[maplab-users] symbol picker in MapEdit

Bruton, Peter
Wed, 17 Jul 2002 13:34:52 -0400

As I understand it, once a user clicks on a specific symbol in the symbol
picker, the symbol "number" is written to the map file.  Would MapEdit not
be more robust if the symbol "name" was written to the map file?

Writing the symbol "name" as opposed to the symbol "number" allows for the
addition and deletion of symbols in MapServer's symbol file, while not
"mixing" up symbol location for maps previously authored.

For example.  Let's say a symbol file has 15 symbols.  Symbols 1 to 5 are
point symbols, symbols 6 - 10 are line symbols, and symbols 11 to 15 are
polygon symbols.  A map file has a polygon layer that uses symbol 11.  There
is a need to add a new point symbol to the symbol file.  Since it makes
sense to group all point symbols together, the new point symbol is inserted
into the sixth position in the symbol file.  As a result what previously was
a polygon symbol in position number 11 is now a line symbol.  Now the map
file cannot render correctly because it is trying to use a line symbol to
represent a polygon feature.

Peter Bruton
GeoAccess Division
Canada Centre for Remote Sensing
615 Booth Street, Room 650
Ottawa, Ontario, K1A 0E9, Canada
telephone 1-613-947-0465
fax 1-613-947-2410

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