/* Does the given edge contain the given point. The point must already
* be known to be contained within the line determined by the edge,
* (most likely the point results from an intersection of this edge
* with another).
*
* If we had exact arithmetic, then this function would simply be a
* matter of examining whether the y value of the point lies within
* the range of y values of the edge. But since intersection points
* are not exact due to being rounded to the nearest integer within
* the available precision, we must also examine the x value of the
* point.
*
* The definition of "contains" here is that the given intersection
* point will be seen by the sweep line after the start event for the
* given edge and before the stop event for the edge. See the comments
* in the implementation for more details.
*/
static cairo_bool_t
_cairo_bo_edge_contains_intersect_point (cairo_bo_edge_t *edge,
cairo_bo_intersect_point_t *point)
{
int cmp_top, cmp_bottom;
/* XXX: When running the actual algorithm, we don't actually need to
* compare against edge->top at all here, since any intersection above
* top is eliminated early via a slope comparison. We're leaving these
* here for now only for the sake of the quadratic-time intersection
* finder which needs them.
*/
cmp_top = _cairo_bo_intersect_ordinate_32_compare (point->y,
edge->edge.top);
cmp_bottom = _cairo_bo_intersect_ordinate_32_compare (point->y,
edge->edge.bottom);
if (cmp_top < 0 || cmp_bottom > 0)
{
return FALSE;
}
if (cmp_top > 0 && cmp_bottom < 0)
{
return TRUE;
}
/* At this stage, the point lies on the same y value as either
* edge->top or edge->bottom, so we have to examine the x value in
* order to properly determine containment. */
/* If the y value of the point is the same as the y value of the
* top of the edge, then the x value of the point must be greater
* to be considered as inside the edge. Similarly, if the y value
* of the point is the same as the y value of the bottom of the
* edge, then the x value of the point must be less to be
* considered as inside. */
if (cmp_top == 0) {
cairo_fixed_t top_x;
top_x = _line_compute_intersection_x_for_y (&edge->edge.line,
edge->edge.top);
return _cairo_bo_intersect_ordinate_32_compare (point->x, top_x) > 0;
} else { /* cmp_bottom == 0 */
cairo_fixed_t bot_x;
bot_x = _line_compute_intersection_x_for_y (&edge->edge.line,
edge->edge.bottom);
return _cairo_bo_intersect_ordinate_32_compare (point->x, bot_x) < 0;
}
}
/* Does the given edge contain the given point. The point must already
* be known to be contained within the line determined by the edge,
* (most likely the point results from an intersection of this edge
* with another).
*
* If we had exact arithmetic, then this function would simply be a
* matter of examining whether the y value of the point lies within
* the range of y values of the edge. But since intersection points
* are not exact due to being rounded to the nearest integer within
* the available precision, we must also examine the x value of the
* point.
*
* The definition of "contains" here is that the given intersection
* point will be seen by the sweep line after the start event for the
* given edge and before the stop event for the edge. See the comments
* in the implementation for more details.
*/
static cairo_bool_t
_cairo_bo_edge_contains_intersect_point (cairo_bo_edge_t *edge,
cairo_bo_intersect_point_t *point)
{
return _cairo_bo_intersect_ordinate_32_compare (point->y,
edge->edge.bottom) < 0;
}
