OMTK_KEY_*

#define OMTK_KEY_CTRL
#define OMTK_KEY_ALT
#define OMTK_KEY_SHIFT

#define OMTK_KEY_A
/* ... */
#define OMTK_KEY_Z

#define OMTK_KEY_0
/* ... */
#define OMTK_KEY_9

OMTK_KEY_CTRL, OMTK_KEY_ALT and OMTK_KEY_SHIFT are modifier keys. Note that OMTK_KEY_CTRL is the apple key on Mac OS X.