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

[Steve Lime]

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