum at the time of releasing the pointer is divided by every 60th of a second.

`self` : | A ClutterPanAction
`rate` : | The deceleration rate

Since 1.12

### clutter_pan_action_get_deceleration ()

    gdouble             clutter_pan_action_get_deceleration (ClutterPanAction *self);

Retrieves the deceleration rate of interpolated ::pan events.

`self` : | A ClutterPanAction
Returns : | The deceleration rate of the interpolated events.

Since 1.12

### clutter_pan_action_set_acceleration_factor ()

    void                clutter_pan_action_set_acceleration_factor
                                                            (ClutterPanAction *self,
                                                             gdouble factor);

Factor applied to the momentum velocity at the time of releasing the pointer when generating interpolated ::pan events.

`self` : | A ClutterPanAction
`factor` : | The acceleration factor

Since 1.12

### clutter_pan_action_get_acceleration_factor ()

    gdouble             clutter_pan_action_get_acceleration_factor
                                                            (ClutterPanAction *self);

Retrieves the initial acceleration factor for interpolated ::pan events.

`self` : | A ClutterPanAction
Returns : | The initial acceleration factor for interpolated events.

Since 1.12

### clutter_pan_action_get_interpolated_coords ()

    void                clutter_pan_action_get_interpolated_coords
                                                            (ClutterPanAction *self,
                                                             gfloat *interpolated_x,
                                                             gfloat *interpolated_y);

Retrieves the coordinates, in stage space, of the latest interpolated event, analogous to `clutter_gesture_action_get_motion_coords()`.

`self` : | A ClutterPanAction
`interpolated_x` : | return location for the latest interpolated event's X coordinate. [out][allow-none]
`interpolated_y` : | return location for the latest interpolated event's Y coordinate. [out][allow-none]

Since 1.12

### clutter_pan_action_get_interpolated_delta ()

    gfloat              clutter_pan_action_get_interpolated_delta
                                                            (ClutterPanAction *self,
                                                             gfloat *delta_x,
                                                             gfloat *delta_y);

Retrieves the delta, in stage space, since the latest interpolated event, analogous to `clutter_gesture_action_get_motion_delta()`.

`self` : | A ClutterPanAction
`delta_x` : | return location for the X delta since the latest interpolated event. [out][allow-none]
`delta_y` : | return location for the Y delta since the latest interpolated event. [out][allow-none]
Returns : | the distance since the latest interpolated event

Since 1.12

### clutter_pan_action_get_motion_coords ()

    void                clutter_pan_action_get_motion_coords
                                                            (ClutterPanAction *self,
                                                             guint point,
                                                             gfloat *motion_x,
                                                             gfloat *motion_y);

Retrieves the coordinates, in stage space, dependent on the current state of the ClutterPanAction. If it is inactive, both fields will be set to 0. If it is panning by user action, the values will be equivalent to those returned by `clutter_gesture_action_get_motion_coords()`. If it is interpolating with some form of kinetic scrolling, the values will be equivalent to those returned by `clutter_pan_action_get_interpolated_coords()`. This is a convenience method designed to be used in replacement "pan" signal handlers.

`self` : | A ClutterPanAction
`point` : | the touch point index, with 0 being the first touch point received by the action
`motion_x` : | return location for the X coordinate. [out][allow-none]
`motion_y` : | return location for the Y coordinate. [out][allow-none]

Since 1.14

### clutter_pan_action_get_motion_delta ()

    gfloat              clutter_pan_action_get_motion_delta (ClutterPanAction *self,
                                                             guint point,
                                                             gfloat *delta_x,
                                                             gfloat *delta_y);

Retrieves the delta, in stage space, dependent on the current state of the ClutterPanAction. If it is inactive, both fields will be set to 0. If it is panning by user action, the values will be equivalent to those returned by `clutter_gesture_action_get_motion_delta()`. If it is interpolating with some form of kinetic scrolling, the values will be equivalent to those returned by `clutter_pan_action_get_interpolated_delta()`. This is a convenience method designed to be used in replacement "pan" signal handlers.

`self` : | A ClutterPanAction
`point` : | the touch point index, with 0 being the first touch point received by the action
`delta_x` : | return location for the X delta. [out][allow-none]
`delta_y` : | return location for the Y delta. [out][allow-none]

Since 1.14

## Property Details

### The `"acceleration-factor"` property

      "acceleration-factor"      gdouble               : Read / Write

The initial acceleration factor

The kinetic momentum measured at the time of releasing the pointer will be multiplied by the factor specified by this property before being used to generate interpolated ::pan events.

Allowed values: >= 1

Default value: 1

Since 1.12

### The `"deceleration"` property

      "deceleration"             gdouble               : Read / Write

The rate at which the interpolated panning will decelerate in

ClutterPanAction will emit interpolated ::pan events with decreasing scroll deltas, using the rate specified by this property.

Allowed values: [1e-15,1]

Default value: 0.95

Since 1.12

### The `"interpolate"` property

      "interpolate"              gboolean              : Read / Write

Whether interpolated events emission is enabled.

Default value: FALSE

Since 1.12

### The `"pan-axis"` property

      "pan-axis"                 ClutterPanAxis        : Read / Write

Constraints the panning action to the specified axis

Default value: CLUTTER_PAN_AXIS_NONE

Since 1.12

## Signal Details

### The `"pan"` signal

    gboolean            user_function                      (ClutterPanAction *action,
                                                            ClutterActor     *actor,
                                                            gboolean          is_interpolated,
                                                            gpointer          user_data)            : Run Last

The ::pan signal is emitted to keep track of the motion during a pan gesture. `is_interpolated` is set to `TRUE` during the interpolation phase of the pan, after the drag has ended and the :interpolate property was set to `TRUE`.

`action` : | the ClutterPanAction that emitted the signal
`actor` : | the ClutterActor attached to the `action`
`is_interpolated` : | if the event is the result of interpolating the motion velocity at the end of the drag
`user_data` : | user data set when the signal handler was connected.
Returns : | `TRUE` if the pan should continue, and `FALSE` if the pan should be cancelled.

Since 1.12

### The `"pan-stopped"` signal

    void                user_function                      (ClutterPanAction *action,
                                                            ClutterActor     *actor,
                                                            gpointer          user_data)      : Run Last

The ::pan-stopped signal is emitted at the end of the interpolation phase of the pan action, only when :interpolate is set to `TRUE`.

`action` : | the ClutterPanAction that emitted the signal
`actor` : | the ClutterActor attached to the `action`
`user_data` : | user data set when the signal handler was connected.

Since 1.12