[mapserver-dev] GAP with TTF symbols changed behavior in MapServer 5.0

[Daniel Morissette]

We upgraded a system from MapServer 4.10 to 5.x recently and noticed 
that the GAP changed behavior for TTF symbols in MapServer 5.0. It seems 
that this may be related to r6546, but there is no mention or 
explanation of the new behavior in the docs.

I have attached an image and a sample mapfile to compare the 4.10 and 
5.x behavior.

With MapServer 4.10 and older, setting a positive GAP value would 
guarantee that the TTF symbol would be drawn "upside up" (see symbol "A" 
for MapServer 4.10 in the attached image)... and using a negative GAP 
value would force the symbol angle to follow the line direction (useful 
for one-way arrows, see symbol B in attached image).

With MapServer 5.x, setting a positive GAP value results in no rotation 
(symbol A)... and a negative GAP value works as before. So we lost the 
ability to get the symbol "upside up"... and a negative GAP value is now 
required in order to get a TTF symbol that follows the angle of the line 
(e.g. for railroad tracks for instance).

Was this an intentional change in behavior, because the old behavior was 
not considered useful? If yes then this needs to be documented properly 
in http://mapserver.org/mapfile/symbol.html

Daniel
-- 
Daniel Morissette
http://www.mapgears.com/
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MAP   
  NAME "test"
  EXTENT 0 0 100 100
  SIZE 400 250
  IMAGECOLOR 242 239 233
  FONTSET "/path/to/fonts.txt"
      
  WEB   
    IMAGEPATH "/var/www/tmp/"
    IMAGEURL "/tmp/"
  END   

SYMBOL
 NAME "A"
 TYPE truetype
 FONT sans
 CHARACTER "A"
 GAP 6 
END
 
SYMBOL
 NAME "B"
 TYPE truetype
 FONT sans
 CHARACTER "B"
 GAP -6 
END
 

  LAYER
    NAME "A"
    STATUS DEFAULT
    TYPE LINE
    FEATURE
      WKT "LINESTRING(20 100, 20 60, 50 60, 100 75, 50 100)"
    END
    CLASS
      STYLE
        COLOR 255 255 255
        WIDTH 13
        ANTIALIAS TRUE
      END
      STYLE
        SYMBOL 'A'
        COLOR 180 176 177
        SIZE 10
      END
    END
  END

  LAYER
    NAME "B"
    STATUS DEFAULT
    TYPE LINE
    FEATURE
      WKT "LINESTRING(20 0, 20 40, 50 40, 100 25, 50 0)"
    END
    CLASS
      STYLE
        COLOR 255 255 255
        WIDTH 13
        ANTIALIAS TRUE
      END
      STYLE
        SYMBOL 'B'
        COLOR 180 176 177
        SIZE 10
      END
    END
  END



END