mutter/clutter/clutter-gesture-action.c

/*
 * Clutter.
 *
 * An OpenGL based 'interactive canvas' library.
 *
 * Copyright (C) 2010  Intel Corporation.
 * Copyright (C) 2011  Robert Bosch Car Multimedia GmbH.
 * Copyright (C) 2012  Intel Corporation.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library. If not, see <http://www.gnu.org/licenses/>.
 *
 * Author:
 *   Tomeu Vizoso <tomeu.vizoso@collabora.co.uk>
 */

/**
 * SECTION:clutter-gesture-action
 * @Title: ClutterGestureAction
 * @Short_Description: Action for gesture gestures
 *
 * #ClutterGestureAction is a sub-class of #ClutterAction that implements
 * the logic for recognizing gesture gestures. It listens for low level events
 * such as #ClutterButtonEvent and #ClutterMotionEvent on the stage to raise
 * the #ClutterGestureAction::gesture-begin, #ClutterGestureAction::gesture-progress,
 * and #ClutterGestureAction::gesture-end signals.
 *
 * To use #ClutterGestureAction you just need to apply it to a #ClutterActor
 * using clutter_actor_add_action() and connect to the signals:
 *
 * |[
 *   ClutterAction *action = clutter_gesture_action_new ();
 *
 *   clutter_actor_add_action (actor, action);
 *
 *   g_signal_connect (action, "gesture-begin", G_CALLBACK (on_gesture_begin), NULL);
 *   g_signal_connect (action, "gesture-progress", G_CALLBACK (on_gesture_progress), NULL);
 *   g_signal_connect (action, "gesture-end", G_CALLBACK (on_gesture_end), NULL);
 * ]|
 *
 * <refsect2 id="creating-gesture-action">
 *   <title>Creating Gesture actions</title>
 *   <para>A #ClutterGestureAction provides four separate states that can be
 *   used to recognize or ignore gestures when writing a new action class:</para>
 *   <informalexample><programlisting><![CDATA[
  Prepare -> Cancel
  Prepare -> Begin -> Cancel
  Prepare -> Begin -> End
  Prepare -> Begin -> Progress -> Cancel
  Prepare -> Begin -> Progress -> End
 * ]]>
 *   </programlisting></informalexample>
 *   <para>Each #ClutterGestureAction starts in the "prepare" state, and calls
 *   the #ClutterGestureActionClass.gesture_prepare() virtual function; this
 *   state can be used to reset the internal state of a #ClutterGestureAction
 *   subclass, but it can also immediately cancel a gesture without going
 *   through the rest of the states.</para>
 *   <para>The "begin" state follows the "prepare" state, and calls the
 *   #ClutterGestureActionClass.gesture_begin() virtual function. This state
 *   signals the start of a gesture recognizing process. From the "begin" state
 *   the gesture recognition process can successfully end, by going to the
 *   "end" state; it can continue in the "progress" state, in case of a
 *   continuous gesture; or it can be terminated, by moving to the "cancel"
 *   state.</para>
 *   <para>In case of continuous gestures, the #ClutterGestureAction will use
 *   the "progress" state, calling the #ClutterGestureActionClass.gesture_progress()
 *   virtual function; the "progress" state will continue until the end of the
 *   gesture, in which case the "end" state will be reached, or until the
 *   gesture is cancelled, in which case the "cancel" gesture will be used
 *   instead.</para>
 * </refsect2>
 *
 * Since: 1.8
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "clutter-gesture-action-private.h"

#include "clutter-debug.h"
#include "clutter-enum-types.h"
#include "clutter-marshal.h"
#include "clutter-private.h"

#include <math.h>

#define MAX_GESTURE_POINTS (10)
#define FLOAT_EPSILON   (1e-15)

typedef struct
{
  ClutterInputDevice *device;
  ClutterEventSequence *sequence;
  ClutterEvent *last_event;

  gfloat press_x, press_y;
  gint64 last_motion_time;
  gfloat last_motion_x, last_motion_y;
  gint64 last_delta_time;
  gfloat last_delta_x, last_delta_y;
  gfloat release_x, release_y;
} GesturePoint;

struct _ClutterGestureActionPrivate
{
  ClutterActor *stage;

  gint requested_nb_points;
  GArray *points;

  guint actor_capture_id;
  gulong stage_capture_id;

