I recently handled one case that wants to get the hierarchy of nested blocks if the nested entity is selected. This is similar to when you double click a block reference (BEdit), AutoCAD will provide you with the hierarchy of the blocks and ask you which one you want to edit.
We can use acedSSGet, passing :N as the argument. When we pick an entity within the block, the method acedSSNameX will return a resbuf which tells the information we need.
Following is from API help reference on acedSSNameX:
For entities selected by a pick point, information about the point will follow the GS marker information. The point information will be bracketed by an RTLB/RTLE pair
The point information describes the pick point in a display independent manner. In a normal view this is done by describing an infinite line that passes through the actual pick point and is parallel to the users line of sight. In a perspective view, or a view with one clipping plane active, the line becomes a ray. If front and back clipping planes are on, the line becomes a line segment.
To describe the line/ray/line-segment, a type descriptor, a point, and either a unit vector describing the direction of the infinite-line/ray or a vector describing the direction and distance to the other side of the line segment are used.
The data items for a complete entity sublist involving a pick point selection are:
| RTLB | start of entity data sublist |
|
RTSHORT |
selection method |
|
RTENAME |
picked entity’s entity name |
|
RTSHORT |
GS marker |
|
RTLB |
start of list for pick point |
|
RTSHORT |
point descriptor |
|
RT3DPOINT |
point descriptor |
|
RT3DPOINT |
vector describing direction of pick line or direction & distance to other end of line segment (only present if viewpoint is not plan WCS) |
|
RTLE |
end of list for pick point |
|
RT3DPOINT |
first of four points that provide a transformation matrix in the same format (and for the same purpose) as provided by acedNEntSel() (only present if :N option of acedSSGet() was used during selection) |
|
RT3DPOINT |
second of four points that provide a transformation matrix in the same format (and for the same purpose) as provided by acedNEntSel() (only present if :N option of acedSSGet() was used during selection) |
|
RT3DPOINT |
third of four points that provide a transformation matrix in the same format (and for the same purpose) as provided by acedNEntSel() (only present if :N option of acedSSGet() was used during selection) |
|
RT3DPOINT |
last of four points that provide a transformation matrix in the same format (and for the same purpose) as provided by acedNEntSel() (only present if :N option of acedSSGet() was used during selection) |
|
RTENAME |
entity name of innermost nested container of the selected entity (only present if :N option of acedSSGet() was used during selection) |
|
entity names of other nested containers in innermost to outermost order (only present if :N option of acedSSGet() was used during selection) |
|
|
RTENAME |
entity name of outermost nested container (in other words, the one in Model Space or Paper Space) of the selected entity (only present if :N option of acedSSGet() was used during selection) |
|
RTLE |
end of entity data sublist |
In a word, this tells many information, including the nested entities/containers. Please pay attention to the type marked in red. So assume we have a block:
top_block
sub_block
entity in sub block (non-block)
other entity (non-block) in top block
With the code demo below:
if we pick the other entity in top block, it will list
other entity (non-block) in top block
top_block
if we pick the entity in sub block (non-block), it will list
entity in sub block (non-block)
sub_block
top_block
static void Retrieving_block_hierarchy(void) { ads_name sset, eName; AcDbObjectId id; // "_:n" return nested entity info // if (RTNORM == acedSSGet(L"_:n", NULL, NULL, NULL, sset)) { acutPrintf(L"n"); long len = 0; acedSSLength(sset, &len); for (long i = 0; i < len; i++) { resbuf *rb = NULL; if (RTNORM == acedSSNameX(&rb, sset, i)) { resbuf *rbWalk = rb; while (NULL != rbWalk) { if (RTENAME == rbWalk->restype) { eName[0] = rbWalk->resval.rlname[0]; eName[1] = rbWalk->resval.rlname[1]; if(Acad::eOk == acdbGetObjectId(id, eName)) { acutPrintf(L"Entity %d: %x", i, id.asOldId()); AcDbEntity *pEnt; if (Acad::eOk == acdbOpenObject(pEnt, id,  
; AcDb::kForRead)) { // dump the entity name acutPrintf(L"(%s)n", pEnt->isA()->name()); if(pEnt->isKindOf( AcDbBlockReference::desc())) { AcDbBlockReference *blkref = (AcDbBlockReference *)pEnt; AcDbObjectId blkid = blkref->blockTableRecord(); AcDbObject *ptmpObj; if (Acad::eOk == acdbOpenObject(ptmpObj, blkid, AcDb::kForRead) ) { // if it is a block reference AcDbBlockTableRecord *blk = (AcDbBlockTableRecord*) ptmpObj; const ACHAR *blkname = NULL; blk->getName(blkname); acutPrintf( L"(block name: %s)n", blkname); ptmpObj->close(); } else { acutPrintf( L"nCouldn't open block"); } } pEnt->close(); } else { acutPrintf( L"nCouldn't open object"); } } } // move to the next resbuf node rbWalk = rbWalk->rbnext; } acutRelRb(rb); } } acedSSFree(sset);
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