ClutterDragAction: Clutter Reference Manual

ClutterDragAction

ClutterDragAction — Action enabling dragging on actors

Functions

ClutterAction *	clutter_drag_action_new ()
void	clutter_drag_action_set_drag_threshold ()
void	clutter_drag_action_get_drag_threshold ()
void	clutter_drag_action_set_drag_handle ()
ClutterActor *	clutter_drag_action_get_drag_handle ()
void	clutter_drag_action_set_drag_axis ()
ClutterDragAxis	clutter_drag_action_get_drag_axis ()
void	clutter_drag_action_set_drag_area ()
gboolean	clutter_drag_action_get_drag_area ()
void	clutter_drag_action_get_press_coords ()
void	clutter_drag_action_get_motion_coords ()

Properties

ClutterRect *	drag-area	Read / Write
gboolean	drag-area-set	Read
ClutterDragAxis	drag-axis	Read / Write
ClutterActor *	drag-handle	Read / Write
gint	x-drag-threshold	Read / Write
gint	y-drag-threshold	Read / Write

Signals

void	drag-begin	Run Last
void	drag-end	Run Last
void	drag-motion	Run Last
gboolean	drag-progress	Run Last

Types and Values

struct	ClutterDragAction
struct	ClutterDragActionClass
enum	ClutterDragAxis

Object Hierarchy

    GObject
    ╰── GInitiallyUnowned
        ╰── ClutterActorMeta
            ╰── ClutterAction
                ╰── ClutterDragAction

Description

ClutterDragAction is a sub-class of ClutterAction that implements all the necessary logic for dragging actors.

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

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

will automatically result in the actor moving to follow the pointer whenever the pointer's button is pressed over the actor and moved across the stage.

The ClutterDragAction will signal the begin and the end of a dragging through the “drag-begin” and “drag-end” signals, respectively. Each pointer motion during a drag will also result in the “drag-motion” signal to be emitted.

It is also possible to set another ClutterActor as the dragged actor by calling clutter_drag_action_set_drag_handle() from within a handle of the “drag-begin” signal. The drag handle must be parented and exist between the emission of “drag-begin” and “drag-end”.

The drag-action example allows dragging the rectangle around the stage using a ClutterDragAction. When pressing the Shift key the actor that is being dragged will be a separate rectangle, and when the drag ends, the original rectangle will be animated to the final drop coordinates.

ClutterDragAction is available since Clutter 1.4

Functions

clutter_drag_action_new ()

ClutterAction *
clutter_drag_action_new (void);

Creates a new ClutterDragAction instance

Returns

the newly created ClutterDragAction

Since: 1.4

clutter_drag_action_set_drag_threshold ()

void
clutter_drag_action_set_drag_threshold
                               (ClutterDragAction *action,
                                gint x_threshold,
                                gint y_threshold);

Sets the horizontal and vertical drag thresholds that must be cleared by the pointer before action can begin the dragging.

If x_threshold or y_threshold are set to -1 then the default drag threshold stored in the “dnd-drag-threshold” property of ClutterSettings will be used.

Parameters

action	a ClutterDragAction
x_threshold	a distance on the horizontal axis, in pixels, or -1 to use the default drag threshold from ClutterSettings
y_threshold	a distance on the vertical axis, in pixels, or -1 to use the default drag threshold from ClutterSettings

Since: 1.4

clutter_drag_action_get_drag_threshold ()

void
clutter_drag_action_get_drag_threshold
                               (ClutterDragAction *action,
                                guint *x_threshold,
                                guint *y_threshold);

Retrieves the values set by clutter_drag_action_set_drag_threshold().

If the “x-drag-threshold” property or the “y-drag-threshold” property have been set to -1 then this function will return the default drag threshold value as stored by the “dnd-drag-threshold” property of ClutterSettings.

Parameters

action	a ClutterDragAction
x_threshold	return location for the horizontal drag threshold value, in pixels.	[out]
y_threshold	return location for the vertical drag threshold value, in pixels.	[out]

Since: 1.4

clutter_drag_action_set_drag_handle ()

void
clutter_drag_action_set_drag_handle (ClutterDragAction *action,
                                     ClutterActor *handle);

Sets the actor to be used as the drag handle.

Parameters

action	a ClutterDragAction
handle	a ClutterActor, or `NULL` to unset.	[allow-none]

Since: 1.4

clutter_drag_action_get_drag_handle ()

ClutterActor *
clutter_drag_action_get_drag_handle (ClutterDragAction *action);

Retrieves the drag handle set by clutter_drag_action_set_drag_handle()

Parameters

action

a ClutterDragAction

Returns

a ClutterActor, used as the drag handle, or NULL if none was set.

