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/* -*- Mode: c; tab-width: 8; c-basic-offset: 4; indent-tabs-mode: t; -*- */
/* cairo - a vector graphics library with display and print output
*
* Copyright © 2002 University of Southern California
* 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 University of Southern
* California.
* Contributor(s):
* Carl D. Worth <cworth@cworth.org>
* Chris Wilson <chris@chris-wilson.co.uk>
*/
#define _DEFAULT_SOURCE /* for hypot() */
#include "cairoint.h"
#include "cairo-box-inline.h"
#include "cairo-boxes-private.h"
#include "cairo-error-private.h"
#include "cairo-path-fixed-private.h"
#include "cairo-slope-private.h"
#include "cairo-stroke-dash-private.h"
typedef struct _segment_t {
cairo_point_t p1, p2;
unsigned flags;
#define HORIZONTAL 0x1
#define FORWARDS 0x2
#define JOIN 0x4
} segment_t;
typedef struct _cairo_rectilinear_stroker {
const cairo_stroke_style_t *stroke_style;
const cairo_matrix_t *ctm;
cairo_antialias_t antialias;
cairo_fixed_t half_line_x, half_line_y;
cairo_boxes_t *boxes;
cairo_point_t current_point;
cairo_point_t first_point;
cairo_bool_t open_sub_path;
cairo_stroker_dash_t dash;
cairo_bool_t has_bounds;
cairo_box_t bounds;
int num_segments;
int segments_size;
segment_t *segments;
segment_t segments_embedded[8]; /* common case is a single rectangle */
} cairo_rectilinear_stroker_t;
static void
_cairo_rectilinear_stroker_limit (cairo_rectilinear_stroker_t *stroker,
const cairo_box_t *boxes,
int num_boxes)
{
stroker->has_bounds = TRUE;
_cairo_boxes_get_extents (boxes, num_boxes, &stroker->bounds);
stroker->bounds.p1.x -= stroker->half_line_x;
stroker->bounds.p2.x += stroker->half_line_x;
stroker->bounds.p1.y -= stroker->half_line_y;
stroker->bounds.p2.y += stroker->half_line_y;
}
static cairo_bool_t
_cairo_rectilinear_stroker_init (cairo_rectilinear_stroker_t *stroker,
const cairo_stroke_style_t *stroke_style,
const cairo_matrix_t *ctm,
cairo_antialias_t antialias,
cairo_boxes_t *boxes)
/* This special-case rectilinear stroker only supports
* miter-joined lines (not curves) and a translation-only matrix
* (though it could probably be extended to support a matrix with
* uniform, integer scaling).
* It also only supports horizontal and vertical line_to
* elements. But we don't catch that here, but instead return
* UNSUPPORTED from _cairo_rectilinear_stroker_line_to if any
* non-rectilinear line_to is encountered.
