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check in direct quad length measure

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Add code so that it at minimum won't bit-rot.
Next: add tests to see if it works.

R=reed@google.com
BUG=skia:1036
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1541523002

Review URL: https://codereview.chromium.org/1541523002
This commit is contained in:
caryclark 2015-12-21 05:32:53 -08:00 committed by Commit bot
parent dd180e795f
commit 17bc0851d3
1 changed files with 35 additions and 1 deletions
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36
src/core/SkPathMeasure.cpp
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@ -90,6 +90,28 @@ static bool cubic_too_curvy(const SkPoint pts[4]) {
SkScalarInterp(pts[0].fY, pts[3].fY, SK_Scalar1*2/3));
}
/* from http://www.malczak.linuxpl.com/blog/quadratic-bezier-curve-length/ */
static SkScalar compute_quad_len(const SkPoint pts[3]) {
SkPoint a,b;
a.fX = pts[0].fX - 2 * pts[1].fX + pts[2].fX;
a.fY = pts[0].fY - 2 * pts[1].fY + pts[2].fY;
b.fX = 2 * (pts[1].fX - pts[0].fX);
b.fY = 2 * (pts[1].fY - pts[0].fY);
SkScalar A = 4 * (a.fX * a.fX + a.fY * a.fY);
SkScalar B = 4 * (a.fX * b.fX + a.fY * b.fY);
SkScalar C = b.fX * b.fX + b.fY * b.fY;
SkScalar Sabc = 2 * SkScalarSqrt(A + B + C);
SkScalar A_2 = SkScalarSqrt(A);
SkScalar A_32 = 2 * A * A_2;
SkScalar C_2 = 2 * SkScalarSqrt(C);
SkScalar BA = B / A_2;
return (A_32 * Sabc + A_2 * B * (Sabc - C_2) +
(4 * C * A - B * B) * SkScalarLog((2 * A_2 + BA + Sabc) / (BA + C_2))) / (4 * A_32);
}
SkScalar SkPathMeasure::compute_quad_segs(const SkPoint pts[3],
SkScalar distance, int mint, int maxt, int ptIndex) {
if (tspan_big_enough(maxt - mint) && quad_too_curvy(pts)) {
@ -209,7 +231,19 @@ void SkPathMeasure::buildSegments() {
case SkPath::kQuad_Verb: {
SkScalar prevD = distance;
distance = this->compute_quad_segs(pts, distance, 0, kMaxTValue, ptIndex);
if (false) {
SkScalar length = compute_quad_len(pts);
if (length) {
distance += length;
Segment* seg = fSegments.append();
seg->fDistance = distance;
seg->fPtIndex = ptIndex;
seg->fType = kQuad_SegType;
seg->fTValue = kMaxTValue;
}
} else {
distance = this->compute_quad_segs(pts, distance, 0, kMaxTValue, ptIndex);
}
if (distance > prevD) {
fPts.append(2, pts + 1);
ptIndex += 2;