diablodale

given an attribute "fooattrib" which is declared on a max class and points to a char field in the class struct

fooattrib is style=enumindex and enumvals="jane, sam" and filterset_clip=0,1

An object in Max has been created based on this class.

Now a state change happens in my external. I want to change the enumvals and filterset_clip to be...

enumvals="jane, sam, melonie" and filterset_clip=0,2

How can I achieve this? Or something similar to this? I have yet to find a way to redefine attr's of attr's of classes. That would be great because then I could make the change and it would cascade to all the objects instantiated.

If not possible to do something like that just mentioned, could I define the class *minus* fooattrib and then on object instantiation create a object attribute on that specific object...and then somehow later during this state change delete/change that specific object attribute?

In the Max SDK...
given an attribute "fooattrib" which is declared on a max class and points to a char field in the class struct
fooattrib is style=enumindex and enumvals="jane, sam" and filterset_clip=0,1
An object in Max has been created based on this class.

Now a state change happens in my external. I want to change the enumvals and filterset_clip to be...
enumvals="jane, sam, melonie" and filterset_clip=0,2

programmatic-change-of-class-attribute-filter-and-enumval-list

since no C74 guru has replied yet, I will give you an example of how this could be accomplished:

Let's say you have two attributes "foonames" and "fooattrib".

We will change the enumindex and filter_clip of "fooattrib" programmatically, based on the values that "foonames" takes on.

#define MAX_NAMES 64

typedef struct _myobj
{
    t_jbox          box;
    t_symbol        *foonames[MAX_NAMES];
    long            foonamecount;
    char            fooattrib;
} t_myobj;


in main we define two class attributes...

CLASS_ATTR_SYM_VARSIZE(c,           "foonames",         ATTR_FLAGS_NONE, t_myobj, foonames, foonamecount, MAX_NAMES);
CLASS_ATTR_DEFAULT_SAVE_PAINT(c,    "foonames",         ATTR_FLAGS_NONE, "Jane Sam");
    
CLASS_ATTR_CHAR(c,                  "fooattrib",        ATTR_FLAGS_NONE, t_myobj, fooattrib);
CLASS_ATTR_ENUMINDEX(c,             "fooattrib",        ATTR_FLAGS_NONE, "Jane Sam");
CLASS_ATTR_DEFAULT_SAVE_PAINT(c,    "fooattrib",        ATTR_FLAGS_NONE, "0");
CLASS_ATTR_FILTER_CLIP(c,        "fooattrib",        0, 1);


the magic happens in the notify function...

t_max_err myobj_notify(t_myobj *x, t_symbol *sym, t_symbol *msg, void *sender, void *data)
{
    t_object *attr;
    t_object *attr2;
    t_symbol *attrname;
    
    if (msg == gensym("attr_modified")) {
        attr = (t_object *)data;
    attrname = (t_symbol *)object_method(attr, gensym("getname"));
    if (attrname == gensym("foonames")) {
            attr2 = object_attr_get(x, gensym("fooattrib"));
            if (attr2) {
                t_atom argv[MAX_NAMES];
                long argc = x->foonamecount;
                long i;
                
                // update enumvals
                for (i = 0; i < argc; i++) {
                    atom_setsym(argv+i, x->foonames[i]);
                }
                object_attr_setvalueof(attr2, gensym("enumvals"), argc, argv);
                
                // update filter_clip
                attr_addfilter_clip(attr2, 0, argc-1, 1, 1);
                
                // check that fooattrib is still in range
                if (x->fooattrib >= argc) {
                    x->fooattrib = argc-1;
                }
                    
                // notify that attribute has been changed
                object_notify(x, gensym("attr_modified"), attr2);
            }
        }
    }
    return jbox_notify((t_jbox *)x, sym, msg, sender, data);
}


There is one thing I am not 100% sure about:

 there should be a new filter_clip object being created and added to the attribute.

I am not sure what happens to the previous filter_clip object...

Logically it should be freed but since I have no access to the C74 codebase I cannot guarantee it.

If it doesn't get freed then we have a memory leak. I don't know if the Max API makes provisions for it to be changed dynamically after creation. I can tell you that in my short and quick tests the code works without problems though.

This could suggest that instead of using a filter_clip object, it could be better to use a custom setter for "fooattrib" and manage the clipping in there. Perhaps this could be a better alternative...

Let's say you have two attributes "foonames" and "fooattrib".
We will change the enumindex and filter_clip of "fooattrib" programmatically, based on the values that "foonames" takes on.

CLASS_ATTR_SYM_VARSIZE(c,           "foonames",         ATTR_FLAGS_NONE, t_myobj, foonames, foonamecount, MAX_NAMES);
CLASS_ATTR_DEFAULT_SAVE_PAINT(c,    "foonames",         ATTR_FLAGS_NONE, "Jane Sam");
	
CLASS_ATTR_CHAR(c,                  "fooattrib",        ATTR_FLAGS_NONE, t_myobj, fooattrib);
CLASS_ATTR_ENUMINDEX(c,             "fooattrib",        ATTR_FLAGS_NONE, "Jane Sam");
CLASS_ATTR_DEFAULT_SAVE_PAINT(c,    "fooattrib",        ATTR_FLAGS_NONE, "0");
CLASS_ATTR_FILTER_CLIP(c,	    "fooattrib",        0, 1);


t_max_err myobj_notify(t_myobj *x, t_symbol *sym, t_symbol *msg, void *sender, void *data)
{
    t_object *attr;
    t_object *attr2;
    t_symbol *attrname;
    
    if (msg == gensym("attr_modified")) {
        attr = (t_object *)data;
	attrname = (t_symbol *)object_method(attr, gensym("getname"));
	if (attrname == gensym("foonames")) {
            attr2 = object_attr_get(x, gensym("fooattrib"));
            if (attr2) {
                t_atom argv[MAX_NAMES];
                long argc = x->foonamecount;
                long i;
                
                // update enumvals
                for (i = 0; i < argc; i++) {
                    atom_setsym(argv+i, x->foonames[i]);
                }
                object_attr_setvalueof(attr2, gensym("enumvals"), argc, argv);
                
                // update filter_clip
                attr_addfilter_clip(attr2, 0, argc-1, 1, 1);
                
                // check that fooattrib is still in range
                if (x->fooattrib >= argc) {
                    x->fooattrib = argc-1;
                }
                    
                // notify that attribute has been changed
                object_notify(x, gensym("attr_modified"), attr2);
            }
        }
    }
    return jbox_notify((t_jbox *)x, sym, msg, sender, data);
}


There is one thing I am not 100% sure about:
when calling attr_addfilter_clip() there should be a new filter_clip object being created and added to the attribute.
I am not sure what happens to the previous filter_clip object...
Logically it should be freed but since I have no access to the C74 codebase I cannot guarantee it.
If it doesn't get freed then we have a memory leak. I don't know if the Max API makes provisions for it to be changed dynamically after creation. I can tell you that in my short and quick tests the code works without problems though.

It would be nice to know what strategy you ended up using and if you go it working in the end...

programmatic change of class attribute filter and enumval list?