Extended Entity Data

Hi all,

We are currently using extended entity data to "attach" size definition to entities within a model. So far, this has worked well when I assign group code 1000. The trouble starts when I want to add other definitions. I believe you can keep adding group codes (must be a limit) say 1041, 1042 etc. As such, I have written the following code to attach additional extended data, but autocad returns a bad DXF group error.

The original dxf list for the entity is:

((-1 . <Entity name: 1c9f748>) (0 . "POLYLINE") (5 . "C81") (102 .
"{ACAD_REACTORS") (330 . <Entity name: 1c9f800>) (102 . "}") (330 . <Entity
name: 1c9e0f8>) (100 . "AcDbEntity") (67 . 0) (410 . "Model") (8 .
"Auto-Purlins") (62 . 4) (100 . "AcDbPolygonMesh") (66 . 1) (10 0.0 0.0 0.0)
(70 . 16) (40 . 0.0) (41 . 0.0) (210 0.0 0.0 1.0) (71 . 2) (72 . 6) (73 . 0)
(74 . 0) (75 . 0) (-3 ("SECTION_SIZE" (1000 . "C15024"))))

I then substitute the list to include the additional data by:

(regapp "SECTION_SIZE")
(setq elist (entget (ssname pursel 0) (list "*")))
(setq olddata (assoc -3 elist))
(setq data (cdr (assoc -3 elist)))
(setq unisize (cdr (nth 1 (car data))))

(setq EXDATA1 (list "SECTION_SIZE"
(cons '1000 unisize)
(cons '1041 pdpflag) ;pdpflag is set to "test"
))
(setq EXDATA1 (cons -3 (list EXDATA1)))
(setq NEWENT (subst EXDATA1 olddata elist))

Newent now returns:

((-1 . <Entity name: 1c9f748>) (0 . "POLYLINE") (5 . "C81") (102 .
"{ACAD_REACTORS") (330 . <Entity name: 1c9f800>) (102 . "}") (330 . <Entity
name: 1c9e0f8>) (100 . "AcDbEntity") (67 . 0) (410 . "Model") (8 .
"Auto-Purlins") (62 . 4) (100 . "AcDbPolygonMesh") (66 . 1) (10 0.0 0.0 0.0)
(70 . 16) (40 . 0.0) (41 . 0.0) (210 0.0 0.0 1.0) (71 . 2) (72 . 6) (73 . 0)
(74 . 0) (75 . 0) (-3 ("SECTION_SIZE" (1000 . "C15024") (1041 . "test"))))

When I try and update the entity:

(entmod NEWENT)

I get the following error:

; error: bad DXF group: (-3 ("SECTION_SIZE" (1000 . "C15024") (1041 . "test")))

I really can't see what I'm doing wrong. If anyone has any thoughts they would be really appreciated.

Thanks
John

 

Hi John

1041 requires a real value (distance), from help:

String:
1000. Strings in extended data can be up to 255 bytes long (with the 256th byte
reserved for the null character).

Application Name:
1001 (also a string value). Application names can be up to 31 bytes long (the
32nd byte is reserved for the null character) and must adhere to the rules for
symbol table names (such as layer names). An application name can contain
letters, digits, and the special characters $ (dollar sign), - (hyphen), and _
(underscore). It cannot contain spaces.

Layer Name:
1003. Name of a layer associated with the xdata.

Database Handle:
1005. Handle of an entity in the drawing database.

3D Point:
1010. Three real values, contained in a point.

Real:
1040. A real value.

Integer:
1070. A 16-bit integer (signed or unsigned).

Long :
1071. A 32-bit signed (long) integer. If the value that appears in a 1071 group
is a short integer or real value, it is converted to a long integer; if it is
invalid (for example, a string), it is converted to a long zero (0L).
Note: AutoLISP manages 1071 groups as real values. If you use entget to retrieve
an entity's definition list that contains a 1071 group, the value is returned as
a real, as shown in the following example:
(1071 . 12.0)
If you want to create a 1071 group in an entity with entmake or entmod, you can
use either a real or an integer value, as shown in the following example:
(entmake '((..... (1071 . 12) .... )))
(entmake '((..... (1071 . 12.0) .... )))
(entmake '((..... (1071 . 65537.0) .... )))
(entmake '((..... (1071 . 65537) .... )))
But AutoLISP still returns the group value as a real:
(entmake '((..... (1071 . 65537) .... )))
The preceding statement returns the following:
(1071 . 65537.0)
ObjectARX always manages 1071 groups as long integers.

Several other extended data groups have special meanings in this context (if the
application chooses to use them):

Control String:
1002. An xdata control string can be either "{" or "}". These braces enable the
application to organize its data by subdividing it into lists. The left brace
begins a list, and the right brace terminates the most recent list. Lists can be
nested.
Note: If a 1001 group appears within a list, it is treated as a string and does
not begin a new application group.

Binary Data:
1004. Binary data that is organized into variable-length chunks, which can be
handled in ObjectARX with the ads_binary structure. The maximum length of each
chunk is 127 bytes.
Note: AutoLISP cannot directly handle binary chunks, so the same precautions
that apply to long (1071) groups apply to binary groups as well.

World Space Position:
1011. Unlike a simple 3D point, the WCS coordinates are moved, scaled, rotated,
and mirrored along with the parent entity to which the extended data belongs.
The WCS position is also stretched when the STRETCH command is applied to the
parent entity and when this point lies within the select window.

World Space Displacement:
1012. A 3D point that is scaled, rotated, or mirrored along with the parent, but
not stretched or moved.

World Direction:
1013. A 3D point that is rotated or mirrored along with the parent, but not
scaled, stretched, or moved. The WCS direction is a normalized displacement that
always has a unit length.

Distance:
1041. A real value that is scaled along with the parent entity.

Scale Factor:
1042. Also a real value that is scaled along with the parent.

Cheers

 

Great info Jürg.
John, I sometimes use more than one Application Name to attach addition
Xdata to entities.
Alan

 

Thanks Juerg,

I was not aware of the restrictions. I was reading from a book and it did not explain the different group codes. Your explanation has been very helful.


Dardo

 

Hi John/Dardo?

Glad to help...¦-)

But the flowers are not belong to me. I copied this informations from AutoLISP
help. There are more usefull informations around Xdata:
AutoLISP Developer's Guide -> Using the AutoLISP Language -> Extended Data --
xdata

Cheeras