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Re: opacity, animate and mask

From: Doug Schepers <schepers@w3.org>
Date: Sat, 04 Aug 2007 16:21:55 -0400
Message-ID: <46B4DFE3.3000105@w3.org>
To: ~:'' ありがとうございました。 <j.chetwynd@btinternet.com>
Cc: SVG List <www-svg@w3.org>

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.

Regards-
-Doug Schepers
W3C Staff Contact, SVG, CDF, and WebAPI
Received on Saturday, 4 August 2007 20:22:11 GMT

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