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path-bounder: Simplify code
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If the path extents are tight, all the extents computations and
approximations become trivial except for the stroke extents.
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Andrea Canciani committed Oct 29, 2010
1 parent 958c56e commit 89e1261
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Showing 2 changed files with 61 additions and 193 deletions.
249 changes: 56 additions & 193 deletions src/cairo-path-bounds.c
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
/* -*- Mode: c; tab-width: 8; c-basic-offset: 4; indent-tabs-mode: t; -*- */
/* cairo - a vector graphics library with display and print output
*
* Copyright © 2003 University of Southern California
Expand Down Expand Up @@ -35,56 +36,30 @@
*/

#include "cairoint.h"
#include "cairo-box-private.h"
#include "cairo-path-fixed-private.h"

typedef struct cairo_path_bounder {
cairo_point_t current_point;
cairo_bool_t has_initial_point;
cairo_bool_t has_point;

typedef struct _cairo_path_bounder {
cairo_point_t current_point;
cairo_bool_t has_extents;
cairo_box_t extents;
} cairo_path_bounder_t;

static void
_cairo_path_bounder_init (cairo_path_bounder_t *bounder)
{
bounder->has_initial_point = FALSE;
bounder->has_point = FALSE;
}

static void
_cairo_path_bounder_add_point (cairo_path_bounder_t *bounder,
const cairo_point_t *point)
{
if (bounder->has_point) {
if (point->x < bounder->extents.p1.x)
bounder->extents.p1.x = point->x;

if (point->y < bounder->extents.p1.y)
bounder->extents.p1.y = point->y;

if (point->x > bounder->extents.p2.x)
bounder->extents.p2.x = point->x;

if (point->y > bounder->extents.p2.y)
bounder->extents.p2.y = point->y;
} else {
bounder->extents.p1.x = point->x;
bounder->extents.p1.y = point->y;
bounder->extents.p2.x = point->x;
bounder->extents.p2.y = point->y;
bounder->has_point = TRUE;
}
}

static cairo_status_t
_cairo_path_bounder_move_to (void *closure,
const cairo_point_t *point)
{
cairo_path_bounder_t *bounder = closure;

bounder->current_point = *point;
bounder->has_initial_point = TRUE;

if (likely (bounder->has_extents)) {
_cairo_box_add_point (&bounder->extents, point);
} else {
bounder->has_extents = TRUE;
_cairo_box_set (&bounder->extents, point, point);
}

return CAIRO_STATUS_SUCCESS;
}
Expand All @@ -95,13 +70,8 @@ _cairo_path_bounder_line_to (void *closure,
{
cairo_path_bounder_t *bounder = closure;

if (bounder->has_initial_point) {
_cairo_path_bounder_add_point (bounder, &bounder->current_point);
bounder->has_initial_point = FALSE;
}

_cairo_path_bounder_add_point (bounder, point);
bounder->current_point = *point;
_cairo_box_add_point (&bounder->extents, point);

return CAIRO_STATUS_SUCCESS;
}
Expand All @@ -114,25 +84,12 @@ _cairo_path_bounder_curve_to (void *closure,
{
cairo_path_bounder_t *bounder = closure;

/* If the bbox of the control points is entirely inside, then we
* do not need to further evaluate the spline.
*/
if (! bounder->has_point ||
b->x < bounder->extents.p1.x || b->x > bounder->extents.p2.x ||
b->y < bounder->extents.p1.y || b->y > bounder->extents.p2.y ||
c->x < bounder->extents.p1.x || c->x > bounder->extents.p2.x ||
c->y < bounder->extents.p1.y || c->y > bounder->extents.p2.y ||
d->x < bounder->extents.p1.x || d->x > bounder->extents.p2.x ||
d->y < bounder->extents.p1.y || d->y > bounder->extents.p2.y)
{
return _cairo_spline_bound (_cairo_path_bounder_line_to, bounder,
&bounder->current_point, b, c, d);
}
else
{
/* All control points are within the current extents. */
return CAIRO_STATUS_SUCCESS;
}
_cairo_box_add_curve_to (&bounder->extents,
&bounder->current_point,
b, c, d);
bounder->current_point = *d;

return CAIRO_STATUS_SUCCESS;
}

static cairo_status_t
Expand All @@ -141,53 +98,40 @@ _cairo_path_bounder_close_path (void *closure)
return CAIRO_STATUS_SUCCESS;
}

