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stroke: Convert rectilinear paths to boxes.
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A quick and efficient method for extracting the set of boxes that
represent the path when stroked.
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Chris Wilson committed Jan 22, 2010
1 parent fe6a7f4 commit b7b65b5
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Showing 2 changed files with 142 additions and 35 deletions.
170 changes: 135 additions & 35 deletions src/cairo-path-stroke.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,7 @@
#define _BSD_SOURCE /* for hypot() */
#include "cairoint.h"

#include "cairo-boxes-private.h"
#include "cairo-error-private.h"
#include "cairo-path-fixed-private.h"
#include "cairo-slope-private.h"
Expand Down Expand Up @@ -1419,7 +1420,8 @@ _cairo_path_fixed_stroke_to_traps (const cairo_path_fixed_t *path,
}

_cairo_polygon_init (&polygon);
_cairo_polygon_limit (&polygon, traps->limits, traps->num_limits);
if (traps->num_limits)
_cairo_polygon_limit (&polygon, traps->limits, traps->num_limits);

status = _cairo_path_fixed_stroke_to_polygon (path,
stroke_style,
Expand Down Expand Up @@ -1454,7 +1456,8 @@ typedef struct _cairo_rectilinear_stroker {
const cairo_matrix_t *ctm;

cairo_fixed_t half_line_width;
cairo_traps_t *traps;
cairo_bool_t do_traps;
void *container;
cairo_point_t current_point;
cairo_point_t first_point;
cairo_bool_t open_sub_path;
Expand Down Expand Up @@ -1485,18 +1488,47 @@ _cairo_rectilinear_stroker_limit (cairo_rectilinear_stroker_t *stroker,
stroker->bounds.p2.y += stroker->half_line_width;
}

static void
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_traps_t *traps)
cairo_bool_t do_traps,
void *container)
{
/* 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)
return FALSE;

if (! (stroke_style->line_cap == CAIRO_LINE_CAP_BUTT ||
stroke_style->line_cap == CAIRO_LINE_CAP_SQUARE))
{
return FALSE;
}

if (! _cairo_matrix_has_unity_scale (ctm))
return FALSE;

stroker->stroke_style = stroke_style;
stroker->ctm = ctm;

stroker->half_line_width =
_cairo_fixed_from_double (stroke_style->line_width / 2.0);
stroker->traps = traps;
stroker->open_sub_path = FALSE;
stroker->segments = stroker->segments_embedded;
stroker->segments_size = ARRAY_LENGTH (stroker->segments_embedded);
Expand All @@ -1506,6 +1538,11 @@ _cairo_rectilinear_stroker_init (cairo_rectilinear_stroker_t *stroker,
_cairo_stroker_dash_init (&stroker->dash, stroke_style, ctm, _cairo_fixed_to_double (2 * CAIRO_FIXED_EPSILON));

stroker->has_bounds = FALSE;

stroker->do_traps = do_traps;
stroker->container = container;

return TRUE;
}

static void
Expand Down Expand Up @@ -1664,7 +1701,16 @@ _cairo_rectilinear_stroker_emit_segments (cairo_rectilinear_stroker_t *stroker)
b->x += half_line_width;
}

status = _cairo_traps_tessellate_rectangle (stroker->traps, a, b);
if (stroker->do_traps) {
status = _cairo_traps_tessellate_rectangle (stroker->container, a, b);
} else {
cairo_box_t box;

box.p1 = *a;
box.p2 = *b;

status = _cairo_boxes_add (stroker->container, &box);
}
if (unlikely (status))
return status;
}
Expand Down Expand Up @@ -1730,8 +1776,16 @@ _cairo_rectilinear_stroker_emit_segments_dashed (cairo_rectilinear_stroker_t *st
p2.x += half_line_width;
}

status = _cairo_traps_tessellate_rectangle (stroker->traps,
&p1, &p2);
if (stroker->do_traps) {
status = _cairo_traps_tessellate_rectangle (stroker->container, &p1, &p2);
} else {
cairo_box_t box;

box.p1 = p1;
box.p2 = p2;

status = _cairo_boxes_add (stroker->container, &box);
}
if (unlikely (status))
return status;
}
Expand Down Expand Up @@ -1784,7 +1838,16 @@ _cairo_rectilinear_stroker_emit_segments_dashed (cairo_rectilinear_stroker_t *st
if (a->x == b->x && a->y == b->y)
continue;

status = _cairo_traps_tessellate_rectangle (stroker->traps, a, b);
if (stroker->do_traps) {
status = _cairo_traps_tessellate_rectangle (stroker->container, a, b);
} else {
cairo_box_t box;

box.p1 = *a;
box.p2 = *b;

status = _cairo_boxes_add (stroker->container, &box);
}
if (unlikely (status))
return status;
}
Expand Down Expand Up @@ -1986,38 +2049,15 @@ _cairo_path_fixed_stroke_rectilinear_to_traps (const cairo_path_fixed_t *path,
cairo_rectilinear_stroker_t rectilinear_stroker;
cairo_int_status_t status;

