[Cartoweb-users] Simple legend dropdown?

Chris Duncan, GISmatters duncan at gismatters.com
Tue Jun 24 21:02:35 EDT 2008

Is it possible to create a single, simple dropdown control for 
choosing one of several layers (or layergroups); when chosen, that 
layer is activated and the others in the dropdown list are de-activated.

Another way of thinking about it is that I want the *behavior* of 
radio buttons (mutually exclusive activation of one layer from a 
group) with the *mechanism* of a drop-down list.

The reason I want this is to save space - it's more compact than radio 
buttons (in my case, I want to let the user choose one of 5 different 
basemap or background layers, so that takes up 5 lines in the legend 
where a drop-down list would take up 1). I'm targeting 1024 x 768 
screen sizes and 40% of the height is already taken up by the 
website's banner, menu, and footer (not my design!), so I don't have 
much left to work with and I want to minimize the need for scrolling 
as much as possible.

The closest I can get is to create a layergroup with rendering = 
dropdown, but this shows the selected layer (or layergroup) below the 
dropdown with a checkbox. This has 2 disadvantages: (a) the layer I'm 
trying to display appears twice in the legend - once as the selected 
value in the dropdown, and once below in its own legend entry; (b) I 
still have to use that layer's checkbox to activate/de-activate it.

Any suggestions, examples? It doesn't seem like a crazy idea, but I 
couldn't find anything to guide me in the documentation or this list.




Chris Duncan, Ph.D.

duncan at GISmatters.com

1 Tuckerman Ln
Amherst, MA 01002

Tel: 413-549-2052
Fax: 508-637-2557

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