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Re: Comments on 'line-height'-related tests for Quirks Mode

From: Simon Pieters <simonp@opera.com>
Date: Fri, 23 Nov 2012 10:25:08 +0100
To: "Kang-Hao (Kenny) Lu" <kanghaol@oupeng.com>
Cc: "W3C CSS Test Suite" <public-css-testsuite@w3.org>
Message-ID: <op.wn7y36d8idj3kv@simon-pieterss-macbook.local>
On Fri, 23 Nov 2012 03:21:39 +0100, Kang-Hao (Kenny) Lu  
<kanghaol@oupeng.com> wrote:

> Hello Simon,
>
>
> While preparing a talk for advanced CSS topics, I have a chance to
> review some of the tests and here are my comments:
>
> == 3.1 The line height calculation quirk ==
>
>   # <div id=test><img src="{png}"> <img src="{png}"></div>
>   # <div id=ref>x</div><div id=s_ref>x</div>
>
> The 5th test duplicates the second, as the test itself already warns you
> at the beginning.

Removed.

>
>   # span { padding:1px 0 }
>   # <div id=test><span></span></div>
>   # <div id=ref></div><div id=s_ref></div>
>
> This is a bit puzzling, in particular about "<div id=s_ref></div>". I
> think what this test runs into is this part of CSS 2.1 9.4.2:
>
>   # Line boxes are created as needed to hold inline-level content
>   # within an inline formatting context. Line boxes that contain no
>   # text, no preserved white space, no inline elements with non-zero
>   # margins, padding, or borders, and no other in-flow content (such as
>   # images, inline blocks or inline tables), and do not end with a
>   # preserved newline must be treated as zero-height line boxes for the
>   # purposes of determining the positions of any elements inside of
>   # them, and must be treated as not existing for any other purpose.
>
> While the condition "no inline elements with non-zero margins, padding,
> or borders" probably has quirks-mode difference too (and should be
> specced), if you are testing the current prose to see if the above
> <span> contributes to line height, I'd suggest the test be written in
> this way:
>
>   | div { line-height: 0} span { padding:1px 0; line-height: normal }
>   | <div id=test>x<span></span></div><div id=ref>x</div>
>   | <div id=s_ref>x<span>x</span></div>
>
> The 'x' at the beginning ensures that the tests don't go into the
> "zero-height line boxes" situation.
>
> Ditto for all others.

I think this is intentional. We could add tests with "x" in as well,  
though, if that still makes the quirk kick in.

Do you have a test case demonstrating quirks-mode differences in "no  
inline elements with non-zero margins, padding, or borders"?

>
>   # span { display:inline-block; height:1px }
>   # <div id=test><i><span></span> </i></div>
>   # <span id=ref></span><div id=s_ref>x</div>
>
> Browsers behave differently for this sort of situation so I think there
> should be more tests like this. For example, we should write tests for
> when <span> is 'inline-table' 'inline-flex' or replaced elements.

Sure!

>
> If you agree with the above comments, I can send you a patch.

Thank you! If you like, you can push changes to the tests directly (ask  
Mike Smith if you don't have access). https://dvcs.w3.org/hg/quirks-mode/

>
> Some relevant comments for the spec:
>
>   # In quirks mode and almost standards mode, an inline box that
>   # matches the following conditions, must, for the purpose of line
>   # height calculation, act as if the box had a height of zero.
>
> I think you meant to say "the box had a 'line-height' of zero" instead,
> as the content height of an inline box never affects the line height,
> the "line-height box" does. This is what CSS 2.1 10.8 says
>
>   # The height of each inline-level box in the line box is calculated.
>   # For replaced elements, inline-block elements, and inline-table
>   # elements, this is the height of their margin box; for inline boxes,
>   # this is their 'line-height'. (See "Calculating heights and margins"
>   # and the height of inline boxes in "Leading and half-leading".)
>
> (What 'window.getComputedStyle' would return for 'height' is sort of a
> parallel, although also interesting, question.)

Filed https://www.w3.org/Bugs/Public/show_bug.cgi?id=20053

>
>   # <div id=test><img src="{png}" border=1></div>
>   # <img id=ref src="{png}" height=3><div id=s_ref>x</div>
>
> This (and the following three), as well as the starting 6 tests seem to
> belong to "3.2 The blocks ignore line-height quirk" instead of this set,
> but you should just consider combining these two, I guess.

I'm not sure I follow why, but I don't mind combining them since they're  
closely related, and a test intending to test one of them probably  
inevitably also tests the other.

>
> == 3.2 The blocks ignore line-height quirk ==
>
> The test seems fine, but for the spec prose,
>
>   # In quirks mode and almost standards mode, a block container element
>   # whose content is composed of inline-level elements, the element's
>   # 'line-height' must be ignored for the purpose of calculating the
>   # minimal height of line boxes within the element.
>
> s/a block/for a block/ ?
>
> , I am wondering if it's easier to understand if the spec just sas the
> "struts"[1] don't exist. But I am not an expert in inline formatting...
> Also, you might consider "a block container element establishing inline
> formatting context" in place of the current wording.
>
> [1] http://www.w3.org/TR/CSS21/visudet.html#strut

Filed https://www.w3.org/Bugs/Public/show_bug.cgi?id=20054

>
>
> Cheers,
> Kenny

Thank you for the review! I look forward to your contribution to the  
tests. :-)

-- 
Simon Pieters
Opera Software
Received on Friday, 23 November 2012 09:26:02 GMT

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