This may cause tall objects be printed before short ones. There are two
possible solutions:
1. do strict ordering only when y-overlap is large enough (the one
chosen in this commit)
2. when considering vertical collision with rod, the actual expansion
can be much smaller (because the rod is only slightly off extruder).
But this solution requires an extra parameter. Let's hold it for a
while.
Change-Id: Icc9a4796d49dad93cbcc20d4103e641a48886e5e
(cherry picked from commit 6a958b1fa9e58e4ca3be63b4918da77bcdc53314)
(cherry picked from commit ceff67789c27ea576afd663a2e5bae9a10241728)
Arthur
c8c073a199