ClutterAlpha

ClutterAlpha — A class for calculating an alpha value as a function of time.

Synopsis

                    ClutterAlpha;
                    ClutterAlphaClass;
gdouble             (*ClutterAlphaFunc)                 (ClutterAlpha *alpha,
                                                         gpointer user_data);
ClutterAlpha *      clutter_alpha_new                   (void);
ClutterAlpha *      clutter_alpha_new_full              (ClutterTimeline *timeline,
                                                         gulong mode);
ClutterAlpha *      clutter_alpha_new_with_func         (ClutterTimeline *timeline,
                                                         ClutterAlphaFunc func,
                                                         gpointer data,
                                                         GDestroyNotify destroy);
void                clutter_alpha_set_timeline          (ClutterAlpha *alpha,
                                                         ClutterTimeline *timeline);
ClutterTimeline *   clutter_alpha_get_timeline          (ClutterAlpha *alpha);
void                clutter_alpha_set_mode              (ClutterAlpha *alpha,
                                                         gulong mode);
gulong              clutter_alpha_get_mode              (ClutterAlpha *alpha);
gdouble             clutter_alpha_get_alpha             (ClutterAlpha *alpha);

void                clutter_alpha_set_func              (ClutterAlpha *alpha,
                                                         ClutterAlphaFunc func,
                                                         gpointer data,
                                                         GDestroyNotify destroy);
void                clutter_alpha_set_closure           (ClutterAlpha *alpha,
                                                         GClosure *closure);

gulong              clutter_alpha_register_closure      (GClosure *closure);
gulong              clutter_alpha_register_func         (ClutterAlphaFunc func,
                                                         gpointer data);

Object Hierarchy

  GObject
   +----GInitiallyUnowned
         +----ClutterAlpha

Properties

  "alpha"                    gdouble               : Read
  "mode"                     gulong                : Read / Write / Construct
  "timeline"                 ClutterTimeline*      : Read / Write

Description

ClutterAlpha is a class for calculating an floating point value dependent only on the position of a ClutterTimeline.

A ClutterAlpha binds a ClutterTimeline to a progress function which translates the time T into an adimensional factor alpha. The factor can then be used to drive a ClutterBehaviour, which will translate the alpha value into something meaningful for a ClutterActor.

You should provide a ClutterTimeline and bind it to the ClutterAlpha instance using clutter_alpha_set_timeline(). You should also set an "animation mode", either by using the ClutterAnimationMode values that Clutter itself provides or by registering custom functions using clutter_alpha_register_func().

Instead of a ClutterAnimationMode you may provide a function returning the alpha value depending on the progress of the timeline, using clutter_alpha_set_func() or clutter_alpha_set_closure(). The alpha function will be executed each time a new frame in the ClutterTimeline is reached.

Since the alpha function is controlled by the timeline instance, you can pause, stop or resume the ClutterAlpha from calling the alpha function by using the appropriate functions of the ClutterTimeline object.

ClutterAlpha is used to "drive" a ClutterBehaviour instance, and it is internally used by the ClutterAnimation API.

Figure 3. Easing modes provided by Clutter

Easing modes provided by Clutter


Details

ClutterAlpha

typedef struct _ClutterAlpha ClutterAlpha;

ClutterAlpha combines a ClutterTimeline and a function. The contents of the ClutterAlpha structure are private and should only be accessed using the provided API.

Since 0.2


ClutterAlphaClass

typedef struct {
} ClutterAlphaClass;

Base class for ClutterAlpha

Since 0.2


ClutterAlphaFunc ()

gdouble             (*ClutterAlphaFunc)                 (ClutterAlpha *alpha,
                                                         gpointer user_data);

A function returning a value depending on the position of the ClutterTimeline bound to alpha.

alpha :

a ClutterAlpha

user_data :

user data passed to the function

Returns :

a floating point value

Since 0.2


clutter_alpha_new ()

ClutterAlpha *      clutter_alpha_new                   (void);

Creates a new ClutterAlpha instance. You must set a function to compute the alpha value using clutter_alpha_set_func() and bind a ClutterTimeline object to the ClutterAlpha instance using clutter_alpha_set_timeline().

You should use the newly created ClutterAlpha instance inside a ClutterBehaviour object.

Returns :

the newly created empty ClutterAlpha instance.

Since 0.2


clutter_alpha_new_full ()

ClutterAlpha *      clutter_alpha_new_full              (ClutterTimeline *timeline,
                                                         gulong mode);

Creates a new ClutterAlpha instance and sets the timeline and animation mode.

