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Re: Transparency and linked objects was Re: javascript dhtml and browser variations

From: David Woolley <david@djwhome.demon.co.uk>
Date: Sat, 30 Jun 2001 20:35:32 +0100 (BST)
Message-Id: <200106301935.f5UJZWJ08814@djwhome.demon.co.uk>
To: w3c-wai-ig@w3.org
> If one object (which has a transparent area) is placed above another, there
> is a logical inconsistency, in that the user sees themselves clicking one
> object, but is taken to the other object's location.

This has been discussed on the www-style and/or www-svg mailing lists.
Have a look in the archives.  I think the feeling was that true transparent
material ought not to be sensitive to clicks but material with a low alpha
value ought to be; as there is no static content on the page, I can't work
out whether it uses transparent GIFs or CSS transparency, although the
use of non-CSS colours suggests that it may not use the latter.  I don't
know whether GIF counts as an alpha channel with two values or as 
true transparency.

I would suggest that any use of overlaid content will give problems
for some browsers, but putting links in a layer below images is asking
for trouble.  It shouldn't be necessary, even if the image is a ragged
mask, as, unless the image is intended to mask out part of the link text,
the links could always be overlaid on the image.

Note that there is an outstanding bug in Mozilla that has not had a release
for fixing assigned, which causes images *below* links to mask them, 
and links below images to be active!

> http://www.peepo.com/crap/lbv/ (ie5 only) is an example.

I would point out that this URL is completely blank except for a title
which is pretending to be user instructions, but is too long to display.

Also, BGSOUND is proprietory and colours, in HTML, require a #.

I suggest you wait for SVG to become standard before trying this sort
of thing, although even then it will be difficult to make it accessible
to people unable to easily use current graphical browsers.

You really need to find a way of doing your things that doesn't require
full programming languages - Javascript is a security risk.
Received on Saturday, 30 June 2001 15:37:00 UTC

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