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Re: [css21] line-height, problem?

From: Andrew Fedoniouk <news@terrainformatica.com>
Date: Mon, 26 Nov 2012 10:51:43 -0800
Message-ID: <CALRQH7_9rnwi5+62fEsw3ec2hhsaHrOjEGtQRNVMCHisPifrqA@mail.gmail.com>
To: "L. David Baron" <dbaron@dbaron.org>
Cc: www-style@w3.org
On Mon, Nov 26, 2012 at 12:14 AM, L. David Baron <dbaron@dbaron.org> wrote:
> On Sunday 2012-11-25 23:21 -0800, Andrew Fedoniouk wrote:
>> This sample:
>>
>> https://dl.dropbox.com/u/14981836/line-height-test.htm
>>
>> contains two identical paragraphs, the only difference is that
>> first one has line-height:normal and second one - line-height:1em;
>>
>> According to the spec [1]:
>>    'line-height' specifies the *minimal* height of line boxes within
>> the element.
>>
...
>>
>> I suspect that I miss something between lines of the spec.
>> My understanding of the spec wording is this:
>>
>> used-line-height = max( {normal-line-height}, {defined-line-height} );
>>
>
> (1) when you're testing line-height, you should really test
> standards mode rather than quirks mode; quirks mode behavior is
> substantially different (and not fully explained by the first two
> items in http://quirks.spec.whatwg.org/#css ).
>
> (2) 'normal' and '1em' are *very* different in terms of how they
> inherit when the font size changes (since '1em' inherits as the
> computed value, which is no longer relative to the changed
> descendent font size).  'normal' and '1' are much more similar.
>
> -David
>

Thanks, David. I've updated the sample with HTML5 doctype.
That actually makes no difference (only IE started to match
all other UAs here).

In fact I've missed that part in the spec:
"On a non-replaced inline element, 'line-height' specifies the height
that is used in the calculation of the line box height."

So for such elements (like <big> in my sample) line-height defines
not "min-line-height" but just 'line-height' allowing to reduce it.
Together with the fact that line-height is an inheritable property
that creates such strange effect.

Actually it is a bug in spec design: if property is inheritable then
it shall not change meaning on child (min-line-height to line-height
transformation).

-- 
Andrew Fedoniouk.

http://terrainformatica.com
Received on Monday, 26 November 2012 18:52:11 GMT

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