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[clip] Use the rectilinear tessellator

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We can ensure that we always produce a clip region when possible by using
the rectilinear tessellator to convert complex, device-aligned polygons to
regions. Prior to using the tessellator, we relied on pixman's region code
which could only handle a union of rectangles.
This commit is contained in:
Chris Wilson 2009-07-29 21:47:11 +01:00
parent e3820bef20
commit 6f0340e2e5
2 changed files with 66 additions and 22 deletions
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9
src/cairo-clip.c
View file

@ -586,16 +586,11 @@ _cairo_clip_path_to_region (cairo_clip_path_t *clip_path)
_cairo_path_fixed_fill_rectilinear_to_region (&clip_path->path,
clip_path->fill_rule,
&clip_path->extents);
if (clip_path->region == NULL) {
clip_path->flags |= CAIRO_CLIP_PATH_REGION_IS_UNSUPPORTED;
return CAIRO_INT_STATUS_UNSUPPORTED;
}
assert (clip_path->region != NULL);
status = clip_path->region->status;
if (unlikely (status)) {
clip_path->flags |= CAIRO_CLIP_PATH_REGION_IS_UNSUPPORTED;
if (unlikely (status))
return status;
}
if (prev != NULL) {
status = cairo_region_intersect (clip_path->region, prev);

79
src/cairo-path-fill.c
View file

@ -36,6 +36,7 @@
#include "cairoint.h"
#include "cairo-path-fixed-private.h"
#include "cairo-region-private.h"
typedef struct cairo_filler {
double tolerance;
@ -177,12 +178,61 @@ _cairo_path_fixed_fill_to_traps (const cairo_path_fixed_t *path,
return status;
}
static cairo_region_t *
_cairo_path_fixed_fill_rectilinear_tessellate_to_region (const cairo_path_fixed_t *path,
cairo_fill_rule_t fill_rule,
const cairo_rectangle_int_t *extents)
{
cairo_polygon_t polygon;
cairo_traps_t traps;
cairo_status_t status;
cairo_region_t *region;
_cairo_polygon_init (&polygon);
if (extents != NULL) {
cairo_box_t box;
_cairo_box_from_rectangle (&box, extents);
_cairo_polygon_limit (&polygon, &box);
}
/* tolerance will be ignored as the path is rectilinear */
status = _cairo_path_fixed_fill_to_polygon (path, 0., &polygon);
if (unlikely (status))
goto CLEANUP_POLYGON;
if (polygon.num_edges == 0) {
region = cairo_region_create ();
} else {
_cairo_traps_init (&traps);
status = _cairo_bentley_ottmann_tessellate_rectilinear_polygon (&traps,
&polygon,
fill_rule);
if (likely (status == CAIRO_STATUS_SUCCESS))
status = _cairo_traps_extract_region (&traps, &region);
_cairo_traps_fini (&traps);
}
CLEANUP_POLYGON:
_cairo_polygon_fini (&polygon);
if (unlikely (status)) { /* XXX _cairo_region_create_in_error() */
region = cairo_region_create ();
if (likely (region->status) == CAIRO_STATUS_SUCCESS)
region->status = status;
}
return region;
}
/* This special-case filler supports only a path that describes a
* device-axis aligned rectangle. It exists to avoid the overhead of
* the general tessellator when drawing very common rectangles.
*
* If the path described anything but a device-axis aligned rectangle,
* this function will return %CAIRO_INT_STATUS_UNSUPPORTED.
* this function will abort.
*/
cairo_region_t *
_cairo_path_fixed_fill_rectilinear_to_region (const cairo_path_fixed_t *path,
@ -212,10 +262,6 @@ _cairo_path_fixed_fill_rectilinear_to_region (const cairo_path_fixed_t *path,
box.p2.y = t;
}
assert (_cairo_fixed_is_integer (box.p1.x) &&
_cairo_fixed_is_integer (box.p1.y));
assert (_cairo_fixed_is_integer (box.p2.x) &&
_cairo_fixed_is_integer (box.p2.y));
rectangle_stack[0].x = _cairo_fixed_integer_part (box.p1.x);
rectangle_stack[0].y = _cairo_fixed_integer_part (box.p1.y);
rectangle_stack[0].width = _cairo_fixed_integer_part (box.p2.x) -
@ -260,13 +306,10 @@ _cairo_path_fixed_fill_rectilinear_to_region (const cairo_path_fixed_t *path,
cw = ! cw;
}
if (last_cw < 0) {
if (last_cw < 0)
last_cw = cw;
} else if (last_cw != cw) {
if (rects != rectangle_stack)
free (rects);
return NULL;
}
else if (last_cw != cw)
goto TESSELLATE;
if (count == size) {
cairo_rectangle_int_t *new_rects;
@ -291,10 +334,6 @@ _cairo_path_fixed_fill_rectilinear_to_region (const cairo_path_fixed_t *path,
rects = new_rects;
}
assert (_cairo_fixed_is_integer (box.p1.x) &&
_cairo_fixed_is_integer (box.p1.y));
assert (_cairo_fixed_is_integer (box.p2.x) &&
_cairo_fixed_is_integer (box.p2.y));
rects[count].x = _cairo_fixed_integer_part (box.p1.x);
rects[count].y = _cairo_fixed_integer_part (box.p1.y);
rects[count].width = _cairo_fixed_integer_part (box.p2.x) - rects[count].x;
@ -306,9 +345,19 @@ _cairo_path_fixed_fill_rectilinear_to_region (const cairo_path_fixed_t *path,
if (_cairo_path_fixed_iter_at_end (&iter))
region = cairo_region_create_rectangles (rects, count);
TESSELLATE:
if (rects != rectangle_stack)
free (rects);
}
if (region == NULL) {
/* Hmm, complex polygon */
region = _cairo_path_fixed_fill_rectilinear_tessellate_to_region (path,
fill_rule,
extents);
}
return region;
}