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Issue 119 (was: [CSS21] Issues with inline formatting model (particularly 10.8))

From: Bert Bos <bert@w3.org>
Date: Wed, 26 May 2010 17:54:18 +0200
To: www-style@w3.org
Message-Id: <201005261754.18974.bert@w3.org>
Issue 119[1] needs a proposal. Here is one.

Context:

This refers to issue 8 in a message by Anton Prowse[2], about the 
undefined/confusing phrase "the block's baseline" in CSSĀ 2.1, section 
10.8.1. I already proposed a first text in answer[3] to that issue 
once. This is an improved version.

The current text:

    On a block-level, table-cell, table-caption or inline-block element
    whose content is composed of inline-level elements, 'line-height'
    specifies the minimal height of line boxes within the element. The
    minimum height consists of a minimum height above the block's
    baseline and a minimum depth below it, exactly as if each line box
    starts with a zero-width inline box with the block's font and line
    height properties (what TEX calls a "strut").

The issue is that "the block's baseline" isn't what it seems. It does 
*not* mean the baseline of the block, because blocks don't have a 
baseline. (Only table rows and inline elements, including inline-blocks 
and inline-tables, do) What it does mean is something like 
the "default" baseline for a line box, i.e., the baseline that all the 
block's line boxes have if we disregard any baseline shifts due to the 
block's child elements.

Here is a proposed replacement:

    On a block-level, table-cell, table-caption or inline-block element
    whose content is composed of inline-level elements, 'line-height'
    specifies the minimal height of line boxes within the element. The
    minimum height consists of a minimum height above the
    baseline and a minimum depth below it, exactly as if each line box
    starts with a zero-width inline box with the element's font and line
    height properties. We call that imaginary box a "strut." (The name
    is inspired by TeX.).

That is, replace "block's baseline" by just "baseline" and "block's 
font" by "element's font".

I also expanded the remark about the name "strut" into a proper 
definition, because that strut box is referred to again further down in 
the chapter.


[1] http://wiki.csswg.org/spec/css2.1#issue-119
[2] http://lists.w3.org/Archives/Public/www-style/2009Mar/0004.html
[3] http://lists.w3.org/Archives/Public/www-style/2009Aug/0650.html



Bert
-- 
  Bert Bos                                ( W 3 C ) http://www.w3.org/
  http://www.w3.org/people/bos                               W3C/ERCIM
  bert@w3.org                             2004 Rt des Lucioles / BP 93
  +33 (0)4 92 38 76 92            06902 Sophia Antipolis Cedex, France
Received on Wednesday, 26 May 2010 15:53:49 GMT

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