Clipping code - history?

[Ethan A M. <merritt@u.washington.edu>]

In gadgets.c we have the very nice clipping routines:
 clip_line() draw_clip_line()

In graphics.c we have a separate collection of very specialized
but also rather complicated routines:
  edge_intersect() two_edge_intersect()
  edge_intersect_steps() edge_intersect_fsteps()
  two_edge_intersect_steps() two_edge_intersect_fsteps() 

Is this a code duplication due to historical artifact?

At first glance all of the 100-200 line *_edge_intersect_* routines
appear to do essentially the same thing as a simple series of calls
to clip_line(). Am I missing a more sophisticated function or
extra benefit of the longer routines?

Many code sections in graphics.c and graph3d.c test and sort line
segments by the inrange/outrange property of their endpoints,
and then call these single-purpose *_edge_intersect_* routines to
perform clipping. I am wondering if these sections can be simplified
dramatically by instead drawing all of the individual segments via
draw_clip_line().

-- 
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle 98195-7742