[MapServer-users] Use SCALETOKEN in FILTER?

[Seth G]

Hi Jesper,

As a workaround (unless this was the intended design), you can use the following approach:

        SCALETOKEN
            NAME "%ne_scalerank%"
            VALUES
                "0" "([scalerank] < 10)"
                "1000" "([scalerank] < 8)"
                "10000000" "([scalerank] < 5)"
            END
        END
        FILTER "%ne_scalerank%"

Seth


--
web:https://geographika.net & https://mapserverstudio.net
mastodon: @geographika at mastodon.social

On Thu, Feb 13, 2025, at 12:31 PM, Seth G via MapServer-users wrote:
> Hi Jesper,
> 
> This looks like a bug - it should work as you expect it to.
> Could you log an issue at https://github.com/MapServer/MapServer/issues ?
> 
> Seth
> 
> --
> web:https://geographika.net & https://mapserverstudio.net
> mastodon: @geographika at mastodon.social
> 
> On Wed, Feb 12, 2025, at 3:13 PM, Jesper Kempe via MapServer-users wrote:
>> Hi
>> 
>> I am trying to show different levels of details based on zoom level in a map based on Natural earth 10m data (ne_10m_lakes.zip from https://www.naturalearthdata.com/downloads/10m-physical-vectors/) using the attribute scalerank in the shape file.
>> 
>> My plan was to use SCALETOKEN to replace the value in a FILTER with the current max scalerank to use.
>> But I cant get it to work. Nothing is shown in the map.
>> 
>> Should it be possible to use a scaletoken in a filter expresssion?
>> 
>> Looking at https://mapserver.org/development/rfc/ms-rfc-86.html#discussion it looks like it at least was planned to work?
>> 
>> Now I get errors like this in the log file:
>> 
>> [Wed Feb 12 13:50:20 2025].23938 replacing scaletoken (%ne_scalerank%) with (5) in layer->filter (ne_10m_lakes) for scale=221471921.250000
>> [Wed Feb 12 13:50:20 2025].24460 msEvalExpression(): General error message. Cannot evaluate expression, no item index defined.
>> [Wed Feb 12 13:50:20 2025].24474 msEvalExpression(): General error message. Cannot evaluate expression, no item index defined.
>> [Wed Feb 12 13:50:20 2025].24482 msEvalExpression(): General error message. Cannot evaluate expression, no item index defined. 
>> 
>> Using this mapfile:
>> MAP
>>     CONFIG "MS_ERRORFILE" "ms_error.txt"
>> 
>>     STATUS ON
>> 
>>     PROJECTION
>>         "init=epsg:4326"
>>     END
>> 
>>     EXTENT -180 -90 180 90
>> 
>>     WEB
>>         METADATA
>>             "wms_title"           "WMS Demo Server"
>>             "wms_srs"             "EPSG:4326"
>>             "wms_enable_request"  "*"
>>         END
>>     END
>> 
>>     LAYER
>>         DEBUG 5
>>         NAME 'ne_10m_lakes'
>> 
>>         TYPE POLYGON
>>         PROJECTION
>>             "init=epsg:4326"
>>         END
>>         EXTENT -180 -90 180 90
>>         DATA "ne_10m_lakes.shp"
>> 
>>         SCALETOKEN
>>             NAME "%ne_scalerank%"
>>             VALUES
>>                 "0" "10"
>>                 "1000" "8"
>>                 "10000000" "5"
>>             END # VALUES
>>         END # SCALETOKEN
>> 
>>         FILTER ([scalerank] < %ne_scalerank% )
>> 
>>         CLASS
>>             STYLE
>>                 OUTLINECOLOR "#647078"
>>                 WIDTH 1
>>                 COLOR "#EBEEF0"
>>             END
>>         END
>> 
>>     END
>> 
>> END
>> 
>> For this request
>> https://myserver/wms?&service=WMS&request=GetMap&layers=ne_10m_lakes&styles=&format=image%2Fpng&transparent=false&version=1.1.1&map=ne_10m_lakes.map&height=512&width=512&srs=EPSG%3A4326&bbox=-180,-90,180,90
>> 
>> Worth noting is if I replace FILTER ([scalerank] < %ne_scalerank% ) with FILTER ([scalerank] < 5 ) in the mapfile it works fine.
>> 
>> Anyone with thoughts or ideas on how this can be solved?
>> 
>> I am on Mapserver 7.6.4. 
>> 
>> Thanks,
>> Jesper
>> 
>> _______________________________________________
>> MapServer-users mailing list
>> MapServer-users at lists.osgeo.org
>> https://lists.osgeo.org/mailman/listinfo/mapserver-users
>> 
> 
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