[Community] Symbolizer Usability

[Kai Hänninen]

Ludwig M Brinckmann wrote:
> Which PCL Version are you using with this?

I'm using the SVN head of both PCL and ZCO.


> 
> 
>> From: Kai Hänninen <kai.hanninen at mbconcert.fi>
>> Reply-To: "gispython.org community projects" 
>> <community at lists.gispython.org>
>> To: "gispython.org community projects" <community at lists.gispython.org>
>> Subject: Re: [Community] Symbolizer Usability
>> Date: Thu, 15 Jun 2006 16:40:57 +0300
>>
>> Kai Hänninen wrote:
>>> Hi Ludwig!
>>>
>>> Thanks for your feedback.
>>>
>>> Ludwig M Brinckmann wrote:
>>
>> [...]
>>
>>>> -- Symbolizers should be reusable across layers (so in that sense 
>>>> the old ZCO style was better) This is maybe not so much an issue 
>>>> now, but I hope we will one day get layer groups.
>>>
>>> Right, PrimaGIS 0.6 will not support this, but later versions based 
>>> on the Zope3 Component Architecture will.
>>
>> I attempted to improve the use case for sharing symbolizers and 
>> committed a proposal in r714 for PrimaGIS.
>>
>> The old implementation (revisions < 714) used a containment based 
>> approach so that the symbolizers used for a given layer needed to be 
>> physically located within that layer.
>>
>> I've replaced that with a reference based implementation so that the 
>> layer stores only references to symbolizer objects within it and this 
>> enables:
>>
>>  - Symbolizers to be shared among different layers
>>  - Symbolizers to be located freely within the Plone site
>>
>> For a site with a single map this approach will work ok, but for 
>> multiple maps per site installations we might wish to constrain the 
>> symbolizers used for a given map to be contained within that 
>> particular map so avoid polluting the symbolizer selection with lots 
>> of unrelated symbolizers.
>>
>> This approach may be a bit slower to render than the one before 
>> because we need to do a catalog query to access the symbolizers 
>> instead of a direct access. If it does prove to be useful, I'm sure we 
>> can optimize it though.
>>
>> This is merely a step in the evolution because in the zope3 based 
>> PrimaGIS the symbolizers are defined in ZCML and not persisted in the 
>> ZODB (although we can implement TTW created persisted symbolizers if 
>> need be).
>>
>> If you try this, I suggest you do it with a fresh installation and use 
>> the createPrimaGISDemo script instead of upgrading an existing setup 
>> because the migration code is not up-to-speed on this.
>>
>> Looking forward to your feedback!
>>
>> cheers,
>> Kai
>>
>>
>> -- 
>> Kai Hänninen                  +358-50-558-7935
>> Software engineer             www.mbconcert.fi
>> MB Concert Ky                 kai.hanninen at mbconcert.fi
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> 
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-- 
Kai Hänninen                  +358-50-558-7935
Software engineer             www.mbconcert.fi
MB Concert Ky                 kai.hanninen at mbconcert.fi