[OpenLayers-Dev] [OpenLayers-Trac] [OpenLayers] #1195: allow for maintaining layer visibility when switching base layers

Pierre GIRAUD bluecarto at gmail.com
Thu Dec 13 04:01:02 EST 2007

This is clear for me now and it makes sense. Isn't something we would
reconsider for 3.0 and write it another way. Will the map still
require a base layer to work ?

On Dec 12, 2007 6:08 PM, OpenLayers <trac at openlayers.org> wrote:
> #1195: allow for maintaining layer visibility when switching base layers
> ----------------------+-----------------------------------------------------
>   Reporter:  tschaub  |       Owner:
>       Type:  feature  |      Status:  new
>   Priority:  minor    |   Milestone:
>  Component:  general  |     Version:  2.5
> Resolution:           |    Keywords:
> ----------------------+-----------------------------------------------------
> Comment (by tschaub):
>  Currently, isBaseLayer means two things:
>  1) can be used by the map to determine projection/extent related
>  properties, and
>  2) can not be displayed at the same time as other layers with isBaseLayer
>  true.
>  The first meaning makes some sense, though in reality any layer could be
>  used for this purpose.  The second meaning is a bit arbitrary.  Just
>  because I want a layer to be used to determine projection/extent related
>  properties doesn't necessarily mean I also never want to display the layer
>  at the same time as another layer that has the same property.
>  Take, for example, a map with many WMS layers - all of them with some
>  transparent areas.  A user may want to reorder these layers, keeping all
>  of them visible.  This same user may want to remove some of these layers
>  and add new ones.  These two requirements mean that the base layer will be
>  changing.  On solution is to use a "dummy layer" as a base layer.  I think
>  this is dumb.  I like the fact that the map determines it's
>  projection/extent related properties based on some real layer.
>  This patch allows an application to have a single layer with isBaseLayer
>  set to true.  This layer is the map.baseLayer.  When the user reorders
>  layers, the map.baseLayer is changed, but the visiblity of the old layer
>  is not turned off.
> --
> Ticket URL: <http://trac.openlayers.org/ticket/1195#comment:2>
> OpenLayers <http://openlayers.org/>
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