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cannot set face attributes to symbols from X resources


From: Vivek Dasmohapatra
Subject: cannot set face attributes to symbols from X resources
Date: Wed, 16 Jun 2004 13:05:31 +0100

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In GNU Emacs 21.2.1 (i386-debian-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2003-12-03 on salmon, modified by Debian
configured using `configure  i386-debian-linux-gnu --prefix=/usr 
--sharedstatedir=/var/lib --libexecdir=/usr/lib --localstatedir=/var/lib 
--infodir=/usr/share/info --mandir=/usr/share/man --with-pop=yes --with-x=yes 
--with-x-toolkit=athena --without-gif'
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: nil
  locale-coding-system: nil
  default-enable-multibyte-characters: t

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

The :inherit, :overline, :underline and :strike-through attributes 
can be set to symbols - in :inherit's case, it must be set to a symbol
or a list of symbols (which happen to be faces themselves).

`set-face-attributes-from-resources' achieves this by calling 
`internal-set-lisp-face-attribute-from-resource' with a symbol,
attribute, value and possibly a frame. The value is passed as a 
string, which for most attributes is fine.

`internal-set-lisp-face-attribute-from-resource' then does some 
sanity checking on the value, based on the value of attribute, 
and calls `internal-set-lisp-face-attribute' with the same arguments
it was called with. However, if the attribute in question needs a 
symbol (eg setting :inherit to 'italic) then this breaks, as neither
function calls intern to coerce the value to the correct type.

For example: 

echo "Emacs.fringe.attributeInherit: highlight" | xrdb -merge
emacs -q --no-site-file

results in the following messages:
############################################################################
(emacs -q --no-site-file)
Loading disp-table...done
Face fringe, frame #<frame address@hidden 0x84adaa0\ >: invalid attribute 
:inherit highlight from X resource [2 times]
############################################################################

I suspect the correct solution is for one or both of the internal-set-*
functions to intern the string and fetch a symbol, however for the time 
being I am using this quick hack in my .emacs (or rather the user who
reported the bug is, it's not actually an issue for me):

############################################################################
(defun set-face-attribute-from-resource (face attribute resource class frame)
  "Set FACE's ATTRIBUTE from X resource RESOURCE, class CLASS on FRAME.
Value is the attribute value specified by the resource, or nil
if not present.  This function displays a message if the resource
specifies an invalid attribute."
  (let* ((face-name (face-name face))
   (value (internal-face-x-get-resource (concat face-name resource)
                                        class frame)))
    (when value
      (if (and (string-match "^'" value)
               (or (eq attribute :inherit       ) 
                   (eq attribute :underline     ) 
                   (eq attribute :overline      ) 
                   (eq attribute :strike-through)))
          (progn
            (setq value (intern (substring value 1)))
            (condition-case ()
                (internal-set-lisp-face-attribute
                 face attribute value frame)
              (error
               (message "Face %s, frame %s: attribute %s %S from XRDB"
                        face-name frame attribute value))))
        (setq value (downcase value))
        (condition-case ()
            (internal-set-lisp-face-attribute-from-resource
             face attribute value frame)
          (error
           (message "Face %s, frame %s: bad attribute %s %s from X resource"
                    face-name frame attribute value)))))
    value))

############################################################################

This allows the following syntax to work:

echo "Emacs.fringe.attributeInherit: 'highlight" | xrdb -merge

It should be noted that this does not provide a mechanism for the user 
to set :inherit to a list of faces, but :underline et al can be set to 
t or nil and :inherit can be set to a single face.

This bug may have been fixed in cvs, I haven't checked there.




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