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Copy pathcairo-botor-scan-converter.c
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cairo-botor-scan-converter.c
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/*
* Copyright © 2004 Carl Worth
* Copyright © 2006 Red Hat, Inc.
* Copyright © 2007 David Turner
* Copyright © 2008 M Joonas Pihlaja
* Copyright © 2008 Chris Wilson
* Copyright © 2009 Intel Corporation
*
* This library is free software; you can redistribute it and/or
* modify it either under the terms of the GNU Lesser General Public
* License version 2.1 as published by the Free Software Foundation
* (the "LGPL") or, at your option, under the terms of the Mozilla
* Public License Version 1.1 (the "MPL"). If you do not alter this
* notice, a recipient may use your version of this file under either
* the MPL or the LGPL.
*
* You should have received a copy of the LGPL along with this library
* in the file COPYING-LGPL-2.1; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA
* You should have received a copy of the MPL along with this library
* in the file COPYING-MPL-1.1
*
* The contents of this file are subject to the Mozilla Public License
* Version 1.1 (the "License"); you may not use this file except in
* compliance with the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
* OF ANY KIND, either express or implied. See the LGPL or the MPL for
* the specific language governing rights and limitations.
*
* The Original Code is the cairo graphics library.
*
* The Initial Developer of the Original Code is Carl Worth
*
* Contributor(s):
* Carl D. Worth <[email protected]>
* M Joonas Pihlaja <[email protected]>
* Chris Wilson <[email protected]>
*/
/* Provide definitions for standalone compilation */
#include "cairoint.h"
#include "cairo-error-private.h"
#include "cairo-list-inline.h"
#include "cairo-freelist-private.h"
#include "cairo-combsort-inline.h"
#include <setjmp.h>
#define STEP_X CAIRO_FIXED_ONE
#define STEP_Y CAIRO_FIXED_ONE
#define UNROLL3(x) x x x
#define STEP_XY (2*STEP_X*STEP_Y) /* Unit area in the step. */
#define AREA_TO_ALPHA(c) (((c)*255 + STEP_XY/2) / STEP_XY)
typedef struct _cairo_bo_intersect_ordinate {
int32_t ordinate;
enum { EXACT, INEXACT } exactness;
} cairo_bo_intersect_ordinate_t;
typedef struct _cairo_bo_intersect_point {
cairo_bo_intersect_ordinate_t x;
cairo_bo_intersect_ordinate_t y;
} cairo_bo_intersect_point_t;
struct quorem {
cairo_fixed_t quo;
cairo_fixed_t rem;
};
struct run {
struct run *next;
int sign;
cairo_fixed_t y;
};
typedef struct edge {
cairo_list_t link;
cairo_edge_t edge;
/* Current x coordinate and advancement.
* Initialised to the x coordinate of the top of the
* edge. The quotient is in cairo_fixed_t units and the
* remainder is mod dy in cairo_fixed_t units.
