On Wed, Jan 25, 2012 at 10:26 AM, Stephen J. Turnbull
<stephen@xemacs.org> wrote:
> In XEmacs you can specify a color or a pixmap as background (bitmaps
> are promoted to pixmaps, but with -- until about a week ago -- less
> than satisfactory results).  So you could specify a background pixmap
> (eg, as an XPM) as
> [...]
> and it will be tiled appropriately over the extent of the face, and
> the text will be printed over that in the foreground color.  Sort of
> like poor man's image layers.

I think it would be simpler to do directly in C. I'm new to this but
it should be simple to add a new field "underwave_p" in struct face (
with underline_p, overline_p) in dispextern.h:1590 and handle it (for
X11) near xterm.c:2756.

See POC program attached for drawing underwaved text in X11.