Error on rendering layers using special OGR attributes

[szekerest]

Rendering layers with using special OGR attributes such as OGR:LabelText or 
OGR:LabelStyle may fail if the layer file contains different type of 
geometries.
The error message is:
msOGRGetValues(): OGR error. Invalid field index!?!

[szekerest]

map file and data to produce the error

[szekerest]

When using layers with multiple geometries there would be useful to have a 
setting for selecting the proper feature type a layer definition applies to.

[fwarmerdam]

I believe there is already an open feature request to support filtering
on geometry type, but I don't recall the id.

[szekerest]

simple patch to support filtering by geometry

[szekerest]

simple patch to support filtering by geometry (ver 2.)

[szekerest]

Dear Frank!

Would you mind sending your comments on this patch, because my project highly 
relies on this filtering mode. I have many mapinfo layers with different 
geometries that should be rendered with different layer settings.

Thanks

Tamas Szekeres

[fwarmerdam]

Tamas, 

A few points of concern:

 o I am thinking that if the special fields all work in the query (WHERE) 
   clause, then they should also be selectable in an OGR SQL select statement.
   This will require changes to ogr/ogrsf_frmts/generic/ogrdatasource.cpp and 
   ogrgensql.cpp.  I am looking into what would be involved.

 o I am also not sure I like ogr_geometry returning just the short geometry
   type.  I wonder if instead it ought to return the whole geometry for 
   greater generality.  A LIKE comparison against the full (WKT) geometry
   would give you a similar test to what you have now.   Alternatively, 
   perhaps ogr_geometry_wkt and ogr_geometry_type ought to be separate 
   special fields.

In general I am impressed with the patch, and am agreeable to incorporating
a variation on it upstream. 

[bartvde@…]

Added myself to the cc.

[taatuut@…]

Frank,

You mentioned the bug being related to another one.

I think you meant 1129

Regards,

Emil

[fwarmerdam]

Emil, 

That is right, and if we write "bug 1129" we can follow a link to it. 

[szekerest]

Frank,

Are you planning this issue to be applied? Since my projects highly depend on
this feature i am continously patching the new releases with it. However it
would be desirable to have a built in functionality to achieve this behaviour.

In addition i am ready to enhance this functionality according to #7 if it is
required.

Best Regards,

Tamas

[fwarmerdam]

I have suggested that Tamas write a GDAL/OGR RFC on this new feature, and 
once approved commit the changes himself. 

[szekerest]

Added GDAL RFC 6 describing the proposed changes.
The corresponding tracking bug can be found at:

http://bugzilla.remotesensing.org/show_bug.cgi?id=1333

[szekerest]

This feature has been implemented and released with gdal 1.4.0
Closing the bug