SkScalar SkPoint::Normalize(SkPoint* pt) {
float x = pt->fX;
float y = pt->fY;
float mag2;
if (isLengthNearlyZero(x, y, &mag2)) {
return 0;
}
float mag, scale;
if (SkScalarIsFinite(mag2)) {
mag = sk_float_sqrt(mag2);
scale = 1 / mag;
} else {
// our mag2 step overflowed to infinity, so use doubles instead.
// much slower, but needed when x or y are very large, other wise we
// divide by inf. and return (0,0) vector.
double xx = x;
double yy = y;
double magmag = sqrt(xx * xx + yy * yy);
mag = (float)magmag;
// we perform the divide with the double magmag, to stay exactly the
// same as setLength. It would be faster to perform the divide with
// mag, but it is possible that mag has overflowed to inf. but still
// have a non-zero value for scale (thanks to denormalized numbers).
scale = (float)(1 / magmag);
}
pt->set(x * scale, y * scale);
return mag;
}
/*
* We have to worry about 2 tricky conditions:
* 1. underflow of mag2 (compared against nearlyzero^2)
* 2. overflow of mag2 (compared w/ isfinite)
*
* If we underflow, we return false. If we overflow, we compute again using
* doubles, which is much slower (3x in a desktop test) but will not overflow.
*/
bool SkPoint::setLength(float x, float y, float length) {
float mag2;
if (isLengthNearlyZero(x, y, &mag2)) {
return false;
}
float scale;
if (SkScalarIsFinite(mag2)) {
scale = length / sk_float_sqrt(mag2);
} else {
// our mag2 step overflowed to infinity, so use doubles instead.
// much slower, but needed when x or y are very large, other wise we
// divide by inf. and return (0,0) vector.
double xx = x;
double yy = y;
#ifdef SK_DISCARD_DENORMALIZED_FOR_SPEED
// The iOS ARM processor discards small denormalized numbers to go faster.
// Casting this to a float would cause the scale to go to zero. Keeping it
// as a double for the multiply keeps the scale non-zero.
double dscale = length / sqrt(xx * xx + yy * yy);
fX = x * dscale;
fY = y * dscale;
return true;
#else
scale = (float)(length / sqrt(xx * xx + yy * yy));
#endif
}
fX = x * scale;
fY = y * scale;
return true;
}
bool SkPoint::setLength(float x, float y, float length) {
float mag2;
if (!isLengthNearlyZero(x, y, &mag2)) {
float scale = length / sk_float_sqrt(mag2);
fX = x * scale;
fY = y * scale;
return true;
}
return false;
}
SkScalar SkPoint::Normalize(SkPoint* pt) {
Sk64 mag2;
if (!isLengthNearlyZero(pt->fX, pt->fY, &mag2)) {
SkScalar mag = mag2.getSqrt();
SkScalar scale = SkScalarInvert(mag);
pt->fX = SkScalarMul(pt->fX, scale);
pt->fY = SkScalarMul(pt->fY, scale);
return mag;
}
return 0;
}
SkScalar SkPoint::Normalize(SkPoint* pt) {
float mag2;
if (!isLengthNearlyZero(pt->fX, pt->fY, &mag2)) {
float mag = sk_float_sqrt(mag2);
float scale = 1.0f / mag;
pt->fX = pt->fX * scale;
pt->fY = pt->fY * scale;
return mag;
}
return 0;
}
bool SkPoint::setLengthFast(float x, float y, float length) {
float mag2;
if (isLengthNearlyZero(x, y, &mag2)) {
return false;
}
float scale;
if (SkScalarIsFinite(mag2)) {
scale = length * sk_float_rsqrt(mag2); // <--- this is the difference
} else {
// our mag2 step overflowed to infinity, so use doubles instead.
// much slower, but needed when x or y are very large, other wise we
// divide by inf. and return (0,0) vector.
double xx = x;
double yy = y;
scale = (float)(length / sqrt(xx * xx + yy * yy));
}
fX = x * scale;
fY = y * scale;
return true;
}
bool SkPoint::CanNormalize(SkScalar dx, SkScalar dy) {
Sk64 mag2_unused;
return !isLengthNearlyZero(dx, dy, &mag2_unused);
}
