From Gentoo Wiki
Blackbox is an open-source stacking window manager written in C++ and licensed under the MIT License.
USE flags for x11-wm/blackbox A small, fast, full-featured window manager for X
||Enable extra debug codepaths, like asserts and extra output. If you want to get meaningful backtraces see https://wiki.gentoo.org/wiki/Project:Quality_Assurance/Backtraces|
||Add Native Language Support (using gettext - GNU locale utilities)|
||Add support for FreeType and/or FreeType2 fonts|
emerge --ask x11-wm/blackbox