Subject: Re: 23.1; face doc unclear - no explanation of "underlying" face or attribute value

From: Chong Yidong <[email-masked]>
Date: Sat, 15 Aug 2009 19:00:10 -0400

"Drew Adams" <[email-masked]> writes:

> 1. "Underlying face" is defined as "a face that has a lower priority
> in the list...". That begs the question, "lower than what"?

Lower than the face to which this attribute applies.  That should be
obvious.

> 2. Related to #1. It's not clear to me whether there is only one
> underlying face for a given face/font/attribute-set (?). You say "a
> face", not "the face", so I guess there can be more than one that has
> a lower priority. But then you speak of "the underlying face".

There's no way to explain this concisely, I'm afraid.  The best thing do
is to read the Displaying Faces node closely (which is why an xref to
that node is probably the best we can do).  Basically, Emacs realizes a
face by the "stacking" procedure described in that node, searching
through the list of applicable faces for each attribute until it finds a
fully-specified value.  The "relative" values for the height are treated
specially.  Thus, in the context of that paragraph in the Face
Attributes node, the "underlying face" refers to that face, X levels
down in the priority list, for which Emacs has found a specified height.

> I see that you just now closed this bug. You close bugs too quickly. I
> don't know if now this reply will even get added to the bug thread,
> without my having to reopen the bug. IIRC, once a bug is closed, no
> further feedback is possible.

It's still possible, IIUC.