  ClutterGestureTriggerEdge edge;

  guint in_gesture : 1;
};

enum
{
  GESTURE_BEGIN,
  GESTURE_PROGRESS,
  GESTURE_END,
  GESTURE_CANCEL,

  LAST_SIGNAL
};

static guint gesture_signals[LAST_SIGNAL] = { 0, };

G_DEFINE_TYPE (ClutterGestureAction, clutter_gesture_action, CLUTTER_TYPE_ACTION);

static GesturePoint *
gesture_register_point (ClutterGestureAction *action, ClutterEvent *event)
{
  ClutterGestureActionPrivate *priv = action->priv;
  GesturePoint *point = NULL;

  if (priv->points->len >= MAX_GESTURE_POINTS)
    return NULL;

  g_array_set_size (priv->points, priv->points->len + 1);
  point = &g_array_index (priv->points, GesturePoint, priv->points->len - 1);

  point->last_event = clutter_event_copy (event);
  point->device = clutter_event_get_device (event);

  clutter_event_get_coords (event, &point->press_x, &point->press_y);
  point->last_motion_x = point->press_x;
  point->last_motion_y = point->press_y;
  point->last_motion_time = clutter_event_get_time (event);

  point->last_delta_x = point->last_delta_y = 0;
  point->last_delta_time = 0;

  if (clutter_event_type (event) != CLUTTER_BUTTON_PRESS)
    point->sequence = clutter_event_get_event_sequence (event);
  else
    point->sequence = NULL;

  return point;
}

static GesturePoint *
gesture_find_point (ClutterGestureAction *action,
                    ClutterEvent *event,
                    gint *position)
{
  ClutterGestureActionPrivate *priv = action->priv;
  GesturePoint *point = NULL;
  ClutterEventType type = clutter_event_type (event);
  ClutterInputDevice *device = clutter_event_get_device (event);
  ClutterEventSequence *sequence = NULL;
  gint i;

  if ((type != CLUTTER_BUTTON_PRESS) &&
      (type != CLUTTER_BUTTON_RELEASE) &&
      (type != CLUTTER_MOTION))
    sequence = clutter_event_get_event_sequence (event);

  for (i = 0; i < priv->points->len; i++)
    {
      if ((g_array_index (priv->points, GesturePoint, i).device == device) &&
          (g_array_index (priv->points, GesturePoint, i).sequence == sequence))
        {
          if (position != NULL)
            *position = i;
          point = &g_array_index (priv->points, GesturePoint, i);
          break;
        }
    }

  return point;
}

static void
gesture_unregister_point (ClutterGestureAction *action, gint position)
{
  ClutterGestureActionPrivate *priv = action->priv;

  g_array_remove_index (priv->points, position);
}

static gint
gesture_get_threshold (ClutterGestureAction *action)
{
  gint threshold;
  ClutterSettings *settings = clutter_settings_get_default ();
  g_object_get (settings, "dnd-drag-threshold", &threshold, NULL);
  return threshold;
}

static void
gesture_point_unset (GesturePoint *point)
{
  clutter_event_free (point->last_event);
}

static void
cancel_gesture (ClutterGestureAction *action)
{
  ClutterGestureActionPrivate *priv = action->priv;
  ClutterActor *actor;

  priv->in_gesture = FALSE;

  if (priv->stage_capture_id != 0)
    {
      g_signal_handler_disconnect (priv->stage, priv->stage_capture_id);
      priv->stage_capture_id = 0;
    }

  actor = clutter_actor_meta_get_actor (CLUTTER_ACTOR_META (action));
  g_signal_emit (action, gesture_signals[GESTURE_CANCEL], 0, actor);

  g_array_set_size (action->priv->points, 0);
}

static gboolean
begin_gesture (ClutterGestureAction *action,
               ClutterActor         *actor)
{
  ClutterGestureActionPrivate *priv = action->priv;
  gboolean return_value;

  priv->in_gesture = TRUE;

  if (!CLUTTER_GESTURE_ACTION_GET_CLASS (action)->gesture_prepare (action, actor))
    {
      cancel_gesture (action);
      return FALSE;
    }

