michael@0: 
michael@0: /*
michael@0:  * Copyright 2008 The Android Open Source Project
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: 
michael@0: 
michael@0: #include "SkPoint.h"
michael@0: 
michael@0: void SkIPoint::rotateCW(SkIPoint* dst) const {
michael@0:     SkASSERT(dst);
michael@0: 
michael@0:     // use a tmp in case this == dst
michael@0:     int32_t tmp = fX;
michael@0:     dst->fX = -fY;
michael@0:     dst->fY = tmp;
michael@0: }
michael@0: 
michael@0: void SkIPoint::rotateCCW(SkIPoint* dst) const {
michael@0:     SkASSERT(dst);
michael@0: 
michael@0:     // use a tmp in case this == dst
michael@0:     int32_t tmp = fX;
michael@0:     dst->fX = fY;
michael@0:     dst->fY = -tmp;
michael@0: }
michael@0: 
michael@0: ///////////////////////////////////////////////////////////////////////////////
michael@0: 
michael@0: void SkPoint::setIRectFan(int l, int t, int r, int b, size_t stride) {
michael@0:     SkASSERT(stride >= sizeof(SkPoint));
michael@0: 
michael@0:     ((SkPoint*)((intptr_t)this + 0 * stride))->set(SkIntToScalar(l),
michael@0:                                                    SkIntToScalar(t));
michael@0:     ((SkPoint*)((intptr_t)this + 1 * stride))->set(SkIntToScalar(l),
michael@0:                                                    SkIntToScalar(b));
michael@0:     ((SkPoint*)((intptr_t)this + 2 * stride))->set(SkIntToScalar(r),
michael@0:                                                    SkIntToScalar(b));
michael@0:     ((SkPoint*)((intptr_t)this + 3 * stride))->set(SkIntToScalar(r),
michael@0:                                                    SkIntToScalar(t));
michael@0: }
michael@0: 
michael@0: void SkPoint::setRectFan(SkScalar l, SkScalar t, SkScalar r, SkScalar b,
michael@0:                          size_t stride) {
michael@0:     SkASSERT(stride >= sizeof(SkPoint));
michael@0: 
michael@0:     ((SkPoint*)((intptr_t)this + 0 * stride))->set(l, t);
michael@0:     ((SkPoint*)((intptr_t)this + 1 * stride))->set(l, b);
michael@0:     ((SkPoint*)((intptr_t)this + 2 * stride))->set(r, b);
michael@0:     ((SkPoint*)((intptr_t)this + 3 * stride))->set(r, t);
michael@0: }
michael@0: 
michael@0: void SkPoint::rotateCW(SkPoint* dst) const {
michael@0:     SkASSERT(dst);
michael@0: 
michael@0:     // use a tmp in case this == dst
michael@0:     SkScalar tmp = fX;
michael@0:     dst->fX = -fY;
michael@0:     dst->fY = tmp;
michael@0: }
michael@0: 
michael@0: void SkPoint::rotateCCW(SkPoint* dst) const {
michael@0:     SkASSERT(dst);
michael@0: 
michael@0:     // use a tmp in case this == dst
michael@0:     SkScalar tmp = fX;
michael@0:     dst->fX = fY;
michael@0:     dst->fY = -tmp;
michael@0: }
michael@0: 
michael@0: void SkPoint::scale(SkScalar scale, SkPoint* dst) const {
michael@0:     SkASSERT(dst);
michael@0:     dst->set(SkScalarMul(fX, scale), SkScalarMul(fY, scale));
michael@0: }
michael@0: 
michael@0: bool SkPoint::normalize() {
michael@0:     return this->setLength(fX, fY, SK_Scalar1);
michael@0: }
michael@0: 
michael@0: bool SkPoint::setNormalize(SkScalar x, SkScalar y) {
michael@0:     return this->setLength(x, y, SK_Scalar1);
michael@0: }
michael@0: 
michael@0: bool SkPoint::setLength(SkScalar length) {
michael@0:     return this->setLength(fX, fY, length);
michael@0: }
michael@0: 
michael@0: // Returns the square of the Euclidian distance to (dx,dy).