/* This computes the extents of all the points in the path, not those of
* the damage area (i.e it does not consider winding and it only inspects
* the control points of the curves, not the flattened path).
*/
cairo_bool_t
_cairo_path_bounder_extents (const cairo_path_fixed_t *path,
cairo_box_t *extents)
{
cairo_path_bounder_t bounder;
cairo_status_t status;

bounder.has_extents = FALSE;
status = _cairo_path_fixed_interpret (path, CAIRO_DIRECTION_FORWARD,
_cairo_path_bounder_move_to,
_cairo_path_bounder_line_to,
_cairo_path_bounder_curve_to,
_cairo_path_bounder_close_path,
&bounder);
assert (!status);

if (bounder.has_extents)
*extents = bounder.extents;

return bounder.has_extents;
}

void
_cairo_path_fixed_approximate_clip_extents (const cairo_path_fixed_t *path,
cairo_rectangle_int_t *extents)
{
if (path->extents.p1.x < path->extents.p2.x) {
_cairo_box_round_to_rectangle (&path->extents, extents);
} else {
extents->x = extents->y = 0;
extents->width = extents->height = 0;
}
_cairo_path_fixed_approximate_fill_extents (path, extents);
}

/* A slightly better approximation than above - we actually decompose the
* Bezier, but we continue to ignore winding.
*/
void
_cairo_path_fixed_approximate_fill_extents (const cairo_path_fixed_t *path,
cairo_rectangle_int_t *extents)
{
cairo_path_bounder_t bounder;
cairo_status_t status;

if (! path->has_curve_to) {
bounder.extents = path->extents;
bounder.has_point = path->extents.p1.x < path->extents.p2.x;
} else {
_cairo_path_bounder_init (&bounder);

status = _cairo_path_fixed_interpret (path, CAIRO_DIRECTION_FORWARD,
_cairo_path_bounder_move_to,
_cairo_path_bounder_line_to,
_cairo_path_bounder_curve_to,
_cairo_path_bounder_close_path,
&bounder);
assert (status == CAIRO_STATUS_SUCCESS);
}

if (bounder.has_point) {
_cairo_box_round_to_rectangle (&bounder.extents, extents);
} else {
extents->x = extents->y = 0;
extents->width = extents->height = 0;
}
_cairo_path_fixed_fill_extents (path, CAIRO_FILL_RULE_WINDING, 0, extents);
}

void
Expand All @@ -196,25 +140,9 @@ _cairo_path_fixed_fill_extents (const cairo_path_fixed_t *path,
double tolerance,
cairo_rectangle_int_t *extents)
{
cairo_path_bounder_t bounder;
cairo_status_t status;

if (! path->has_curve_to) {
bounder.extents = path->extents;
bounder.has_point = path->extents.p1.x < path->extents.p2.x;
} else {
_cairo_path_bounder_init (&bounder);

status = _cairo_path_fixed_interpret_flat (path, CAIRO_DIRECTION_FORWARD,
_cairo_path_bounder_move_to,
_cairo_path_bounder_line_to,
_cairo_path_bounder_close_path,
&bounder, tolerance);
assert (status == CAIRO_STATUS_SUCCESS);
}

if (bounder.has_point) {
_cairo_box_round_to_rectangle (&bounder.extents, extents);
if (path->extents.p1.x < path->extents.p2.x &&
path->extents.p1.y < path->extents.p2.y) {
_cairo_box_round_to_rectangle (&path->extents, extents);
} else {
extents->x = extents->y = 0;
extents->width = extents->height = 0;
Expand All @@ -228,65 +156,18 @@ _cairo_path_fixed_approximate_stroke_extents (const cairo_path_fixed_t *path,
const cairo_matrix_t *ctm,
cairo_rectangle_int_t *extents)
{
cairo_path_bounder_t bounder;
cairo_status_t status;

if (! path->has_curve_to) {
bounder.extents = path->extents;

