[PD-dev] Observable, class_setfieldnames

[Mathieu Bouchard]

On Thu, 6 Oct 2005, Mathieu Bouchard wrote:

> hi everybody, I just added this:
>   EXTERN void class_setfieldnames(t_class *x, const char *s);

Ok, now WHY I've added it: this is so that objects uploaded from server to
client don't have to be completely uploaded each time. I number the fields 
so that I have a bitfield of which fields are "dirty".

This is very similar to how XSetWindowAttributes() sends data to an X11
server, except that it uses a bunch of #defines instead and it deals with
only one struct type and is not extensible.



nota bene: the following is only enabled with "scons desire=1".

I am implementing an observer/observable interface in t_gobj. Because I 
want to keep ABI compatibility with most externals, I've taken out the one 
field I could, g_next, and replaced it with a pointer to t_observable 
called g_obs. The g_next field is now in that struct and so are the other 
infos we need:

typedef struct _observable {
	struct _gobj *master; /* pointer back to our t_gobj */
	struct _gobj *next; /* formerly in t_gobj */
/* actual observable */
	int dirty;          /* bitset of fields */
	int nobs;           /* number of spies */
	struct _gobj **obs;
/* virtual func for observer */
	void (*notice)(struct _gobj *x, struct _gobj *origin, int dirty);
} t_observable;

And then there are a few functions for managing notifications.

EXTERN void   observable_subscribe (t_observable *self, t_gobj *observer);
EXTERN void observable_unsubscribe (t_observable *self, t_gobj *observer);

Those two manage the relationships so that the observables know where to 
forward their notifications.

EXTERN void observable_changed (t_observable *self, const char *k);

This records a change so that later a notification may be emitted.

EXTERN void observable_notify (t_observable *self);

This makes the observable notify its subscribers when asked to.

EXTERN void gobj_notice(t_gobj *x, t_gobj *origin, int dirty);

This is the function called on each subscribed object (observer). It 
must have had glist_add called on it and then g_obs->notify must be set to 
a valid function.



TODO:

 * Pools of observables so that _notify may be batch-called on all of them 
   at once during idle time (or something...)

 * Support for notices on portions of array data (intervals of indices)

 * Something that actually uses that API

____________________________________________________________________
Mathieu Bouchard - tél:+1.514.383.3801 - http://artengine.ca/matju
Freelance Digital Arts Engineer, Montréal QC Canada