Display progress bar while waiting for data

[Frank Warmerdam]

On 5/17/05, Norman Barker <nbarker at rsinc.com> wrote:
> Having been spending some time looking at the socket connection between a client and
> Mapserver I don't think this is possible because the content-length attribute in the
> http response isn't set, so when you read the data you read until an EOF exception.
> 
> It is only possible to show a busy icon, and the number of bytes currently downloaded, something
> Firefox does when it downloads from MapServer to.
> 
> I will gladly be corrected though!

Norman, 

For at least some return data types it might be practical to embed
the content type in the return image header from MapServer.  For
instance, any "gdal" based output formats are first spooled to disk
and then returned to the web connection so we could include 
content-length.

However, the client side would still have no information to report
to the user until the head arrived.  For the whole time that mapserver
is rendering the image, there would be no progress information on the
client side. 

Overall, I am dubious about the practically of meaningful progress
information.  The only case it would help is big return images over
slow links where the image transmission is the bulk of the time. 

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent