I found a pad-osd.css file in /usr/share/gnome-shell/gnome-shell-theme.gresource. May I know which GDM widget is it used to style? It's contents are shown below.
.Leader { stroke-width: .5 !important; stroke: #535353; fill: none !important; } .Button { stroke-width: .25; stroke: #ededed; fill: #ededed; } .Ring { stroke-width: .5 !important; stroke: #535353 !important; fill: none !important; } .Label { stroke: none !important; stroke-width: .1 !important; font-size: .1 !important; fill: transparent !important; } .TouchStrip, .TouchRing { stroke-width: .1 !important; stroke: #ededed !important; fill: #535353 !important; } 1 Answer
The OSD is usually stand for On Screen Display. There is a CSS property for it.
This CSS file is loaded by GNOME Shell to extend properties of DrawingArea - see search results in Debian's source code.
The DrawingArea widget is a blank window that gives you the freedom to create any graphic you desire.
[see GNOME Developer Manual for details]
