[mapserver-dev] Support for the MapInfo style zoom layering option.

[David Fuhry]

Steve,

    I too like the REQUIRES approach for its consistency and power.  All 
of the {MIN,MAX}SCALE[DENOM], (and proposed) DISPLAY{MIN,MAX} parameters 
could be rolled into it, and those parameters deprecated.  Even STATUS 
could be handled by the same logic.

    I wonder if there's a convenient and sensible way for expression 
values to exist in a more organized hierarchy.  Something like the RFC 
31 syntax to load mapserver objects from strings (but in reverse) would 
allow powerful (and perhaps wacky) expressions like:

REQUIRES "map.layer[lakes] AND map.imagetype = 'PNG' OR map.width > 1000"
# map.width could be an alias of map.size[0]

-Dave

Steve Lime wrote:
> Ok, I see, zoom really means width. Why not just use that term instead of zoom?
> 
> I guess I'm not seeing the advantage of using this method then. MapServer scale is based
> on the width as well but applies a constant multiplier to that value. I would expect zoom to
> track linearly with scaledenom. 
> 
> What do others think? Would this be an easier way to define display floors and ceilings?
> 
> Perhaps this is an opportunity to generalize things a bit. I could see defining general 
> parameters like so:
> 
> DISPLAYMETHOD WIDTH|SCALEDENOM|others?
> DISPLAYMIN 1500
> DISPLAYMAX 2500
> 
> or perhaps we should be using the REQUIRES functionality. Traditionally that is used to look
> at other layer state but there's no reason we couldn't look at extent properties as well. For
> example (pick your favorite parameter names):
> 
>   REQUIRES ([width] > 1500 AND [width] < 2500)
>   REQUIRES ([scaledenom] < 100000)
> 
> That way we'd have no new parameters and we could depricate MINSCALEDENOM and
> MAXSCALEDENOM. I kinda like that.
> 
> Steve
> 
>>>> On 6/23/2008 at 10:34 AM, in message
> <f3b73b7d0806230834v7b2bdaeftedcee74ef74a394d at mail.gmail.com>, "Tamas Szekeres"
> <szekerest at gmail.com> wrote:
>> Steve,
>>
>>> So how is a current ZOOM value computed?
>> I would only rely on the width of the map extent. The specified values
>> would be compared to the actual width in map coordinates.
>>
>>> How would this impact symbol and font scaling?
>> It wouldn`t impact the current scale calculation. It would only affect
>> the decision whether a layer, class or symbol should be drawn at the
>> given extent or not. So in general we should only change those parts
>> of the code where maxscaledenom and minscaledenom do play a role.
>>
>> Best regards,
>>
>> Tamas
> 
> _______________________________________________
> mapserver-dev mailing list
> mapserver-dev at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/mapserver-dev