The Tor Browser: gfx/skia/trunk/src/pathops/SkDLineIntersection.cpp@6474c204b198 (annotated)

gfx/skia/trunk/src/pathops/SkDLineIntersection.cpp@6474c204b198 (annotated)

gfx/skia/trunk/src/pathops/SkDLineIntersection.cpp

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkIntersections.h"
 #include "SkPathOpsLine.h"
 /* Determine the intersection point of two lines. This assumes the lines are not parallel,
    and that that the lines are infinite.
    From http://en.wikipedia.org/wiki/Line-line_intersection
  */
 SkDPoint SkIntersections::Line(const SkDLine& a, const SkDLine& b) {
     double axLen = a[1].fX - a[0].fX;
     double ayLen = a[1].fY - a[0].fY;
     double bxLen = b[1].fX - b[0].fX;
     double byLen = b[1].fY - b[0].fY;
     double denom = byLen * axLen - ayLen * bxLen;
     SkASSERT(denom);
     double term1 = a[1].fX * a[0].fY - a[1].fY * a[0].fX;
     double term2 = b[1].fX * b[0].fY - b[1].fY * b[0].fX;
     SkDPoint p;
     p.fX = (term1 * bxLen - axLen * term2) / denom;
     p.fY = (term1 * byLen - ayLen * term2) / denom;
     return p;
 }
 void SkIntersections::cleanUpCoincidence() {
     SkASSERT(fUsed == 2);
     // both t values are good
     bool startMatch = fT[0][0] == 0 && (fT[1][0] == 0 || fT[1][0] == 1);
     bool endMatch = fT[0][1] == 1 && (fT[1][1] == 0 || fT[1][1] == 1);
     if (startMatch || endMatch) {
         removeOne(startMatch);
         return;
     }
     // either t value is good
     bool pStartMatch = fT[0][0] == 0 || fT[1][0] == 0 || fT[1][0] == 1;
     bool pEndMatch = fT[0][1] == 1 || fT[1][1] == 0 || fT[1][1] == 1;
     removeOne(pStartMatch || !pEndMatch);
 }
 void SkIntersections::cleanUpParallelLines(bool parallel) {
     while (fUsed > 2) {
         removeOne(1);
     }
     if (fUsed == 2 && !parallel) {
         bool startMatch = fT[0][0] == 0 || fT[1][0] == 0 || fT[1][0] == 1;
         bool endMatch = fT[0][1] == 1 || fT[1][1] == 0 || fT[1][1] == 1;
         if ((!startMatch && !endMatch) || approximately_equal(fT[0][0], fT[0][1])) {
             SkASSERT(startMatch || endMatch);
             removeOne(endMatch);
         }
     }
 }
 void SkIntersections::computePoints(const SkDLine& line, int used) {
     fPt[0] = line.ptAtT(fT[0][0]);
     if ((fUsed = used) == 2) {
         fPt[1] = line.ptAtT(fT[0][1]);
     }
 }
 int SkIntersections::intersectRay(const SkDLine& a, const SkDLine& b) {
     fMax = 2;
     SkDVector aLen = a[1] - a[0];
     SkDVector bLen = b[1] - b[0];
     /* Slopes match when denom goes to zero:
                       axLen / ayLen ==                   bxLen / byLen
     (ayLen * byLen) * axLen / ayLen == (ayLen * byLen) * bxLen / byLen
              byLen  * axLen         ==  ayLen          * bxLen
              byLen  * axLen         -   ayLen          * bxLen == 0 ( == denom )
      */
     double denom = bLen.fY * aLen.fX - aLen.fY * bLen.fX;
     SkDVector ab0 = a[0] - b[0];
     double numerA = ab0.fY * bLen.fX - bLen.fY * ab0.fX;
     double numerB = ab0.fY * aLen.fX - aLen.fY * ab0.fX;
     numerA /= denom;
     numerB /= denom;
     int used;
     if (!approximately_zero(denom)) {
         fT[0][0] = numerA;
         fT[1][0] = numerB;
         used = 1;
     } else {
        /* See if the axis intercepts match:
                   ay - ax * ayLen / axLen  ==          by - bx * ayLen / axLen
          axLen * (ay - ax * ayLen / axLen) == axLen * (by - bx * ayLen / axLen)
          axLen *  ay - ax * ayLen          == axLen *  by - bx * ayLen
         */
         if (!AlmostEqualUlps(aLen.fX * a[0].fY - aLen.fY * a[0].fX,
