I extracted the EMX calls for 32bit to 16bit thunking so I could make a stand alone program to erase the text buffer, leaning heavily on the Q59837 sample from Microsoft.
This only works in full screen and assumes a VGA card!
You need a GA or release os2386.lib, as the ability to thunk is not in the Pre-Release 2 SDK
thunk0.obj(thunk0.asm) : error L2029: 'DosSelToFlat' : unresolved external
thunk0.obj(thunk0.asm) : error L2029: 'DosFlatToSel' : unresolved external