<geekosaur (@geekosaur:matrix.org)> shadow-exclude = [
  "_NET_WM_STATE@:a *= '_NET_WM_STATE_FULLSCREEN'"
 ,"class_g = 'Mate-notification-daemon'"
];
fade-exclude = [
  "_NET_WM_STATE@:a *= '_NET_WM_STATE_FULLSCREEN'"
 ,"class_g = 'Mate-notification-daemon'"
 ,"class_g = 'Sxiv'"
];
focus-exclude = [
  "_NET_WM_STATE@:a *= '_NET_WM_STATE_FULLSCREEN'"
 ,"class_g = 'Mate-notification-daemon'"
 ,"class_g = 'Sxiv'"
];
wintypes:
{
  tooltip = {fade = false; shadow = true; opacity = 1; focus = true; };
  splash = {fade = false; shadow = true; opacity = 1; focus = true; };
  menu = {fade = false; shadow = true; opacity = 1; focus = true; };
  notify = {fade = false; shadow = false; opacity = 1; focus = true; };
};
from my "picom.conf"