/* 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;
}
}
static cairo_status_t
_cairo_bo_event_queue_insert_stop (cairo_bo_event_queue_t *event_queue,
cairo_bo_edge_t *edge)
{
cairo_bo_point32_t point;
point.y = edge->edge.bottom;
point.x = _line_compute_intersection_x_for_y (&edge->edge.line,
point.y);
return _cairo_bo_event_queue_insert (event_queue,
CAIRO_BO_EVENT_TYPE_STOP,
edge, NULL,
&point);
}
static cairo_status_t
event_queue_insert_stop (cairo_bo_event_queue_t *event_queue,
cairo_bo_edge_t *edge)
{
cairo_bo_intersect_point_t point;
point.y.ordinate = edge->edge.bottom;
point.y.approx = EXACT;
point.x.ordinate = _line_compute_intersection_x_for_y (&edge->edge.line,
point.y.ordinate);
point.x.approx = EXACT;
return _cairo_bo_event_queue_insert (event_queue,
CAIRO_BO_EVENT_TYPE_STOP,
edge, NULL,
&point);
}
void
_cairo_traps_extents (const cairo_traps_t *traps,
cairo_box_t *extents)
{
int i;
if (traps->num_traps == 0) {
extents->p1.x = extents->p1.y = 0;
extents->p2.x = extents->p2.y = 0;
return;
}
extents->p1.x = extents->p1.y = INT32_MAX;
extents->p2.x = extents->p2.y = INT32_MIN;
for (i = 0; i < traps->num_traps; i++) {
const cairo_trapezoid_t *trap = &traps->traps[i];
if (trap->top < extents->p1.y)
extents->p1.y = trap->top;
if (trap->bottom > extents->p2.y)
extents->p2.y = trap->bottom;
if (trap->left.p1.x < extents->p1.x) {
cairo_fixed_t x = trap->left.p1.x;
if (trap->top != trap->left.p1.y) {
x = _line_compute_intersection_x_for_y (&trap->left,
trap->top);
if (x < extents->p1.x)
extents->p1.x = x;
} else
extents->p1.x = x;
}
if (trap->left.p2.x < extents->p1.x) {
cairo_fixed_t x = trap->left.p2.x;
if (trap->bottom != trap->left.p2.y) {
x = _line_compute_intersection_x_for_y (&trap->left,
trap->bottom);
if (x < extents->p1.x)
extents->p1.x = x;
} else
extents->p1.x = x;
}
if (trap->right.p1.x > extents->p2.x) {
cairo_fixed_t x = trap->right.p1.x;
if (trap->top != trap->right.p1.y) {
x = _line_compute_intersection_x_for_y (&trap->right,
trap->top);
if (x > extents->p2.x)
extents->p2.x = x;
} else
extents->p2.x = x;
}
if (trap->right.p2.x > extents->p2.x) {
cairo_fixed_t x = trap->right.p2.x;
if (trap->bottom != trap->right.p2.y) {
x = _line_compute_intersection_x_for_y (&trap->right,
trap->bottom);
if (x > extents->p2.x)
extents->p2.x = x;
} else
extents->p2.x = x;
}
}
}
cairo_status_t
_cairo_polygon_intersect (cairo_polygon_t *a, int winding_a,
cairo_polygon_t *b, int winding_b)
{
cairo_status_t status;
cairo_bo_start_event_t stack_events[CAIRO_STACK_ARRAY_LENGTH (cairo_bo_start_event_t)];
cairo_bo_start_event_t *events;
cairo_bo_event_t *stack_event_ptrs[ARRAY_LENGTH (stack_events) + 1];
cairo_bo_event_t **event_ptrs;
int num_events;
int i, j;
/* XXX lazy */
if (winding_a != CAIRO_FILL_RULE_WINDING) {
status = _cairo_polygon_reduce (a, winding_a);
if (unlikely (status))
return status;
}
if (winding_b != CAIRO_FILL_RULE_WINDING) {
status = _cairo_polygon_reduce (b, winding_b);
if (unlikely (status))
return status;
}
if (unlikely (0 == a->num_edges))
return CAIRO_STATUS_SUCCESS;
if (unlikely (0 == b->num_edges)) {
a->num_edges = 0;
return CAIRO_STATUS_SUCCESS;
}
events = stack_events;
event_ptrs = stack_event_ptrs;
num_events = a->num_edges + b->num_edges;
if (num_events > ARRAY_LENGTH (stack_events)) {
events = _cairo_malloc_ab_plus_c (num_events,
sizeof (cairo_bo_start_event_t) +
sizeof (cairo_bo_event_t *),
sizeof (cairo_bo_event_t *));
if (unlikely (events == NULL))
