static int
_cairo_bo_sweep_line_compare_edges (cairo_bo_sweep_line_t *sweep_line,
const cairo_bo_edge_t *a,
const cairo_bo_edge_t *b)
{
int cmp;
/* compare the edges if not identical */
if (! _line_equal (&a->edge.line, &b->edge.line)) {
cmp = edges_compare_x_for_y (a, b, sweep_line->current_y);
if (cmp)
return cmp;
/* The two edges intersect exactly at y, so fall back on slope
* comparison. We know that this compare_edges function will be
* called only when starting a new edge, (not when stopping an
* edge), so we don't have to worry about conditionally inverting
* the sense of _slope_compare. */
cmp = _slope_compare (a, b);
if (cmp)
return cmp;
}
/* We've got two collinear edges now. */
return b->edge.bottom - a->edge.bottom;
}
static inline cairo_status_t
event_queue_insert_if_intersect_below_current_y (cairo_bo_event_queue_t *event_queue,
cairo_bo_edge_t *left,
cairo_bo_edge_t *right)
{
cairo_bo_intersect_point_t intersection;
if (_line_equal (&left->edge.line, &right->edge.line))
return CAIRO_STATUS_SUCCESS;
/* The names "left" and "right" here are correct descriptions of
* the order of the two edges within the active edge list. So if a
* slope comparison also puts left less than right, then we know
* that the intersection of these two segments has already
* occurred before the current sweep line position. */
if (_slope_compare (left, right) <= 0)
return CAIRO_STATUS_SUCCESS;
if (! _cairo_bo_edge_intersect (left, right, &intersection))
return CAIRO_STATUS_SUCCESS;
return _cairo_bo_event_queue_insert (event_queue,
CAIRO_BO_EVENT_TYPE_INTERSECTION,
left, right,
&intersection);
}
static inline cairo_bool_t
edges_colinear (const cairo_bo_edge_t *a, const cairo_bo_edge_t *b)
{
if (_line_equal (&a->edge.line, &b->edge.line))
return TRUE;
if (_slope_compare (a, b))
return FALSE;
/* The choice of y is not truly arbitrary since we must guarantee that it
* is greater than the start of either line.
*/
if (a->edge.line.p1.y == b->edge.line.p1.y) {
return a->edge.line.p1.x == b->edge.line.p1.x;
} else if (a->edge.line.p2.y == b->edge.line.p2.y) {
return a->edge.line.p2.x == b->edge.line.p2.x;
} else if (a->edge.line.p1.y < b->edge.line.p1.y) {
return edge_compare_for_y_against_x (b,
a->edge.line.p1.y,
a->edge.line.p1.x) == 0;
} else {
return edge_compare_for_y_against_x (a,
b->edge.line.p1.y,
b->edge.line.p1.x) == 0;
}
}
