static void
_add_edge (struct reduce *r,
const cairo_point_t *p1,
const cairo_point_t *p2)
{
int top, bottom;
int top_y, bot_y;
int n;
if (p1->y < p2->y) {
top = p1->y;
bottom = p2->y;
} else {
top = p2->y;
bottom = p1->y;
}
if (bottom < r->limit.p1.y || top > r->limit.p2.y)
return;
if (p1->x > p2->x) {
const cairo_point_t *t = p1;
p1 = p2;
p2 = t;
}
if (p2->x <= r->limit.p1.x || p1->x >= r->limit.p2.x)
return;
for (n = 0; n < r->clip->num_boxes; n++) {
const cairo_box_t *limits = &r->clip->boxes[n];
if (bottom < limits->p1.y || top > limits->p2.y)
continue;
if (p2->x <= limits->p1.x || p1->x >= limits->p2.x)
continue;
if (p1->x >= limits->p1.x && p2->x <= limits->p1.x) {
top_y = top;
bot_y = bottom;
} else {
int p1_y, p2_y;
p1_y = _cairo_edge_compute_intersection_y_for_x (p1, p2,
limits->p1.x);
p2_y = _cairo_edge_compute_intersection_y_for_x (p1, p2,
limits->p2.x);
if (p1_y < p2_y) {
top_y = p1_y;
bot_y = p2_y;
} else {
top_y = p2_y;
bot_y = p1_y;
}
if (top_y < top)
top_y = top;
if (bot_y > bottom)
bot_y = bottom;
}
if (top_y < limits->p1.y)
top_y = limits->p1.y;
if (bot_y > limits->p2.y)
bot_y = limits->p2.y;
if (bot_y > top_y)
_add_clipped_edge (r, p1, p2, top_y, bot_y);
}
}
static void
_add_clipped_edge (cairo_polygon_t *polygon,
const cairo_point_t *p1,
const cairo_point_t *p2,
const int top, const int bottom,
const int dir)
{
cairo_point_t bot_left, top_right;
cairo_fixed_t top_y, bot_y;
int n;
for (n = 0; n < polygon->num_limits; n++) {
const cairo_box_t *limits = &polygon->limits[n];
cairo_fixed_t pleft, pright;
if (top >= limits->p2.y)
continue;
if (bottom <= limits->p1.y)
continue;
bot_left.x = limits->p1.x;
bot_left.y = limits->p2.y;
top_right.x = limits->p2.x;
top_right.y = limits->p1.y;
/* The useful region */
top_y = MAX (top, limits->p1.y);
bot_y = MIN (bottom, limits->p2.y);
/* The projection of the edge on the horizontal axis */
pleft = MIN (p1->x, p2->x);
pright = MAX (p1->x, p2->x);
if (limits->p1.x <= pleft && pright <= limits->p2.x) {
/* Projection of the edge completely contained in the box:
* clip vertically by restricting top and bottom */
_add_edge (polygon, p1, p2, top_y, bot_y, dir);
assert_last_edge_is_valid (polygon, limits);
} else if (pright <= limits->p1.x) {
/* Projection of the edge to the left of the box:
* replace with the left side of the box (clipped top/bottom) */
_add_edge (polygon, &limits->p1, &bot_left, top_y, bot_y, dir);
assert_last_edge_is_valid (polygon, limits);
} else if (limits->p2.x <= pleft) {
/* Projection of the edge to the right of the box:
* replace with the right side of the box (clipped top/bottom) */
_add_edge (polygon, &top_right, &limits->p2, top_y, bot_y, dir);
assert_last_edge_is_valid (polygon, limits);
} else {
/* The edge and the box intersect in a generic way */
cairo_fixed_t left_y, right_y;
cairo_bool_t top_left_to_bottom_right;
/*
* The edge intersects the lines corresponding to the left
* and right sides of the limit box at left_y and right_y,
* but we need to add edges for the range from top_y to
* bot_y.