return _cairo_error (CAIRO_STATUS_NO_MEMORY);
event_ptrs = (cairo_bo_event_t **) (events + num_events);
}
j = 0;
for (i = 0; i < a->num_edges; i++) {
event_ptrs[j] = (cairo_bo_event_t *) &events[j];
events[j].type = CAIRO_BO_EVENT_TYPE_START;
events[j].point.y.ordinate = a->edges[i].top;
events[j].point.y.approx = EXACT;
events[j].point.x.ordinate =
_line_compute_intersection_x_for_y (&a->edges[i].line,
events[j].point.y.ordinate);
events[j].point.x.approx = EXACT;
events[j].edge.a_or_b = 0;
events[j].edge.edge = a->edges[i];
events[j].edge.deferred.other = NULL;
events[j].edge.prev = NULL;
events[j].edge.next = NULL;
j++;
}
for (i = 0; i < b->num_edges; i++) {
event_ptrs[j] = (cairo_bo_event_t *) &events[j];
events[j].type = CAIRO_BO_EVENT_TYPE_START;
events[j].point.y.ordinate = b->edges[i].top;
events[j].point.y.approx = EXACT;
events[j].point.x.ordinate =
_line_compute_intersection_x_for_y (&b->edges[i].line,
events[j].point.y.ordinate);
events[j].point.x.approx = EXACT;
events[j].edge.a_or_b = 1;
events[j].edge.edge = b->edges[i];
events[j].edge.deferred.other = NULL;
events[j].edge.prev = NULL;
events[j].edge.next = NULL;
j++;
}
assert (j == num_events);
#if 0
{
FILE *file = fopen ("clip_a.txt", "w");
_cairo_debug_print_polygon (file, a);
fclose (file);
}
{
FILE *file = fopen ("clip_b.txt", "w");
_cairo_debug_print_polygon (file, b);
fclose (file);
}
#endif
a->num_edges = 0;
status = intersection_sweep (event_ptrs, num_events, a);
if (events != stack_events)
free (events);
#if 0
{
FILE *file = fopen ("clip_result.txt", "w");
_cairo_debug_print_polygon (file, a);
fclose (file);
}
#endif
return status;
}
cairo_status_t
_cairo_polygon_reduce (cairo_polygon_t *polygon,
cairo_fill_rule_t fill_rule)
{
cairo_status_t status;
cairo_bo_start_event_t stack_events[CAIRO_STACK_ARRAY_LENGTH (cairo_bo_start_event_t)];
cairo_bo_start_event_t *events;
cairo_bo_event_t *stack_event_ptrs[ARRAY_LENGTH (stack_events) + 1];
cairo_bo_event_t **event_ptrs;
int num_limits;
int num_events;
int i;
num_events = polygon->num_edges;
if (unlikely (0 == num_events))
return CAIRO_STATUS_SUCCESS;
if (DEBUG_POLYGON) {
FILE *file = fopen ("reduce_in.txt", "w");
_cairo_debug_print_polygon (file, polygon);
fclose (file);
}
events = stack_events;
event_ptrs = stack_event_ptrs;
if (num_events > ARRAY_LENGTH (stack_events)) {
events = _cairo_malloc_ab_plus_c (num_events,
sizeof (cairo_bo_start_event_t) +
sizeof (cairo_bo_event_t *),
sizeof (cairo_bo_event_t *));
if (unlikely (events == NULL))
return _cairo_error (CAIRO_STATUS_NO_MEMORY);
event_ptrs = (cairo_bo_event_t **) (events + num_events);
}
for (i = 0; i < num_events; i++) {
event_ptrs[i] = (cairo_bo_event_t *) &events[i];
events[i].type = CAIRO_BO_EVENT_TYPE_START;
events[i].point.y = polygon->edges[i].top;
events[i].point.x =
_line_compute_intersection_x_for_y (&polygon->edges[i].line,
events[i].point.y);
events[i].edge.edge = polygon->edges[i];
events[i].edge.deferred.right = NULL;
events[i].edge.prev = NULL;
events[i].edge.next = NULL;
}
num_limits = polygon->num_limits; polygon->num_limits = 0;
polygon->num_edges = 0;
status = _cairo_bentley_ottmann_tessellate_bo_edges (event_ptrs,
num_events,
fill_rule,
polygon);
polygon->num_limits = num_limits;
if (events != stack_events)
free (events);
if (DEBUG_POLYGON) {
FILE *file = fopen ("reduce_out.txt", "w");
_cairo_debug_print_polygon (file, polygon);
fclose (file);
}
return status;
}
