static void
edge_end_box (sweep_line_t *sweep_line, edge_t *left, int32_t bot)
{
cairo_status_t status = CAIRO_STATUS_SUCCESS;
/* Only emit (trivial) non-degenerate trapezoids with positive height. */
if (likely (left->top < bot)) {
if (sweep_line->do_traps) {
cairo_line_t _left = {
{ left->x, left->top },
{ left->x, bot },
}, _right = {
{ left->right->x, left->top },
{ left->right->x, bot },
};
_cairo_traps_add_trap (sweep_line->container, left->top, bot, &_left, &_right);
status = _cairo_traps_status ((cairo_traps_t *) sweep_line->container);
} else {
cairo_box_t box;
box.p1.x = left->x;
box.p1.y = left->top;
box.p2.x = left->right->x;
box.p2.y = bot;
status = _cairo_boxes_add (sweep_line->container,
CAIRO_ANTIALIAS_DEFAULT,
&box);
}
}
if (unlikely (status))
longjmp (sweep_line->unwind, status);
left->right = NULL;
}
static cairo_status_t
_cairo_bo_edge_end_trap (cairo_bo_edge_t *left,
int32_t bot,
cairo_bool_t do_traps,
void *container)
{
cairo_bo_trap_t *trap = &left->deferred_trap;
cairo_status_t status = CAIRO_STATUS_SUCCESS;
/* Only emit (trivial) non-degenerate trapezoids with positive height. */
if (likely (trap->top < bot)) {
if (do_traps) {
_cairo_traps_add_trap (container,
trap->top, bot,
&left->edge.line, &trap->right->edge.line);
status = _cairo_traps_status ((cairo_traps_t *) container);
} else {
cairo_box_t box;
box.p1.x = left->edge.line.p1.x;
box.p1.y = trap->top;
box.p2.x = trap->right->edge.line.p1.x;
box.p2.y = bot;
status = _cairo_boxes_add (container, CAIRO_ANTIALIAS_DEFAULT, &box);
}
}
trap->right = NULL;
return status;
}
static cairo_status_t
span_to_traps (void *abstract_renderer, int y, int h,
const cairo_half_open_span_t *spans, unsigned num_spans)
{
struct cairo_trap_renderer *r = abstract_renderer;
cairo_fixed_t top, bot;
if (num_spans == 0)
return CAIRO_STATUS_SUCCESS;
top = _cairo_fixed_from_int (y);
bot = _cairo_fixed_from_int (y + h);
do {
if (spans[0].coverage) {
cairo_fixed_t x0 = _cairo_fixed_from_int(spans[0].x);
cairo_fixed_t x1 = _cairo_fixed_from_int(spans[1].x);
cairo_line_t left = { { x0, top }, { x0, bot } },
right = { { x1, top }, { x1, bot } };
_cairo_traps_add_trap (r->traps, top, bot, &left, &right);
}
spans++;
} while (--num_spans > 1);
return CAIRO_STATUS_SUCCESS;
}
static cairo_status_t
_cairo_traps_add_trap_from_points (cairo_traps_t *traps, cairo_fixed_t top, cairo_fixed_t bottom,
cairo_point_t left_p1, cairo_point_t left_p2,
cairo_point_t right_p1, cairo_point_t right_p2)
{
cairo_line_t left;
cairo_line_t right;
left.p1 = left_p1;
left.p2 = left_p2;
right.p1 = right_p1;
right.p2 = right_p2;
return _cairo_traps_add_trap (traps, top, bottom, &left, &right);
}
cairo_status_t
_cairo_traps_tessellate_rectangle (cairo_traps_t *traps,
const cairo_point_t *top_left,
const cairo_point_t *bottom_right)
{
cairo_line_t left;
cairo_line_t right;
left.p1.x = left.p2.x = top_left->x;
left.p1.y = right.p1.y = top_left->y;
right.p1.x = right.p2.x = bottom_right->x;
left.p2.y = right.p2.y = bottom_right->y;
_cairo_traps_add_trap (traps, top_left->y, bottom_right->y, &left, &right);
return traps->status;
}
static cairo_status_t
_cairo_bo_edge_end_trap (cairo_bo_edge_t *left,
int32_t bot,
cairo_traps_t *traps)
{
cairo_bo_trap_t *trap = &left->deferred_trap;
/* Only emit (trivial) non-degenerate trapezoids with positive height. */
if (likely (trap->top < bot)) {
_cairo_traps_add_trap (traps,
trap->top, bot,
&left->edge.line, &trap->right->edge.line);
}
trap->right = NULL;
return _cairo_traps_status (traps);
}
cairo_status_t
_cairo_traps_tessellate_rectangle (cairo_traps_t *traps,
const cairo_point_t *top_left,
const cairo_point_t *bottom_right)
{
cairo_line_t left;
cairo_line_t right;
cairo_fixed_t top, bottom;
if (top_left->y == bottom_right->y)
return CAIRO_STATUS_SUCCESS;
if (top_left->x == bottom_right->x)
return CAIRO_STATUS_SUCCESS;
left.p1.x = left.p2.x = top_left->x;
left.p1.y = right.p1.y = top_left->y;