if (stroke_style->line_join != CAIRO_LINE_JOIN_MITER)
return FALSE;
/* If the miter limit turns right angles into bevels, then we
* can't use this optimization. Remember, the ratio is
* 1/sin(ɸ/2). So the cutoff is 1/sin(π/4.0) or ⎷2,
* which we round for safety. */
if (stroke_style->miter_limit < M_SQRT2)
if (! (stroke_style->line_cap == CAIRO_LINE_CAP_BUTT ||
stroke_style->line_cap == CAIRO_LINE_CAP_SQUARE))
if (! _cairo_matrix_is_scale (ctm))
stroker->stroke_style = stroke_style;
stroker->ctm = ctm;
stroker->antialias = antialias;
stroker->half_line_x =
_cairo_fixed_from_double (fabs(ctm->xx) * stroke_style->line_width / 2.0);
stroker->half_line_y =
_cairo_fixed_from_double (fabs(ctm->yy) * stroke_style->line_width / 2.0);
stroker->open_sub_path = FALSE;
stroker->segments = stroker->segments_embedded;
stroker->segments_size = ARRAY_LENGTH (stroker->segments_embedded);
stroker->num_segments = 0;
_cairo_stroker_dash_init (&stroker->dash, stroke_style);
stroker->has_bounds = FALSE;
stroker->boxes = boxes;
return TRUE;
_cairo_rectilinear_stroker_fini (cairo_rectilinear_stroker_t *stroker)
if (stroker->segments != stroker->segments_embedded)
free (stroker->segments);
static cairo_status_t
_cairo_rectilinear_stroker_add_segment (cairo_rectilinear_stroker_t *stroker,
const cairo_point_t *p1,
const cairo_point_t *p2,
unsigned flags)
if (CAIRO_INJECT_FAULT ())
return _cairo_error (CAIRO_STATUS_NO_MEMORY);
if (stroker->num_segments == stroker->segments_size) {
int new_size = stroker->segments_size * 2;
segment_t *new_segments;
if (stroker->segments == stroker->segments_embedded) {
new_segments = _cairo_malloc_ab (new_size, sizeof (segment_t));
if (unlikely (new_segments == NULL))
memcpy (new_segments, stroker->segments,
stroker->num_segments * sizeof (segment_t));
} else {
new_segments = _cairo_realloc_ab (stroker->segments,
new_size, sizeof (segment_t));
stroker->segments_size = new_size;
stroker->segments = new_segments;
stroker->segments[stroker->num_segments].p1 = *p1;
stroker->segments[stroker->num_segments].p2 = *p2;
stroker->segments[stroker->num_segments].flags = flags;
stroker->num_segments++;
return CAIRO_STATUS_SUCCESS;
_cairo_rectilinear_stroker_emit_segments (cairo_rectilinear_stroker_t *stroker)
cairo_line_cap_t line_cap = stroker->stroke_style->line_cap;
cairo_fixed_t half_line_x = stroker->half_line_x;
cairo_fixed_t half_line_y = stroker->half_line_y;
cairo_status_t status;
int i, j;
/* For each segment we generate a single rectangle.
* This rectangle is based on a perpendicular extension (by half the
* line width) of the segment endpoints * after some adjustments of the
* endpoints to account for caps and joins.
for (i = 0; i < stroker->num_segments; i++) {
cairo_bool_t lengthen_initial, lengthen_final;
cairo_point_t *a, *b;
cairo_box_t box;
a = &stroker->segments[i].p1;
b = &stroker->segments[i].p2;
/* We adjust the initial point of the segment to extend the
* rectangle to include the previous cap or join, (this
* adjustment applies to all segments except for the first
* segment of open, butt-capped paths). However, we must be
* careful not to emit a miter join across a degenerate segment
* which has been elided.
* Overlapping segments will be eliminated by the tessellation.
* Ideally, we would not emit these self-intersections at all,
* but that is tricky with segments shorter than half_line_width.
j = i == 0 ? stroker->num_segments - 1 : i-1;
lengthen_initial = (stroker->segments[i].flags ^ stroker->segments[j].flags) & HORIZONTAL;
j = i == stroker->num_segments - 1 ? 0 : i+1;
lengthen_final = (stroker->segments[i].flags ^ stroker->segments[j].flags) & HORIZONTAL;
if (stroker->open_sub_path) {
if (i == 0)
lengthen_initial = line_cap != CAIRO_LINE_CAP_BUTT;
if (i == stroker->num_segments - 1)
lengthen_final = line_cap != CAIRO_LINE_CAP_BUTT;
/* Perform the adjustments of the endpoints. */
if (lengthen_initial | lengthen_final) {
if (a->y == b->y) {
if (a->x < b->x) {