  /* clutter_gesture_action_cancel() may have been called during
   * gesture_prepare(), check that the gesture is still active. */
  if (!priv->in_gesture)
    return FALSE;

  g_signal_emit (action, gesture_signals[GESTURE_BEGIN], 0, actor,
                 &return_value);

  if (!return_value)
    {
      cancel_gesture (action);
      return FALSE;
    }

  return TRUE;
}

static gboolean
stage_captured_event_cb (ClutterActor       *stage,
                         ClutterEvent       *event,
                         ClutterGestureAction *action)
{
  ClutterGestureActionPrivate *priv = action->priv;
  ClutterActor *actor;
  gint position, drag_threshold;
  gboolean return_value;
  GesturePoint *point;
  gfloat motion_x, motion_y;
  gint64 time;

  if ((point = gesture_find_point (action, event, &position)) == NULL)
    return CLUTTER_EVENT_PROPAGATE;

  actor = clutter_actor_meta_get_actor (CLUTTER_ACTOR_META (action));

  switch (clutter_event_type (event))
    {
    case CLUTTER_MOTION:
      {
        ClutterModifierType mods = clutter_event_get_state (event);

        /* we might miss a button-release event in case of grabs,
         * so we need to check whether the button is still down
         * during a motion event
         */
        if (!(mods & CLUTTER_BUTTON1_MASK))
          {
            cancel_gesture (action);
            return CLUTTER_EVENT_PROPAGATE;
          }
      }
      /* Follow same code path as a touch event update */

    case CLUTTER_TOUCH_UPDATE:
      clutter_event_get_coords (event,
                                &motion_x,
                                &motion_y);

      if (priv->points->len < priv->requested_nb_points)
        return CLUTTER_EVENT_PROPAGATE;

      drag_threshold = gesture_get_threshold (action);

      if (!priv->in_gesture)
        {
          /* Wait until the drag threshold has been exceeded
           * before starting _TRIGGER_EDGE_AFTER gestures. */
          if (priv->edge == CLUTTER_GESTURE_TRIGGER_EDGE_AFTER &&
              (fabsf (point->press_y - motion_y) < drag_threshold) &&
              (fabsf (point->press_x - motion_x) < drag_threshold))
            return CLUTTER_EVENT_PROPAGATE;

          if (!begin_gesture(action, actor))
            return CLUTTER_EVENT_PROPAGATE;
        }

      clutter_event_free (point->last_event);
      point->last_event = clutter_event_copy (event);

      point->last_delta_x = motion_x - point->last_motion_x;
      point->last_delta_y = motion_y - point->last_motion_y;
      point->last_motion_x = motion_x;
      point->last_motion_y = motion_y;

      time = clutter_event_get_time (event);
      point->last_delta_time = time - point->last_motion_time;
      point->last_motion_time = time;

      g_signal_emit (action, gesture_signals[GESTURE_PROGRESS], 0, actor,
                     &return_value);
      if (!return_value)
        {
          cancel_gesture (action);
          return CLUTTER_EVENT_PROPAGATE;
        }

      /* Check if a _TRIGGER_EDGE_BEFORE gesture needs to be cancelled because
       * the drag threshold has been exceeded. */
      if (priv->edge == CLUTTER_GESTURE_TRIGGER_EDGE_BEFORE &&
          ((fabsf (point->press_y - motion_y) > drag_threshold) ||
           (fabsf (point->press_x - motion_x) > drag_threshold)))
        {
          cancel_gesture (action);
          return CLUTTER_EVENT_PROPAGATE;
        }
      break;

    case CLUTTER_BUTTON_RELEASE:
    case CLUTTER_TOUCH_END:
      {
        clutter_event_get_coords (event, &point->release_x, &point->release_y);

        clutter_event_free (point->last_event);
        point->last_event = clutter_event_copy (event);

