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Re: lynx-dev Loading images from "post" pages

From: David Woolley
Subject: Re: lynx-dev Loading images from "post" pages
Date: Fri, 28 Jun 2002 07:27:40 +0100 (BST)

> 1) Slow connection, when page expire quickly.

These will break for GUI browsers as well.  The slow link will cause a
long delay between the GUI browser requesting the HTML and its requesting
the image.  It will certainly break for GUI browsers with images off,
which may well be needed for such a slow link.  In fact, Lynx will
probably be much faster, as you will be able to go straight to the one
image that matters, and request that, rather than having to take it
turn with all the cosmetic images.  Pages with multiple synchronised
real time images are unrealistic, as the user cannot take in the data
within the real time constraints.

> 2) not allowed to reload page or its part.

This will break for GUI browsers.  A GUI browser will generate exactly 
the same number of HTTP transactions as Lynx followed by an image
request.  The web site has to treat the image request and HTML request
as separate transactions - even with keep alive and pipelining, the images
are likely to be requested on a separate connection from that used for
the HTML.
> 3) real time processes shown on page (like temperature from above example, 
> or stock quotes mentioned).

Stock market data in the UK has to be delayed by 15 minutes.

Generally, if you want to force images and text to be downloaded at the
same time, you need to use a format that supports that, such as PDF
with no byte range HTTP support.  Images in HTML are a hack.  They
are conceptually a special form of link, if you really treat HTML
as a hypertext format.

Incidentally, I wonder if what you are really doing here is auto-loading
the HTML, in which case you are probably in breach of the terms of service
of the page in question, but could otherwise use wget, which can be configured
to load a page and its images.

And can I repeat that POST is irrelevant, the same applies to GET pages with
caching disabled, which seems to be the norm for commercial sites these days.
(NB the images on an HTML page returned in response to a POST will be cachable,
so will have to be be aggressively labelled as uncachable in the HTTP if they
do not have time dependent names - most commercial site designers don't seem
to understand how to control any real HTTP headers, let alone cachability

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