Issue is not in unico, neither Gtk+, but in the themes.
With updated Gtk+ 3.x, widgets must specify or inherit background colors, otherwise theming engines (unico or gtk default theming engine) won't render the background (cause the default background color is NULL, indeed).
All themes, like lubuntu or light-themes, must add a line like:
background-color: @bg_color;
...n the widgets which are affected by this black background, because this black background means background-color is currently unset.
Set it to a color and unico or gtk+ will render with the background-color, black gone.
Issue is not in unico, neither Gtk+, but in the themes.
With updated Gtk+ 3.x, widgets must specify or inherit background colors, otherwise theming engines (unico or gtk default theming engine) won't render the background (cause the default background color is NULL, indeed).
All themes, like lubuntu or light-themes, must add a line like:
background- color: @bg_color;
...n the widgets which are affected by this black background, because this black background means background-color is currently unset.
Set it to a color and unico or gtk+ will render with the background-color, black gone.
Cheers