        if (priv->in_gesture &&
            ((priv->points->len - 1) < priv->requested_nb_points))
          {
            /* Treat the release event as the continuation of the last motion,
             * in case the user keeps the pointer still for a while before
             * releasing it. */
            time = clutter_event_get_time (event);
            point->last_delta_time += time - point->last_motion_time;

            priv->in_gesture = FALSE;
            g_signal_emit (action, gesture_signals[GESTURE_END], 0, actor);
          }

        gesture_unregister_point (action, position);
      }
      break;

    case CLUTTER_TOUCH_CANCEL:
      {
        if (priv->in_gesture)
          {
            priv->in_gesture = FALSE;
            cancel_gesture (action);
          }

        gesture_unregister_point (action, position);
      }
      break;

    default:
      break;
    }

  if (priv->points->len == 0)
    {
      g_signal_handler_disconnect (priv->stage, priv->stage_capture_id);
      priv->stage_capture_id = 0;
    }

  return CLUTTER_EVENT_PROPAGATE;
}

static gboolean
actor_captured_event_cb (ClutterActor *actor,
                         ClutterEvent *event,
                         ClutterGestureAction *action)
{
  ClutterGestureActionPrivate *priv = action->priv;
  GesturePoint *point G_GNUC_UNUSED;

  if ((clutter_event_type (event) != CLUTTER_BUTTON_PRESS) &&
      (clutter_event_type (event) != CLUTTER_TOUCH_BEGIN))
    return CLUTTER_EVENT_PROPAGATE;

  if (!clutter_actor_meta_get_enabled (CLUTTER_ACTOR_META (action)))
    return CLUTTER_EVENT_PROPAGATE;

  point = gesture_register_point (action, event);

  if (priv->stage == NULL)
    priv->stage = clutter_actor_get_stage (actor);

  if (priv->stage_capture_id == 0)
    priv->stage_capture_id =
      g_signal_connect_after (priv->stage, "captured-event",
                              G_CALLBACK (stage_captured_event_cb),
                              action);

  /* Start the gesture immediately if the gesture has no
   * _TRIGGER_EDGE_AFTER drag threshold. */
  if (priv->edge != CLUTTER_GESTURE_TRIGGER_EDGE_AFTER)
    begin_gesture (action, actor);

  return CLUTTER_EVENT_PROPAGATE;
}

static void
clutter_gesture_action_set_actor (ClutterActorMeta *meta,
                                  ClutterActor     *actor)
{
  ClutterGestureActionPrivate *priv = CLUTTER_GESTURE_ACTION (meta)->priv;
  ClutterActorMetaClass *meta_class =
    CLUTTER_ACTOR_META_CLASS (clutter_gesture_action_parent_class);

  if (priv->actor_capture_id != 0)
    {
      ClutterActor *old_actor = clutter_actor_meta_get_actor (meta);

      if (old_actor != NULL)
        g_signal_handler_disconnect (old_actor, priv->actor_capture_id);

      priv->actor_capture_id = 0;
    }

  if (priv->stage_capture_id != 0)
    {
      if (priv->stage != NULL)
        g_signal_handler_disconnect (priv->stage, priv->stage_capture_id);

      priv->stage_capture_id = 0;
      priv->stage = NULL;
    }

  if (actor != NULL)
    {
      priv->actor_capture_id =
        g_signal_connect (actor, "captured-event",
                          G_CALLBACK (actor_captured_event_cb),
                          meta);
    }

  meta_class->set_actor (meta, actor);
}

static gboolean
default_event_handler (ClutterGestureAction *action,
                       ClutterActor *actor)
{
  return TRUE;
}


