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Try a different calculation for computing convexity.

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Change-Id: I3b4a6a95ec9f890b35948d745dd02a2b05a8d7cb
Reviewed-on: https://skia-review.googlesource.com/10116
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
This commit is contained in:
Jim Van Verth 2017-03-24 14:28:57 -04:00 committed by Skia Commit-Bot
parent 31f96a68af
commit 0513f14308
1 changed files with 28 additions and 16 deletions
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44
src/utils/SkInsetConvexPolygon.cpp
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@ -108,6 +108,33 @@ static bool compute_intersection(const InsetSegment& s0, const InsetSegment& s1,
return true;
}
#ifdef SK_DEBUG
static bool is_convex(const SkTDArray<SkPoint>& poly) {
if (poly.count() <= 3) {
return true;
}
SkVector v0 = poly[0] - poly[poly.count() - 1];
SkVector v1 = poly[1] - poly[poly.count() - 1];
SkScalar winding = v0.cross(v1);
for (int i = 0; i < poly.count() - 1; ++i) {
int j = i + 1;
int k = (i + 2) % poly.count();
SkVector v0 = poly[j] - poly[i];
SkVector v1 = poly[k] - poly[i];
SkScalar perpDot = v0.cross(v1);
int side = winding*perpDot;
if (side < 0) {
return false;
}
}
return true;
}
#endif
// The objective here is to inset all of the edges by the given distance, and then
// remove any invalid inset edges by detecting right-hand turns. In a ccw polygon,
// we should only be making left-hand turns (for cw polygons, we use the winding
@ -213,22 +240,7 @@ bool SkInsetConvexPolygon(const SkPoint* inputPolygonVerts, int inputPolygonSize
*insetPolygon->push() = edgeData[i].fIntersection;
}
}
//#ifdef SK_DEBUG
// bool convex = true;
// for (int i = 0; i < insetPolygon->count(); ++i) {
// int j = (i + 1) % insetPolygon->count();
// int k = (i + 2) % insetPolygon->count();
//
// int side = winding*compute_side((*insetPolygon)[i], (*insetPolygon)[j],
// (*insetPolygon)[k]);
// if (side < 0) {
// convex = false;
// break;
// }
// }
// SkASSERT(convex);
//#endif
SkASSERT(is_convex(*insetPolygon));
return (insetPolygon->count() >= 3);
}