RE: [Feature request] face property `raise'

["Wedler, Christoph" <christoph.wedler@sap.com>]

 >     I would like to see a face property `raise' with the same semantics as
 >     the display property `raise'.

 > I don't think so.  Raising is not a matter of how something is
 > displayed, but where it is displayed.

Where something is displayed (at least relatively, and that's what
`raise' is about) is a special case of how something is displayed.

The question of face (style-class like in HTML/CSS would be a better
name) vs display property is determined by the following:

  * display property: determines the display style of ONE SPECIFIC
    buffer part,

  * face property: assigns a style class to a buffer part.  By
    customizing the face, you determine the display style of all buffer
    parts having this style class.

In my previous mail, I've given you an example where face properties are
much better (super-/subscripts: after all, you want to raise subscripts
consistently by e.g. 5 pixels), a face for footnote numberings would be
another example.  (I also gave 5 general reasons.)

I've yet to see an example where display properties are useful for
`raise', except for some Emacs painting package.  (But even that example
would not invalidate my examples, i.e., a face property `raise' would
still be useful.)

Looking how things are done outside the Emacs world would also be
useful: let's assume HTML wouldn't have a SUP element.  Then everyone
would advice you to use

    <SPAN class="SUP">superscript</SPAN>

and define

    SPAN.SUP { vertical-align: super; font-size: smaller; }

instead using

    <SPAN style="vertical-align: super; font-size: smaller;">
       superscript
    </SPAN>

for every superscript.  In Emacs, the recommendation (using the class
attribute) corresponds to setting a face, the non-recommendation (using
the style attribute) corresponds to setting display properties.

 > Some unsophisticated text formatters treated superscript as if it
 > were a font, but more sophisticated ones don't.

I don't know where this is related to the question whether a face
property `raise' would be useful.

- Christoph