[OpenLayers-Dev] Dynamic SLD in a GetMap-Request via HTTP-POST

[Ingo Weinzierl]

Hi people,

after a little research yesterday I found out that the W3C specification of 
the XMLHttpRequest does not provide the responseStream attribute. So the 
implementation of FireFox3 does not implement it as well.

Thinking about a resolution to display images in a browser requested via 
HTTP-POST, the only idea I have at moment is to decode the bytes of the image 
into base64 encoding and to put this into the 'src'-attribute of the <img> 
tag.
Resulting problems out of this are:
 - base64 encoding in the <img> tag is supported  in FireFox3 and IE8 only
 - decoding the byte stream of the image with JavaScript is maybe slow 

Do you have any other ideas?

Regards, 
Ingo

On Wednesday 06 May 2009 09:25:18 Ingo Weinzierl Hi wrote:
> Hi,
>
> On Thursday 30 April 2009 20:20:46 Tim Schaub wrote:
> > Hey-
> >
> > Andreas Hocevar wrote:
> > > Hi Ingo,
> > >
> > > Ingo Weinzierl wrote:
> > >> I am thinking about a topic of my thesis in the next month. While
> > >> working on a project using OpenLayers, I asked myself if it's possible
> > >> to send a WMS GetMap-Request via HTTP-POST to include a SLD.
> > >> I have searched for this problem via google, the mailing-lists and in
> > >> the examples of OL, but the only way to use SLDs in a GetMap-Request I
> > >> could find is via url to a file or in a HTTP-GET url, which has
> > >> limited length. The idea of my tutor and me is to realize a WMS
> > >> GetMap-Request via HTTP-POST to be able to include longer SLDs.
> > >>
> > >> What are you thinking about this idea? Or is it absolutely impossible?
> > >
> > > It is actually a good idea, and I would already have developed
> > > OpenLayers support for it if there weren't other things of higher
> > > priority. Sending WMS requests via POST is covered by the WMS spec, but
> > > things become complicated when you want to display the resulting image
> > > in a browser. Tim Schaub and I have played around a bit with
> > > XMLHttpRequest and responseStream [1], but it did not work as described
> > > there. Maybe we were just missing something obvious.
> >
> > Yeah, my (quick) assumption was that responseStream was not available in
> > FF3 (at least).
> >
> >  >>> var req = new XMLHttpRequest()
> >  >>> req.open("GET", ".", false);
> >  >>> req.send(null)
> >
> > GET http://localhost/    200 OK    15ms
> >
> >  >>> typeof req.responseStream
> >
> > "undefined"
> >
> > So, despite being a "perfectly reasonable way" [1] to request images, I
> > haven't seen it work.  Happy to be shown otherwise.
>
> After a little investigation, it seems that there are more people arround
> having this problem with responseStream. Maybe I can find somebody of the
> google team who can help at that point. Otherwise I will search the web for
> this problem.
>
> > Tim
> >
> > [1]
> > http://n2.nabble.com/Request---ProxyHost-Question-td2190618.html#a2191803
> >
> > > Having said that: if you want to develop this for OpenLayers, I'll be
> > > willing to mentor.
>
> Thanks, that sounds nice. My thesis starts not until july, but I gonna
> contact you when I start working on it.
>
> > > Regards,
> > > Andreas.
> > >
> > > [1]
> > > http://code.google.com/support/bin/answer.py?answer=79663&topic=11366#s
> > >ce nario1
> > >
> > >> Regards,
> > >> Ingo
> > >>
> > >>
> > >> ----------------------------------------------------------------------
> > >>--
> > >>
> > >> _______________________________________________
> > >> Dev mailing list
> > >> Dev at openlayers.org
> > >> http://openlayers.org/mailman/listinfo/dev
>
> Regards,
> Ingo


-- 
Ingo Weinzierl				              OpenPGP key: 0x2D2E2573
http://www.intevation.de/
Intevation GmbH, Neuer Graben 17, 49074 Osnabrück; AG Osnabrück, HR B 18998
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