right.p1.x = right.p2.x = bottom_right->x;
left.p2.y = right.p2.y = bottom_right->y;
top = top_left->y;
bottom = bottom_right->y;
if (traps->num_limits) {
cairo_bool_t reversed;
int n;
if (top >= traps->bounds.p2.y || bottom <= traps->bounds.p1.y)
return CAIRO_STATUS_SUCCESS;
/* support counter-clockwise winding for rectangular tessellation */
reversed = top_left->x > bottom_right->x;
if (reversed) {
right.p1.x = right.p2.x = top_left->x;
left.p1.x = left.p2.x = bottom_right->x;
}
if (left.p1.x >= traps->bounds.p2.x || right.p1.x <= traps->bounds.p1.x)
return CAIRO_STATUS_SUCCESS;
for (n = 0; n < traps->num_limits; n++) {
const cairo_box_t *limits = &traps->limits[n];
cairo_line_t _left, _right;
cairo_fixed_t _top, _bottom;
if (top >= limits->p2.y)
continue;
if (bottom <= limits->p1.y)
continue;
/* Trivially reject if trapezoid is entirely to the right or
* to the left of the limits. */
if (left.p1.x >= limits->p2.x)
continue;
if (right.p1.x <= limits->p1.x)
continue;
/* Otherwise, clip the trapezoid to the limits. */
_top = top;
if (_top < limits->p1.y)
_top = limits->p1.y;
_bottom = bottom;
if (_bottom > limits->p2.y)
_bottom = limits->p2.y;
if (_bottom <= _top)
continue;
_left = left;
if (_left.p1.x < limits->p1.x) {
_left.p1.x = limits->p1.x;
_left.p1.y = limits->p1.y;
_left.p2.x = limits->p1.x;
_left.p2.y = limits->p2.y;
}
_right = right;
if (_right.p1.x > limits->p2.x) {
_right.p1.x = limits->p2.x;
_right.p1.y = limits->p1.y;
_right.p2.x = limits->p2.x;
_right.p2.y = limits->p2.y;
}
if (left.p1.x >= right.p1.x)
continue;
if (reversed)
_cairo_traps_add_trap (traps, _top, _bottom, &_right, &_left);
else
_cairo_traps_add_trap (traps, _top, _bottom, &_left, &_right);
}
} else {
_cairo_traps_add_trap (traps, top, bottom, &left, &right);
}
return traps->status;
}
static void
_cairo_traps_add_clipped_trap (cairo_traps_t *traps,
cairo_fixed_t _top, cairo_fixed_t _bottom,
const cairo_line_t *_left,
const cairo_line_t *_right)
{
/* Note: With the goofy trapezoid specification, (where an
* arbitrary two points on the lines can specified for the left
* and right edges), these limit checks would not work in
* general. For example, one can imagine a trapezoid entirely
* within the limits, but with two points used to specify the left
* edge entirely to the right of the limits. Fortunately, for our
* purposes, cairo will never generate such a crazy
* trapezoid. Instead, cairo always uses for its points the
* extreme positions of the edge that are visible on at least some
* trapezoid. With this constraint, it's impossible for both
* points to be outside the limits while the relevant edge is
* entirely inside the limits.
*/
if (traps->num_limits) {
const cairo_box_t *b = &traps->bounds;
cairo_fixed_t top = _top, bottom = _bottom;
cairo_line_t left = *_left, right = *_right;
/* Trivially reject if trapezoid is entirely to the right or
* to the left of the limits. */
if (left.p1.x >= b->p2.x && left.p2.x >= b->p2.x)
return;
if (right.p1.x <= b->p1.x && right.p2.x <= b->p1.x)
return;
/* And reject if the trapezoid is entirely above or below */
if (top >= b->p2.y || bottom <= b->p1.y)
return;
/* Otherwise, clip the trapezoid to the limits. We only clip
* where an edge is entirely outside the limits. If we wanted
* to be more clever, we could handle cases where a trapezoid
* edge intersects the edge of the limits, but that would
* require slicing this trapezoid into multiple trapezoids,
* and I'm not sure the effort would be worth it. */
if (top < b->p1.y)
top = b->p1.y;
if (bottom > b->p2.y)
bottom = b->p2.y;
if (left.p1.x <= b->p1.x && left.p2.x <= b->p1.x)
left.p1.x = left.p2.x = b->p1.x;
if (right.p1.x >= b->p2.x && right.p2.x >= b->p2.x)
right.p1.x = right.p2.x = b->p2.x;
/* Trivial discards for empty trapezoids that are likely to
* be produced by our tessellators (most notably convex_quad
* when given a simple rectangle).
