[mapserver-users] Usage: PROCESSING FORCE_DRAW_LABEL_CACHE=FLUSH

[Havard Tveite]

It would be useful if someone (preferably a developer ...)
could file a documentation issue for this (and issues for
other enhancements that have not yet been documented).

http://github.org/mapserver/docs

Håvard

On 26/10/2015 22:54:PM, lars.schylberg at blixtmail.se wrote:
> Since I mentioned the command "PROCESSING FORCE_DRAW_LABEL_CACHE=FLUSH" in a previous entry I thought it could be good to describe how it is used. Maybe this could be the basis for some description in the manual.
>
> In my mind this is best improvement in Mapserver 7.0
>
> The use case:
>
> To produce a WMS service where You could zoom in from a very small scale like Europe down to a very detailed city map. You only have detailed data in certain parts.
>
> One data set larger area like the Nordic countries 1:1M, one data set a nation like Sweden 250K and one detailed data set over one town 50K. I don't have detailed data in the other countries and I only have town data covering one town.
>
> The usage is like this:
>
> Draw all layers in the small scale data set without any MAXSCALEDENOM.
>
> Do a FORCE DRAW LABEL CACHE
>
> Draw all layer in the 250k data set on top with a MAXSCALEDENOM=500000, or whatever is good for each layer when You would like to turn on your data.
>
> Do another FORCE DRAW LABEL CACHE
>
> Draw all the layers in the 50k town data set on top of that with a MAXSCALEDENOM=70000
>
> The following mapfile shows the principle for using the command. The example shows the effect of using and not using the FORCE DRAW LABEL CACHE command. Just run the example with shp2img.
>
> ----------------------------------------------------------------------------------------------------------------------------------------
>
> MAP
>   NAME FDLC
>
> # Author: Lars Schylberg,  2015-09-26
> #
> # Requires Mapserver 7-0
> #
> # shp2img -m force_draw_label_cache.map -o without_force_label_cache.png -s 500 300 -e -80 42 -74 46 -l "towns big_city"
> #
> # Result is that the unwanted red Big City label is showing up on top of the Big city polygon.
> #
> # shp2img -m force_draw_label_cache.map -o with_force_label_cache.png -s 500 300  -e -80 42 -74 46 -l "towns force_cache big_city"
> #
> # Result is the wanted, label cache is drawn after the towns layer and the big_city polygon can draw its new label.
> #
>   PROJECTION
>    "init=epsg:4326"
>   END
>
>   SYMBOL
>    NAME "circle"
>    TYPE ellipse
>    FILLED true
>    POINTS
>      1 1
>    END
>   END
>
>   WEB
>    METADATA
>     "ows_enable_request" "*"
>     "ows_title" "foo server"
>    END
>   END
>
>   LAYER
>    NAME "towns"
>    STATUS ON
>    TYPE POINT
>    FEATURE
>      POINTS -75 45 END
>      TEXT "Village"
>    END
>    FEATURE
>      POINTS -79 43 END
>      TEXT "Town"
>    END
>    FEATURE
>      POINTS -77 44 END
>      TEXT "Big City"
>    END
>    FEATURE
>      POINTS -75 43 END
>      TEXT "Village2"
>    END
>    FEATURE
>      POINTS -79 45 END
>      TEXT "Town2"
>    END
>    CLASS
>     NAME "PopulatedPlaces"
>     STYLE
>      SYMBOL "circle"
>      SIZE 10
>      COLOR 10 10 0
>     END
>     LABEL
>       SIZE large
>       COLOR 255 0 0
>       POSITION AUTO
>       FORCE TRUE
>     END
>    END
>   END # Layer
>
>   LAYER
>      NAME "force_cache"
>      TYPE POINT
>      PROCESSING "FORCE_DRAW_LABEL_CACHE=FLUSH"
>      TRANSFORM FALSE
>      STATUS ON
>      FEATURE
>        POINTS 1 1 END
>      END
>   END  # Layer
>
>   LAYER
>      NAME "big_city"
>      TYPE POLYGON
>      FEATURE
>         POINTS
>          -78 44.5
>          -76 44.5
>          -76 43.5
>          -78 43.5
>          -78 44.5
>         END
>         TEXT 'Big City'
>      END
>      CLASS
>         STYLE
>            COLOR 255 250 0
>         END
>         LABEL
>          SIZE giant
>          COLOR 0 0 0
>          POSITION AUTO
>          FORCE TRUE
>        END
>      END
>    END # Layer
> END # Map
>
>
>
>
>
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