/* 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.
*/
assert (path->is_rectilinear);

if (stroke_style->line_join != CAIRO_LINE_JOIN_MITER)
return CAIRO_INT_STATUS_UNSUPPORTED;
/* 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)
return CAIRO_INT_STATUS_UNSUPPORTED;
if (! (stroke_style->line_cap == CAIRO_LINE_CAP_BUTT ||
stroke_style->line_cap == CAIRO_LINE_CAP_SQUARE))
if (! _cairo_rectilinear_stroker_init (&rectilinear_stroker,
stroke_style, ctm,
TRUE, traps))
{
return CAIRO_INT_STATUS_UNSUPPORTED;
}
if (! _cairo_matrix_has_unity_scale (ctm))
return CAIRO_INT_STATUS_UNSUPPORTED;

_cairo_rectilinear_stroker_init (&rectilinear_stroker,
stroke_style,
ctm,
traps);
if (traps->num_limits) {
_cairo_rectilinear_stroker_limit (&rectilinear_stroker,
traps->limits,
Expand Down Expand Up @@ -2053,3 +2093,63 @@ _cairo_path_fixed_stroke_rectilinear_to_traps (const cairo_path_fixed_t *path,

return status;
}

cairo_int_status_t
_cairo_path_fixed_stroke_rectilinear_to_boxes (const cairo_path_fixed_t *path,
const cairo_stroke_style_t *stroke_style,
const cairo_matrix_t *ctm,
cairo_boxes_t *boxes)
{
cairo_rectilinear_stroker_t rectilinear_stroker;
cairo_int_status_t status;

assert (path->is_rectilinear);

if (! _cairo_rectilinear_stroker_init (&rectilinear_stroker,
stroke_style, ctm,
FALSE, boxes))
{
return CAIRO_INT_STATUS_UNSUPPORTED;
}

if (boxes->num_limits) {
_cairo_rectilinear_stroker_limit (&rectilinear_stroker,
boxes->limits,
boxes->num_limits);
}

status = _cairo_path_fixed_interpret (path,
CAIRO_DIRECTION_FORWARD,
_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);
if (unlikely (status))
goto BAIL;

if (rectilinear_stroker.dash.dashed)
status = _cairo_rectilinear_stroker_emit_segments_dashed (&rectilinear_stroker);
else
status = _cairo_rectilinear_stroker_emit_segments (&rectilinear_stroker);
if (unlikely (status))
goto BAIL;

/* As we incrementally tessellate, we do not eliminate self-intersections */
status = _cairo_bentley_ottmann_tessellate_boxes (boxes,
CAIRO_FILL_RULE_WINDING,
boxes);
if (unlikely (status))
goto BAIL;

_cairo_rectilinear_stroker_fini (&rectilinear_stroker);

return CAIRO_STATUS_SUCCESS;

BAIL:
_cairo_rectilinear_stroker_fini (&rectilinear_stroker);
_cairo_boxes_clear (boxes);
return status;
}
7 changes: 7 additions & 0 deletions src/cairoint.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1591,6 +1591,13 @@ _cairo_path_fixed_stroke_rectilinear_to_traps (const cairo_path_fixed_t *path,
const cairo_stroke_style_t *stroke_style,
const cairo_matrix_t *ctm,
cairo_traps_t *traps);

cairo_private cairo_int_status_t
_cairo_path_fixed_stroke_rectilinear_to_boxes (const cairo_path_fixed_t *path,
const cairo_stroke_style_t *stroke_style,
const cairo_matrix_t *ctm,
cairo_boxes_t *boxes);

cairo_private cairo_status_t
_cairo_path_fixed_stroke_to_traps (const cairo_path_fixed_t *path,
const cairo_stroke_style_t *stroke_style,
Expand Down

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