michael@0: static inline float getLengthSquared(float dx, float dy) {
michael@0:     return dx * dx + dy * dy;
michael@0: }
michael@0: 
michael@0: // Calculates the square of the Euclidian distance to (dx,dy) and stores it in
michael@0: // *lengthSquared.  Returns true if the distance is judged to be "nearly zero".
michael@0: //
michael@0: // This logic is encapsulated in a helper method to make it explicit that we
michael@0: // always perform this check in the same manner, to avoid inconsistencies
michael@0: // (see http://code.google.com/p/skia/issues/detail?id=560 ).
michael@0: static inline bool isLengthNearlyZero(float dx, float dy,
michael@0:                                       float *lengthSquared) {
michael@0:     *lengthSquared = getLengthSquared(dx, dy);
michael@0:     return *lengthSquared <= (SK_ScalarNearlyZero * SK_ScalarNearlyZero);
michael@0: }
michael@0: 
michael@0: SkScalar SkPoint::Normalize(SkPoint* pt) {
michael@0:     float x = pt->fX;
michael@0:     float y = pt->fY;
michael@0:     float mag2;
michael@0:     if (isLengthNearlyZero(x, y, &mag2)) {
michael@0:         return 0;
michael@0:     }
michael@0: 
michael@0:     float mag, scale;
michael@0:     if (SkScalarIsFinite(mag2)) {
michael@0:         mag = sk_float_sqrt(mag2);
michael@0:         scale = 1 / mag;
michael@0:     } else {
michael@0:         // our mag2 step overflowed to infinity, so use doubles instead.
michael@0:         // much slower, but needed when x or y are very large, other wise we
michael@0:         // divide by inf. and return (0,0) vector.
michael@0:         double xx = x;
michael@0:         double yy = y;
michael@0:         double magmag = sqrt(xx * xx + yy * yy);
michael@0:         mag = (float)magmag;
michael@0:         // we perform the divide with the double magmag, to stay exactly the
michael@0:         // same as setLength. It would be faster to perform the divide with
michael@0:         // mag, but it is possible that mag has overflowed to inf. but still
michael@0:         // have a non-zero value for scale (thanks to denormalized numbers).
michael@0:         scale = (float)(1 / magmag);
michael@0:     }
michael@0:     pt->set(x * scale, y * scale);
michael@0:     return mag;
michael@0: }
michael@0: 
michael@0: SkScalar SkPoint::Length(SkScalar dx, SkScalar dy) {
michael@0:     float mag2 = dx * dx + dy * dy;
michael@0:     if (SkScalarIsFinite(mag2)) {
michael@0:         return sk_float_sqrt(mag2);
michael@0:     } else {
michael@0:         double xx = dx;
michael@0:         double yy = dy;
michael@0:         return (float)sqrt(xx * xx + yy * yy);
michael@0:     }
michael@0: }
michael@0: 
michael@0: /*
michael@0:  *  We have to worry about 2 tricky conditions:
michael@0:  *  1. underflow of mag2 (compared against nearlyzero^2)
michael@0:  *  2. overflow of mag2 (compared w/ isfinite)
michael@0:  *
michael@0:  *  If we underflow, we return false. If we overflow, we compute again using
michael@0:  *  doubles, which is much slower (3x in a desktop test) but will not overflow.
michael@0:  */
michael@0: bool SkPoint::setLength(float x, float y, float length) {
michael@0:     float mag2;
michael@0:     if (isLengthNearlyZero(x, y, &mag2)) {
michael@0:         return false;
michael@0:     }
michael@0: 
michael@0:     float scale;
michael@0:     if (SkScalarIsFinite(mag2)) {
michael@0:         scale = length / sk_float_sqrt(mag2);
michael@0:     } else {
michael@0:         // our mag2 step overflowed to infinity, so use doubles instead.
michael@0:         // much slower, but needed when x or y are very large, other wise we
michael@0:         // divide by inf. and return (0,0) vector.