See also clutter_alpha_set_timeline() and clutter_alpha_set_mode().

timeline :

ClutterTimeline timeline

mode :

animation mode

Returns :

the newly created ClutterAlpha

Since 1.0


clutter_alpha_new_with_func ()

ClutterAlpha *      clutter_alpha_new_with_func         (ClutterTimeline *timeline,
                                                         ClutterAlphaFunc func,
                                                         gpointer data,
                                                         GDestroyNotify destroy);

Creates a new ClutterAlpha instances and sets the timeline and the alpha function.

This function will not register func as a global alpha function.

See also clutter_alpha_set_timeline() and clutter_alpha_set_func().

timeline :

a ClutterTimeline

func :

a ClutterAlphaFunc

data :

data to pass to the function, or NULL

destroy :

function to call when removing the alpha function, or NULL

Returns :

the newly created ClutterAlpha

Since 1.0


clutter_alpha_set_timeline ()

void                clutter_alpha_set_timeline          (ClutterAlpha *alpha,
                                                         ClutterTimeline *timeline);

Binds alpha to timeline.

alpha :

A ClutterAlpha

timeline :

A ClutterTimeline

Since 0.2


clutter_alpha_get_timeline ()

ClutterTimeline *   clutter_alpha_get_timeline          (ClutterAlpha *alpha);

Gets the ClutterTimeline bound to alpha.

alpha :

A ClutterAlpha

Returns :

a ClutterTimeline instance. transfer none.

Since 0.2


clutter_alpha_set_mode ()

void                clutter_alpha_set_mode              (ClutterAlpha *alpha,
                                                         gulong mode);

Sets the progress function of alpha using the symbolic value of mode, as taken by the ClutterAnimationMode enumeration or using the value returned by clutter_alpha_register_func().

alpha :

a ClutterAlpha

mode :

a ClutterAnimationMode

Since 1.0


clutter_alpha_get_mode ()

gulong              clutter_alpha_get_mode              (ClutterAlpha *alpha);

Retrieves the ClutterAnimationMode used by alpha.

alpha :

a ClutterAlpha

Returns :

the animation mode

Since 1.0


clutter_alpha_get_alpha ()

gdouble             clutter_alpha_get_alpha             (ClutterAlpha *alpha);

Query the current alpha value.

alpha :

A ClutterAlpha

Returns :

The current alpha value for the alpha

Since 0.2


clutter_alpha_set_func ()

void                clutter_alpha_set_func              (ClutterAlpha *alpha,
                                                         ClutterAlphaFunc func,
                                                         gpointer data,
                                                         GDestroyNotify destroy);

Sets the ClutterAlphaFunc function used to compute the alpha value at each frame of the ClutterTimeline bound to alpha.

This function will not register func as a global alpha function.

alpha :

A ClutterAlpha

func :

A ClutterAlphaFunc

data :

user data to be passed to the alpha function, or NULL

destroy :

notify function used when disposing the alpha function

Since 0.2


clutter_alpha_set_closure ()

void                clutter_alpha_set_closure           (ClutterAlpha *alpha,
                                                         GClosure *closure);

Sets the GClosure used to compute the alpha value at each frame of the ClutterTimeline bound to alpha.

alpha :

A ClutterAlpha

closure :

A GClosure

Since 0.8


clutter_alpha_register_closure ()

gulong              clutter_alpha_register_closure      (GClosure *closure);

GClosure variant of clutter_alpha_register_func().

Registers a global alpha function and returns its logical id to be used by clutter_alpha_set_mode() or by ClutterAnimation.

The logical id is always greater than CLUTTER_ANIMATION_LAST.

closure :

a GClosure

Returns :

the logical id of the alpha function

Since 1.0


clutter_alpha_register_func ()

gulong              clutter_alpha_register_func         (ClutterAlphaFunc func,
                                                         gpointer data);

Registers a global alpha function and returns its logical id to be used by clutter_alpha_set_mode() or by ClutterAnimation.

The logical id is always greater than CLUTTER_ANIMATION_LAST.

func :

a ClutterAlphaFunc

data :

user data to pass to func, or NULL

Returns :

the logical id of the alpha function

Since 1.0

Property Details

The "alpha" property

  "alpha"                    gdouble               : Read

The alpha value as computed by the alpha function. The linear interval is 0.0 to 1.0, but the Alpha allows overshooting by one unit in each direction, so the valid interval is -1.0 to 2.0.

Allowed values: [-1,2]

Default value: 0

Since 0.2


The "mode" property

  "mode"                     gulong                : Read / Write / Construct

The progress function logical id - either a value from the ClutterAnimationMode enumeration or a value returned by clutter_alpha_register_func().

If CLUTTER_CUSTOM_MODE is used then the function set using clutter_alpha_set_closure() or clutter_alpha_set_func() will be used.

Since 1.0


The "timeline" property

  "timeline"                 ClutterTimeline*      : Read / Write

A ClutterTimeline instance used to drive the alpha function.

Since 0.2