vg4->object->create()

Create an object-instance.

SYNTAX

struct VG_Object * vg4->object->create(const char *objid, int subid, unsigned int parent_instanceid, int drawlevel, void *opriv)

FUNCTION PARAMETERS

objid	Object-ID (e.g. name of object)
subid	Arbitrary sub-ID for object-ID, or 0 = no sub-ID
parent_instanceid	Instance-ID of parent, or 0 = irrelevant
drawlevel	Level-number for drawing order (begins with 1 = lowest level)
opriv	Private struct for object-instance

RETURN VALUE

Returns created object-instance

DESCRIPTION

Create an object-instance. From the object objid a new instance will be created. The subid may be used to sub-classify this instance. If the object-instance is related to a parent-instance, parent_instanceid should be set. This calls the function f_childexit() of the parent-instance, if exists, when this object-instance is destroyed, to inform the parent, that the child was gone. The drawlevel indicates the order of drawing when the function f_draw() is called for all object-instances. At first all object-instances of drawlevel=1 will be drawn, then all of drawlevel=2 and so on. opriv is the private structure of the object-instance holding its variables, e.g. position, healthiness ... The functions of the returned object-instance must be set individually. Not all functions must exist, their values may remain NULL: - f_free() is used to destroy the private struct of the object-instance will be called from vg4->object->destroy() - f_run() is used to move the object-instance will be called from vg4->object->call_run() - f_draw() is used to draw the object-instance will be called from vg4->object->call_draw() - f_data() is used to exchange data of the object-instance will be called from vg4->object->call_data() The instance-ID for this object-instance will be set automatically. Instance-IDs are always unique over all object-instances.

EXAMPLE

obj-otest.c

/* object "OTEST" */
#define OBJID "OTEST"

/* private structure */
struct s_objvars {
  int posx, posy;
  struct VG_Image *imgp;
};

unsigned int new_OTEST(int, int);

static void f_free(void *, void *);
static VG_BOOL f_run(void *, struct VG_Object *);
static void f_draw(void *, struct VG_Object *);

/* export-function to create a new object-instance of "OTEST" */
unsigned int
new_OTEST(int subid, int drawlevel)
{
  struct VG_Object *objp;
  struct s_objvars *objvars;

  /* allocate private struct */
  objvars = calloc(1, sizeof(*objvars));
  if (objvars == NULL) { return 0; }

  /* set private struct */
  objvars->posx = 0;
  objvars->posy = 0;
  objvars->imgp = vg4->image->load("img/otest.bmp");

  /* create object-instance */
  objp = vg4->object->create(OBJID, subid, 0, drawlevel, objvars);
  /* set functions */
  objp->f_free = f_free;
  objp->f_run = f_run;
  objp->f_draw = f_draw;
  /* f_data() and f_childexit() are not needed here */

  return objp->instanceid;
}

/* free private struct of object-instance, called from vg4->object->destroy() */
static void
f_free(void *vgame, void *opriv)
{
  struct s_objvars *objvars = (struct s_objvars *)opriv;

  (void)vgame;

  /* free contents of private struct and itself */
  vg4->image->destroy(objvars->imgp);
  free(objvars);
}

/* move object-instance, called from vg4->object->call_run() */
static VG_BOOL
f_run(void *vgame, struct VG_Object *objp)
{
  struct s_objvars *objvars = (struct s_objvars *)objp->opriv;

  /* move it and check for collisions */
  [...]

  return VG_TRUE;
}

/* draw object-instance, called from vg4->object->call_draw() */
static void
f_draw(void *vgame, struct VG_Object *objp)
{
  struct s_objvars *objvars = (struct s_objvars *)objp->opriv;

  /* draw it */
  [...]
}


game.c

/* create new object-instance of "OTEST" */
new_OTEST(0, 1);