*/
cairo_fixed_t dy;
struct quorem x;
struct quorem dxdy;
struct quorem dxdy_full;
cairo_bool_t vertical;
unsigned int flags;
int current_sign;
struct run *runs;
} edge_t;
enum {
START = 0x1,
STOP = 0x2,
};
/* the parent is always given by index/2 */
#define PQ_PARENT_INDEX(i) ((i) >> 1)
#define PQ_FIRST_ENTRY 1
/* left and right children are index * 2 and (index * 2) +1 respectively */
#define PQ_LEFT_CHILD_INDEX(i) ((i) << 1)
typedef enum {
EVENT_TYPE_STOP,
EVENT_TYPE_INTERSECTION,
EVENT_TYPE_START
} event_type_t;
typedef struct _event {
cairo_fixed_t y;
event_type_t type;
} event_t;
typedef struct _start_event {
cairo_fixed_t y;
event_type_t type;
edge_t *edge;
} start_event_t;
typedef struct _queue_event {
cairo_fixed_t y;
event_type_t type;
edge_t *e1;
edge_t *e2;
} queue_event_t;
typedef struct _pqueue {
int size, max_size;
event_t **elements;
event_t *elements_embedded[1024];
} pqueue_t;
struct cell {
struct cell *prev;
struct cell *next;
int x;
int uncovered_area;
int covered_height;
};
typedef struct _sweep_line {
cairo_list_t active;
cairo_list_t stopped;
cairo_list_t *insert_cursor;
cairo_bool_t is_vertical;
cairo_fixed_t current_row;
cairo_fixed_t current_subrow;
struct coverage {
struct cell head;
struct cell tail;
struct cell *cursor;
int count;
cairo_freepool_t pool;
} coverage;
struct event_queue {
pqueue_t pq;
event_t **start_events;
cairo_freepool_t pool;
} queue;
cairo_freepool_t runs;
jmp_buf unwind;
} sweep_line_t;
cairo_always_inline static struct quorem
floored_divrem (int a, int b)
{
struct quorem qr;
qr.quo = a/b;
qr.rem = a%b;
if ((a^b)<0 && qr.rem) {
qr.quo--;
qr.rem += b;
}
return qr;
}
static struct quorem
floored_muldivrem(int x, int a, int b)
{
struct quorem qr;
long long xa = (long long)x*a;
qr.quo = xa/b;
qr.rem = xa%b;
if ((xa>=0) != (b>=0) && qr.rem) {
qr.quo--;
qr.rem += b;
}
return qr;
}
static cairo_fixed_t
line_compute_intersection_x_for_y (const cairo_line_t *line,
cairo_fixed_t y)
{
cairo_fixed_t x, dy;
if (y == line->p1.y)
return line->p1.x;
if (y == line->p2.y)
return line->p2.x;
x = line->p1.x;
dy = line->p2.y - line->p1.y;
if (dy != 0) {
x += _cairo_fixed_mul_div_floor (y - line->p1.y,
line->p2.x - line->p1.x,
dy);
}
return x;
}
/*
* We need to compare the x-coordinates of a pair of lines for a particular y,
* without loss of precision.
*
* The x-coordinate along an edge for a given y is:
* X = A_x + (Y - A_y) * A_dx / A_dy
*
* So the inequality we wish to test is:
* A_x + (Y - A_y) * A_dx / A_dy ∘ B_x + (Y - B_y) * B_dx / B_dy,
* where ∘ is our inequality operator.
*
* By construction, we know that A_dy and B_dy (and (Y - A_y), (Y - B_y)) are
* all positive, so we can rearrange it thus without causing a sign change:
* A_dy * B_dy * (A_x - B_x) ∘ (Y - B_y) * B_dx * A_dy
* - (Y - A_y) * A_dx * B_dy
*
* Given the assumption that all the deltas fit within 32 bits, we can compute
* this comparison directly using 128 bit arithmetic. For certain, but common,
* input we can reduce this down to a single 32 bit compare by inspecting the
* deltas.
*
* (And put the burden of the work on developing fast 128 bit ops, which are
* required throughout the tessellator.)
*
* See the similar discussion for _slope_compare().
*/
static int
edges_compare_x_for_y_general (const cairo_edge_t *a,
const cairo_edge_t *b,
int32_t y)
{
/* XXX: We're assuming here that dx and dy will still fit in 32
* bits. That's not true in general as there could be overflow. We
* should prevent that before the tessellation algorithm
* begins.