/*< private >
 * _clutter_gesture_action_set_threshold_trigger_edge:
 * @action: a #ClutterGestureAction
 * @edge: the %ClutterGestureTriggerEdge
 *
 * Sets the edge trigger for the gesture drag threshold, if any.
 *
 * This function can be called by #ClutterGestureAction subclasses that needs
 * to change the %CLUTTER_GESTURE_TRIGGER_EDGE_AFTER default.
 *
 * Since: 1.14
 */
void
_clutter_gesture_action_set_threshold_trigger_edge  (ClutterGestureAction     *action,
                                                     ClutterGestureTriggerEdge edge)
{
  action->priv->edge = edge;
}

static void
clutter_gesture_action_class_init (ClutterGestureActionClass *klass)
{
  ClutterActorMetaClass *meta_class = CLUTTER_ACTOR_META_CLASS (klass);

  g_type_class_add_private (klass, sizeof (ClutterGestureActionPrivate));

  meta_class->set_actor = clutter_gesture_action_set_actor;

  klass->gesture_begin = default_event_handler;
  klass->gesture_progress = default_event_handler;
  klass->gesture_prepare = default_event_handler;

  /**
   * ClutterGestureAction::gesture-begin:
   * @action: the #ClutterGestureAction that emitted the signal
   * @actor: the #ClutterActor attached to the @action
   *
   * The ::gesture_begin signal is emitted when the #ClutterActor to which
   * a #ClutterGestureAction has been applied starts receiving a gesture.
   *
   * Return value: %TRUE if the gesture should start, and %FALSE if
   *   the gesture should be ignored.
   *
   * Since: 1.8
   */
  gesture_signals[GESTURE_BEGIN] =
    g_signal_new (I_("gesture-begin"),
                  G_TYPE_FROM_CLASS (klass),
                  G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (ClutterGestureActionClass, gesture_begin),
                  _clutter_boolean_continue_accumulator, NULL,
                  _clutter_marshal_BOOLEAN__OBJECT,
                  G_TYPE_BOOLEAN, 1,
                  CLUTTER_TYPE_ACTOR);

  /**
   * ClutterGestureAction::gesture-progress:
   * @action: the #ClutterGestureAction that emitted the signal
   * @actor: the #ClutterActor attached to the @action
   *
   * The ::gesture-progress signal is emitted for each motion event after
   * the #ClutterGestureAction::gesture-begin signal has been emitted.
   *
   * Return value: %TRUE if the gesture should continue, and %FALSE if
   *   the gesture should be cancelled.
   *
   * Since: 1.8
   */
  gesture_signals[GESTURE_PROGRESS] =
    g_signal_new (I_("gesture-progress"),
                  G_TYPE_FROM_CLASS (klass),
                  G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (ClutterGestureActionClass, gesture_progress),
                  _clutter_boolean_continue_accumulator, NULL,
                  _clutter_marshal_BOOLEAN__OBJECT,
                  G_TYPE_BOOLEAN, 1,
                  CLUTTER_TYPE_ACTOR);

  /**
   * ClutterGestureAction::gesture-end:
   * @action: the #ClutterGestureAction that emitted the signal
   * @actor: the #ClutterActor attached to the @action
   *
   * The ::gesture-end signal is emitted at the end of the gesture gesture,
   * when the pointer's button is released
   *
   * This signal is emitted if and only if the #ClutterGestureAction::gesture-begin
   * signal has been emitted first.
   *
   * Since: 1.8
   */
  gesture_signals[GESTURE_END] =
    g_signal_new (I_("gesture-end"),
                  G_TYPE_FROM_CLASS (klass),
                  G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (ClutterGestureActionClass, gesture_end),
                  NULL, NULL,
                  _clutter_marshal_VOID__OBJECT,
                  G_TYPE_NONE, 1,
                  CLUTTER_TYPE_ACTOR);

  /**
   * ClutterGestureAction::gesture-cancel:
   * @action: the #ClutterGestureAction that emitted the signal
   * @actor: the #ClutterActor attached to the @action
   *
   * The ::gesture-cancel signal is emitted when the ongoing gesture gets
   * cancelled from the #ClutterGestureAction::gesture-progress signal handler.
   *
   * This signal is emitted if and only if the #ClutterGestureAction::gesture-begin
   * signal has been emitted first.
   *
   * Since: 1.8
   */
  gesture_signals[GESTURE_CANCEL] =
    g_signal_new (I_("gesture-cancel"),
                  G_TYPE_FROM_CLASS (klass),
                  G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (ClutterGestureActionClass, gesture_cancel),
                  NULL, NULL,
                  _clutter_marshal_VOID__OBJECT,
                  G_TYPE_NONE, 1,
                  CLUTTER_TYPE_ACTOR);
}

