Dear Maintainer,

When changing the theme to Adwaita (or High Contrast) in mate-appearance-
properties, it says:

    This theme will not look as intended because the required window manager
theme 'Adwaita' is not installed.

And indeed, the window borders do not change theme when switching to Adwaita.

Maybe some other package needs to be installed, but I don't know which. And I
would expect that package to be a Depends or a Recommends of gnome-themes-
standard[-data].

This bug was reported before as #632181 but was closed as gnome-appearance-
properties was removed. I believe this bug is independent of gnome-appearances-
properties.