michael@0:         double xx = x;
michael@0:         double yy = y;
michael@0:         scale = (float)(length / sqrt(xx * xx + yy * yy));
michael@0:     }
michael@0:     fX = x * scale;
michael@0:     fY = y * scale;
michael@0:     return true;
michael@0: }
michael@0: 
michael@0: bool SkPoint::setLengthFast(float length) {
michael@0:     return this->setLengthFast(fX, fY, length);
michael@0: }
michael@0: 
michael@0: bool SkPoint::setLengthFast(float x, float y, float length) {
michael@0:     float mag2;
michael@0:     if (isLengthNearlyZero(x, y, &mag2)) {
michael@0:         return false;
michael@0:     }
michael@0: 
michael@0:     float scale;
michael@0:     if (SkScalarIsFinite(mag2)) {
michael@0:         scale = length * sk_float_rsqrt(mag2);  // <--- this is the difference
michael@0:     } else {
michael@0:         // our mag2 step overflowed to infinity, so use doubles instead.
michael@0:         // much slower, but needed when x or y are very large, other wise we
michael@0:         // divide by inf. and return (0,0) vector.
michael@0:         double xx = x;
michael@0:         double yy = y;
michael@0:         scale = (float)(length / sqrt(xx * xx + yy * yy));
michael@0:     }
michael@0:     fX = x * scale;
michael@0:     fY = y * scale;
michael@0:     return true;
michael@0: }
michael@0: 
michael@0: 
michael@0: ///////////////////////////////////////////////////////////////////////////////
michael@0: 
michael@0: SkScalar SkPoint::distanceToLineBetweenSqd(const SkPoint& a,
michael@0:                                            const SkPoint& b,
michael@0:                                            Side* side) const {
michael@0: 
michael@0:     SkVector u = b - a;
michael@0:     SkVector v = *this - a;
michael@0: 
michael@0:     SkScalar uLengthSqd = u.lengthSqd();
michael@0:     SkScalar det = u.cross(v);
michael@0:     if (NULL != side) {
michael@0:         SkASSERT(-1 == SkPoint::kLeft_Side &&
michael@0:                   0 == SkPoint::kOn_Side &&
michael@0:                   1 == kRight_Side);
michael@0:         *side = (Side) SkScalarSignAsInt(det);
michael@0:     }
michael@0:     return SkScalarMulDiv(det, det, uLengthSqd);
michael@0: }
michael@0: 
michael@0: SkScalar SkPoint::distanceToLineSegmentBetweenSqd(const SkPoint& a,
michael@0:                                                   const SkPoint& b) const {
michael@0:     // See comments to distanceToLineBetweenSqd. If the projection of c onto
michael@0:     // u is between a and b then this returns the same result as that
michael@0:     // function. Otherwise, it returns the distance to the closer of a and
michael@0:     // b. Let the projection of v onto u be v'.  There are three cases:
michael@0:     //    1. v' points opposite to u. c is not between a and b and is closer
michael@0:     //       to a than b.
michael@0:     //    2. v' points along u and has magnitude less than y. c is between
michael@0:     //       a and b and the distance to the segment is the same as distance
michael@0:     //       to the line ab.
michael@0:     //    3. v' points along u and has greater magnitude than u. c is not
michael@0:     //       not between a and b and is closer to b than a.
michael@0:     // v' = (u dot v) * u / |u|. So if (u dot v)/|u| is less than zero we're
michael@0:     // in case 1. If (u dot v)/|u| is > |u| we are in case 3. Otherwise
michael@0:     // we're in case 2. We actually compare (u dot v) to 0 and |u|^2 to
michael@0:     // avoid a sqrt to compute |u|.
michael@0: 
michael@0:     SkVector u = b - a;
michael@0:     SkVector v = *this - a;
michael@0: 
michael@0:     SkScalar uLengthSqd = u.lengthSqd();
michael@0:     SkScalar uDotV = SkPoint::DotProduct(u, v);
michael@0: 
michael@0:     if (uDotV <= 0) {
michael@0:         return v.lengthSqd();
michael@0:     } else if (uDotV > uLengthSqd) {
michael@0:         return b.distanceToSqd(*this);
michael@0:     } else {
michael@0:         SkScalar det = u.cross(v);
michael@0:         return SkScalarMulDiv(det, det, uLengthSqd);
michael@0:     }
michael@0: }