Specifically, in general antisymmetric case src[-1] (S0) should be
subtracted from from src[1] (S2), and not the opposite.

Signed-off-by: Yan Wang <yan.wang@linux.intel.com>

Signed-off-by: Yan Wang <yan.wang@linux.intel.com>

Removed a leading whitespace from a parenthetical comment and corrected the spelling of "maybe"

There is necessary to account also x-coordinate of the end of the edge when determining bounding box of the edge collection.