03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsyncCopyright 1987, 1998 The Open Group
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03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsyncdocumentation.
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03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsyncin all copies or substantial portions of the Software.
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03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsyncfrom The Open Group.
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * Written by Brian Kelleher; Jan 1985
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * This file contains a few macros to help track
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * the edge of a filled object. The object is assumed
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * to be filled in scanline order, and thus the
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * algorithm used is an extension of Bresenham's line
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * drawing algorithm which assumes that y is always the
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * major axis.
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * Since these pieces of code are the same for any filled shape,
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * it is more convenient to gather the library in one
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * place, but since these pieces of code are also in
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * the inner loops of output primitives, procedure call
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * overhead is out of the question.
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * See the author for a derivation if needed.
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * In scan converting polygons, we want to choose those pixels
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * which are inside the polygon. Thus, we add .5 to the starting
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * x coordinate for both left and right edges. Now we choose the
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * first pixel which is inside the pgon for the left edge and the
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * first pixel which is outside the pgon for the right edge.
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * Draw the left pixel, but not the right.
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * How to add .5 to the starting x coordinate:
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * If the edge is moving to the right, then subtract dy from the
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * error term from the general form of the algorithm.
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * If the edge is moving to the left, then add dy to the error term.
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * The reason for the difference between edges moving to the left
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * and edges moving to the right is simple: If an edge is moving
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * to the right, then we want the algorithm to flip immediately.
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * If it is moving to the left, then we don't want it to flip until
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * we traverse an entire pixel.
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync#define BRESINITPGON(dy, x1, x2, xStart, d, m, m1, incr1, incr2) { \
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * if the edge is horizontal, then it is ignored \
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * and assumed not to be processed. Otherwise, do this stuff. \
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync if ((dy) != 0) { \
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync if (dx < 0) { \
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync#define BRESINCRPGON(d, minval, m, m1, incr1, incr2) { \
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync if (m1 > 0) { \
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync if (d > 0) { \
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync if (d >= 0) { \
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * This structure contains all of the information needed
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * to run the bresenham algorithm.
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * The variables may be hardcoded into the declarations
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * instead of using this structure to make use of
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync * register declarations.
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsynctypedef struct {
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync int d; /* decision variable */
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync#define BRESINITPGONSTRUCT(dmaj, min1, min2, bres) \
03532efdc331b598d3dedc8cc7477641c3b0dd12vboxsync BRESINITPGON(dmaj, min1, min2, bres.minor, bres.d, \