xosd-xft (on screen display for X11, with Xft/TTF font support)

xosd-xft is inspired by xosd, but adds modern features such as Xft/TTF
font support (including antialiasing), XrandR and Xinerama (multihead)
support, alpha blending (transparency), and "Nerd Glyphs" (embedded
icons, basically).

Example Nerd Glyph command to try:

  osd-echo -d 5000 :linux-slackware:

Notes:

This doesn't conflict with xosd, but be aware that xosd has an osd_cat
command, whereas xosd-xft has osd-cat. This won't confuse Slackware,
but it might confuse the user.

For transparency to work, you'll have to have an X compositing manager
running. For KDE and XFCE, this should already be the case. For simple
window managers, try adding "xcompmgr -n" to your ~/.xinitrc, or have
a look at desktop/picom.