*
* For both intersections, there are three cases:
*
* 1) It is outside the vertical range of the limit
* box. In this case we can simply further clip the
* edge we will be emitting (i.e. restrict its
* top/bottom limits to those of the limit box).
*
* 2) It is inside the vertical range of the limit
* box. In this case, we need to add the vertical edge
* connecting the correct vertex to the intersection,
* in order to preserve the winding count.
*
* 3) It is exactly on the box. In this case, do nothing.
*
* These operations restrict the active range (stored in
* top_y/bot_y) so that the p1-p2 edge is completely
* inside the box if it is clipped to this vertical range.
*/
top_left_to_bottom_right = (p1->x <= p2->x) == (p1->y <= p2->y);
if (top_left_to_bottom_right) {
if (pleft >= limits->p1.x) {
left_y = top_y;
} else {
left_y = _cairo_edge_compute_intersection_y_for_x (p1, p2,
limits->p1.x);
if (_cairo_edge_compute_intersection_x_for_y (p1, p2, left_y) < limits->p1.x)
left_y++;
}
left_y = MIN (left_y, bot_y);
if (top_y < left_y) {
_add_edge (polygon, &limits->p1, &bot_left,
top_y, left_y, dir);
assert_last_edge_is_valid (polygon, limits);
top_y = left_y;
}
if (pright <= limits->p2.x) {
right_y = bot_y;
} else {
right_y = _cairo_edge_compute_intersection_y_for_x (p1, p2,
limits->p2.x);
if (_cairo_edge_compute_intersection_x_for_y (p1, p2, right_y) > limits->p2.x)
right_y--;
}
right_y = MAX (right_y, top_y);
if (bot_y > right_y) {
_add_edge (polygon, &top_right, &limits->p2,
right_y, bot_y, dir);
assert_last_edge_is_valid (polygon, limits);
bot_y = right_y;
}
} else {
if (pright <= limits->p2.x) {
right_y = top_y;
} else {
right_y = _cairo_edge_compute_intersection_y_for_x (p1, p2,
limits->p2.x);
if (_cairo_edge_compute_intersection_x_for_y (p1, p2, right_y) > limits->p2.x)
right_y++;
}
right_y = MIN (right_y, bot_y);
if (top_y < right_y) {
_add_edge (polygon, &top_right, &limits->p2,
top_y, right_y, dir);
assert_last_edge_is_valid (polygon, limits);
top_y = right_y;
}
if (pleft >= limits->p1.x) {
left_y = bot_y;
} else {
left_y = _cairo_edge_compute_intersection_y_for_x (p1, p2,
limits->p1.x);
if (_cairo_edge_compute_intersection_x_for_y (p1, p2, left_y) < limits->p1.x)
left_y--;
}
left_y = MAX (left_y, top_y);
if (bot_y > left_y) {
_add_edge (polygon, &limits->p1, &bot_left,
left_y, bot_y, dir);
assert_last_edge_is_valid (polygon, limits);
bot_y = left_y;
}
}
if (top_y != bot_y) {
_add_edge (polygon, p1, p2, top_y, bot_y, dir);
assert_last_edge_is_valid (polygon, limits);
}
}
}
}
static void
_add_clipped_edge (cairo_polygon_t *polygon,
const cairo_point_t *p1,
const cairo_point_t *p2,
const int top, const int bottom,
const int dir)
{
cairo_point_t p[2];
int top_y, bot_y;
int n;
for (n = 0; n < polygon->num_limits; n++) {
const cairo_box_t *limits = &polygon->limits[n];
