Example

Example
	Appendix A. Implementing Actors

The following example demonstrates the implementation of a new triangle Actor type.

Figure A.1. Behaviour

File: triangle_actor.h

#ifndef _CLUTTER_TUTORIAL_TRIANGLE_ACTOR_H
#define _CLUTTER_TUTORIAL_TRIANGLE_ACTOR_H

#include <glib-object.h>
#include <clutter/clutter.h>

G_BEGIN_DECLS

#define CLUTTER_TYPE_TRIANGLE clutter_triangle_get_type()

#define CLUTTER_TRIANGLE(obj) \
  (G_TYPE_CHECK_INSTANCE_CAST ((obj), \
  CLUTTER_TYPE_TRIANGLE, ClutterTriangle))

#define CLUTTER_TRIANGLE_CLASS(klass) \
  (G_TYPE_CHECK_CLASS_CAST ((klass), \
  CLUTTER_TYPE_TRIANGLE, ClutterTriangleClass))

#define CLUTTER_IS_TRIANGLE(obj) \
  (G_TYPE_CHECK_INSTANCE_TYPE ((obj), \
  CLUTTER_TYPE_TRIANGLE))

#define CLUTTER_IS_TRIANGLE_CLASS(klass) \
  (G_TYPE_CHECK_CLASS_TYPE ((klass), \
  CLUTTER_TYPE_TRIANGLE))

#define CLUTTER_TRIANGLE_GET_CLASS(obj) \
  (G_TYPE_INSTANCE_GET_CLASS ((obj), \
  CLUTTER_TYPE_TRIANGLE, ClutterTriangleClass))

typedef struct _ClutterTriangle        ClutterTriangle;
typedef struct _ClutterTriangleClass   ClutterTriangleClass;
typedef struct _ClutterTrianglePrivate ClutterTrianglePrivate;

struct _ClutterTriangle
{
  ClutterActor           parent;

  /*< private >*/
  ClutterTrianglePrivate *priv;
}; 

struct _ClutterTriangleClass 
{
  ClutterActorClass parent_class;
};

GType clutter_triangle_get_type (void) G_GNUC_CONST;

ClutterActor *clutter_triangle_new              (void);
ClutterActor *clutter_triangle_new_with_color   (const ClutterColor *color);

void          clutter_triangle_get_color        (ClutterTriangle   *triangle,
                                                  ClutterColor       *color);
void          clutter_triangle_set_color        (ClutterTriangle   *triangle,
						  const ClutterColor *color);

G_END_DECLS

#endif

File: triangle_actor.c

#include "triangle_actor.h"

#include <cogl/cogl.h>

G_DEFINE_TYPE (ClutterTriangle, clutter_triangle, CLUTTER_TYPE_ACTOR);

enum
{
  PROP_0,

  PROP_COLOR
};

#define CLUTTER_TRIANGLE_GET_PRIVATE(obj) \
(G_TYPE_INSTANCE_GET_PRIVATE ((obj), CLUTTER_TYPE_TRIANGLE, ClutterTrianglePrivate))

struct _ClutterTrianglePrivate
{
  ClutterColor color;
};

static void
do_triangle_paint (ClutterActor *self, const CoglColor *color)
{
  ClutterTriangle        *triangle;
  ClutterTrianglePrivate *priv;
  ClutterGeometry         geom;
  float                  coords[6];

  triangle = CLUTTER_TRIANGLE(self);
  priv = triangle->priv;

  cogl_push_matrix();

  clutter_actor_get_geometry (self, &geom);

  cogl_set_source_color (color);

  /* Paint a triangle:
   *
   * The parent paint call will have translated us into position so
   * paint from 0, 0 */
  coords[0] = 0;
  coords[1] = 0;

  coords[2] = 0;
  coords[3] = geom.height;

  coords[4] = geom.width;
  coords[5] = geom.height;

  cogl_path_polygon (coords, 3);
  cogl_path_fill ();

  cogl_pop_matrix();
}

static void
clutter_triangle_paint (ClutterActor *self)
{
  ClutterTrianglePrivate *priv;
  CoglColor color;

  priv = CLUTTER_TRIANGLE(self)->priv;

  /* Paint the triangle with the actor's color: */
  cogl_color_set_from_4ub(&color,
                          priv->color.red,
                          priv->color.green,
                          priv->color.blue,
                          clutter_actor_get_opacity (self));

  do_triangle_paint (self, &color);
}

static void
clutter_triangle_pick (ClutterActor *self, const ClutterColor *color)
{
  CoglColor coglcolor;
  /* Paint the triangle with the pick color, offscreen.
     This is used by Clutter to detect the actor under the cursor 
     by identifying the unique color under the cursor. */
  cogl_color_set_from_4ub(&coglcolor,
                          color->red, color->green, color->blue, color->alpha);
  do_triangle_paint (self, &coglcolor);
}

static void
clutter_triangle_set_property (GObject      *object,
				guint         prop_id,
				const GValue *value,
				GParamSpec   *pspec)
{
  ClutterTriangle *triangle = CLUTTER_TRIANGLE(object);

  switch (prop_id)
    {
    case PROP_COLOR:
      clutter_triangle_set_color (triangle, g_value_get_boxed (value));
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
clutter_triangle_get_property (GObject    *object,
				guint       prop_id,
				GValue     *value,
				GParamSpec *pspec)
{
  ClutterTriangle *triangle = CLUTTER_TRIANGLE(object);
  ClutterColor      color;

  switch (prop_id)
    {
    case PROP_COLOR:
      clutter_triangle_get_color (triangle, &color);
      g_value_set_boxed (value, &color);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
    }
}


static void
clutter_triangle_finalize (GObject *object)
{
  G_OBJECT_CLASS (clutter_triangle_parent_class)->finalize (object);
}

static void
clutter_triangle_dispose (GObject *object)
{
  G_OBJECT_CLASS (clutter_triangle_parent_class)->dispose (object);
}


static void
clutter_triangle_class_init (ClutterTriangleClass *klass)
{
  GObjectClass        *gobject_class = G_OBJECT_CLASS (klass);
  ClutterActorClass *actor_class = CLUTTER_ACTOR_CLASS (klass);