*/
if (top >= bottom)
return;
/* cheap colinearity check */
if (right.p1.x <= left.p1.x && right.p1.y == left.p1.y &&
right.p2.x <= left.p2.x && right.p2.y == left.p2.y)
return;
_cairo_traps_add_trap (traps, top, bottom, &left, &right);
} else
_cairo_traps_add_trap (traps, _top, _bottom, _left, _right);
}
/* The algorithm here is pretty simple:
inactive = [edges]
y = min_p1_y (inactive)
while (num_active || num_inactive) {
active = all edges containing y
next_y = min ( min_p2_y (active), min_p1_y (inactive), min_intersection (active) )
fill_traps (active, y, next_y, fill_rule)
y = next_y
}
The invariants that hold during fill_traps are:
All edges in active contain both y and next_y
No edges in active intersect within y and next_y
These invariants mean that fill_traps is as simple as sorting the
active edges, forming a trapezoid between each adjacent pair. Then,
either the even-odd or winding rule is used to determine whether to
emit each of these trapezoids.
Warning: This function obliterates the edges of the polygon provided.
*/
cairo_status_t
_cairo_traps_tessellate_polygon (cairo_traps_t *traps,
cairo_polygon_t *poly,
cairo_fill_rule_t fill_rule)
{
cairo_status_t status;
int i, active, inactive;
cairo_fixed_t y, y_next, intersect;
int in_out, num_edges = poly->num_edges;
cairo_edge_t *edges = poly->edges;
if (num_edges == 0)
return CAIRO_STATUS_SUCCESS;
qsort (edges, num_edges, sizeof (cairo_edge_t), _compare_cairo_edge_by_top);
y = edges[0].edge.p1.y;
active = 0;
inactive = 0;
while (active < num_edges) {
while (inactive < num_edges && edges[inactive].edge.p1.y <= y)
inactive++;
for (i = active; i < inactive; i++)
edges[i].current_x = _compute_x (&edges[i].edge, y);
qsort (&edges[active], inactive - active,
sizeof (cairo_edge_t), _compare_cairo_edge_by_current_x_slope);
/* find next inflection point */
y_next = edges[active].edge.p2.y;
for (i = active; i < inactive; i++) {
if (edges[i].edge.p2.y < y_next)
y_next = edges[i].edge.p2.y;
/* check intersect */
if (i != inactive - 1 && edges[i].current_x != edges[i+1].current_x)
if (_line_segs_intersect_ceil (&edges[i].edge, &edges[i+1].edge,
&intersect))
if (intersect > y && intersect < y_next)
y_next = intersect;
}
/* check next inactive point */
if (inactive < num_edges && edges[inactive].edge.p1.y < y_next)
y_next = edges[inactive].edge.p1.y;
/* walk the active edges generating trapezoids */
in_out = 0;
for (i = active; i < inactive - 1; i++) {
if (fill_rule == CAIRO_FILL_RULE_WINDING) {
if (edges[i].clockWise)
in_out++;
else
in_out--;
if (in_out == 0)
continue;
} else {
in_out++;
if ((in_out & 1) == 0)
continue;
}
status = _cairo_traps_add_trap (traps, y, y_next, &edges[i].edge, &edges[i+1].edge);
if (status)
return status;
}
/* delete inactive edges */
for (i = active; i < inactive; i++) {
if (edges[i].edge.p2.y <= y_next) {
memmove (&edges[active+1], &edges[active], (i - active) * sizeof (cairo_edge_t));
active++;
}
}
y = y_next;
}
return CAIRO_STATUS_SUCCESS;
}
cairo_status_t
_cairo_traps_tessellate_convex_quad (cairo_traps_t *traps,
const cairo_point_t q[4])
{
int a, b, c, d;
int i;
cairo_slope_t ab, ad;
cairo_bool_t b_left_of_d;
cairo_line_t left;
cairo_line_t right;
/* Choose a as a point with minimal y */
a = 0;
for (i = 1; i < 4; i++)
if (_compare_point_fixed_by_y (&q[i], &q[a]) < 0)
a = i;
/* b and d are adjacent to a, while c is opposite */
b = (a + 1) % 4;
c = (a + 2) % 4;
d = (a + 3) % 4;
/* Choose between b and d so that b.y is less than d.y */
if (_compare_point_fixed_by_y (&q[d], &q[b]) < 0) {
b = (a + 3) % 4;
d = (a + 1) % 4;
}
/* Without freedom left to choose anything else, we have four
* cases to tessellate.
