static void center_of_mass(const SegmentArray& segments, SkPoint* c) {
SkScalar area = 0;
SkPoint center = {0, 0};
int count = segments.count();
SkPoint p0 = {0, 0};
if (count > 2) {
// We translate the polygon so that the first point is at the origin.
// This avoids some precision issues with small area polygons far away
// from the origin.
p0 = segments[0].endPt();
SkPoint pi;
SkPoint pj;
// the first and last iteration of the below loop would compute
// zeros since the starting / ending point is (0,0). So instead we start
// at i=1 and make the last iteration i=count-2.
pj = segments[1].endPt() - p0;
for (int i = 1; i < count - 1; ++i) {
pi = pj;
const SkPoint pj = segments[i + 1].endPt() - p0;
SkScalar t = SkScalarMul(pi.fX, pj.fY) - SkScalarMul(pj.fX, pi.fY);
area += t;
center.fX += (pi.fX + pj.fX) * t;
center.fY += (pi.fY + pj.fY) * t;
}
}
// If the poly has no area then we instead return the average of
// its points.
if (SkScalarNearlyZero(area)) {
SkPoint avg;
avg.set(0, 0);
for (int i = 0; i < count; ++i) {
const SkPoint& pt = segments[i].endPt();
avg.fX += pt.fX;
avg.fY += pt.fY;
}
SkScalar denom = SK_Scalar1 / count;
avg.scale(denom);
*c = avg;
} else {
area *= 3;
area = SkScalarDiv(SK_Scalar1, area);
center.fX = SkScalarMul(center.fX, area);
center.fY = SkScalarMul(center.fY, area);
// undo the translate of p0 to the origin.
*c = center + p0;
}
SkASSERT(!SkScalarIsNaN(c->fX) && !SkScalarIsNaN(c->fY));
}
static void create_vertices(const SegmentArray& segments,
const SkPoint& fanPt,
DrawArray* draws,
QuadVertex* verts,
uint16_t* idxs) {
Draw* draw = &draws->push_back();
// alias just to make vert/index assignments easier to read.
int* v = &draw->fVertexCnt;
int* i = &draw->fIndexCnt;
int count = segments.count();
for (int a = 0; a < count; ++a) {
const Segment& sega = segments[a];
int b = (a + 1) % count;
const Segment& segb = segments[b];
// Check whether adding the verts for this segment to the current draw would cause index
// values to overflow.
int vCount = 4;
if (Segment::kLine == segb.fType) {
vCount += 5;
} else {
vCount += 6;
}
if (draw->fVertexCnt + vCount > (1 << 16)) {
verts += *v;
idxs += *i;
draw = &draws->push_back();
v = &draw->fVertexCnt;
i = &draw->fIndexCnt;
}
// FIXME: These tris are inset in the 1 unit arc around the corner
verts[*v + 0].fPos = sega.endPt();
verts[*v + 1].fPos = verts[*v + 0].fPos + sega.endNorm();
verts[*v + 2].fPos = verts[*v + 0].fPos + segb.fMid;
verts[*v + 3].fPos = verts[*v + 0].fPos + segb.fNorms[0];
verts[*v + 0].fUV.set(0,0);
verts[*v + 1].fUV.set(0,-SK_Scalar1);
verts[*v + 2].fUV.set(0,-SK_Scalar1);
verts[*v + 3].fUV.set(0,-SK_Scalar1);
verts[*v + 0].fD0 = verts[*v + 0].fD1 = -SK_Scalar1;