*/
int32_t dx;
int32_t adx, ady;
int32_t bdx, bdy;
enum {
HAVE_NONE = 0x0,
HAVE_DX = 0x1,
HAVE_ADX = 0x2,
HAVE_DX_ADX = HAVE_DX | HAVE_ADX,
HAVE_BDX = 0x4,
HAVE_DX_BDX = HAVE_DX | HAVE_BDX,
HAVE_ADX_BDX = HAVE_ADX | HAVE_BDX,
HAVE_ALL = HAVE_DX | HAVE_ADX | HAVE_BDX
} have_dx_adx_bdx = HAVE_ALL;
/* don't bother solving for abscissa if the edges' bounding boxes
* can be used to order them. */
{
int32_t amin, amax;
int32_t bmin, bmax;
if (a->line.p1.x < a->line.p2.x) {
amin = a->line.p1.x;
amax = a->line.p2.x;
} else {
amin = a->line.p2.x;
amax = a->line.p1.x;
}
if (b->line.p1.x < b->line.p2.x) {
bmin = b->line.p1.x;
bmax = b->line.p2.x;
} else {
bmin = b->line.p2.x;
bmax = b->line.p1.x;
}
if (amax < bmin) return -1;
if (amin > bmax) return +1;
}
ady = a->line.p2.y - a->line.p1.y;
adx = a->line.p2.x - a->line.p1.x;
if (adx == 0)
have_dx_adx_bdx &= ~HAVE_ADX;
bdy = b->line.p2.y - b->line.p1.y;
bdx = b->line.p2.x - b->line.p1.x;
if (bdx == 0)
have_dx_adx_bdx &= ~HAVE_BDX;
dx = a->line.p1.x - b->line.p1.x;
if (dx == 0)
have_dx_adx_bdx &= ~HAVE_DX;
#define L _cairo_int64x32_128_mul (_cairo_int32x32_64_mul (ady, bdy), dx)
#define A _cairo_int64x32_128_mul (_cairo_int32x32_64_mul (adx, bdy), y - a->line.p1.y)
#define B _cairo_int64x32_128_mul (_cairo_int32x32_64_mul (bdx, ady), y - b->line.p1.y)
switch (have_dx_adx_bdx) {
default:
case HAVE_NONE:
return 0;
case HAVE_DX:
/* A_dy * B_dy * (A_x - B_x) ∘ 0 */
return dx; /* ady * bdy is positive definite */
case HAVE_ADX:
/* 0 ∘ - (Y - A_y) * A_dx * B_dy */
return adx; /* bdy * (y - a->top.y) is positive definite */
case HAVE_BDX:
/* 0 ∘ (Y - B_y) * B_dx * A_dy */
return -bdx; /* ady * (y - b->top.y) is positive definite */
case HAVE_ADX_BDX:
/* 0 ∘ (Y - B_y) * B_dx * A_dy - (Y - A_y) * A_dx * B_dy */
if ((adx ^ bdx) < 0) {
return adx;
} else if (a->line.p1.y == b->line.p1.y) { /* common origin */
cairo_int64_t adx_bdy, bdx_ady;
/* ∴ A_dx * B_dy ∘ B_dx * A_dy */
adx_bdy = _cairo_int32x32_64_mul (adx, bdy);
bdx_ady = _cairo_int32x32_64_mul (bdx, ady);
return _cairo_int64_cmp (adx_bdy, bdx_ady);
} else
return _cairo_int128_cmp (A, B);
case HAVE_DX_ADX:
/* A_dy * (A_x - B_x) ∘ - (Y - A_y) * A_dx */
if ((-adx ^ dx) < 0) {
return dx;
} else {
cairo_int64_t ady_dx, dy_adx;
ady_dx = _cairo_int32x32_64_mul (ady, dx);
dy_adx = _cairo_int32x32_64_mul (a->line.p1.y - y, adx);
return _cairo_int64_cmp (ady_dx, dy_adx);
}
case HAVE_DX_BDX:
/* B_dy * (A_x - B_x) ∘ (Y - B_y) * B_dx */
if ((bdx ^ dx) < 0) {
return dx;
} else {
cairo_int64_t bdy_dx, dy_bdx;
bdy_dx = _cairo_int32x32_64_mul (bdy, dx);
dy_bdx = _cairo_int32x32_64_mul (y - b->line.p1.y, bdx);
return _cairo_int64_cmp (bdy_dx, dy_bdx);
}
case HAVE_ALL:
/* XXX try comparing (a->line.p2.x - b->line.p2.x) et al */
return _cairo_int128_cmp (L, _cairo_int128_sub (B, A));
}
#undef B
#undef A
#undef L
}
/*
* We need to compare the x-coordinate of a line for a particular y wrt to a
* given x, without loss of precision.
*
* The x-coordinate along an edge for a given y is:
* X = A_x + (Y - A_y) * A_dx / A_dy
*
* So the inequality we wish to test is:
* A_x + (Y - A_y) * A_dx / A_dy ∘ X
* where ∘ is our inequality operator.
