[MapServer-users] Use SCALETOKEN in FILTER?

[Trygve Aspenes]

Hi Jesper.

The only thing I see at a first glance is the filter run-time 
substitution missing ''. See documentation how it is done there 
https://mapserver.org/cgi/runsub.html#filters

Not sure if this is your problem, but maybe worth a try.

Trygve

Den 2025-02-12 15:13, skrev Jesper Kempe via MapServer-users:
> 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
> [1]
> 
> 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
> 
> 
> 
> Links:
> ------
> [1] 
> 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
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