FW: [Chameleon] mapDHTMLwidget occasionally fails

Thu Aug 12 22:13:48 EDT 2004

Hi all,

I'm still kind of stuck with my problem, and I was hoping anyone might have come up with any ideas / solutions. In short, instead of getting a mapimage, I get a 'broken image', or 'red cross', once every so many times. It happens far more often as the jpeg quality factor is higher, and as there are more layers (definitely with an ecw). I only had it since I started using apache instead of IIS. Would this problem be solved by running PHP as a module, rather than an executable? How do I actually do this, because the last time I tried, it just didn't work......

Can I force the browser to delay requesting the DHTML image for about 0.2s? Or anything else to compensate? Can I force chameleon to start generating the image before it serves out any part of the page?
It occurs in both cwc1.0.4 and chameleon 1.99 beta2.

regards,

Jacob

-----Original Message-----
From: Delfos, Jacob 
Sent: 4 June 2004 09:41
To: 'spencer at dmsolutions.ca'; Delfos, Jacob
Cc: chameleon at lists.maptools.org
Subject: RE: [Chameleon] mapDHTMLwidget occasionally fails

Actually, when it happens, it happens instantly (1 second). In other words, the failed-image occurs immediately as the image began loading. I have not seen it happen in Mapserver, only chameleon. It happens much more in explorer than Firefox/mozilla. With a JPEG quality of 100, it happens roughly about 1 in 10 times (depending on the mood of my computer). The URL is valid (if I understand correctly, the url to the image is pretty constant in each session anyway if the page is not resubmitted). If I try the URL in another browser, it usually shows up after a long time. It appears the 'session' is stuck on the server. In version 1.0.4, other images often don't show either on the first load of the page (compasspoints, etc.). Again, only with apache. I think it's just a matter of the browser requesting things from the php document that the server has not yet been able to create. Is there a way to make the server wait with serving the php page until certain elements have been created?

Jacob

-----Original Message-----
From: Paul Spencer [mailto:pagameba at magma.ca] 
Sent: Thursday, 3 June 2004 9:51 PM
To: Delfos, Jacob
Cc: chameleon at lists.maptools.org
Subject: Re: [Chameleon] mapDHTMLwidget occasionally fails

Jacob,

is it possible that something is timing out?  Does it take more than 30 
seconds to render the image (seems unlikely).

I've never seen this problem if it wasn't also associated with some 
other error like a layer failing to draw or something.  If mapserver 
generates any warnings or errors, the image will typically be invalid. 
One way to test this is to right-click on the image and copy the image 
location into another browser tab/window and see if there are any 
mapserver error messages?  If you are using Mozilla, you can also 
right-click on the page, view page info, click the media tab and find 
the image that refers to drawmap.php and use the URL from there (should 
be the same).

Cheers,

Paul

Delfos, Jacob wrote:

> Hi All,
> 
> Occasionally I have the problem that instead of the mapimage, I get
> the
> red cross (explorer), or the broken image (mozilla). I am not certain 
> what the cause for this is. I have only seen this happen since I started 
> using Apache. IIS didn't not seem to suffer from this. It happens more 
> frequently when the JPEG quality factor is higher (especially above '80').
> 
> It appears that part of the site runs ahead of itself. Is Apache
> trying
> to serve out the image before PHP started creating it? Is there anything 
> in the configuration of Apache or PHP that I need to tweak?
> 
> One point to note is that the server needs to do quite a bit of 
> processing (ECW's and vector data).
> 
> This happens in Chameleon 1.0.4 and 1.99 beta1.
> 
> Regards,
> 
> Jacob
> 
> 
> *JACOB DELFOS
> SPATIAL INFORMATION ANALYST
> *Maunsell Australia Pty Ltd
> 629 Newcastle Street
> PO Box 81
> Leederville 6902
> Western Australia
> ABN 20 093 846 925
> 
> Tel     + 61 8 9281 6185
> Fax    + 61 8 9281 6297
> _jacob.delfos at maunsell.com_
> 
> 
> ----------------------------------------------------------------------
> --
> 
> _______________________________________________
> Chameleon mailing list
> Chameleon at lists.maptools.org
> http://lists.maptools.org/mailman/listinfo/chameleon

-- 
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|Paul Spencer                           pspencer at dmsolutions.ca   |
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|Applications & Software Development                              |
|DM Solutions Group Inc                 http://www.dmsolutions.ca/|
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