*
* By construction, we know that A_dy (and (Y - A_y)) are
* all positive, so we can rearrange it thus without causing a sign change:
* (Y - A_y) * A_dx ∘ (X - A_x) * A_dy
*
* Given the assumption that all the deltas fit within 32 bits, we can compute
* this comparison directly using 64 bit arithmetic.
*
* See the similar discussion for _slope_compare() and
* edges_compare_x_for_y_general().
*/
static int
edge_compare_for_y_against_x (const cairo_edge_t *a,
int32_t y,
int32_t x)
{
int32_t adx, ady;
int32_t dx, dy;
cairo_int64_t L, R;
if (a->line.p1.x <= a->line.p2.x) {
if (x < a->line.p1.x)
return 1;
if (x > a->line.p2.x)
return -1;
} else {
if (x < a->line.p2.x)
return 1;
if (x > a->line.p1.x)
return -1;
}
adx = a->line.p2.x - a->line.p1.x;
dx = x - a->line.p1.x;
if (adx == 0)
return -dx;
if (dx == 0 || (adx ^ dx) < 0)
return adx;
dy = y - a->line.p1.y;
ady = a->line.p2.y - a->line.p1.y;
L = _cairo_int32x32_64_mul (dy, adx);
R = _cairo_int32x32_64_mul (dx, ady);
return _cairo_int64_cmp (L, R);
}
static int
edges_compare_x_for_y (const cairo_edge_t *a,
const cairo_edge_t *b,
int32_t y)
{
/* If the sweep-line is currently on an end-point of a line,
* then we know its precise x value (and considering that we often need to
* compare events at end-points, this happens frequently enough to warrant
* special casing).
*/
enum {
HAVE_NEITHER = 0x0,
HAVE_AX = 0x1,
HAVE_BX = 0x2,
HAVE_BOTH = HAVE_AX | HAVE_BX
} have_ax_bx = HAVE_BOTH;
int32_t ax, bx;
/* XXX given we have x and dx? */
if (y == a->line.p1.y)
ax = a->line.p1.x;
else if (y == a->line.p2.y)
ax = a->line.p2.x;
else
have_ax_bx &= ~HAVE_AX;
if (y == b->line.p1.y)
bx = b->line.p1.x;
else if (y == b->line.p2.y)
bx = b->line.p2.x;
else
have_ax_bx &= ~HAVE_BX;
switch (have_ax_bx) {
default:
case HAVE_NEITHER:
return edges_compare_x_for_y_general (a, b, y);
case HAVE_AX:
return -edge_compare_for_y_against_x (b, y, ax);
case HAVE_BX:
return edge_compare_for_y_against_x (a, y, bx);
case HAVE_BOTH:
return ax - bx;
}
}
static inline int
slope_compare (const edge_t *a,
const edge_t *b)
{
cairo_int64_t L, R;
int cmp;
cmp = a->dxdy.quo - b->dxdy.quo;
if (cmp)
return cmp;
if (a->dxdy.rem == 0)
return -b->dxdy.rem;
if (b->dxdy.rem == 0)
return a->dxdy.rem;
L = _cairo_int32x32_64_mul (b->dy, a->dxdy.rem);
R = _cairo_int32x32_64_mul (a->dy, b->dxdy.rem);
return _cairo_int64_cmp (L, R);
}
static inline int
line_equal (const cairo_line_t *a, const cairo_line_t *b)
{
return a->p1.x == b->p1.x && a->p1.y == b->p1.y &&
a->p2.x == b->p2.x && a->p2.y == b->p2.y;
}
static inline int
sweep_line_compare_edges (const edge_t *a,
const edge_t *b,
cairo_fixed_t y)
{
int cmp;
if (line_equal (&a->edge.line, &b->edge.line))
return 0;
cmp = edges_compare_x_for_y (&a->edge, &b->edge, y);
if (cmp)
return cmp;
return slope_compare (a, b);
}
static inline cairo_int64_t
det32_64 (int32_t a, int32_t b,
int32_t c, int32_t d)
{
/* det = a * d - b * c */
return _cairo_int64_sub (_cairo_int32x32_64_mul (a, d),
_cairo_int32x32_64_mul (b, c));
}
static inline cairo_int128_t
det64x32_128 (cairo_int64_t a, int32_t b,
cairo_int64_t c, int32_t d)
{
/* det = a * d - b * c */
return _cairo_int128_sub (_cairo_int64x32_128_mul (a, d),
_cairo_int64x32_128_mul (c, b));
}
/* Compute the intersection of two lines as defined by two edges. The
* result is provided as a coordinate pair of 128-bit integers.