if (lengthen_initial)
a->x -= half_line_x;
if (lengthen_final)
b->x += half_line_x;
a->x += half_line_x;
b->x -= half_line_x;
if (a->y < b->y) {
a->y -= half_line_y;
b->y += half_line_y;
a->y += half_line_y;
b->y -= half_line_y;
/* Form the rectangle by expanding by half the line width in
* either perpendicular direction. */
box.p1.x = a->x;
box.p2.x = b->x;
box.p1.x = b->x;
box.p2.x = a->x;
box.p1.y = a->y;
box.p2.y = b->y;
box.p1.y = b->y;
box.p2.y = a->y;
status = _cairo_boxes_add (stroker->boxes, stroker->antialias, &box);
if (unlikely (status))
return status;
_cairo_rectilinear_stroker_emit_segments_dashed (cairo_rectilinear_stroker_t *stroker)
int i;
cairo_bool_t is_horizontal;
is_horizontal = stroker->segments[i].flags & HORIZONTAL;
/* Handle the joins for a potentially degenerate segment. */
if (line_cap == CAIRO_LINE_CAP_BUTT &&
stroker->segments[i].flags & JOIN &&
(i != stroker->num_segments - 1 ||
(! stroker->open_sub_path && stroker->dash.dash_starts_on)))
cairo_slope_t out_slope;
int j = (i + 1) % stroker->num_segments;
cairo_bool_t forwards = !!(stroker->segments[i].flags & FORWARDS);
_cairo_slope_init (&out_slope,
&stroker->segments[j].p1,
&stroker->segments[j].p2);
box.p2 = box.p1 = stroker->segments[i].p2;
if (is_horizontal) {
if (forwards)
box.p2.x += half_line_x;
else
box.p1.x -= half_line_x;
if (out_slope.dy > 0)
box.p1.y -= half_line_y;
box.p2.y += half_line_y;
if (out_slope.dx > 0)
if (line_cap == CAIRO_LINE_CAP_SQUARE) {
if (a->x <= b->x) {
if (a->y <= b->y) {
if (a->x == b->x && a->y == b->y)
continue;
_cairo_rectilinear_stroker_move_to (void *closure,
const cairo_point_t *point)
cairo_rectilinear_stroker_t *stroker = closure;
if (stroker->dash.dashed)
status = _cairo_rectilinear_stroker_emit_segments_dashed (stroker);
status = _cairo_rectilinear_stroker_emit_segments (stroker);
/* reset the dash pattern for new sub paths */
_cairo_stroker_dash_start (&stroker->dash);
stroker->current_point = *point;
stroker->first_point = *point;
_cairo_rectilinear_stroker_line_to (void *closure,
const cairo_point_t *b)
cairo_point_t *a = &stroker->current_point;
/* We only support horizontal or vertical elements. */
assert (a->x == b->x || a->y == b->y);
/* We don't draw anything for degenerate paths. */
status = _cairo_rectilinear_stroker_add_segment (stroker, a, b,
(a->y == b->y) | JOIN);
stroker->current_point = *b;
stroker->open_sub_path = TRUE;
_cairo_rectilinear_stroker_line_to_dashed (void *closure,
const cairo_point_t *a = &stroker->current_point;
const cairo_point_t *b = point;
cairo_bool_t fully_in_bounds;
double sf, sign, remain;
cairo_fixed_t mag;
cairo_line_t segment;
cairo_bool_t dash_on = FALSE;
unsigned is_horizontal;
fully_in_bounds = TRUE;
if (stroker->has_bounds &&
(! _cairo_box_contains_point (&stroker->bounds, a) ||
! _cairo_box_contains_point (&stroker->bounds, b)))
fully_in_bounds = FALSE;
is_horizontal = a->y == b->y;
mag = b->x - a->x;
sf = fabs (stroker->ctm->xx);
mag = b->y - a->y;
sf = fabs (stroker->ctm->yy);
if (mag < 0) {
remain = _cairo_fixed_to_double (-mag);
sign = 1.;
remain = _cairo_fixed_to_double (mag);
is_horizontal |= FORWARDS;
sign = -1.;
segment.p2 = segment.p1 = *a;
while (remain > 0.) {
double step_length;
step_length = MIN (sf * stroker->dash.dash_remain, remain);
remain -= step_length;
mag = _cairo_fixed_from_double (sign*remain);
if (is_horizontal & 0x1)
segment.p2.x = b->x + mag;
segment.p2.y = b->y + mag;
if (stroker->dash.dash_on &&
(fully_in_bounds ||
_cairo_box_intersects_line_segment (&stroker->bounds, &segment)))
status = _cairo_rectilinear_stroker_add_segment (stroker,
&segment.p1,
&segment.p2,
is_horizontal | (remain <= 0.) << 2);
dash_on = TRUE;
dash_on = FALSE;
_cairo_stroker_dash_step (&stroker->dash, step_length / sf);
segment.p1 = segment.p2;
if (stroker->dash.dash_on && ! dash_on &&
/* This segment ends on a transition to dash_on, compute a new face
* and add cap for the beginning of the next dash_on step.
