SLD label implementation is non-conformant to OGC SLD spec

[bartvde@…]

Hi list,

I am trying to get Mapserver (version 4.8.4) to display labels for a certain
attribute column. This works fine if I use the non-conformant OGC request (only
part of my SLD):

<TextSymbolizer><Label>MY_COLUMN</Label>

According to the OGC SLD spec Mapserver should just label with MY_COLUMN as a
static string.

But it does not work if I use it the way the example in the SLD spec indicates
(using ogc:PropertyName):

<TextSymbolizer><Label><ogc:PropertyName>MY_COLUMN</ogc:PropertyName></Label>

I get:
[Thu Aug 10 08:06:30 2006] [error] [client 145.50.39.34] Thu Aug 10 08:06:30
2006 - msDBFGetItemIndex(): DBASE file error. Item 'PropertyName' not found.

Example from SLD spec:
<TextSymbolizer>
<Geometry>
<ogc:PropertyName>locatedAt</ogc:PropertyName>
</Geometry>
<Label>
<ogc:PropertyName>hospitalName</ogc:PropertyName>
</Label>

Why is this important? So that you can label using attribute values and static
strings combined, like:
<Label>This is city "<ogc:PropertyName>NAME</ogc:PropertyName>"
of state <ogc:PropertyName>STATE</ogc:PropertyName></Label>

Can this be fixed?

[bartvde@…]

The code for this seems to be mostly in place, but commented (see below).

I think the way to do this would be to use TEXT instead of LABELITEM. So that
one can mix static text with column names.

So <Label>bla <ogc:PropertyName>mycolumn</ogc:PropertyName></Label> would become

TEXT "bla [mycolumn]"

The code in mapogcsld.c:

        /* label  */
        /* support only literal expression instead of propertyname */
        psLabel = CPLGetXMLNode(psRoot, "Label");
        if (psLabel )
        {
            if (psLabel->psChild && psLabel->psChild->pszValue)
            /* psPropertyName = CPLGetXMLNode(psLabel, "PropertyName"); */
              /* if (psPropertyName && psPropertyName->psChild && */
              /* psPropertyName->psChild->pszValue) */
            {
                if (psLayer->labelitem)
                  free (psLayer->labelitem);
                psLayer->labelitem = strdup(psLabel->psChild->pszValue);
                  /* strdup(psPropertyName->psChild->pszValue); */

[bartvde@…]

Setting target to 4.10 to implement support for both:

<TextSymbolizer><Label><ogc:PropertyName>MY_COLUMN</ogc:PropertyName></Label>

<TextSymbolizer><Label>MY_COLUMN</Label>

[tomkralidis]

Is this one a dup of bug 1737?

[dmorissette]

Looks like a dup to me. Assigned bug to Assefa since SLD is his territory.

[bartvde@…]

*** Bug 1737 has been marked as a duplicate of this bug. ***

[assefa]

add support for parsing label tags with property name :

<TextSymbolizer><Label><ogc:PropertyName>MY_COLUMN</ogc:PropertyName></Label>.

Old way of doing is still supported.

 Does not do support things like  <Label>This is 
city "<ogc:PropertyName>NAME</ogc:PropertyName>"
of state <ogc:PropertyName>STATE</ogc:PropertyName></Label>

 If statifactory, please close the bug.

[bartvde@…]

I have verified this one and it works fine now. Thanks! Closing.

[assefa]

Reopen bug : support of mixing  static text with column names is missing.

[assefa]

I have added in the CVS HEAD the support of mixing the static text and
attributes.  The way it is done is that all text symbolizers now set the
class.text attribute instead of using the layer's label item. These cases seem
to work for me :

  * <Label><ogc:PropertyName>MY_COLUMN</ogc:PropertyName></Label> would give as
class text ([MY_COLUMN])
  * <Label>MY_COLUMN</Label>  would give ([MY_COLUMN])
  * <Label>aaa <ogc:PropertyName>TXT</ogc:PropertyName> bbb
<ogc:PropertyName>TXT</ogc:PropertyName>ccc</Label>  would give (aaa [TXT]bbb
[TXT]ccc)

 Couple of things :
   * do you see any problem of always using the class text instead of the layer
label item ?
   * I saw a problem when parsing the xml where the white spaces in front of the
label values are stripped out (in the 3rd example above, spaces before the sting
"bbb" are striped out). I think this comes from  the CPL xml paring code (gdal)
but I need to confirm that with Frank. 

[tomkralidis]

FYI the schema does not allow for whitespace _and_ an element, so:

<Label>aaa <ogc:PropertyName>TXT</ogc:PropertyName> bbb<ogc:PropertyName>TXT</ogc:PropertyName>ccc</Label> 

would not work.

[assefa]

Tom, I guess it would be for the user to validate the SLD (or should we do that ?). As it stands now, we use OGR to parse the xml and if the xml is valid (just the structure), we assume it is a valid SLD.

Closing this bug. Changes have benn in for some time. If there are specific bugs, we will open new ones.