static cairo_status_t
_cairo_pen_stroke_spline_half (cairo_pen_t *pen,
cairo_spline_t *spline,
cairo_direction_t dir,
cairo_polygon_t *polygon)
{
int i;
cairo_status_t status;
int start, stop, step;
int active = 0;
cairo_point_t hull_point;
cairo_slope_t slope, initial_slope, final_slope;
cairo_point_t *point = spline->points;
int num_points = spline->num_points;
if (dir == CAIRO_DIRECTION_FORWARD) {
start = 0;
stop = num_points;
step = 1;
initial_slope = spline->initial_slope;
final_slope = spline->final_slope;
} else {
start = num_points - 1;
stop = -1;
step = -1;
initial_slope = spline->final_slope;
initial_slope.dx = -initial_slope.dx;
initial_slope.dy = -initial_slope.dy;
final_slope = spline->initial_slope;
final_slope.dx = -final_slope.dx;
final_slope.dy = -final_slope.dy;
}
_cairo_pen_find_active_cw_vertex_index (pen, &initial_slope, &active);
i = start;
while (i != stop) {
hull_point.x = point[i].x + pen->vertices[active].point.x;
hull_point.y = point[i].y + pen->vertices[active].point.y;
status = _cairo_polygon_line_to (polygon, &hull_point);
if (status)
return status;
if (i + step == stop)
slope = final_slope;
else
_cairo_slope_init (&slope, &point[i], &point[i+step]);
if (_cairo_slope_counter_clockwise (&slope, &pen->vertices[active].slope_ccw)) {
if (++active == pen->num_vertices)
active = 0;
} else if (_cairo_slope_clockwise (&slope, &pen->vertices[active].slope_cw)) {
if (--active == -1)
active = pen->num_vertices - 1;
} else {
i += step;
}
}
return CAIRO_STATUS_SUCCESS;
}
/* Find active pen vertex for counterclockwise edge of stroke at the given slope.
*
* NOTE: The behavior of this function is sensitive to the sense of
* the inequality within _cairo_slope_clockwise/_cairo_slope_counter_clockwise.
*/
cairo_status_t
_cairo_pen_find_active_ccw_vertex_index (cairo_pen_t *pen,
cairo_slope_t *slope,
int *active)
{
int i;
cairo_slope_t slope_reverse;
slope_reverse = *slope;
slope_reverse.dx = -slope_reverse.dx;
slope_reverse.dy = -slope_reverse.dy;
for (i=pen->num_vertices-1; i >= 0; i--) {
if (_cairo_slope_counter_clockwise (&pen->vertices[i].slope_ccw, &slope_reverse)
&& _cairo_slope_clockwise (&pen->vertices[i].slope_cw, &slope_reverse))
break;
}
/* If the desired slope cannot be found between any of the pen
* vertices, then we must have a degenerate pen, (such as a pen
* that's been transformed to a line). In that case, we consider
* the last pen vertex as the appropriate counterclockwise vertex.
*/
if (i < 0)
i = pen->num_vertices - 1;
*active = i;
return CAIRO_STATUS_SUCCESS;
}
/*
* Find active pen vertex for clockwise edge of stroke at the given slope.
*
* NOTE: The behavior of this function is sensitive to the sense of
* the inequality within _cairo_slope_clockwise/_cairo_slope_counter_clockwise.
*
* The issue is that the slope_ccw member of one pen vertex will be
* equivalent to the slope_cw member of the next pen vertex in a
* counterclockwise order. However, for this function, we care
* strongly about which vertex is returned.
*/
cairo_status_t
_cairo_pen_find_active_cw_vertex_index (cairo_pen_t *pen,
cairo_slope_t *slope,
int *active)
{
int i;
for (i=0; i < pen->num_vertices; i++) {
if (_cairo_slope_clockwise (slope, &pen->vertices[i].slope_ccw)
&& _cairo_slope_counter_clockwise (slope, &pen->vertices[i].slope_cw))
break;
}
/* If the desired slope cannot be found between any of the pen
* vertices, then we must have a degenerate pen, (such as a pen
* that's been transformed to a line). In that case, we consider
* the first pen vertex as the appropriate clockwise vertex.
*/
if (i == pen->num_vertices)
i = 0;
*active = i;
return CAIRO_STATUS_SUCCESS;
}
/*
* Find active pen vertex for clockwise edge of stroke at the given slope.
*
* NOTE: The behavior of this function is sensitive to the sense of
* the inequality within _cairo_slope_clockwise/_cairo_slope_counter_clockwise.
*
* The issue is that the slope_ccw member of one pen vertex will be
* equivalent to the slope_cw member of the next pen vertex in a
* counterclockwise order. However, for this function, we care
* strongly about which vertex is returned.
*/
cairo_status_t
_cairo_pen_find_active_cw_vertex_index (cairo_pen_t *pen,
cairo_slope_t *slope,
int *active)
{
int i;
for (i=0; i < pen->num_vertices; i++) {
if (_cairo_slope_clockwise (slope, &pen->vertices[i].slope_ccw)
&& _cairo_slope_counter_clockwise (slope, &pen->vertices[i].slope_cw))
break;
}
*active = i;
return CAIRO_STATUS_SUCCESS;
}
/* Find active pen vertex for counterclockwise edge of stroke at the given slope.
*
* NOTE: The behavior of this function is sensitive to the sense of
* the inequality within _cairo_slope_clockwise/_cairo_slope_counter_clockwise.
*/
cairo_status_t
_cairo_pen_find_active_ccw_vertex_index (cairo_pen_t *pen,
cairo_slope_t *slope,
int *active)
{
int i;
cairo_slope_t slope_reverse;
slope_reverse = *slope;
slope_reverse.dx = -slope_reverse.dx;
slope_reverse.dy = -slope_reverse.dy;
for (i=pen->num_vertices-1; i >= 0; i--) {
if (_cairo_slope_counter_clockwise (&pen->vertices[i].slope_ccw, &slope_reverse)
&& _cairo_slope_clockwise (&pen->vertices[i].slope_cw, &slope_reverse))
break;
}
*active = i;
return CAIRO_STATUS_SUCCESS;
}
