Re: Comments on Draft 5 (was Re: STYLE attributes)

> You raise an important point. We could extend the generality by
> improving addressing while simplifying properties. E.g., if we can
> address characters and lines on the left side, we could drop the
> alternate set of properties:
>
>   P:char[1] { text-effect: drop-cap }
>
>   P:line[1:2] { font-size: 120% }  -- the first and second line --

I believe this is the wrong way to go about doing this and that this
method would produce considerable difficulty for implementors (myself
being one).

At the Paris workshop, I suggested an alternative way to address this
which I'm afraid I haven't had time to elaborate for this forum.
The basic idea is to employ a structured specification for property names
rather than the flat namespace used now.

For example, in our style manager, we employ a destructured style property
namespace which employs the notion of a styled part.  A styled part consists
of a key and a value.  The key consists of the following components:

  part
  part-subset
  subpart
  subpart-subset
  property

Both part and subpart components may be wildcards or a token that specifies
a specific part or subpart of a part.  In the case that more than one part
or subpart of the same kind exists, then the part-subset and subpart-subset
permit more specificity.

Parts and subparts denote layout objects rather than flow objects; that
is, they denote areas or subareas produced by the proceess of formatting
a flow object.  For a paragraph flow object, one can identify a variety
of parts and subparts; e.g.,

  background
  margins
  borders
  lines
  sub-lines
  glyphs

So, given the following notation:

part '.' part-subset '.' subpart '.' subpart-subset '.' property

we can specify:

(1) fancy dropped cap

 glyph.1...drop             : 3          -- drop 3 lines --
 glyph.1.pad.right          : 8pts       -- add space to right --
 glyph.1.pad.bottom         : 8pts       -- add space below --
 glyph.1.body..color        : red        -- stroke glyph body red
 glyph.1.outline..color     : green      -- stroke glyph outline green
 glyph.1.background.color   : gray       -- paint background gray

Here I use 'glyph' as a part.  The part-subset specifies the 1st glyph
produced when formatting the current element.

(2) swash starts and ends of odd lines

 line.odd.glyph.^.subst    : swash      -- enable 'swash' substitutions -
 line.odd.glyph.$.subst    : swash      -- enable 'swash' substitutions --

Here I use line as a part, with the part-subset expressing a built-in set of
(odd) indices.  I use glyph as a sub-part, with the subpart-subset taking the
form of standard regexp syntax to express first and last glyphs (on the line).

(3) small caps on first line except for first glyph (which is presumably
    using a drop cap style like (1) above)

 line.1.glyph.[^1].subst   : small-cap  -- enable 'small-cap' substitutions --

Here the subpart-subset specifies all glyphs but the first glyph.

---------------

Many of the current CSS style properties could be expressed more clearly
by using expressions which distinguish between the various layout areas
or graphical objects which result from formatting and the basic properties
which apply to those areas/objects.  For example, the margins, paddings,
and borders associated with the areas (boxes) used to format an element
are all essentially distinct graphical objects each having its own set
of intrinsic properties (size, color, etc.)   The set of all such intrinsic
properties is actually quite small and can be considerably reduced by
extracting the layout part/subpart to which the property applies from
the property name as is currently used in CSS.

Regards
Glenn Adams

Received on Wednesday, 29 November 1995 23:22:59 UTC