[MapServer-users] Clipped labels in mapcache/mapserver map

[Steve Lime]

So I checked a map here and found similar settings:

   - label-level: PARTIALS FALSE,
   - map-level metadata: "labelcache_map_edge_buffer" "-20"
   - mapcache: <metabuffer>20</metabuffer>

I don't use the LABEL_NO_CLIP processing directive. The one obvious
difference is the negative value for the map edge buffer - I know negative
values were originally how that was specified but I thought we generalized
that value some time ago.

I wonder if the "ANGLE follow" might be the cause - perhaps there's an
error in the size computation of the rotated text - perhaps at different
position values? Just guessing though.

The only way to easily debug/test is going to be examining a metatile that
results in a clipped label. You could delete an affected tile and then let
mapcache generate a replacement. You should be able to pick up the metatile
WMS call from the logs.

--Steve

On Tue, Nov 1, 2022 at 8:25 PM Steve Lime <sdlime at gmail.com> wrote:

> Have you tried a larger edge buffer? I suppose that’s tough to to test
> given the randomness. I’ll check my settings on a similar setup when I’m in
> the office tomorrow and let you know. It would be interesting to see the
> corresponding metatile to see if the label is whole there. I wouldn’t think
> so but having a reproducible test case would help immensely.
>
> Anyone know how to compute a metatile URL for a given tile x/y/z?
>
> —Steve
>
> On Mon, Oct 31, 2022 at 10:16 AM Thomas Ellett von Brasch <
> Thomas.Ellett at kartverket.no> wrote:
>
>> Hi all,
>>
>>
>>
>> I'm really struggling to fix a longstanding issue with clipped labels in
>> a couple of our wmts services.
>>
>> I've tried following the mapserver/mapcache docs and numerous variations
>> of different attributes, but with no luck.
>>
>>
>>
>> The main problem bug fixing is that the issue seems to be quite random,
>> just popping up here and there.
>>
>>
>>
>> Examples can be seen in these urls:
>>
>>
>>
>>
>> https://norgeskart.no/#!?project=norgeskart&layers=1002&zoom=11&lat=6879652.31&lon=167744.51
>>
>>
>>
>> (the 'Stor rar' and 'S' names in the centre of the map)
>>
>>
>>
>>
>> https://norgeskart.no/#!?project=norgeskart&layers=1002&zoom=6&lat=6440416.41&lon=127931.07
>>
>>
>>
>> ('Kristiansan' , which should be 'Kristiansand')
>>
>>
>>
>> I have "labelcache_map_edge_buffer" "10" in the mapfile and
>> <metabuffer>10</metabuffer> set in the mapcache file.
>>
>>
>>
>> In the source WMS, the placenames layers are line layers (with very small
>> line geometries used just to give curved lines) and the layers (we have
>> several name layers for the different zoom levels, but they're all set up
>> in the same way) look like (truncated):
>>
>>
>>
>> LAYER
>>
>> NAME "N100Stedsnavn"
>>
>> PROCESSING "CLOSE_CONNECTION=DEFER"
>>
>> PROCESSING "LABEL_NO_CLIP=True"
>>
>> TYPE LINE
>>
>>
>>
>>     CLASS
>>
>>       NAME "N100 Stedsnavn"
>>
>>       EXPRESSION ([fmx_rotation] != 0)
>>
>>       LABEL
>>
>>                   *PARTIALS FALSE*
>>
>>                 *ANGLE follow*
>>
>>                 ANTIALIAS TRUE
>>
>>                 FONT "verdana"
>>
>>                 SIZE [fontsize]
>>
>>                 COLOR [geodb_color]
>>
>>                 ENCODING "UTF-8"
>>
>>                   PRIORITY [fontsize]
>>
>>                 *FORCE FALSE*
>>
>>                   MINDISTANCE 50
>>
>>                  OUTLINECOLOR 254 254 254
>>
>>                  POSITION [horizontalalignment]
>>
>>                  TYPE TRUETYPE
>>
>>       END
>>
>>       TEXT "[textstring]"
>>
>>     END
>>
>> END
>>
>>
>>
>> And the tileset definition in the mapcache config file looks like:
>>
>>
>>
>> <tileset name="norgeskart_bakgrunn">
>>
>>         <source>norgeskart_bakgrunn</source>
>>
>>         <cache>norgeskart_bakgrunn</cache>
>>
>>         <metadata>
>>
>>             <title>Topografisk Norgeskart og dybdedata og svalbard minus
>> matrikkel</title>
>>
>>            <abstract>Cache for Norgeskart</abstract>
>>
>>         </metadata>
>>
>>         <grid>googlemaps</grid>
>>
>>         <grid>utm33n</grid>
>>
>>         <format>PNG</format>
>>
>>         *<metatile>8 8</metatile>*
>>
>>         *<metabuffer>10</metabuffer>*
>>
>> </tileset>
>>
>>
>>
>> Is it possible the metatiles being used in the original seed job and
>> later seeding jobs are different somehow?
>>
>>
>>
>> Given that the labelcache_map_edge_buffer is set (along with metabuffer)
>> and we have PARTIALS FALSE in the mapfile, I didn't think that cut labels
>> would be possible?
>>
>>
>>
>> Any thoughts or ideas would be great J
>>
>>
>>
>> Thanks in advance!
>>
>>
>>
>> Tom
>>
>>
>>
>>
>>
>> [image: cid:image001.jpg at 01D3A415.20CB4FE0]
>>
>> *Tom Ellett von Brasch*
>> Sjefsingeniør
>> *Geodatatjenester*
>>
>> Direkte: 32 11 84 73
>>
>> Mobil: 45806402
>>
>> E-post: thomas.ellett at kartverket.no
>>
>>
>> Tlf. sentralbord: 32 11 80 00
>> www.kartverket.no
>>
>>
>>
>>
>> _______________________________________________
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>> MapServer-users at lists.osgeo.org
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>>
>
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