  /* Provide implementations for ClutterActor vfuncs: */
  actor_class->paint = clutter_triangle_paint;
  actor_class->pick = clutter_triangle_pick;

  gobject_class->finalize     = clutter_triangle_finalize;
  gobject_class->dispose      = clutter_triangle_dispose;
  gobject_class->set_property = clutter_triangle_set_property;
  gobject_class->get_property = clutter_triangle_get_property;

  /**
   * ClutterTriangle:color:
   *
   * The color of the triangle.
   */
  g_object_class_install_property (gobject_class,
                                   PROP_COLOR,
                                   g_param_spec_boxed ("color",
                                                       "Color",
                                                       "The color of the triangle",
                                                       CLUTTER_TYPE_COLOR,
                                                       G_PARAM_READABLE | G_PARAM_WRITABLE));

  g_type_class_add_private (gobject_class, sizeof (ClutterTrianglePrivate));
}

static void
clutter_triangle_init (ClutterTriangle *self)
{
  ClutterTrianglePrivate *priv;

  self->priv = priv = CLUTTER_TRIANGLE_GET_PRIVATE (self);

  priv->color.red = 0xff;
  priv->color.green = 0xff;
  priv->color.blue = 0xff;
  priv->color.alpha = 0xff;
}

/**
 * clutter_triangle_new:
 *
 * Creates a new #ClutterActor with a rectangular shape.
 *
 * Return value: a new #ClutterActor
 */
ClutterActor*
clutter_triangle_new (void)
{
  return g_object_new (CLUTTER_TYPE_TRIANGLE, NULL);
}

/**
 * clutter_triangle_new_with_color:
 * @color: a #ClutterColor
 *
 * Creates a new #ClutterActor with a rectangular shape
 * and with @color.
 *
 * Return value: a new #ClutterActor
 */
ClutterActor *
clutter_triangle_new_with_color (const ClutterColor *color)
{
  return g_object_new (CLUTTER_TYPE_TRIANGLE,
		       "color", color,
		       NULL);
}

/**
 * clutter_triangle_get_color:
 * @triangle: a #ClutterTriangle
 * @color: return location for a #ClutterColor
 *
 * Retrieves the color of @triangle.
 */
void
clutter_triangle_get_color (ClutterTriangle *triangle,
			     ClutterColor     *color)
{
  ClutterTrianglePrivate *priv;

  g_return_if_fail (CLUTTER_IS_TRIANGLE (triangle));
  g_return_if_fail (color != NULL);

  priv = triangle->priv;

  color->red = priv->color.red;
  color->green = priv->color.green;
  color->blue = priv->color.blue;
  color->alpha = priv->color.alpha;
}

/**
 * clutter_triangle_set_color:
 * @triangle: a #ClutterTriangle
 * @color: a #ClutterColor
 *
 * Sets the color of @triangle.
 */
void
clutter_triangle_set_color (ClutterTriangle   *triangle,
			     const ClutterColor *color)
{
  ClutterTrianglePrivate *priv;

  g_return_if_fail (CLUTTER_IS_TRIANGLE (triangle));
  g_return_if_fail (color != NULL);

  g_object_ref (triangle);

  priv = triangle->priv;

  priv->color.red = color->red;
  priv->color.green = color->green;
  priv->color.blue = color->blue;
  priv->color.alpha = color->alpha;

  clutter_actor_set_opacity (CLUTTER_ACTOR (triangle),
		  	       priv->color.alpha);

  if (CLUTTER_ACTOR_IS_VISIBLE (CLUTTER_ACTOR (triangle)))
    clutter_actor_queue_redraw (CLUTTER_ACTOR (triangle));

  g_object_notify (G_OBJECT (triangle), "color");
  g_object_unref (triangle);
}

File: main.c

#include <clutter/clutter.h>
#include "triangle_actor.h"
#include <stdlib.h>


int main(int argc, char *argv[])
{
  ClutterColor stage_color = { 0x00, 0x00, 0x00, 0xff };
  ClutterColor actor_color = { 0xff, 0xff, 0xff, 0x99 };

  clutter_init (&argc, &argv);

  /* Get the stage and set its size and color: */
  ClutterActor *stage = clutter_stage_get_default ();
  clutter_actor_set_size (stage, 200, 200);
  clutter_stage_set_color (CLUTTER_STAGE (stage), &stage_color);

  /* Add our custom actor to the stage: */
  ClutterActor *actor = clutter_triangle_new_with_color (&actor_color);
  clutter_actor_set_size (actor, 100, 100);
  clutter_actor_set_position (actor, 20, 20);
  clutter_container_add_actor (CLUTTER_CONTAINER (stage), actor);
  clutter_actor_show (actor);

  /* Show the stage: */
  clutter_actor_show (stage);

  /* Start the main loop, so we can respond to events: */
  clutter_main ();

  return EXIT_SUCCESS;

}


Appendix A. Implementing Actors		Implementing Container Actors