[Zope] Re: ZGDChart refresh

[Ayhan Ergul]

In my experience, IE was particularly persistent about
caching images, even with all sorts of http headers
(pragma, etc.) in place. I ended up referencing images
with an additional URL parameter that has a randomly
generated value, eg:

http://www.foo.com/charts/mychart?param1=12&param2=34
becomes
http://www.foo.com/charts/mychart?param1=12&param2=34*anticache=99582223529

this fools the browser into thinking it's a different
chart every time since the URL looks different
(assuming your RNG is sufficiently good). Obviously
the side effect is that now every image gets to be
downloaded every time even if it hasn't changed. This
was the behavior I needed (with realtime data), so no
problem. If your data is determined solely by
parameters instead, then you might construct your URL
to reflect those parameters, so the same chart gets
loaded as long as the parameters are the same (good
for static/quasi-static data).

Ayhan Ergul

--- In zope@y..., Derek Simkowiak <dereks@r...> wrote:
> -> Control/Shift when reload or something like that
> 
> 	No, no, no... he needs a solution for his
*customers*.  He's 
> looking for a "pragma: no-cache" header or some
such.
> 
> 	How does one tell Zope to send no-caching HTTP
headers?
> 


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