【转帖】determine a used layer
 

determine a used layer
determine a used layer
dear all,
does someone know whether there is some way to determine whether a layer "contains" some entities (i.e. is used), away form the normal database traversal and checking individually for each entity?
thanks in advance for any help.
best regards
chudomir

it is a good question. i'd like to know too.
arno歵
i *think* we have plans to add entity selection sets / filtering and the like in a future release after 1.10.
thank you for your replies.
so at this stags may be:
code:
bool islayerused(oddbobjectid idlayer)
{
for_each(block table record) {
oddbobjectiteratorptr pi = current_block->newiterator();
for (; !pi->done(); pi->step()) {
if (pi->entity()->layerid()==idlayer)
return true;
} //for
}
return false; // not found
}
i know it is a nightmare but it's better than nothing.
(besides i'm not quite sure that this should work on xref layers...)
another thing is that the entities have oddbhardpointerid link to their layers - so the question is: is there a core check implemented that would throw an exception if we try to erase a layer that has some hard pointers to it?
if there is such a check, can we use it too (some internal map or so?)
regards
chudomir
there is no protection mechanism in place for deleting referenced items - you'll have to traverse everything yourself and seek that out.
thank you for your replies, walt.
you saved me lots of "choice" time.
best regards.
chudomir
checking each entity by (layerid() == idlayer) is not absolutely correct. layer may be hard referenced from some custom entity (if it references more than one layer for example) or object.
standard method of checking if an object is hard referenced by some other object is using oddbdatabase:urge() method.
btw, entities from model or paper space on specific layer can be selected using oddbselectionset (see dbsset.h)
sergey slezkin
thank you sergey,
but i just need to make a dialog with list of layers and to indicate which layer is used and which not, so purge wouldn't help here.
there is some layer state dictionary in autocad 2004 arx - can it help in this case? (directly read some flag for used layer).
regards
chudomir
oddbdatabase:urge() does not modify database. it takes id array of objects you are interested in and removes hard referenced ones from it. remaining ids in array are of not referenced objects. see description in oddbdatabase.h
autocad may be configured to store layer index in file. but it may be absent. we do not generate it.
sergey slezkin
thank you for your help.
now the concept seems very clear:
get the layers, call the purge method for them and the result are the layers that are not hard referenced. this is what i needed.
regards
chudomir