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Re: [css3-background] background-clip-009.html has 1 issue

From: Gérard Talbot <css21testsuite@gtalbot.org>
Date: Mon, 13 May 2013 23:24:01 -0400
Message-ID: <bb17e2a202bf5a1a2e0b80852f59cdd3.squirrel@ed-sh-cp3.entirelydigital.com>
To: "Alan Gresley" <alan@css-class.com>
Cc: "Julien Chaffraix" <jchaffraix@webkit.org>, "Public CSS test suite mailing list" <public-css-testsuite@w3.org>

Le Lun 13 mai 2013 22:45, Alan Gresley a écrit :
> On 14/05/2013 8:56 AM, "Gérard Talbot" wrote:
>>
>> Le Dim 5 mai 2013 21:18, Julien Chaffraix a écrit :
>>> Hi Gérard,
>>>
>>>> http://test.csswg.org/source/contributors/google/submitted/background-clip-009.html
>>>>
>>>> There is still an issue with that test.
>>>>
>>>> You added a margin-bottom and wrote
>>>> "
>>>> Added a margin-bottom to this test as it doesn't change the output
>>>> but
>>>> make it fail if the browser clips at the margin box.
>>>> "
>>>> http://lists.w3.org/Archives/Public/public-css-testsuite/2013Feb/0011.html
>>>>
>>>> but the thing is the background (background-color and/or
>>>> background-image) of an element never paints its own margin area
>>>> (with
>>>> only the root element as the sole exception to this). Your comment
>>>> suggests that the margin area would be painted with black color (the
>>>> background-color of the element) if the clipping would not be
>>>> executed
>>>> or would be wrongly executed. But the margin area should not be
>>>> painted
>>>> by the background-color to begin with.
>>>
>>> That wasn't the intent of my reply actually. I expect the browser to
>>> clip at the border box. The extra margin was designed to catch the
>>> case where the browser actually paints the margin box with the
>>> background color.
>>
>> What if it would have painted the margin box and then clip at the
>> border
>> box? Then we would not know that the background painting
>> implementation
>> is wrong.
>>
>> We have at least one test checking, verifying that background-color
>> does
>> not (never!) paint the margin area of an element:
>>
>> [RC6]
>> http://test.csswg.org/suites/css2.1/20110323/html4/margin-backgrounds-001.htm
>>
>> [nightly-build]
>> http://test.csswg.org/suites/css2.1/nightly-unstable/html4/margin-backgrounds-001.htm
>>
>> ... albeit the text assert of those tests seems awkward and
>> perfectible
>> to me...
>
> At least one test is required to make sure that backgrounds do not paint
> in the margin box.
>
>
>>> In retrospect it's probably not that much of an
>>> issue but I thought it was nice to have.
>>>
>>>> So, I believe we should remove
>>>>
>>>> line 23:     margin-bottom: 50px;
>>>>      /*
>>>>      Added a margin-bottom to this test as it doesn't change
>>>>      the output but make it fail if the browser clips at the
>>>>      margin box. Julien
>>>> line 27: */
>>>
>>> I removed these lines as they seem to have confused you
>>
>> They have confused me. In my mind, in CSS 2.1, background painting is
>> one distinct, separate thing and then there is background clipping
>> (cisaillement, rogner, découper) which is another distinct, separate
>> thing. CSS3 seems to be merging both things together under one single
>> property: background-clip.
>>
>> Maybe (really not sure of this as it would decisively affect all of
>> margin collapsing spec) CSS3 background-clip should have been split
>> into
>> 2 other properties: background-painting and background-clip ..
>
> Gérard, please see the 'background-origin' property [1]? Note the part
> about 'background painting area'.

I have read it; there is no mention of 'background painting area' in
'background-origin' property [1].

>
> Also read up on the 'background painting area' that is reference in
> 'background-clip' [2],

I have read it. It clearly is about the painting area. "3.7. Painting
Area: the ‘background-clip’ property".

> 'backgrounds of special elements' [3] and also in
> 3.4., 3.9., 3.6. and 7.1.

Well, I have read it all. And I have not changed my mind.

Background-color is not painted, is never painted in the margin area of
an element (except the root one, eg body in HTML4, html), regardless of
the background-clip property value.

I am working on submitting another test:
margin-backgrounds-003

Gérard

>
> 1. http://dev.w3.org/csswg/css-backgrounds/#the-background-origin
> 2. http://dev.w3.org/csswg/css-backgrounds/#the-background-clip
> 3. http://dev.w3.org/csswg/css-backgrounds/#background-painting-area
>
>
> Alan
>
>
> --
> Alan Gresley
> http://css-3d.org/
> http://css-class.com/
>


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Received on Tuesday, 14 May 2013 03:24:31 UTC

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