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Re: opacity, animate and mask

From: ~:'' ありがとうございました。 <j.chetwynd@btinternet.com>
Date: Sun, 5 Aug 2007 08:02:33 +0100
Message-Id: <7BE1C101-AE1D-4447-9C88-EBD6A5E766CE@btinternet.com>
Cc: SVG List <www-svg@w3.org>
To: Doug Schepers <schepers@w3.org>


Thank you once again for your reply, your example as many others I  
can imagine is simply resolved by providing a shield with  
opacity="0.00001" rather than 0 or none.

regarding "The SVG WG has discussed this very issue at length..." who  
on the working group has a learning disability or represents the  
needs and abilities of people other than expert authors?


Jonathan Chetwynd

On 4 Aug 2007, at 21:21, Doug Schepers wrote:

Hi, Jonathan-

~:'' ありがとうございました。 wrote (on 8/4/2007 7:26 AM):
> please could you provide an example to substantiate your assertion  
> that:
> "there would be no way to achieve certain effects"

I don't understand your confusion.  Jeff already elaborated on this  
with a pragmatic example, I was merely reiterating the point in  
simpler terms.

Nevertheless, here's a very commonly used real-world example.   
Because text is selectable, there's no way in SVG 1.1 to make it  
clickable without having it selectable (that is, the cursor will  
change to a caret, and the user may inadvertently select text on what  
is supposed to be a part of the interface, not some prose.  If you  
set the text to have pointer-events='none', you would solve this  
problem of selection, but then the user couldn't grab, click, or  
otherwise interact with this text.  So the solution is to make a  
rectangle that covers the text and set it to opacity='0'.  Though it  
is now invisible, it is not intangible, so it blocks all text  
selection events while still allowing the user to seemingly interact  
with the text.

Further, use cases aside, we now have a very consistent model for  
opacity/transparency that is intuitive for authoring and can be  
implemented interoperably so that authors can expect to author once  
and not worry about difference on platforms.  There are no tricks or  
special cases to it that would prove to be stumbling blocks.

> Established authors should be expected to be more able than naive  
> users, without such evidence it seems unlikely that:
> "authors would be more limited in what they can achieve."

The use case solution I showed is very simple, and I've seen it  
reinvented on the svg-dev list by many authors, so I think that it  
adequately addresses your skepticism.

I don't think you've seriously taken the time to consider my last  
suggestion, that of finding another solution to your problem.  If you  
do try, and find that you can't figure out a solution, please write  
to svg-dev, where there is a large community of helpful people who  
will almost certainly come up with a way to make it work.

The SVG WG has discussed this very issue at length only a short while  
ago, as per the errata Cameron showed you, and we covered the same  
considerations that you have brought up.  We did not come to the  
table with the same opinions (in fact, I argued briefly for the very  
feature that you've requested, where opacity on masks might be  
intangible), but after considering all the arguments, we unanimously  
agreed that the behavior as we have specified it is the only logical  
and consistent choice.  For this reason, we will have to decline your  
request unless we are presented with substantive new evidence, and  
will consider this matter closed.  It's not that your idea was bad,  
just that it doesn't work as well as the currently specified behavior.

-Doug Schepers
W3C Staff Contact, SVG, CDF, and WebAPI
Received on Sunday, 5 August 2007 07:02:48 UTC

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