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curve: Handle self-intersection

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This commit is contained in:
Matthias Clasen
2022-03-21 00:14:52 -04:00
parent 8637ea8fb8
commit 4b6223e07d
1 changed files with 73 additions and 0 deletions
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73
gsk/gskcurveintersect.c
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@@ -517,6 +517,76 @@ general_intersect (const GskCurve *curve1,
return pos;
}
static int
curve_self_intersect (const GskCurve *curve,
float *t1,
float *t2,
graphene_point_t *p,
int n)
{
float tt[3], ss[3], s;
graphene_point_t pp[3];
int m;
GskCurve cs, ce;
if (curve->op != GSK_PATH_CURVE)
return 0;
s = 0.5;
m = gsk_curve_get_curvature_points (curve, tt);
for (int i = 0; i < m; i++)
{
if (gsk_curve_get_curvature (curve, tt[i], NULL) == 0)
{
s = tt[i];
break;
}
}
gsk_curve_split (curve, s, &cs, &ce);
m = gsk_curve_intersect (&cs, &ce, tt, ss, pp, 3);
if (m > 1)
{
if (tt[0] != 1)
{
t1[0] = t2[0] = tt[0] * s;
p[0] = pp[0];
}
else if (tt[1] != 1)
{
t1[0] = t2[0] = tt[1] * s;
p[0] = pp[1];
}
if (ss[0] != 0)
{
t1[1] = t2[1] = s + ss[0] * (1 - s);
p[1] = pp[0];
}
else if (ss[1] != 0)
{
t1[1] = t2[1] = s + ss[1] * (1 - s);
p[1] = pp[1];
}
return 2;
}
else if (m == 1)
{
if (tt[0] != 1 && ss[0] != 0)
{
t1[0] = t2[0] = tt[0] * s;
t1[1] = t2[1] = s + ss[0] * (1 - s);
p[0] = p[1] = pp[0];
return 2;
}
}
return 0;
}
/* Place intersections between the curves in p, and their Bezier positions
* in t1 and t2, up to n. Return the number of intersections found.
*
@@ -539,6 +609,9 @@ gsk_curve_intersect (const GskCurve *curve1,
if (op2 == GSK_PATH_CLOSE)
op2 = GSK_PATH_LINE;
if (memcmp (curve1, curve2, sizeof (GskCurve)) == 0)
return curve_self_intersect (curve1, t1, t2, p, n);
/* We special-case line-line and line-curve intersections,
* since we can solve them directly.
* Everything else is done via bisection.