W3C home > Mailing lists > Public > www-style@w3.org > April 2014

Re: [css-backgrounds] background-position-x/-y, logical positions, and initial value failure

From: Simon Sapin <simon.sapin@exyr.org>
Date: Wed, 23 Apr 2014 20:07:37 +0100
Message-ID: <53580F79.20702@exyr.org>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
CC: fantasai <fantasai.lists@inkedblade.net>, "www-style@w3.org" <www-style@w3.org>, MURAKAMI Shinyu <murakami@antenna.co.jp>
On 23/04/2014 17:08, Tab Atkins Jr. wrote:
> On Wed, Apr 23, 2014 at 8:01 AM, Simon Sapin <simon.sapin@exyr.org> wrote:
>> On 18/04/2014 01:50, fantasai wrote:
>>> Now, what's the initial value of these properties?
>>> With margin it's 0. No problem. Everybody is zero, we get
>>> zero margins. No conflicts.
>>>      margin-left: 0;
>>>      margin-right: 0;
>>>      margin-top: 0;
>>>      margin-bottom: 0;
>>> is exactly equivalent to
>>>      margin-inline-start: 0;
>>>      margin-inline-end: 0;
>>>      margin-block-start: 0;
>>>      margin-block-end: 0;
>>> no matter the writing mode. If you tweak any values, the
>>> cascade then says which wins.
>> Where is this defined? How does the cascade say which wins?
> In the normal way?

What is the normal way to pick between unrelated properties?

> Note the assumption that the physical and logical
> properties are aliases of each other, based on WM/direction.
> (Implicitly requiring separate cascade of WM/direction first.)

I’m asking precisely about that assumption and implication. Is there a 
spec for it? I don’t see anything relevant in css-cascade.

> Once you've figured out that, say, margin-left and margin-inline-start
> are aliasing each other, then the cascade works as normal.  The only
> issue of this thread was what fantasai brought up, about which wins
> when there are *no* declarations and the initial values differ between
> the two sets.

I’m not saying there is another issue here, just that the discussion 
(apparently) relies on assumptions of what some spec is gonna say in the 
future. I’d just like to know what the assumptions are so I (and other 
people) can follow the discussion :)

Simon Sapin
Received on Wednesday, 23 April 2014 19:08:03 UTC

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