[maplab-users] symbol picker in MapEdit

[Paul Spencer]

Peter, you are correct.  There are a couple of technical limitations 
that prevent this from working.  First, symbol names are optional in the 
symbol file, so we aren't guaranteed to have it available and this makes 
it a little tricky in figuring out what to use.  Second, MapServer 
doesn't provide the capability to return symbol names for a given index 
value so there is no way of knowing what symbol names are actually 
available.  We have discussed adding this kind of functionality to 
MapServer but it is very low priority since MapEdit is the only 
application that would use this.  Perhaps if someone were to offer 
funding ... ;)

Cheers,

Paul Spencer
Applications and Software Development
DM Solutions Group

Bruton, Peter wrote:

>Hello;
>
>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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>  
>