Re: Question about display engine

[martin rudalics <rudalics@gmx.at>]

 > And, of course, this leaves the more general problem I described in my
 > message: what is the right behavior for extending the face that
 > crosses a newline.  (Note that the display engine in general doesn't
 > know whether a face that doesn't end before a newline will or won't
 > continue on the next screen line.)

Recalling your proposal

(defcustom face-extend-to-window-edge t
    "Non-nil means extend face of last character on line to window edge.

Certain face attributes, if present in the face of the last character
of a line and different from those of the default face, cause the
empty space following the end of text on the line to be drawn with
those attributes, to give the empty space appearance similar to that
of the preceding text.  These attributes are those which affect the
background of a face: `:background', `:stipple', `:box', `:underline',
`:overline', and `:strike-through'.  By default, if the face of a
line's last character has any of these attributes, and the value is
different from that of the default face, the empty space following the
line's text will be drawn in the face of the last character.

This variable allows fine-tuning which attributes trigger the face
extension.  The default value of t means any of the mentioned
attributes will cause face extension.  The value of nil means face
extension is turned off.  A value that is a list of attributes will
extend the face only if any of the attributes from the list are
present in the last character's face.  Note that only attributes from
the above list are meaningful in list values of this variable.")

in the discussion of Bug#23574.

martin