if (top >= limits->p2.y)
continue;
if (bottom <= limits->p1.y)
continue;
if (p1->x >= limits->p1.x && p2->x >= limits->p1.x &&
p1->x <= limits->p2.x && p2->x <= limits->p2.x)
{
top_y = top;
if (top_y < limits->p1.y)
top_y = limits->p1.y;
bot_y = bottom;
if (bot_y > limits->p2.y)
bot_y = limits->p2.y;
_add_edge (polygon, p1, p2, top_y, bot_y, dir);
}
else if (p1->x <= limits->p1.x && p2->x <= limits->p1.x)
{
p[0].x = limits->p1.x;
p[0].y = limits->p1.y;
top_y = top;
if (top_y < p[0].y)
top_y = p[0].y;
p[1].x = limits->p1.x;
p[1].y = limits->p2.y;
bot_y = bottom;
if (bot_y > p[1].y)
bot_y = p[1].y;
_add_edge (polygon, &p[0], &p[1], top_y, bot_y, dir);
}
else if (p1->x >= limits->p2.x && p2->x >= limits->p2.x)
{
p[0].x = limits->p2.x;
p[0].y = limits->p1.y;
top_y = top;
if (top_y < p[0].y)
top_y = p[0].y;
p[1].x = limits->p2.x;
p[1].y = limits->p2.y;
bot_y = bottom;
if (bot_y > p[1].y)
bot_y = p[1].y;
_add_edge (polygon, &p[0], &p[1], top_y, bot_y, dir);
}
else
{
int left_y, right_y;
int p1_y, p2_y;
left_y = _cairo_edge_compute_intersection_y_for_x (p1, p2,
limits->p1.x);
right_y = _cairo_edge_compute_intersection_y_for_x (p1, p2,
limits->p2.x);
if (left_y == right_y) /* horizontal within bounds */
continue;
p1_y = top;
p2_y = bottom;
if (left_y < right_y) {
if (p1->x < limits->p1.x && left_y > limits->p1.y) {
p[0].x = limits->p1.x;
p[0].y = limits->p1.y;
top_y = p1_y;
if (top_y < p[0].y)
top_y = p[0].y;
p[1].x = limits->p1.x;
p[1].y = limits->p2.y;
bot_y = left_y;
if (bot_y > p[1].y)
bot_y = p[1].y;
if (bot_y > top_y)
_add_edge (polygon, &p[0], &p[1], top_y, bot_y, dir);
p1_y = bot_y;
}
if (p2->x > limits->p2.x && right_y < limits->p2.y) {
p[0].x = limits->p2.x;
p[0].y = limits->p1.y;
top_y = right_y;
if (top_y < p[0].y)
top_y = p[0].y;
p[1].x = limits->p2.x;
p[1].y = limits->p2.y;
bot_y = p2_y;
if (bot_y > p[1].y)
bot_y = p[1].y;
if (bot_y > top_y)
_add_edge (polygon, &p[0], &p[1], top_y, bot_y, dir);
p2_y = top_y;
}
} else {
if (p1->x > limits->p2.x && right_y > limits->p1.y) {
p[0].x = limits->p2.x;
p[0].y = limits->p1.y;
top_y = p1_y;
if (top_y < p[0].y)
top_y = p[0].y;
p[1].x = limits->p2.x;
p[1].y = limits->p2.y;
bot_y = right_y;
if (bot_y > p[1].y)
bot_y = p[1].y;
if (bot_y > top_y)
_add_edge (polygon, &p[0], &p[1], top_y, bot_y, dir);
p1_y = bot_y;
}
if (p2->x < limits->p1.x && left_y < limits->p2.y) {
p[0].x = limits->p1.x;
p[0].y = limits->p1.y;
top_y = left_y;
if (top_y < p[0].y)
top_y = p[0].y;
p[1].x = limits->p1.x;
p[1].y = limits->p2.y;
bot_y = p2_y;
if (bot_y > p[1].y)
bot_y = p[1].y;
if (bot_y > top_y)
_add_edge (polygon, &p[0], &p[1], top_y, bot_y, dir);
p2_y = top_y;
}
}
if (p1_y < limits->p1.y)
p1_y = limits->p1.y;
if (p2_y > limits->p2.y)
p2_y = limits->p2.y;
if (p2_y > p1_y)
_add_edge (polygon, p1, p2, p1_y, p2_y, dir);
}
}
}