*
* Returns %CAIRO_BO_STATUS_INTERSECTION if there is an intersection or
* %CAIRO_BO_STATUS_PARALLEL if the two lines are exactly parallel.
*/
static cairo_bool_t
intersect_lines (const edge_t *a, const edge_t *b,
cairo_bo_intersect_point_t *intersection)
{
cairo_int64_t a_det, b_det;
/* XXX: We're assuming here that dx and dy will still fit in 32
* bits. That's not true in general as there could be overflow. We
* should prevent that before the tessellation algorithm begins.
* What we're doing to mitigate this is to perform clamping in
* cairo_bo_tessellate_polygon().
*/
int32_t dx1 = a->edge.line.p1.x - a->edge.line.p2.x;
int32_t dy1 = a->edge.line.p1.y - a->edge.line.p2.y;
int32_t dx2 = b->edge.line.p1.x - b->edge.line.p2.x;
int32_t dy2 = b->edge.line.p1.y - b->edge.line.p2.y;
cairo_int64_t den_det;
cairo_int64_t R;
cairo_quorem64_t qr;
den_det = det32_64 (dx1, dy1, dx2, dy2);
/* Q: Can we determine that the lines do not intersect (within range)
* much more cheaply than computing the intersection point i.e. by
* avoiding the division?
*
* X = ax + t * adx = bx + s * bdx;
* Y = ay + t * ady = by + s * bdy;
* ∴ t * (ady*bdx - bdy*adx) = bdx * (by - ay) + bdy * (ax - bx)
* => t * L = R
*
* Therefore we can reject any intersection (under the criteria for
* valid intersection events) if:
* L^R < 0 => t < 0, or
* L<R => t > 1
*
* (where top/bottom must at least extend to the line endpoints).
*
* A similar substitution can be performed for s, yielding:
* s * (ady*bdx - bdy*adx) = ady * (ax - bx) - adx * (ay - by)
*/
R = det32_64 (dx2, dy2,
b->edge.line.p1.x - a->edge.line.p1.x,
b->edge.line.p1.y - a->edge.line.p1.y);
if (_cairo_int64_negative (den_det)) {
if (_cairo_int64_ge (den_det, R))
return FALSE;
} else {
if (_cairo_int64_le (den_det, R))
return FALSE;
}
R = det32_64 (dy1, dx1,
a->edge.line.p1.y - b->edge.line.p1.y,
a->edge.line.p1.x - b->edge.line.p1.x);
if (_cairo_int64_negative (den_det)) {
if (_cairo_int64_ge (den_det, R))
return FALSE;
} else {
if (_cairo_int64_le (den_det, R))
return FALSE;
}
/* We now know that the two lines should intersect within range. */
a_det = det32_64 (a->edge.line.p1.x, a->edge.line.p1.y,
a->edge.line.p2.x, a->edge.line.p2.y);
b_det = det32_64 (b->edge.line.p1.x, b->edge.line.p1.y,
b->edge.line.p2.x, b->edge.line.p2.y);
/* x = det (a_det, dx1, b_det, dx2) / den_det */
qr = _cairo_int_96by64_32x64_divrem (det64x32_128 (a_det, dx1,
b_det, dx2),
den_det);
if (_cairo_int64_eq (qr.rem, den_det))
return FALSE;
#if 0
intersection->x.exactness = _cairo_int64_is_zero (qr.rem) ? EXACT : INEXACT;
#else
intersection->x.exactness = EXACT;
if (! _cairo_int64_is_zero (qr.rem)) {
if (_cairo_int64_negative (den_det) ^ _cairo_int64_negative (qr.rem))
qr.rem = _cairo_int64_negate (qr.rem);
qr.rem = _cairo_int64_mul (qr.rem, _cairo_int32_to_int64 (2));
if (_cairo_int64_ge (qr.rem, den_det)) {
qr.quo = _cairo_int64_add (qr.quo,
_cairo_int32_to_int64 (_cairo_int64_negative (qr.quo) ? -1 : 1));
} else
intersection->x.exactness = INEXACT;
}
#endif
intersection->x.ordinate = _cairo_int64_to_int32 (qr.quo);
/* y = det (a_det, dy1, b_det, dy2) / den_det */
