static cairo_int_status_t
_draw_trap (cairo_gl_context_t *ctx,
cairo_gl_composite_t *setup,
cairo_trapezoid_t *trap)
{
cairo_point_t quad[4];
quad[0].x = _cairo_edge_compute_intersection_x_for_y (&trap->left.p1,
&trap->left.p2,
trap->top);
quad[0].y = trap->top;
quad[1].x = _cairo_edge_compute_intersection_x_for_y (&trap->left.p1,
&trap->left.p2,
trap->bottom);
quad[1].y = trap->bottom;
quad[2].x = _cairo_edge_compute_intersection_x_for_y (&trap->right.p1,
&trap->right.p2,
trap->bottom);
quad[2].y = trap->bottom;
quad[3].x = _cairo_edge_compute_intersection_x_for_y (&trap->right.p1,
&trap->right.p2,
trap->top);
quad[3].y = trap->top;
return _cairo_gl_composite_emit_quad_as_tristrip (ctx, setup, quad);
}
static void
assert_last_edge_is_valid(cairo_polygon_t *polygon,
const cairo_box_t *limit)
{
cairo_edge_t *edge;
cairo_fixed_t x;
edge = &polygon->edges[polygon->num_edges-1];
XASSERT (edge->bottom > edge->top);
XASSERT (edge->top >= limit->p1.y);
XASSERT (edge->bottom <= limit->p2.y);
x = _cairo_edge_compute_intersection_x_for_y (&edge->line.p1,
&edge->line.p2,
edge->top);
XASSERT (x >= limit->p1.x);
XASSERT (x <= limit->p2.x);
x = _cairo_edge_compute_intersection_x_for_y (&edge->line.p1,
&edge->line.p2,
edge->bottom);
XASSERT (x >= limit->p1.x);
XASSERT (x <= limit->p2.x);
}
static void
_add_edge (cairo_polygon_t *polygon,
const cairo_point_t *p1,
const cairo_point_t *p2,
int top, int bottom,
int dir)
{
cairo_edge_t *edge;
XASSERT (top < bottom);
if (unlikely (polygon->num_edges == polygon->edges_size)) {
if (! _cairo_polygon_grow (polygon))
return;
}
edge = &polygon->edges[polygon->num_edges++];
edge->line.p1 = *p1;
edge->line.p2 = *p2;
edge->top = top;
edge->bottom = bottom;
edge->dir = dir;
if (top < polygon->extents.p1.y)
polygon->extents.p1.y = top;
if (bottom > polygon->extents.p2.y)
polygon->extents.p2.y = bottom;
if (p1->x < polygon->extents.p1.x || p1->x > polygon->extents.p2.x) {
cairo_fixed_t x = p1->x;
if (top != p1->y)
x = _cairo_edge_compute_intersection_x_for_y (p1, p2, top);
if (x < polygon->extents.p1.x)
polygon->extents.p1.x = x;
if (x > polygon->extents.p2.x)
polygon->extents.p2.x = x;
}
if (p2->x < polygon->extents.p1.x || p2->x > polygon->extents.p2.x) {
cairo_fixed_t x = p2->x;
if (bottom != p2->y)
x = _cairo_edge_compute_intersection_x_for_y (p1, p2, bottom);
if (x < polygon->extents.p1.x)
polygon->extents.p1.x = x;
if (x > polygon->extents.p2.x)
polygon->extents.p2.x = x;
}
}
static void
_add_clipped_edge (struct reduce *r,
const cairo_point_t *p1,
const cairo_point_t *p2,
int y1, int y2)
{
cairo_fixed_t x;
x = _cairo_edge_compute_intersection_x_for_y (p1, p2, y1);
if (x < r->extents.p1.x)
r->extents.p1.x = x;
x = _cairo_edge_compute_intersection_x_for_y (p1, p2, y2);
if (x > r->extents.p2.x)
r->extents.p2.x = x;
if (y1 < r->extents.p1.y)
r->extents.p1.y = y1;
if (y2 > r->extents.p2.y)
r->extents.p2.y = y2;
r->inside = TRUE;
}
static cairo_fixed_t
_line_compute_intersection_x_for_y (const cairo_line_t *line,
cairo_fixed_t y)
{
return _cairo_edge_compute_intersection_x_for_y (&line->p1, &line->p2, 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);
}
}
}
}
