[Mapnik-users] Is there "One True Way" to get ShieldSymbolizer to not cut off shields?

[Mak Kolybabi]

I've been trying to solve this problem for months, now. Every time I solve it
for a while, I then get asked to change the spacing of shields, or add another
highway, and the problem crops back up. It's time for me to ask for help.

I'm rendering tiles using the Python bindings, and occasionally I'll get a
single shield at a single zoom level that gets cut off. I've used a bunch of
settings, but nothing I do fixes the general problem, it only fixes the shield
for a specific spacing/tile size/highway.

Today's problem looks like http://i.imgur.com/s51Z3.png, with the XML used to
generate it being:

<Map srs="&projection;" bgcolor="#FFFFFF" buffer_size="128">
...
<Rule>
  <Filter>...</Filter>
  <ShieldSymbolizer
     base="badges"
     name="highway"
     face_name="DejaVu Sans Bold"
     size="8"
     file="sign-3digit.png"
     type="png"
     width="23"
     height="17"
     dy="-1"
     min_distance="100"
     placement="line"
     avoid_edges="true">
  </ShieldSymbolizer>
</Rule>
...
</Map>

Is there a group of settings that will ensure that a shield will *never* be cut
off, regardless of spacing, image size, shield size, and data?

--
Mak Kolybabi
Programmer
Telenium Inc.
204-957-2821
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