qr = _cairo_int_96by64_32x64_divrem (det64x32_128 (a_det, dy1,
b_det, dy2),
den_det);
if (_cairo_int64_eq (qr.rem, den_det))
return FALSE;
#if 0
intersection->y.exactness = _cairo_int64_is_zero (qr.rem) ? EXACT : INEXACT;
#else
intersection->y.exactness = EXACT;
if (! _cairo_int64_is_zero (qr.rem)) {
/* compute ceiling away from zero */
qr.quo = _cairo_int64_add (qr.quo,
_cairo_int32_to_int64 (_cairo_int64_negative (qr.quo) ? -1 : 1));
intersection->y.exactness = INEXACT;
}
#endif
intersection->y.ordinate = _cairo_int64_to_int32 (qr.quo);
return TRUE;
}
static int
bo_intersect_ordinate_32_compare (int32_t a, int32_t b, int exactness)
{
int cmp;
/* First compare the quotient */
cmp = a - b;
if (cmp)
return cmp;
/* With quotient identical, if remainder is 0 then compare equal */
/* Otherwise, the non-zero remainder makes a > b */
return -(INEXACT == exactness);
}
/* 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
bo_edge_contains_intersect_point (const 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 = bo_intersect_ordinate_32_compare (point->y.ordinate,
edge->edge.top,
point->y.exactness);
if (cmp_top < 0)
return FALSE;
cmp_bottom = bo_intersect_ordinate_32_compare (point->y.ordinate,
edge->edge.bottom,
point->y.exactness);
if (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 bo_intersect_ordinate_32_compare (top_x, point->x.ordinate, point->x.exactness) < 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 bo_intersect_ordinate_32_compare (point->x.ordinate, bot_x, point->x.exactness) < 0;
}
}
static cairo_bool_t
edge_intersect (const edge_t *a,
const edge_t *b,
cairo_point_t *intersection)
{
cairo_bo_intersect_point_t quorem;
if (! intersect_lines (a, b, &quorem))
return FALSE;
if (a->edge.top != a->edge.line.p1.y || a->edge.bottom != a->edge.line.p2.y) {
if (! bo_edge_contains_intersect_point (a, &quorem))
return FALSE;
}
if (b->edge.top != b->edge.line.p1.y || b->edge.bottom != b->edge.line.p2.y) {
if (! bo_edge_contains_intersect_point (b, &quorem))
return FALSE;
}
/* Now that we've correctly compared the intersection point and
* determined that it lies within the edge, then we know that we
* no longer need any more bits of storage for the intersection
* than we do for our edge coordinates. We also no longer need the
* remainder from the division. */
intersection->x = quorem.x.ordinate;
intersection->y = quorem.y.ordinate;
return TRUE;
}
static inline int
event_compare (const event_t *a, const event_t *b)
{
return a->y - b->y;
}
static void
pqueue_init (pqueue_t *pq)
{
pq->max_size = ARRAY_LENGTH (pq->elements_embedded);
pq->size = 0;
pq->elements = pq->elements_embedded;
}
static void
pqueue_fini (pqueue_t *pq)
{
if (pq->elements != pq->elements_embedded)
free (pq->elements);
}
static cairo_bool_t
pqueue_grow (pqueue_t *pq)
{
event_t **new_elements;
pq->max_size *= 2;
if (pq->elements == pq->elements_embedded) {
new_elements = _cairo_malloc_ab (pq->max_size,
sizeof (event_t *));
if (unlikely (new_elements == NULL))
return FALSE;
memcpy (new_elements, pq->elements_embedded,
sizeof (pq->elements_embedded));
