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39.12.6 Functions for Working with Faces

Here are additional functions for creating and working with faces.

— Function: face-list

This function returns a list of all defined face names.

— Function: face-id face

This function returns the face number of face face. This is a number that uniquely identifies a face at low levels within Emacs. It is seldom necessary to refer to a face by its face number. However, functions that manipulate glyphs, such as make-glyph-code and glyph-face (see Glyphs) access the face numbers internally. Note that the face number is stored as the value of the face property of the face symbol, so we recommend not to set that property of a face to any value of your own.

— Function: face-documentation face

This function returns the documentation string of face face, or nil if none was specified for it.

— Function: face-equal face1 face2 &optional frame

This returns t if the faces face1 and face2 have the same attributes for display.

— Function: face-differs-from-default-p face &optional frame

This returns non-nil if the face face displays differently from the default face.

A face alias provides an equivalent name for a face. You can define a face alias by giving the alias symbol the face-alias property, with a value of the target face name. The following example makes modeline an alias for the mode-line face. 

     (put 'modeline 'face-alias 'mode-line)
— Macro: define-obsolete-face-alias obsolete-face current-face when

This macro defines obsolete-face as an alias for current-face, and also marks it as obsolete, indicating that it may be removed in future. when should be a string indicating when obsolete-face was made obsolete (usually a version number string).