Hi,

I have made an attempt at implementing scaled drawing of wave style
underlines for hidpi displays, X only for now.
This is my first contribution to emacs so any feedback would be great!
I've followed the commit and patch style from CONTRIBUTE as closely as
I could but let me know if there's any issue.

It works by determining a scale factor from x_display_info's resx and
resy members then setting the wave_height and wave_length values
accordingly. Thickness was added using XSetLineAttributes and scaled
as well. Tested on displays with various scales from 1 to 3.


Cheers,
Steve Pegoraro