Re: Summary line format and gnus-face-X

[Wolfgang Jenkner <wjenkner@inode.at>]

On Wed, Sep 05 2012, Lars Ingebrigtsen wrote:

> Tassilo Horn <tsdh@gnu.org> writes:
>
>> That's nice for (2), but bad for (1).  Now I can have
>> colorized/boldified subjects with proportional fonts, but my column
>> separators and stuff are also mangled which I don't want.
>
> The problem is really more practical than theoretical.  Emacs doesn't
> provide "combining" faces when using text properties.  You can put
> overlays over text (say, italic and then green), but you can't do that
> with text properties.  So Gnus has the option of either overwriting your
> carefully chosen faces, or not touching them, and there isn't much of a
> third choice.
>
> Until Emacs implements combining `face' text properties, which is
> something that I really really really want to have.  Overlays are yucky.

What's the difference to using list of faces as the `face' text
property, i.e., addressing something like Tassilo's use-case:

(defun gnus-combine-text-property (beg end prop val)
  "Combine PROP with text properties between BEG and END.
This combines attributes if PROP is `face' otherwise this is just
like `put-text-property', more or less.
Beware: Proof-of-concept."
  (let ((b beg))
    (while (< b end)
      (let ((oldval (get-text-property b prop)))
	(gnus-put-text-property
	 b (setq b (next-single-property-change b prop nil end))
	 prop (cond ((or (not (eq prop 'face))
			 (null oldval))
		     val)
		    ((and (consp oldval)
			  (not (keywordp (car oldval))))
		     (cons val oldval))
		    (t
		     (list val oldval))))))))
(fset 'gnus-put-text-property-excluding-characters-with-faces
      'gnus-combine-text-property)

;; So, in my case, the face text property in the subject of an unread
;; article is (gnus-summary-normal-unread variable-pitch) and when
;; selected it becomes (gnus-summary-normal-read gnus-summary-normal-unread variable-pitch).
;; For each attribute, the first non-`unspecified' value of a face in
;; the list wins.
(setq gnus-face-9 'variable-pitch)
(setq gnus-summary-line-format
      "%U%R%z%I%(%[%4L: %-23,23f%]%) %9{%s%}
")