*
* First, we have to determine the Y-axis sort of the four
* vertices, (either abcd or abdc). After that we need to detemine
* which edges will be "left" and which will be "right" in the
* resulting trapezoids. This can be determined by computing a
* slope comparison of ab and ad to determine if b is left of d or
* not.
*
* Note that "left of" here is in the sense of which edges should
* be the left vs. right edges of the trapezoid. In particular, b
* left of d does *not* mean that b.x is less than d.x.
*
* This should hopefully be made clear in the lame ASCII art
* below. Since the same slope comparison is used in all cases, we
* compute it before testing for the Y-value sort. */
/* Note: If a == b then the ab slope doesn't give us any
* information. In that case, we can replace it with the ac (or
* equivalenly the bc) slope which gives us exactly the same
* information we need. At worst the names of the identifiers ab
* and b_left_of_d are inaccurate in this case, (would be ac, and
* c_left_of_d). */
if (q[a].x == q[b].x && q[a].y == q[b].y)
_cairo_slope_init (&ab, &q[a], &q[c]);
else
_cairo_slope_init (&ab, &q[a], &q[b]);
_cairo_slope_init (&ad, &q[a], &q[d]);
b_left_of_d = (_cairo_slope_compare (&ab, &ad) > 0);
if (q[c].y <= q[d].y) {
if (b_left_of_d) {
/* Y-sort is abcd and b is left of d, (slope(ab) > slope (ad))
*
* top bot left right
* _a a a
* / / /| |\ a.y b.y ab ad
* b / b | b \
* / / | | \ \ b.y c.y bc ad
* c / c | c \
* | / \| \ \ c.y d.y cd ad
* d d d
*/
left.p1 = q[a]; left.p2 = q[b];
right.p1 = q[a]; right.p2 = q[d];
_cairo_traps_add_trap (traps, q[a].y, q[b].y, &left, &right);
left.p1 = q[b]; left.p2 = q[c];
_cairo_traps_add_trap (traps, q[b].y, q[c].y, &left, &right);
left.p1 = q[c]; left.p2 = q[d];
_cairo_traps_add_trap (traps, q[c].y, q[d].y, &left, &right);
} else {
/* Y-sort is abcd and b is right of d, (slope(ab) <= slope (ad))
*
* a a a_
* /| |\ \ \ a.y b.y ad ab
* / b | b \ b
* / / | | \ \ b.y c.y ad bc
* / c | c \ c
* / / |/ \ | c.y d.y ad cd
* d d d
*/
left.p1 = q[a]; left.p2 = q[d];
right.p1 = q[a]; right.p2 = q[b];
_cairo_traps_add_trap (traps, q[a].y, q[b].y, &left, &right);
right.p1 = q[b]; right.p2 = q[c];
_cairo_traps_add_trap (traps, q[b].y, q[c].y, &left, &right);
right.p1 = q[c]; right.p2 = q[d];
_cairo_traps_add_trap (traps, q[c].y, q[d].y, &left, &right);
}
} else {
if (b_left_of_d) {
/* Y-sort is abdc and b is left of d, (slope (ab) > slope (ad))
*
* a a a
* // / \ |\ a.y b.y ab ad
* /b/ b \ b \
* / / \ \ \ \ b.y d.y bc ad
* /d/ \ d \ d
* // \ / \| d.y c.y bc dc
* c c c
*/
left.p1 = q[a]; left.p2 = q[b];
right.p1 = q[a]; right.p2 = q[d];
_cairo_traps_add_trap (traps, q[a].y, q[b].y, &left, &right);
left.p1 = q[b]; left.p2 = q[c];
_cairo_traps_add_trap (traps, q[b].y, q[d].y, &left, &right);
right.p1 = q[d]; right.p2 = q[c];
_cairo_traps_add_trap (traps, q[d].y, q[c].y, &left, &right);
} else {
/* Y-sort is abdc and b is right of d, (slope (ab) <= slope (ad))
*
* a a a
* /| / \ \\ a.y b.y ad ab
* / b / b \b\
* / / / / \ \ b.y d.y ad bc
* d / d / \d\
* |/ \ / \\ d.y c.y dc bc
* c c c
*/
left.p1 = q[a]; left.p2 = q[d];
right.p1 = q[a]; right.p2 = q[b];
_cairo_traps_add_trap (traps, q[a].y, q[b].y, &left, &right);
right.p1 = q[b]; right.p2 = q[c];
_cairo_traps_add_trap (traps, q[b].y, q[d].y, &left, &right);
left.p1 = q[d]; left.p2 = q[c];
_cairo_traps_add_trap (traps, q[d].y, q[c].y, &left, &right);
}
}
return traps->status;
}
