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/*
* Copyright 2008 The Android Open Source Project
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SkMathPriv.h"
#include "SkPointPriv.h"
#if 0
void SkIPoint::rotateCW(SkIPoint* dst) const {
SkASSERT(dst);
// use a tmp in case this == dst
int32_t tmp = fX;
dst->fX = -fY;
dst->fY = tmp;
}
void SkIPoint::rotateCCW(SkIPoint* dst) const {
SkASSERT(dst);
// use a tmp in case this == dst
int32_t tmp = fX;
dst->fX = fY;
dst->fY = -tmp;
}
#endif
///////////////////////////////////////////////////////////////////////////////
void SkPoint::scale(SkScalar scale, SkPoint* dst) const {
SkASSERT(dst);
dst->set(fX * scale, fY * scale);
}
bool SkPoint::normalize() {
return this->setLength(fX, fY, SK_Scalar1);
}
bool SkPoint::setNormalize(SkScalar x, SkScalar y) {
return this->setLength(x, y, SK_Scalar1);
}
bool SkPoint::setLength(SkScalar length) {
return this->setLength(fX, fY, length);
}
// Returns the square of the Euclidian distance to (dx,dy).
static inline float getLengthSquared(float dx, float dy) {
return dx * dx + dy * dy;
}
// Calculates the square of the Euclidian distance to (dx,dy) and stores it in
// *lengthSquared. Returns true if the distance is judged to be "nearly zero".
//
// This logic is encapsulated in a helper method to make it explicit that we
// always perform this check in the same manner, to avoid inconsistencies
// (see http://code.google.com/p/skia/issues/detail?id=560 ).
static inline bool is_length_nearly_zero(float dx, float dy,
float *lengthSquared) {
*lengthSquared = getLengthSquared(dx, dy);
return *lengthSquared <= (SK_ScalarNearlyZero * SK_ScalarNearlyZero);
}
/*
* 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.
*/
template <bool use_rsqrt> bool set_point_length(SkPoint* pt, float x, float y, float length,
float* orig_length = nullptr) {
SkASSERT(!use_rsqrt || (orig_length == nullptr));
float mag = 0;
float mag2;
if (is_length_nearly_zero(x, y, &mag2)) {
pt->set(0, 0);
return false;
}
if (sk_float_isfinite(mag2)) {
float scale;
if (use_rsqrt) {
scale = length * sk_float_rsqrt(mag2);
} else {
mag = sk_float_sqrt(mag2);
scale = length / mag;
}
x *= scale;
y *= scale;
} 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 dmag = sqrt(xx * xx + yy * yy);
double dscale = length / dmag;
x *= dscale;
y *= dscale;
// check if we're not finite, or we're zero-length
if (!sk_float_isfinite(x) || !sk_float_isfinite(y) || (x == 0 && y == 0)) {
pt->set(0, 0);
return false;
}
if (orig_length) {
mag = sk_double_to_float(dmag);
}
}
pt->set(x, y);
if (orig_length) {
*orig_length = mag;
}
return true;
}
SkScalar SkPoint::Normalize(SkPoint* pt) {
float mag;
if (set_point_length<false>(pt, pt->fX, pt->fY, 1.0f, &mag)) {
return mag;
}
return 0;
}
SkScalar SkPoint::Length(SkScalar dx, SkScalar dy) {
float mag2 = dx * dx + dy * dy;
if (SkScalarIsFinite(mag2)) {
return sk_float_sqrt(mag2);
} else {
double xx = dx;
double yy = dy;
return sk_double_to_float(sqrt(xx * xx + yy * yy));
}
}
bool SkPoint::setLength(float x, float y, float length) {
return set_point_length<false>(this, x, y, length);
}
bool SkPointPriv::SetLengthFast(SkPoint* pt, float length) {
return set_point_length<true>(pt, pt->fX, pt->fY, length);
}
///////////////////////////////////////////////////////////////////////////////
SkScalar SkPointPriv::DistanceToLineBetweenSqd(const SkPoint& pt, const SkPoint& a,
const SkPoint& b,
Side* side) {
SkVector u = b - a;
SkVector v = pt - a;
SkScalar uLengthSqd = LengthSqd(u);
SkScalar det = u.cross(v);
if (side) {
SkASSERT(-1 == kLeft_Side &&
0 == kOn_Side &&
1 == kRight_Side);
*side = (Side) SkScalarSignAsInt(det);
}
SkScalar temp = det / uLengthSqd;
temp *= det;
return temp;
}
SkScalar SkPointPriv::DistanceToLineSegmentBetweenSqd(const SkPoint& pt, const SkPoint& a,
const SkPoint& b) {
// See comments to distanceToLineBetweenSqd. If the projection of c onto
// u is between a and b then this returns the same result as that
// function. Otherwise, it returns the distance to the closer of a and
// b. Let the projection of v onto u be v'. There are three cases:
// 1. v' points opposite to u. c is not between a and b and is closer
// to a than b.
// 2. v' points along u and has magnitude less than y. c is between
// a and b and the distance to the segment is the same as distance
// to the line ab.
// 3. v' points along u and has greater magnitude than u. c is not
// not between a and b and is closer to b than a.
// v' = (u dot v) * u / |u|. So if (u dot v)/|u| is less than zero we're
// in case 1. If (u dot v)/|u| is > |u| we are in case 3. Otherwise
// we're in case 2. We actually compare (u dot v) to 0 and |u|^2 to
// avoid a sqrt to compute |u|.
SkVector u = b - a;
SkVector v = pt - a;
SkScalar uLengthSqd = LengthSqd(u);
SkScalar uDotV = SkPoint::DotProduct(u, v);
if (uDotV <= 0) {
return LengthSqd(v);
} else if (uDotV > uLengthSqd) {
return DistanceToSqd(b, pt);
} else {
SkScalar det = u.cross(v);
SkScalar temp = det / uLengthSqd;
temp *= det;
return temp;
}
}
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