While ExtGraph's GrayClipDrawLine_R is faster than calling PedroM's DrawClipLine twice, PedroM's DrawClipLine is faster than ExtGraph's ClipDrawLine_R...
NOTE: you could make the ClipLine macro of src/c/clipline.c several bytes smaller (and several clocks faster), by using inline assembly for the "swap" macro:
#define ASM_EXCHANGE(val1,val2) asm volatile ("exg %0,%1" : "=da" (val1),"=da" (val2) : "0" (val1),"1" (val2) : "cc")
In the src folder, `make CAS=1` works, but `make` doesn't, due to an undefined reference on the following line:
xdef Zs_function_call
Moving this line down by one line, under the
ifd USE_MAIN_PROGRAM
conditional section, should fix the problem.