ColinDuquesnoy/QDarkStyleSheet — pull request #16 by MHendricks (2014-12-19 02:44:06+00:00)
Title: Adding various checkable options

Added support for Tri-State QCheckBox, Checkable QGroupBox, Checkable
QMenu indicators.

checkbox_indeterminate.png is something I did quickly to make sure it worked, feel free to make your own image, I just mirrored how Qt handles the Qt.PartiallyChecked state.