I'm trying to make a task list popup with transparency, but I ran into a problem with the borders. Can't find a way to remove the black bars around the popup.
I tried border_width = 0 and theme.border_width = 0 but it just doesn't work.
Thanks to @Uli I managed to remove the borders (shadows) of the popup.
The problem was that the picom compositor was creating shadows around the popup.
Making the widget type = "desktop" makes picom ignore it.
github.com/yshui/picom/blob/...
Enabled client-side shadows on windows. Note desktop windows (windows with '_NET_WM_WINDOW_TYPE_DESKTOP') never get shadow, unless explicitly requested using the wintypes option.