A subset of possible encodings are presented in the Encoding submenu. This is a list of encodings to appear there. The special encoding name "current" means to display the encoding of the current locale.
A value between 0.0 and 1.0 indicating how much to darken the background image. 0.0 means no darkness, 1.0 means fully dark. In the current implementation, there are only two levels of darkness possible, so the setting behaves as a boolean, where 0.0 disables the darkening effect.
