mutter/doc/cookbook/examples/animations-path-circle.c

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#include <stdlib.h>
#include <clutter/clutter.h>
#define STAGE_SIDE 400.0
static const ClutterColor stage_color = { 0x33, 0x33, 0x55, 0xff };
static const ClutterColor red_color = { 0xff, 0x00, 0x00, 0xff };
/* Build a "circular" path out of 4 Bezier curves
*
* code modified from
* http://git.clutter-project.org/dax/tree/dax/dax-traverser-clutter.c#n328
*
* see http://www.whizkidtech.redprince.net/bezier/circle/
* for further explanation
*/
static ClutterPath *
build_circular_path (gfloat cx,
gfloat cy,
gfloat r)
{
ClutterPath *path;
static gfloat kappa = 4 * (G_SQRT2 - 1) / 3;
path = clutter_path_new ();
clutter_path_add_move_to (path, cx + r, cy);
clutter_path_add_curve_to (path,
cx + r, cy + r * kappa,
cx + r * kappa, cy + r,
cx, cy + r);
clutter_path_add_curve_to (path,
cx - r * kappa, cy + r,
cx - r, cy + r * kappa,
cx - r, cy);
clutter_path_add_curve_to (path,
cx - r, cy - r * kappa,
cx - r * kappa, cy - r,
cx, cy - r);
clutter_path_add_curve_to (path,
cx + r * kappa, cy - r,
cx + r, cy - r * kappa,
cx + r, cy);
clutter_path_add_close (path);
return path;
}
static gboolean
key_pressed_cb (ClutterActor *actor,
ClutterEvent *event,
gpointer user_data)
{
ClutterTimeline *timeline = CLUTTER_TIMELINE (user_data);
if (!clutter_timeline_is_playing (timeline))
clutter_timeline_start (timeline);
return TRUE;
}
int
main (int argc,
char *argv[])
{
ClutterPath *path;
ClutterConstraint *constraint;
ClutterAnimator *animator;
ClutterTimeline *timeline;
ClutterActor *stage;
ClutterActor *rectangle;
if (clutter_init (&argc, &argv) != CLUTTER_INIT_SUCCESS)
return 1;
stage = clutter_stage_new ();
clutter_actor_set_size (stage, STAGE_SIDE, STAGE_SIDE);
clutter_stage_set_color (CLUTTER_STAGE (stage), &stage_color);
g_signal_connect (stage, "destroy", G_CALLBACK (clutter_main_quit), NULL);
rectangle = clutter_rectangle_new_with_color (&red_color);
clutter_actor_set_size (rectangle, STAGE_SIDE / 8, STAGE_SIDE / 8);
clutter_actor_set_position (rectangle,
STAGE_SIDE / 2,
STAGE_SIDE / 2);
clutter_container_add_actor (CLUTTER_CONTAINER (stage),
rectangle);
/* set up a path and make a constraint with it */
path = build_circular_path (STAGE_SIDE / 2,
STAGE_SIDE / 2,
STAGE_SIDE / 4);
constraint = clutter_path_constraint_new (path, 0.0);
/* apply the constraint to the rectangle; note that there
* is no need to name the constraint, as we will be animating
* the constraint's offset property directly using ClutterAnimator
*/
clutter_actor_add_constraint (rectangle, constraint);
/* animation to animate the path offset */
animator = clutter_animator_new ();
clutter_animator_set_duration (animator, 5000);
/* use ClutterAnimator to animate the constraint directly */
clutter_animator_set (animator,
constraint, "offset", CLUTTER_LINEAR, 0.0, 0.0,
constraint, "offset", CLUTTER_LINEAR, 1.0, 1.0,
NULL);
timeline = clutter_animator_get_timeline (animator);
clutter_timeline_set_repeat_count (timeline, -1);
clutter_timeline_set_auto_reverse (timeline, TRUE);
g_signal_connect (stage,
"key-press-event",
G_CALLBACK (key_pressed_cb),
timeline);
clutter_actor_show (stage);
clutter_main ();
/* clean up */
g_object_unref (animator);
return EXIT_SUCCESS;
}