} else {
new_elements = _cairo_realloc_ab (pq->elements,
pq->max_size,
sizeof (event_t *));
if (unlikely (new_elements == NULL))
return FALSE;
}
pq->elements = new_elements;
return TRUE;
}
static inline void
pqueue_push (sweep_line_t *sweep_line, event_t *event)
{
event_t **elements;
int i, parent;
if (unlikely (sweep_line->queue.pq.size + 1 == sweep_line->queue.pq.max_size)) {
if (unlikely (! pqueue_grow (&sweep_line->queue.pq))) {
longjmp (sweep_line->unwind,
_cairo_error (CAIRO_STATUS_NO_MEMORY));
}
}
elements = sweep_line->queue.pq.elements;
for (i = ++sweep_line->queue.pq.size;
i != PQ_FIRST_ENTRY &&
event_compare (event,
elements[parent = PQ_PARENT_INDEX (i)]) < 0;
i = parent)
{
elements[i] = elements[parent];
}
elements[i] = event;
}
static inline void
pqueue_pop (pqueue_t *pq)
{
event_t **elements = pq->elements;
event_t *tail;
int child, i;
tail = elements[pq->size--];
if (pq->size == 0) {
elements[PQ_FIRST_ENTRY] = NULL;
return;
}
for (i = PQ_FIRST_ENTRY;
(child = PQ_LEFT_CHILD_INDEX (i)) <= pq->size;
i = child)
{
if (child != pq->size &&
event_compare (elements[child+1],
elements[child]) < 0)
{
child++;
}
if (event_compare (elements[child], tail) >= 0)
break;
elements[i] = elements[child];
}
elements[i] = tail;
}
static inline void
event_insert (sweep_line_t *sweep_line,
event_type_t type,
edge_t *e1,
edge_t *e2,
cairo_fixed_t y)
{
queue_event_t *event;
event = _cairo_freepool_alloc (&sweep_line->queue.pool);
if (unlikely (event == NULL)) {
longjmp (sweep_line->unwind,
_cairo_error (CAIRO_STATUS_NO_MEMORY));
}
event->y = y;
event->type = type;
event->e1 = e1;
event->e2 = e2;
pqueue_push (sweep_line, (event_t *) event);
}
static void
event_delete (sweep_line_t *sweep_line,
event_t *event)
{
_cairo_freepool_free (&sweep_line->queue.pool, event);
}
static inline event_t *
event_next (sweep_line_t *sweep_line)
{
event_t *event, *cmp;
event = sweep_line->queue.pq.elements[PQ_FIRST_ENTRY];
cmp = *sweep_line->queue.start_events;
if (event == NULL ||
(cmp != NULL && event_compare (cmp, event) < 0))
{
event = cmp;
sweep_line->queue.start_events++;
}
else
{
pqueue_pop (&sweep_line->queue.pq);
}
return event;
}
CAIRO_COMBSORT_DECLARE (start_event_sort, event_t *, event_compare)
static inline void
event_insert_stop (sweep_line_t *sweep_line,
edge_t *edge)
{
event_insert (sweep_line,
EVENT_TYPE_STOP,
edge, NULL,
edge->edge.bottom);
}
static inline void
event_insert_if_intersect_below_current_y (sweep_line_t *sweep_line,
edge_t *left,
edge_t *right)
{
cairo_point_t intersection;
/* start points intersect */
if (left->edge.line.p1.x == right->edge.line.p1.x &&
left->edge.line.p1.y == right->edge.line.p1.y)
{
return;
}
/* end points intersect, process DELETE events first */
if (left->edge.line.p2.x == right->edge.line.p2.x &&
left->edge.line.p2.y == right->edge.line.p2.y)
{
return;
}
if (slope_compare (left, right) <= 0)
return;
if (! edge_intersect (left, right, &intersection))
return;
event_insert (sweep_line,
EVENT_TYPE_INTERSECTION,
left, right,
intersection.y);
}
static inline edge_t *
link_to_edge (cairo_list_t *link)
{
return (edge_t *) link;
}