All Cadcorp SIS API Methods

GetOverlayThemeLegend Method


Gets an overlay Theme legend as a Blob string within a Coordinate Reference System .


Visual Basic
Public Function GetOverlayThemeLegend( _
   ByVal pos As Integer, _
   ByVal nTheme As Integer, _
   ByVal projection As String, _
   ByVal fmt As Integer, _
   ByVal precision As Integer _
) As String


The position in the overlays list of the overlay whose Theme legend is required.
The index of the Theme, starting at 0. Use the Number of themes property to find out the number of Theme objects in an overlay.
The named Coordinate Reference System of the returned Blob string. The content of the projection string is always ignored and only required for completeness of the API.
The format of the returned Blob string.

SIS_BLOB_OGIS_WKT 2 = OGC Well-Known-Text format
SIS_BLOB_OGIS_GML 3 = OGC Geographic Markup Language
SIS_BLOB_GEOJSON 6 = Geographic Objects for JSON format


This parameter is ignored and will always return 64-bit precision.

Return Type

A string describing the overlay Theme legend item in the chosen format. The string will be blank if no overlay Theme legend exists. SIS format strings are encoded and cannot be interpreted except by SIS.


  • There is no limit on the length of Blob strings generated by Cadcorp SIS.
  • There are however limits elsewhere: GisLink can only handle strings of a few Kb (this does not apply to the SIS Control); SIS datasets which read Blobs from data sources can use a fixed size communication buffer (use the Cadcorp OGC SQL92 Database Maximum Blob size and Cadcorp View Geometry Maximum Blob size properties to change the size of the communication buffer).

Available: GEO D OD OM OV SISpy



LegendBlob = sis.GetOverlayThemeLegend (0, 0, "*APrjNatGrid", 0, 0, 64)

Returns the blob string for the first theme on the first overlay in the current window within the National Grid coordinate reference system.