[maplab-users] Question about Legends and Layers

Daniel Morissette
Wed, 03 Jul 2002 14:05:08 -0400

I can't tell about the way GMapFactory apps deal with the legend
specifically (if there are any exceptions to be aware of?), but I think
you should be able to control layer visibility based on scale via the
legend template.

See the HTML legend docs for the full details:

Look at the opt_flag value in the [leg_layer_html] tag (or
leg_group_html?) and unset bit '1' in the value (e.g. if it's
opt_flag=15 then set opt_flag=14).. this will restore the default
behavior which is to hide layers that are currently out of scale.

About the [if ...] tags that remain there if your layer has no name,
that's the intended behavior of the HTML legend template so that if you
type a value that's never set in an [if...] (or do a typo) then it's not
just treated as being false by default.  Whether this is a good thing or
not is arguable, but we thought that doing things this way would make
things easier to debug.

I hope that helps,


Stephen Woodbridge wrote:
> Hi all,
> I have a guestion regarding Layers and Legends.
> History, I used maplab and gmap factory to create an application
> starting point then, the resulting files were modified by hand to
> integrate other features - mention this because it is possible that I
> broke something.
> I have two Roads layers where the only difference is that they render as
> different scale factors with different characteristics. In my HTML
> legend I always get 2 Roads lines showing one for each rendering style.
> What I would like to get it only one line where the icon changes based
> on the scale factor of the applied map since the two layer are mutually
> exclusive.
> To generalize this, I would like legend entries that can't be seen
> because of the scale factor to not be rendered in the legend. Why should
> we confused the user with a lot of extraneous legend entries that are
> not rendered because they are out of scale.
> I also tried to make the Roads layer into a group hoping that it would
> only show the group name in the legend, but that didn't work either :(
> I have a similar thing happening with ANNOTATION layers. It would be
> nice if I could specify what items I WANT in the legend and/or what I
> would like EXCLUDED from the legend.
> Also, if I don't NAME the layer I get a bunch of [if ... ] that looks
> like code in my legend.
> Any suggestions or ideas?
> -Steve
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