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path: Fix gsk_path_measure_in_fill

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This was getting some simple polygon cases wrong :(

The problem here is a misunderstanding in line_get_crossing.
It was returning 'on edge' when a point of the polygon is
on the ray, which is not what 'on edge' is about.

Add some test cases involving horizontal edges that coincide
with the test point.
This commit is contained in:
Matthias Clasen
2022-03-27 11:26:45 -04:00
parent c816eee4d1
commit f58513e4dd
2 changed files with 58 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
gsk/gskcontour.c
View File

@@ -1583,6 +1583,9 @@ gsk_standard_contour_add_segment (const GskContour *contour,
}
}
/* Returns twice the winding number, so we can record the
* 'point on ray' case by returning an odd number.
*/
static inline int
line_get_crossing (const graphene_point_t *p,
const graphene_point_t *p1,
@@ -1590,6 +1593,7 @@ line_get_crossing (const graphene_point_t *p,
gboolean *on_edge)
{
int dir = 1;
float r;
if (p1->x >= p->x && p2->x >= p->x)
return 0;
@@ -1603,21 +1607,32 @@ line_get_crossing (const graphene_point_t *p,
dir = -1;
}
if ((p1->x >= p->x && p1->y == p->y) ||
(p2->x >= p->x && p2->y == p->y))
if ((p1->x <= p->x && p1->y == p->y) ||
(p2->x <= p->x && p2->y == p->y))
{
*on_edge = TRUE;
return 0;
if (p1->y == p2->y)
{
if (p1->x >= p->x || p2->x >= p->x)
*on_edge = TRUE;
return 0;
}
return dir;
}
if (p2->y <= p->y || p1->y > p->y)
return 0;
if (p1->x <= p->x && p2->x <= p->x)
return dir;
return 2 * dir;
if (p->x > p1->x + (p->y - p1->y) * (p2->x - p1->x) / (p2->y - p1->y))
return dir;
r = p1->x + (p->y - p1->y) * (p2->x - p1->x) / (p2->y - p1->y);
if (p->x > r)
return 2 * dir;
if (p->x == r)
*on_edge = TRUE;
return 0;
}
@@ -1653,6 +1668,8 @@ gsk_standard_contour_get_winding (const GskContour *contour,
winding += line_get_crossing (point, &last_point, &self->points[0], on_edge);
winding /= 2;
return winding;
}

34
testsuite/gsk/path-special-cases.c
View File

@@ -306,6 +306,39 @@ test_serialize_custom_contours (void)
gsk_path_unref (path1);
}
static void
test_path_winding (void)
{
struct {
const char *path;
graphene_point_t point;
gboolean result;
} tests[] = {
{ "M 150 103 L 250 100 L 300 103 L 250 180 Z", GRAPHENE_POINT_INIT (175, 100), FALSE },
{ "M 100 100 L 300 200 L 300 0 Z", GRAPHENE_POINT_INIT (250, 100), TRUE },
{ "M 100 100 L 300 200 L 300 0 Z", GRAPHENE_POINT_INIT (400, 100), FALSE},
{ "M 100 100 L 200 100 L 300 200 L 300 0 Z", GRAPHENE_POINT_INIT (50, 100), FALSE },
{ "M 100 100 L 200 100 L 300 200 L 300 0 Z", GRAPHENE_POINT_INIT (150, 100), TRUE },
{ "M 100 100 L 200 100 L 300 200 L 300 0 Z", GRAPHENE_POINT_INIT (250, 100), TRUE },
{ "M 100 100 L 200 100 L 300 200 L 300 0 Z", GRAPHENE_POINT_INIT (400, 100), FALSE },
};
GskPath *path;
GskPathMeasure *measure;
gboolean res;
for (int i = 0; i < G_N_ELEMENTS (tests); i++)
{
path = gsk_path_parse (tests[i].path);
measure = gsk_path_measure_new (path);
res = gsk_path_measure_in_fill (measure, &tests[i].point, GSK_FILL_RULE_WINDING);
g_assert_true (res == tests[i].result);
gsk_path_measure_unref (measure);
gsk_path_unref (path);
}
}
int
main (int argc,
char *argv[])
@@ -314,6 +347,7 @@ main (int argc,
g_test_add_func ("/path/rsvg-parse", test_rsvg_parse);
g_test_add_func ("/path/serialize-custom-contours", test_serialize_custom_contours);
g_test_add_func ("/path/winding", test_path_winding);
return g_test_run ();
}