Re: face-remapping patch

[Stephen J. Turnbull]

David Kastrup writes:

 > However, I don't think the price for the generality of specifiers is
 > worth the complexity in the particular implementation and documentation
 > state of XEmacs.  I did not understand them after trying for a
 > considerable amount of time,

AFAIK David never did review the documentation after it was revised to
address his problem report.  Specifiers really are not that
complicated for most uses.

In practice, it turns out that 

    (specifier-instance SPECIFIER)

tells you what value is used at point in the selected window, and

    (specifier-instance SPECIFIER DOMAIN)

tells you would value would be used in DOMAIN, which may be a window,
frame, or device (terminal in Emacs lingo).  Note that because a
buffer may be visible in several places with different physical
characteristics that affect rendering (a feature that Emacs did not
support before multi-tty, AIUI), DOMAIN cannot be a buffer.

To set a specifier, use

    (set-specifier SPECIFIER VALUE LOCALE)

where LOCALE defaults to 'global, and may be a window, buffer, frame,
or device.  Typically `specifier-instance' does not return the same
VALUE that `set-specifier' sets, for example you can set the
background color of the default face to "gray80" in the current
buffer, but if you then check the value using `specifier-instance' it
will be "white".  Also `specifier-instance' returns face, font, and
glyph objects rather than their names IIRC.