[OpenLayers-Dev] Map Initialization (was [GeoExt] Map widgets)

[Björn Harrtell]

I have put some thought into this too and created a widget with an
event that triggers when the map instance is created/rendered in an
Ext JS panel, here:

http://webgispublic.blogspot.com/2008/12/webgismappanel.html

Just a FYI.. I think the additions to OL.Map above are great too!

On Thu, Jan 15, 2009 at 16:23, Andreas Hocevar <ahocevar at opengeo.org> wrote:
> This is awesome! Thanks Tim.
>
> Andreas.
>
> On Wed, Jan 14, 2009 at 8:55 PM, Tim Coulter <tcoulter at opengeo.org> wrote:
>> FYI:
>>
>> http://trac.openlayers.org/ticket/1901
>>
>> Tim
>>
>> --
>> Tim Coulter
>> OpenGeo - http://www.opengeo.org
>> Expert service straight from the developers.
>>
>> On Wed, 2009-01-14 at 12:38 -0500, Tim Coulter wrote:
>>> Thanks for the feedback, Eric. CC'ing to the OL dev list.
>>>
>>> Back story for the OL developers:
>>>
>>> When working with Ext and OpenLayers, I realized that due to
>>> OpenLayer's
>>> Map class requiring a div on initialization, my code contained a
>>> circular dependency. The problem was that Ext's Viewport code needed
>>> things initialized before it laid out HTML elements for each
>>> component;
>>> on the other hand, OL needed HTML elements defined before it could
>>> create a map. Because they both needed each other, I was at an
>>> impasse.
>>>
>>> To get around this, I edited OpenLayers to not require a div on
>>> initialization. At the same time, I added the named argument
>>> "renderTo"
>>> to get rid of the reliance on positional arguments if
>>> rendering-on-initialization was required.
>>>
>>> http://trac.openlayers.org/changeset/8608
>>>
>>> Examples of this code's use are here[1] and here[2]. Note that in the
>>> second case, I'm initializing a map with no parameters.
>>>
>>> The implementation (as far as arguments are concerned) is backwards
>>> compatible. You can still use the positional argument if you'd like
>>> to,
>>> but preference is given to renderTo. Neither are required.
>>>
>>> I'd be very interested if this is helpful for others in the community.
>>> I'd also be happy to give more back story if needed.
>>>
>>> On the GeoExt list (geoext at lists.opengoe.org), Eric Lemoine asked the
>>> question:
>>>
>>> > With your new OpenLayers code, can one do:
>>> >
>>> > 1 map = new OpenLayers.Map();
>>> > 2 map.addLayer(new OpenLayers.Layer.WMS());
>>> > 3 map.render("map-div")
>>>
>>> That was the intention, yes. Aside from needing to call some form of
>>> setCenter/zoomToExtent/etc. after render(), the above should work.
>>>
>>> He brought up a good bug:
>>>
>>> > I'm concerned with addLayer failing if maxResolution is "auto" - the
>>> > map doesn't have a div at addLayer time, so resolutions can't be
>>> > calculated. Even if I'm correct, that may be ok, users should just
>>> be
>>> > warned.
>>>
>>> Is the default value for maxResolution "auto"? If not, I haven't run
>>> into a case where this happens. Can you provide an example?
>>>
>>> What does everyone think? I plan on opening a ticket today and
>>> submitting a patch to get this discussion going there.
>>>
>>> Tim
>>>
>>> [1]
>>> http://dev.openlayers.org/sandbox/tcoulter/teleporter/examples/teleportation.html
>>> [2]
>>> http://dev.openlayers.org/sandbox/tcoulter/teleporter/examples/late-render.html
>>>
>>> On Wed, 2009-01-14 at 07:34 +0100, Eric Lemoine wrote:
>>> > On Tue, Jan 13, 2009 at 6:55 PM, Tim Coulter <tcoulter at opengeo.org>
>>> wrote:
>>> > > 2) It supports both passing an already-created map (as per my last
>>> > > email), as well as allowing a configuration to be passed as
>>> this.map. In
>>> > > the latter case, the map is created for the developer by the
>>> MapPanel.
>>> >
>>> > I like the idea of having the map option either be a Map instance or
>>> a
>>> > Map config.
>>> >
>>> > > 3) I've removed synonymous functions. I've also removed TimS's
>>> layer and
>>> > > control convenience functions/features; I think these could be put
>>> back
>>> > > in, though if OpenLayers allows the "layers" and "controls" named
>>> > > parameters (I know "controls" is there), then there may be no need
>>> for
>>> > > MapPanel to handle it.
>>> >
>>> > Adding support to OpenLayers for a "layers" map option would be very
>>> > useful I think. Otherwise, if I'm correct with the above
>>> > "maxResolution set to auto" issue, we'd need the MapPanel to trigger
>>> > an event to know when layers can be safely added to the map.
>>> >
>>> > In any way, I think we'd need our map panel to trigger events, at
>>> > least one to tell the world that the map instance is created. This
>>> > discussed with Andreas and Bart, they even started coding things
>>> > around that if I remember correctly.
>>> >
>>> > > 4) I haven't yet gotten the changes to Map.js looked at or
>>> approved by
>>> > > the OpenLayers folks, so if it's something we'd like to use, we
>>> should
>>> > > start some conversation over there. (I know a lot of you guys are
>>> on
>>> > > this list. :) )
>>> > >
>>> > > Given that the circular dependencies in Map.js are removed, and
>>> the
>>> > > MapPanel accepts a map as well as a configuration, it more
>>> reflects my
>>> > > coding style while (I think) supporting everyone else's.
>>> > >
>>> > > Let me know what you guys think. I'm really interested in knowing
>>> if
>>> > > others find this useful.
>>> >
>>> > Thanks Tim,
>>> >
>>> > --
>>> > Eric
>>> >
>>> >
>>> > --
>>> > Archive:
>>> http://lists.opengeo.org/geoext/archive/2009/01/1231915041656
>>> > To unsubscribe send an email with subject "unsubscribe" to
>>> geoext at lists.opengeo.org.  Please contact
>>> geoext-manager at lists.opengeo.org for questions.
>>>
>>>
>>>
>>> --
>>> Archive: http://lists.opengeo.org/geoext/archive/2009/01/1231954920273
>>> To unsubscribe send an email with subject "unsubscribe" to
>>> geoext at lists.opengeo.org.  Please contact
>>> geoext-manager at lists.opengeo.org for questions.
>>
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>
>
> --
> Andreas Hocevar
> OpenGeo - http://opengeo.org/
> Expert service straight from the developers.
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