is_horizontal | JOIN);
_cairo_rectilinear_stroker_close_path (void *closure)
if (! stroker->open_sub_path)
if (stroker->dash.dashed) {
status = _cairo_rectilinear_stroker_line_to_dashed (stroker,
&stroker->first_point);
status = _cairo_rectilinear_stroker_line_to (stroker,
cairo_int_status_t
_cairo_path_fixed_stroke_rectilinear_to_boxes (const cairo_path_fixed_t *path,
cairo_rectilinear_stroker_t rectilinear_stroker;
cairo_int_status_t status;
assert (_cairo_path_fixed_stroke_is_rectilinear (path));
if (! _cairo_rectilinear_stroker_init (&rectilinear_stroker,
stroke_style, ctm, antialias,
boxes))
return CAIRO_INT_STATUS_UNSUPPORTED;
if (! rectilinear_stroker.dash.dashed &&
_cairo_path_fixed_is_stroke_box (path, &box) &&
/* if the segments overlap we need to feed them into the tessellator */
box.p2.x - box.p1.x > 2* rectilinear_stroker.half_line_x &&
box.p2.y - box.p1.y > 2* rectilinear_stroker.half_line_y)
cairo_box_t b;
/* top */
b.p1.x = box.p1.x - rectilinear_stroker.half_line_x;
b.p2.x = box.p2.x + rectilinear_stroker.half_line_x;
b.p1.y = box.p1.y - rectilinear_stroker.half_line_y;
b.p2.y = box.p1.y + rectilinear_stroker.half_line_y;
status = _cairo_boxes_add (boxes, antialias, &b);
assert (status == CAIRO_INT_STATUS_SUCCESS);
/* left (excluding top/bottom) */
b.p2.x = box.p1.x + rectilinear_stroker.half_line_x;
b.p1.y = box.p1.y + rectilinear_stroker.half_line_y;
b.p2.y = box.p2.y - rectilinear_stroker.half_line_y;
/* right (excluding top/bottom) */
b.p1.x = box.p2.x - rectilinear_stroker.half_line_x;
/* bottom */
b.p1.y = box.p2.y - rectilinear_stroker.half_line_y;
b.p2.y = box.p2.y + rectilinear_stroker.half_line_y;
goto done;
if (boxes->num_limits) {
_cairo_rectilinear_stroker_limit (&rectilinear_stroker,
boxes->limits,
boxes->num_limits);
status = _cairo_path_fixed_interpret (path,
_cairo_rectilinear_stroker_move_to,
rectilinear_stroker.dash.dashed ?
_cairo_rectilinear_stroker_line_to_dashed :
_cairo_rectilinear_stroker_line_to,
NULL,
_cairo_rectilinear_stroker_close_path,
&rectilinear_stroker);
goto BAIL;
if (rectilinear_stroker.dash.dashed)
status = _cairo_rectilinear_stroker_emit_segments_dashed (&rectilinear_stroker);
status = _cairo_rectilinear_stroker_emit_segments (&rectilinear_stroker);
/* As we incrementally tessellate, we do not eliminate self-intersections */
status = _cairo_bentley_ottmann_tessellate_boxes (boxes,
CAIRO_FILL_RULE_WINDING,
boxes);
done:
_cairo_rectilinear_stroker_fini (&rectilinear_stroker);
BAIL:
_cairo_boxes_clear (boxes);