One of my modes uses the header line to display a progress bar/document summary, concatenating spaces with varying background colors and widths (using the
display attribute). To clarify the distinction between the header line and the document, I'd like to separate them with a solid line.
How can I draw a thin solid line under the header line?
Things I tried without success:
'face (:box (:line-width -1 :color "grey")): Shows a line all around the mode line, not just under it
'face (:underline (:color "grey")): background color of header line shows below underline