Fingering chart for bassoon

This is the lilypond source of a fingering chart I give to my students to make sure they use good fingerings. Due to lilypond's bassoon fingering chart wonkery, there is no nice way to specify a half hole for the first finger of the left hand. I chose grey to represent that. For the octave keys in the left hand, grey means "flick" or "hold" at the players discretion. For all other keys, grey means "ad libitum".