[transfer none]

Since: 1.4

clutter_drag_action_set_drag_axis ()

void
clutter_drag_action_set_drag_axis (ClutterDragAction *action,
                                   ClutterDragAxis axis);

Restricts the dragging action to a specific axis

Parameters

action	a ClutterDragAction
axis	the axis to constraint the dragging to

Since: 1.4

clutter_drag_action_get_drag_axis ()

ClutterDragAxis
clutter_drag_action_get_drag_axis (ClutterDragAction *action);

Retrieves the axis constraint set by clutter_drag_action_set_drag_axis()

Parameters

action

a ClutterDragAction

Returns

the axis constraint

Since: 1.4

clutter_drag_action_set_drag_area ()

void
clutter_drag_action_set_drag_area (ClutterDragAction *action,
                                   const ClutterRect *drag_area);

Sets drag_area to constrain the dragging of the actor associated with action , so that it position is always within drag_area , expressed in parent's coordinates. If drag_area is NULL, the actor is not constrained.

Parameters

action	a ClutterDragAction
drag_area	a ClutterRect.	[allow-none]

clutter_drag_action_get_drag_area ()

gboolean
clutter_drag_action_get_drag_area (ClutterDragAction *action,
                                   ClutterRect *drag_area);

Retrieves the "drag area" associated with action , that is a ClutterRect that constrains the actor movements, in parents coordinates.

Parameters

action	a ClutterDragAction
drag_area	a ClutterRect to be filled.	[out caller-allocates]

Returns

TRUE if the actor is actually constrained (and thus drag_area is valid), FALSE otherwise

clutter_drag_action_get_press_coords ()

void
clutter_drag_action_get_press_coords (ClutterDragAction *action,
                                      gfloat *press_x,
                                      gfloat *press_y);

Retrieves the coordinates, in stage space, of the press event that started the dragging

Parameters

action	a ClutterDragAction
press_x	return location for the press event's X coordinate.	[out]
press_y	return location for the press event's Y coordinate.	[out]

Since: 1.4

clutter_drag_action_get_motion_coords ()

void
clutter_drag_action_get_motion_coords (ClutterDragAction *action,
                                       gfloat *motion_x,
                                       gfloat *motion_y);

Retrieves the coordinates, in stage space, of the latest motion event during the dragging

Parameters

action	a ClutterDragAction
motion_x	return location for the latest motion event's X coordinate.	[out]
motion_y	return location for the latest motion event's Y coordinate.	[out]

Since: 1.4

Types and Values

struct ClutterDragAction

struct ClutterDragAction;

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

Since: 1.4

struct ClutterDragActionClass

struct ClutterDragActionClass {
  void          (* drag_begin)          (ClutterDragAction   *action,
                                         ClutterActor        *actor,
                                         gfloat               event_x,
                                         gfloat               event_y,
                                         ClutterModifierType  modifiers);
  void          (* drag_motion)         (ClutterDragAction   *action,
                                         ClutterActor        *actor,
                                         gfloat               delta_x,
                                         gfloat               delta_y);
  void          (* drag_end)            (ClutterDragAction   *action,
                                         ClutterActor        *actor,
                                         gfloat               event_x,
                                         gfloat               event_y,
                                         ClutterModifierType  modifiers);
  gboolean      (* drag_progress)       (ClutterDragAction   *action,
                                         ClutterActor        *actor,
                                         gfloat               delta_x,
                                         gfloat               delta_y);
};

The ClutterDragActionClass structure contains only private data

Members

`drag_begin` ()	class handler of the “drag-begin” signal
`drag_motion` ()	class handler of the “drag-motion” signal
`drag_end` ()	class handler of the “drag-end” signal
`drag_progress` ()	class handler of the “drag-progress” signal

Since: 1.4

enum ClutterDragAxis

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

Members

CLUTTER_DRAG_AXIS_NONE	No constraint
CLUTTER_DRAG_X_AXIS	Set a constraint on the X axis
CLUTTER_DRAG_Y_AXIS	Set a constraint on the Y axis

Since: 1.4

Property Details

The `“drag-area”` property

  “drag-area”                ClutterRect *

Constains the dragging action (or in particular, the resulting actor position) to the specified ClutterRect, in parent's coordinates.

Flags: Read / Write

Since: 1.12

The `“drag-area-set”` property

  “drag-area-set”            gboolean

Whether the “drag-area” property has been set.

Flags: Read

Default value: FALSE

Since: 1.12

The `“drag-axis”` property

  “drag-axis”                ClutterDragAxis

Constraints the dragging action to the specified axis

Flags: Read / Write

Default value: CLUTTER_DRAG_AXIS_NONE

Since: 1.4

The `“drag-handle”` property

  “drag-handle”              ClutterActor *

The ClutterActor that is effectively being dragged

A ClutterDragAction will, be default, use the ClutterActor that has been attached to the action; it is possible to create a separate ClutterActor and use it instead.

