`Sep` widget inconsistent rendering on `0.20` release

Description

The Sep widget fails to render correctly when used via an assigned variable. eg:

basic_sep = Sep(foreground="#1e222a", linewidth=4)
line_sep = Sep(foreground="#abb2bf", linewidth=1, padding=10)

I’ve been experiencing this since the 0.20 release, and rolling back to 0.19 resolves this issue.

Steps to reproduce

1. Be on 0.20 release of qtile
2. Use this as part of your Qtile config.py (replacing your widget_defaults and screens)
3. Restart Qtile

Expected Behavior

Click into and zoom in for better look. The Sep widget renders with the correct foreground, linewidth and padding.

Actual Behavior

Click into and zoom in for better look. Notice on the left hand side, the Sep widgets are rendering transparently. Moving to the right, they seem to fail to render at all, causing all sorts of clashing between the other widgets. The two Sep widgets (line_sep left of the Clock and basic_sep after the Systray) finally renders as indented.

Replacing each of the line_sep and basic_sep with Sep(foreground="#abb2bf", linewidth=1, padding=10) and Sep(foreground="#1e222a", linewidth=4) respectively resolves this issue. Try here.

Interestingly, I also tried both 0.19 and 0.20 with & without a second monitor and on my second monitor, the Sep widgets render correctly in all scenarios. I suspect this issue has something to do with the render orders.

System Info

System: Linux 5.16.3-arch1-1

@elParaguayo I noticed many of your PRs on the widgets where incorporated into the latest release, maybe you have an idea of what may be happening here?

[elParaguayo]

Cool. Thanks. Always nice to see my own name on the offending commit 😉

Let me look at fixing this.

[jamestrew]

#3278 resolves this issue 👍