static void
clutter_gesture_action_init (ClutterGestureAction *self)
{
  self->priv = G_TYPE_INSTANCE_GET_PRIVATE (self, CLUTTER_TYPE_GESTURE_ACTION,
                                            ClutterGestureActionPrivate);

  self->priv->points = g_array_sized_new (FALSE, TRUE, sizeof (GesturePoint), 3);
  g_array_set_clear_func (self->priv->points, (GDestroyNotify) gesture_point_unset);

  self->priv->requested_nb_points = 1;
  self->priv->edge = CLUTTER_GESTURE_TRIGGER_EDGE_AFTER;
}

/**
 * clutter_gesture_action_new:
 *
 * Creates a new #ClutterGestureAction instance.
 *
 * Return value: the newly created #ClutterGestureAction
 *
 * Since: 1.8
 */
ClutterAction *
clutter_gesture_action_new (void)
{
  return g_object_new (CLUTTER_TYPE_GESTURE_ACTION, NULL);
}

/**
 * clutter_gesture_action_get_press_coords:
 * @action: a #ClutterGestureAction
 * @device: currently unused, set to 0
 * @press_x: (out) (allow-none): return location for the press
 *   event's X coordinate
 * @press_y: (out) (allow-none): return location for the press
 *   event's Y coordinate
 *
 * Retrieves the coordinates, in stage space, of the press event
 * that started the dragging for an specific pointer device
 *
 * Since: 1.8
 */
void
clutter_gesture_action_get_press_coords (ClutterGestureAction *action,
                                         guint                 device,
                                         gfloat               *press_x,
                                         gfloat               *press_y)
{
  g_return_if_fail (CLUTTER_IS_GESTURE_ACTION (action));
  g_return_if_fail (action->priv->points->len > device);

  if (press_x)
    *press_x = g_array_index (action->priv->points,
                              GesturePoint,
                              device).press_x;

  if (press_y)
    *press_y = g_array_index (action->priv->points,
                              GesturePoint,
                              device).press_y;
}

/**
 * clutter_gesture_action_get_motion_coords:
 * @action: a #ClutterGestureAction
 * @device: currently unused, set to 0
 * @motion_x: (out) (allow-none): return location for the latest motion
 *   event's X coordinate
 * @motion_y: (out) (allow-none): return location for the latest motion
 *   event's Y coordinate
 *
 * Retrieves the coordinates, in stage space, of the latest motion
 * event during the dragging
 *
 * Since: 1.8
 */
void
clutter_gesture_action_get_motion_coords (ClutterGestureAction *action,
                                          guint                 device,
                                          gfloat               *motion_x,
                                          gfloat               *motion_y)
{
  g_return_if_fail (CLUTTER_IS_GESTURE_ACTION (action));
  g_return_if_fail (action->priv->points->len > device);

  if (motion_x)
    *motion_x = g_array_index (action->priv->points,
                               GesturePoint,
                               device).last_motion_x;

  if (motion_y)
    *motion_y = g_array_index (action->priv->points,
                               GesturePoint,
                               device).last_motion_y;
}

/**
 * clutter_gesture_action_get_motion_delta:
 * @action: a #ClutterGestureAction
 * @device: currently unused, set to 0
 * @delta_x: (out) (allow-none): return location for the X axis
 *   component of the incremental motion delta
 * @delta_y: (out) (allow-none): return location for the Y axis
 *   component of the incremental motion delta
 *
 * Retrieves the incremental delta since the last motion event
 * during the dragging.
 *
 * Return value: the distance since last motion event
 *
 * Since: 1.12
 */
gfloat
clutter_gesture_action_get_motion_delta (ClutterGestureAction *action,
                                         guint                 device,
                                         gfloat               *delta_x,
                                         gfloat               *delta_y)
{
  gfloat d_x, d_y;

  g_return_val_if_fail (CLUTTER_IS_GESTURE_ACTION (action), 0);
  g_return_val_if_fail (action->priv->points->len > device, 0);

  d_x = g_array_index (action->priv->points,
                       GesturePoint,
                       device).last_delta_x;
  d_y = g_array_index (action->priv->points,
                       GesturePoint,
                       device).last_delta_y;

  if (delta_x)
    *delta_x = d_x;

  if (delta_y)
    *delta_y = d_y;

  return sqrt ((d_x * d_x) + (d_y * d_y));
}

/**
 * clutter_gesture_action_get_release_coords:
 * @action: a #ClutterGestureAction
 * @device: currently unused, set to 0
 * @release_x: (out) (allow-none): return location for the X coordinate of
 *   the last release
 * @release_y: (out) (allow-none): return location for the Y coordinate of
 *   the last release
 *
 * Retrieves the coordinates, in stage space, of the point where the pointer
 * device was last released.
 *
 * Since: 1.8
 */
void
clutter_gesture_action_get_release_coords (ClutterGestureAction *action,
                                           guint                 device,
                                           gfloat               *release_x,
                                           gfloat               *release_y)
{
  g_return_if_fail (CLUTTER_IS_GESTURE_ACTION (action));
  g_return_if_fail (action->priv->points->len > device);

  if (release_x)
    *release_x = g_array_index (action->priv->points,
                                GesturePoint,
                                device).release_x;

  if (release_y)
    *release_y = g_array_index (action->priv->points,
                                GesturePoint,
                                device).release_y;
}

/**
 * clutter_gesture_action_get_velocity:
 * @action: a #ClutterGestureAction
 * @device: currently unused, set to 0
 * @velocity_x: (out) (allow-none): return location for the latest motion
 *   event's X velocity
 * @velocity_y: (out) (allow-none): return location for the latest motion
 *   event's Y velocity
 *
 * Retrieves the velocity, in stage pixels per milliseconds, of the
 * latest motion event during the dragging
 *
 * Since: 1.12
 */
gfloat
clutter_gesture_action_get_velocity (ClutterGestureAction *action,
                                     guint                 device,
                                     gfloat               *velocity_x,
                                     gfloat               *velocity_y)
{
  gfloat d_x, d_y, distance, velocity;
  gint64 d_t;

  g_return_val_if_fail (CLUTTER_IS_GESTURE_ACTION (action), 0);
  g_return_val_if_fail (action->priv->points->len > device, 0);

  distance = clutter_gesture_action_get_motion_delta (action, device,
                                                      &d_x, &d_y);

  d_t = g_array_index (action->priv->points,
                       GesturePoint,
                       device).last_delta_time;

  if (velocity_x)
    *velocity_x = d_t > FLOAT_EPSILON ? d_x / d_t : 0;

  if (velocity_y)
    *velocity_y = d_t > FLOAT_EPSILON ? d_y / d_t : 0;

  velocity = d_t > FLOAT_EPSILON ? distance / d_t : 0;
  return velocity;
}

/**
 * clutter_gesture_action_get_n_touch_points:
 * @action: a #ClutterGestureAction
 *
 * Retrieves the number of requested points to trigger the gesture.
 *
 * Return value: the number of points to trigger the gesture.
 *
 * Since: 1.12
 */
gint
clutter_gesture_action_get_n_touch_points (ClutterGestureAction *action)
{
  g_return_val_if_fail (CLUTTER_IS_GESTURE_ACTION (action), 0);

  return action->priv->requested_nb_points;
}

/**
 * clutter_gesture_action_set_n_touch_points:
 * @action: a #ClutterGestureAction
 * @nb_points: a number of points
 *
 * Sets the number of points needed to trigger the gesture.
 *
 * Since: 1.12
 */
void
clutter_gesture_action_set_n_touch_points (ClutterGestureAction *action,
                                           gint                  nb_points)
{
  ClutterGestureActionPrivate *priv;

  g_return_if_fail (CLUTTER_IS_GESTURE_ACTION (action));
  g_return_if_fail (nb_points >= 1);

