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

[Andreas Hocevar]

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
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>>
>>
>>
>> --
>> Archive: http://lists.opengeo.org/geoext/archive/2009/01/1231954920273
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>
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-- 
Andreas Hocevar
OpenGeo - http://opengeo.org/
Expert service straight from the developers.