Setting this property has no effect on the ClutterActor argument passed to the ClutterDragAction signals

Flags: Read / Write

Since: 1.4

The `“x-drag-threshold”` property

  “x-drag-threshold”         gint

The horizontal threshold, in pixels, that the cursor must travel in order to begin a drag action.

When set to a positive value, ClutterDragAction will only emit “drag-begin” if the pointer has moved horizontally at least of the given amount of pixels since the button press event.

When set to -1, ClutterDragAction will use the default threshold stored in the “dnd-drag-threshold” property of ClutterSettings.

When read, this property will always return a valid drag threshold, either as set or the default one.

Flags: Read / Write

Allowed values: >= -1

Default value: 0

Since: 1.4

The `“y-drag-threshold”` property

  “y-drag-threshold”         gint

The vertical threshold, in pixels, that the cursor must travel in order to begin a drag action.

When set to a positive value, ClutterDragAction will only emit “drag-begin” if the pointer has moved vertically at least of the given amount of pixels since the button press event.

When set to -1, ClutterDragAction will use the value stored in the “dnd-drag-threshold” property of ClutterSettings.

When read, this property will always return a valid drag threshold, either as set or the default one.

Flags: Read / Write

Allowed values: >= -1

Default value: 0

Since: 1.4

Signal Details

The `“drag-begin”` signal

void
user_function (ClutterDragAction  *action,
               ClutterActor       *actor,
               gfloat              event_x,
               gfloat              event_y,
               ClutterModifierType modifiers,
               gpointer            user_data)

The ::drag-begin signal is emitted when the ClutterDragAction starts the dragging

The emission of this signal can be delayed by using the “x-drag-threshold” and “y-drag-threshold” properties

Parameters

action	the ClutterDragAction that emitted the signal
actor	the ClutterActor attached to the action
event_x	the X coordinate (in stage space) of the press event
event_y	the Y coordinate (in stage space) of the press event
modifiers	the modifiers of the press event
user_data	user data set when the signal handler was connected.

Flags: Run Last

Since: 1.4

The `“drag-end”` signal

void
user_function (ClutterDragAction  *action,
               ClutterActor       *actor,
               gfloat              event_x,
               gfloat              event_y,
               ClutterModifierType modifiers,
               gpointer            user_data)

The ::drag-end signal is emitted at the end of the dragging, when the pointer button's is released

This signal is emitted if and only if the “drag-begin” signal has been emitted first

Parameters

action	the ClutterDragAction that emitted the signal
actor	the ClutterActor attached to the action
event_x	the X coordinate (in stage space) of the release event
event_y	the Y coordinate (in stage space) of the release event
modifiers	the modifiers of the release event
user_data	user data set when the signal handler was connected.

Flags: Run Last

Since: 1.4

The `“drag-motion”` signal

void
user_function (ClutterDragAction *action,
               ClutterActor      *actor,
               gfloat             delta_x,
               gfloat             delta_y,
               gpointer           user_data)

The ::drag-motion signal is emitted for each motion event after the “drag-begin” signal has been emitted.

The components of the distance between the press event and the latest motion event are computed in the actor's coordinate space, to take into account eventual transformations. If you want the stage coordinates of the latest motion event you can use clutter_drag_action_get_motion_coords().

The default handler of the signal will call clutter_actor_move_by() either on actor or, if set, of “drag-handle” using the delta_x and delta_y components of the dragging motion. If you want to override the default behaviour, you can connect to the “drag-progress” signal and return FALSE from the handler.

Parameters

action	the ClutterDragAction that emitted the signal
actor	the ClutterActor attached to the action
delta_x	the X component of the distance between the press event that began the dragging and the current position of the pointer, as of the latest motion event
delta_y	the Y component of the distance between the press event that began the dragging and the current position of the pointer, as of the latest motion event
user_data	user data set when the signal handler was connected.

Flags: Run Last

Since: 1.4

The `“drag-progress”` signal

gboolean
user_function (ClutterDragAction *action,
               ClutterActor      *actor,
               gfloat             delta_x,
               gfloat             delta_y,
               gpointer           user_data)

The ::drag-progress signal is emitted for each motion event after the “drag-begin” signal has been emitted.

The default handler will emit “drag-motion”, if “drag-progress” emission returns TRUE.

Parameters

action	the ClutterDragAction that emitted the signal
actor	the ClutterActor attached to the action
delta_x	the X component of the distance between the press event that began the dragging and the current position of the pointer, as of the latest motion event
delta_y	the Y component of the distance between the press event that began the dragging and the current position of the pointer, as of the latest motion event
user_data	user data set when the signal handler was connected.

Returns

TRUE if the drag should continue, and FALSE if it should be stopped.

Flags: Run Last

Since: 1.12