  priv = action->priv;

  priv->requested_nb_points = nb_points;

  if (priv->in_gesture)
    {
      if (priv->points->len < priv->requested_nb_points)
        cancel_gesture (action);
    }
  else if (priv->edge == CLUTTER_GESTURE_TRIGGER_EDGE_AFTER)
    {
      if (priv->points->len >= priv->requested_nb_points)
        {
          ClutterActor *actor =
            clutter_actor_meta_get_actor (CLUTTER_ACTOR_META (action));
          gint i, drag_threshold;

          drag_threshold = gesture_get_threshold (action);

          for (i = 0; i < priv->points->len; i++)
            {
              GesturePoint *point = &g_array_index (priv->points, GesturePoint, i);

              if ((ABS (point->press_y - point->last_motion_y) >= drag_threshold) ||
                  (ABS (point->press_x - point->last_motion_x) >= drag_threshold))
                {
                  begin_gesture (action, actor);
                  break;
                }
            }
        }
    }
}

/**
 * clutter_gesture_action_get_n_current_points:
 * @action: a #ClutterGestureAction
 *
 * Retrieves the number of points currently active.
 *
 * Return value: the number of points currently active.
 *
 * Since: 1.12
 */
guint
clutter_gesture_action_get_n_current_points (ClutterGestureAction *action)
{
  g_return_val_if_fail (CLUTTER_IS_GESTURE_ACTION (action), 0);

  return action->priv->points->len;
}

/**
 * clutter_gesture_action_get_sequence:
 * @action: a #ClutterGestureAction
 * @point: index of a point currently active
 *
 * Retrieves the #ClutterEventSequence of a touch point.
 *
 * Return value: (transfer none): the #ClutterEventSequence of a touch point.
 *
 * Since: 1.12
 */
ClutterEventSequence *
clutter_gesture_action_get_sequence (ClutterGestureAction *action,
                                     guint                 point)
{
  g_return_val_if_fail (CLUTTER_IS_GESTURE_ACTION (action), NULL);
  g_return_val_if_fail (action->priv->points->len > point, NULL);

  return g_array_index (action->priv->points, GesturePoint, point).sequence;
}

/**
 * clutter_gesture_action_get_device:
 * @action: a #ClutterGestureAction
 * @point: index of a point currently active
 *
 * Retrieves the #ClutterInputDevice of a touch point.
 *
 * Return value: (transfer none): the #ClutterInputDevice of a touch point.
 *
 * Since: 1.12
 */
ClutterInputDevice *
clutter_gesture_action_get_device (ClutterGestureAction *action,
                                   guint                 point)
{
  g_return_val_if_fail (CLUTTER_IS_GESTURE_ACTION (action), NULL);
  g_return_val_if_fail (action->priv->points->len > point, NULL);

  return g_array_index (action->priv->points, GesturePoint, point).device;
}

/**
 * clutter_gesture_action_get_last_event:
 * @action: a #ClutterGestureAction
 * @point: index of a point currently active
 *
 * Retrieves a reference to the last #ClutterEvent for a touch point. Call
 * clutter_event_copy() if you need to store the reference somewhere.
 *
 * Return value: (transfer none): the last #ClutterEvent for a touch point.
 *
 * Since: 1.14
 */
const ClutterEvent *
clutter_gesture_action_get_last_event (ClutterGestureAction *action,
                                       guint                 point)
{
  GesturePoint *gesture_point;

  g_return_val_if_fail (CLUTTER_IS_GESTURE_ACTION (action), NULL);
  g_return_val_if_fail (action->priv->points->len > point, NULL);

  gesture_point = &g_array_index (action->priv->points, GesturePoint, point);

  return gesture_point->last_event;
}

/**
 * clutter_gesture_action_cancel:
 * @action: a #ClutterGestureAction
 *
 * Cancel a #ClutterGestureAction before it begins
 *
 * Since: 1.12
 */
void
clutter_gesture_action_cancel (ClutterGestureAction *action)
{
  g_return_if_fail (CLUTTER_IS_GESTURE_ACTION (action));

  cancel_gesture (action);
}