[Zope] really really refresh again

[Kent Polk]

On 15 Jul 1999 07:40:01 -0500, Robin Becker wrote:
>I started the stupid refresh question last month. Now I'm trying to use
>the Poll product as a starter/learner. I cannot get the images to
>refresh properly.
>
>I know about
>
><!--# call "RESPONSE.setHeader( 'Expires', '0')"-->
><!--# call "RESPONSE.setHeader( 'Pragma', 'no-cache')"-->
>
>and have tried putting these in the document containing the image. This
>has no obvious effect.
>
>This gif refresh problem must happen to others. Any ideas?

The primary clients don't necessarily obey either the cache pragmas
or the HTTP1.1 cache-control headers. The only solution I ever
found was to change the image URL each time it was to be refreshed.
Now at first, this seems like a major problem, however, especially
in Zope, it isn't as much of a problem as might first appear if
the URL references a method which simply returns the correct
information.  You could tag a parameter such as a timestamp (clipped
within an allowable time frame) onto the method URL 'picb/56159'
and possibly even ignore the timestamp information when the method
retrieves the current image data.  The image URL does need to be
changed in the main document each time, but most clients can be
coerced to reload the main document without much travail.

Kent Polk