Doc fixes related to face heights. (Bug#2659)

* lisp/faces.el (set-face-attribute): Doc fix.

* src/xfaces.c (Finternal_set_lisp_face_attribute):
Try to clarify some error messages.

2 files changed, 12 insertions, 4 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 3b8da6fa373..6d0a352ca3c 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,7 @@
+2011-02-03  Glenn Morris  <rgm@gnu.org>
+
+	* faces.el (set-face-attribute): Doc fix.  (Bug#2659)
+
 2011-02-02  Stefan Monnier  <monnier@iro.umontreal.ca>
 
 	* pcomplete.el (pcomplete-here*): Backport fix for mistaken change
diff --git a/lisp/faces.el b/lisp/faces.el
index a3831084ad8..4a4acefa04c 100644
--- a/lisp/faces.el
+++ b/lisp/faces.el
@@ -616,10 +616,14 @@ It must be one of the symbols `ultra-condensed', `extra-condensed',
 
 `:height'
 
-VALUE must be either an integer specifying the height of the font to use
-in 1/10 pt, a floating point number specifying the amount by which to
-scale any underlying face, or a function, which is called with the old
-height (from the underlying face), and should return the new height.
+VALUE specifies the height of the font, in either absolute or relative
+terms.  An absolute height is an integer, and specifies font height in
+units of 1/10 pt.  A relative height is either a floating point number,
+which specifies a scaling factor for the underlying face height;
+or a function that takes a single argument (the underlying face height)
+and returns the new height.  Note that for the `default' face,
+you can only specify an absolute height (since there is nothing
+for it to be relative to).
 
 `:weight'