For what it's worth, X11 no longer sets a default background so things just linger on screen. There's an extension to set a black background.

On Sat, May 9, 2020, 03:04 Alain Bertrand <alainbe@free.fr> wrote:
Le 08/05/2020 à 11:30, Sylvain Henry a écrit :
> Hi,
>
> Try to run: xsetroot -solid black

Hi,

Thanks. It works now.

Best regards,

A.B.

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