_f_l_a_g Specifies a pointer to an array that contains a single boolean
element, which replaces the current edge flag value.
DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
Each vertex of a polygon, separate triangle, or separate quadrilateral
specified between a ffffggggllllBBBBeeeeggggiiiinnnn/ffffggggllllEEEEnnnndddd pair is marked as the start of either
a boundary or nonboundary edge. If the current edge flag is true when
the vertex is specified, the vertex is marked as the start of a boundary
edge. Otherwise, the vertex is marked as the start of a nonboundary
edge. ffffggggllllEEEEddddggggeeeeFFFFllllaaaagggg sets the edge flag bit to GGGGLLLL____TTTTRRRRUUUUEEEE if _f_l_a_g is GGGGLLLL____TTTTRRRRUUUUEEEE,
and to GGGGLLLL____FFFFAAAALLLLSSSSEEEE otherwise.
The vertices of connected triangles and connected quadrilaterals are
always marked as boundary, regardless of the value of the edge flag.
Boundary and nonboundary edge flags on vertices are significant only if
GGGGLLLL____PPPPOOOOLLLLYYYYGGGGOOOONNNN____MMMMOOOODDDDEEEE is set to GGGGLLLL____PPPPOOOOIIIINNNNTTTT or GGGGLLLL____LLLLIIIINNNNEEEE. See ffffggggllllPPPPoooollllyyyyggggoooonnnnMMMMooooddddeeee.
NNNNOOOOTTTTEEEESSSS
The current edge flag can be updated at any time. In particular,
ffffggggllllEEEEddddggggeeeeFFFFllllaaaagggg can be called between a call to ffffggggllllBBBBeeeeggggiiiinnnn and the