/* include trailing move-to for degenerate segments */
if (path->needs_move_to) {
const cairo_point_t *point = &path->current_point;

if (point->x < bounder.extents.p1.x)
bounder.extents.p1.x = point->x;
if (point->y < bounder.extents.p1.y)
bounder.extents.p1.y = point->y;

if (point->x > bounder.extents.p2.x)
bounder.extents.p2.x = point->x;
if (point->y > bounder.extents.p2.y)
bounder.extents.p2.y = point->y;
}

bounder.has_point = bounder.extents.p1.x <= bounder.extents.p2.x;
bounder.has_initial_point = FALSE;
} else {
_cairo_path_bounder_init (&bounder);

status = _cairo_path_fixed_interpret (path, CAIRO_DIRECTION_FORWARD,
_cairo_path_bounder_move_to,
_cairo_path_bounder_line_to,
_cairo_path_bounder_curve_to,
_cairo_path_bounder_close_path,
&bounder);
assert (status == CAIRO_STATUS_SUCCESS);
}

if (bounder.has_point) {
double dx, dy;

_cairo_stroke_style_max_distance_from_path (style, ctm, &dx, &dy);

bounder.extents.p1.x -= _cairo_fixed_from_double (dx);
bounder.extents.p2.x += _cairo_fixed_from_double (dx);
bounder.extents.p1.y -= _cairo_fixed_from_double (dy);
bounder.extents.p2.y += _cairo_fixed_from_double (dy);

_cairo_box_round_to_rectangle (&bounder.extents, extents);
} else if (bounder.has_initial_point) {
if (path->has_extents) {
cairo_box_t box_extents;
double dx, dy;

/* accommodate capping of degenerate paths */

box_extents = path->extents;
_cairo_stroke_style_max_distance_from_path (style, ctm, &dx, &dy);
box_extents.p1.x -= _cairo_fixed_from_double (dx);
box_extents.p1.y -= _cairo_fixed_from_double (dy);
box_extents.p2.x += _cairo_fixed_from_double (dx);
box_extents.p2.y += _cairo_fixed_from_double (dy);

bounder.extents.p1.x = bounder.current_point.x - _cairo_fixed_from_double (dx);
bounder.extents.p2.x = bounder.current_point.x + _cairo_fixed_from_double (dx);
bounder.extents.p1.y = bounder.current_point.y - _cairo_fixed_from_double (dy);
bounder.extents.p2.y = bounder.current_point.y + _cairo_fixed_from_double (dy);

_cairo_box_round_to_rectangle (&bounder.extents, extents);
_cairo_box_round_to_rectangle (&box_extents, extents);
} else {
extents->x = extents->y = 0;
extents->width = extents->height = 0;
Expand Down Expand Up @@ -326,24 +207,6 @@ cairo_bool_t
_cairo_path_fixed_extents (const cairo_path_fixed_t *path,
cairo_box_t *box)
{
cairo_path_bounder_t bounder;
cairo_status_t status;

if (! path->has_curve_to) {
*box = path->extents;
return path->has_extents;
}

_cairo_path_bounder_init (&bounder);

status = _cairo_path_fixed_interpret (path, CAIRO_DIRECTION_FORWARD,
_cairo_path_bounder_move_to,
_cairo_path_bounder_line_to,
_cairo_path_bounder_curve_to,
_cairo_path_bounder_close_path,
&bounder);
assert (status == CAIRO_STATUS_SUCCESS);

*box = bounder.extents;
return bounder.has_point;
*box = path->extents;
return path->has_extents;
}
5 changes: 5 additions & 0 deletions src/cairoint.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1217,6 +1217,11 @@ _cairo_path_fixed_interpret_flat (const cairo_path_fixed_t *path,
void *closure,
double tolerance);


cairo_private cairo_bool_t
_cairo_path_bounder_extents (const cairo_path_fixed_t *path,
cairo_box_t *box);

cairo_private cairo_bool_t
_cairo_path_fixed_extents (const cairo_path_fixed_t *path,
cairo_box_t *box);
Expand Down

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