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curve: Handle degenerate cases

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Nothing prevents control points from being identical,
and if that happens, some of our constructions involving
tangents and normals break down. Handle these cases in
get_{start,end}_tangent and offset, for the case of
cubics.
This commit is contained in:
Matthias Clasen
2020-12-19 22:14:26 -05:00
parent e13cbd9af3
commit 44bccbcf70
1 changed files with 18 additions and 2 deletions
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20
gsk/gskcurve.c
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@@ -877,7 +877,15 @@ gsk_cubic_curve_get_start_tangent (const GskCurve *curve,
{
const GskCubicCurve *self = &curve->cubic;
get_tangent (&self->points[0], &self->points[1], tangent);
if (graphene_point_near (&self->points[0], &self->points[1], 0.0001))
{
if (graphene_point_near (&self->points[0], &self->points[2], 0.0001))
get_tangent (&self->points[0], &self->points[3], tangent);
else
get_tangent (&self->points[0], &self->points[2], tangent);
}
else
get_tangent (&self->points[0], &self->points[1], tangent);
}
static void
@@ -886,7 +894,15 @@ gsk_cubic_curve_get_end_tangent (const GskCurve *curve,
{
const GskCubicCurve *self = &curve->cubic;
get_tangent (&self->points[2], &self->points[3], tangent);
if (graphene_point_near (&self->points[2], &self->points[3], 0.0001))
{
if (graphene_point_near (&self->points[1], &self->points[3], 0.0001))
get_tangent (&self->points[0], &self->points[3], tangent);
else
get_tangent (&self->points[1], &self->points[3], tangent);
}
else
get_tangent (&self->points[2], &self->points[3], tangent);
}
static void