verts[*v + 1].fD0 = verts[*v + 1].fD1 = -SK_Scalar1;
verts[*v + 2].fD0 = verts[*v + 2].fD1 = -SK_Scalar1;
verts[*v + 3].fD0 = verts[*v + 3].fD1 = -SK_Scalar1;
idxs[*i + 0] = *v + 0;
idxs[*i + 1] = *v + 2;
idxs[*i + 2] = *v + 1;
idxs[*i + 3] = *v + 0;
idxs[*i + 4] = *v + 3;
idxs[*i + 5] = *v + 2;
*v += 4;
*i += 6;
if (Segment::kLine == segb.fType) {
verts[*v + 0].fPos = fanPt;
verts[*v + 1].fPos = sega.endPt();
verts[*v + 2].fPos = segb.fPts[0];
verts[*v + 3].fPos = verts[*v + 1].fPos + segb.fNorms[0];
verts[*v + 4].fPos = verts[*v + 2].fPos + segb.fNorms[0];
// we draw the line edge as a degenerate quad (u is 0, v is the
// signed distance to the edge)
SkScalar dist = fanPt.distanceToLineBetween(verts[*v + 1].fPos,
verts[*v + 2].fPos);
verts[*v + 0].fUV.set(0, dist);
verts[*v + 1].fUV.set(0, 0);
verts[*v + 2].fUV.set(0, 0);
verts[*v + 3].fUV.set(0, -SK_Scalar1);
verts[*v + 4].fUV.set(0, -SK_Scalar1);
verts[*v + 0].fD0 = verts[*v + 0].fD1 = -SK_Scalar1;
verts[*v + 1].fD0 = verts[*v + 1].fD1 = -SK_Scalar1;
verts[*v + 2].fD0 = verts[*v + 2].fD1 = -SK_Scalar1;
verts[*v + 3].fD0 = verts[*v + 3].fD1 = -SK_Scalar1;
verts[*v + 4].fD0 = verts[*v + 4].fD1 = -SK_Scalar1;
idxs[*i + 0] = *v + 0;
idxs[*i + 1] = *v + 2;
idxs[*i + 2] = *v + 1;
idxs[*i + 3] = *v + 3;
idxs[*i + 4] = *v + 1;
idxs[*i + 5] = *v + 2;
idxs[*i + 6] = *v + 4;
idxs[*i + 7] = *v + 3;
idxs[*i + 8] = *v + 2;
*v += 5;
*i += 9;
} else {
SkPoint qpts[] = {sega.endPt(), segb.fPts[0], segb.fPts[1]};
SkVector midVec = segb.fNorms[0] + segb.fNorms[1];
midVec.normalize();
verts[*v + 0].fPos = fanPt;
verts[*v + 1].fPos = qpts[0];
verts[*v + 2].fPos = qpts[2];
verts[*v + 3].fPos = qpts[0] + segb.fNorms[0];
verts[*v + 4].fPos = qpts[2] + segb.fNorms[1];
verts[*v + 5].fPos = qpts[1] + midVec;
SkScalar c = segb.fNorms[0].dot(qpts[0]);
verts[*v + 0].fD0 = -segb.fNorms[0].dot(fanPt) + c;
verts[*v + 1].fD0 = 0.f;
verts[*v + 2].fD0 = -segb.fNorms[0].dot(qpts[2]) + c;
verts[*v + 3].fD0 = -SK_ScalarMax/100;
verts[*v + 4].fD0 = -SK_ScalarMax/100;
verts[*v + 5].fD0 = -SK_ScalarMax/100;
c = segb.fNorms[1].dot(qpts[2]);
verts[*v + 0].fD1 = -segb.fNorms[1].dot(fanPt) + c;
verts[*v + 1].fD1 = -segb.fNorms[1].dot(qpts[0]) + c;
verts[*v + 2].fD1 = 0.f;
verts[*v + 3].fD1 = -SK_ScalarMax/100;
verts[*v + 4].fD1 = -SK_ScalarMax/100;
verts[*v + 5].fD1 = -SK_ScalarMax/100;
GrPathUtils::QuadUVMatrix toUV(qpts);
toUV.apply<6, sizeof(QuadVertex), sizeof(SkPoint)>(verts + *v);
idxs[*i + 0] = *v + 3;
idxs[*i + 1] = *v + 1;
idxs[*i + 2] = *v + 2;
idxs[*i + 3] = *v + 4;
idxs[*i + 4] = *v + 3;
idxs[*i + 5] = *v + 2;
idxs[*i + 6] = *v + 5;
idxs[*i + 7] = *v + 3;
idxs[*i + 8] = *v + 4;
idxs[*i + 9] = *v + 0;
idxs[*i + 10] = *v + 2;
idxs[*i + 11] = *v + 1;
*v += 6;
*i += 12;
}
}
}