                 aLen.fX * b[0].fY - aLen.fY * b[0].fX)) {
             return fUsed = 0;
         }
         // there's no great answer for intersection points for coincident rays, but return something
         fT[0][0] = fT[1][0] = 0;
         fT[1][0] = fT[1][1] = 1;
         used = 2;
     }
     computePoints(a, used);
     return fUsed;
 }
 // note that this only works if both lines are neither horizontal nor vertical
 int SkIntersections::intersect(const SkDLine& a, const SkDLine& b) {
     fMax = 3;  // note that we clean up so that there is no more than two in the end
     // see if end points intersect the opposite line
     double t;
     for (int iA = 0; iA < 2; ++iA) {
         if ((t = b.exactPoint(a[iA])) >= 0) {
             insert(iA, t, a[iA]);
         }
     }
     for (int iB = 0; iB < 2; ++iB) {
         if ((t = a.exactPoint(b[iB])) >= 0) {
             insert(t, iB, b[iB]);
         }
     }
     /* Determine the intersection point of two line segments
        Return FALSE if the lines don't intersect
        from: http://paulbourke.net/geometry/lineline2d/ */
     double axLen = a[1].fX - a[0].fX;
     double ayLen = a[1].fY - a[0].fY;
     double bxLen = b[1].fX - b[0].fX;
     double byLen = b[1].fY - b[0].fY;
     /* Slopes match when denom goes to zero:
                       axLen / ayLen ==                   bxLen / byLen
     (ayLen * byLen) * axLen / ayLen == (ayLen * byLen) * bxLen / byLen
              byLen  * axLen         ==  ayLen          * bxLen
              byLen  * axLen         -   ayLen          * bxLen == 0 ( == denom )
      */
     double axByLen = axLen * byLen;
     double ayBxLen = ayLen * bxLen;
     // detect parallel lines the same way here and in SkOpAngle operator <
     // so that non-parallel means they are also sortable
     bool unparallel = fAllowNear ? NotAlmostEqualUlps(axByLen, ayBxLen)
             : NotAlmostDequalUlps(axByLen, ayBxLen);
     if (unparallel && fUsed == 0) {
         double ab0y = a[0].fY - b[0].fY;
         double ab0x = a[0].fX - b[0].fX;
         double numerA = ab0y * bxLen - byLen * ab0x;
         double numerB = ab0y * axLen - ayLen * ab0x;
         double denom = axByLen - ayBxLen;
         if (between(0, numerA, denom) && between(0, numerB, denom)) {
             fT[0][0] = numerA / denom;
             fT[1][0] = numerB / denom;
             computePoints(a, 1);
         }
     }
     if (fAllowNear || !unparallel) {
         for (int iA = 0; iA < 2; ++iA) {
             if ((t = b.nearPoint(a[iA])) >= 0) {
                 insert(iA, t, a[iA]);
             }
         }
         for (int iB = 0; iB < 2; ++iB) {
             if ((t = a.nearPoint(b[iB])) >= 0) {
                 insert(t, iB, b[iB]);
             }
         }
     }
     cleanUpParallelLines(!unparallel);
     SkASSERT(fUsed <= 2);
     return fUsed;
 }
 static int horizontal_coincident(const SkDLine& line, double y) {
     double min = line[0].fY;
     double max = line[1].fY;
     if (min > max) {
         SkTSwap(min, max);
     }
     if (min > y || max < y) {
         return 0;
     }
     if (AlmostEqualUlps(min, max) && max - min < fabs(line[0].fX - line[1].fX)) {
         return 2;
     }
     return 1;
 }
 static double horizontal_intercept(const SkDLine& line, double y) {
      return SkPinT((y - line[0].fY) / (line[1].fY - line[0].fY));
 }
 int SkIntersections::horizontal(const SkDLine& line, double y) {
     fMax = 2;
     int horizontalType = horizontal_coincident(line, y);
     if (horizontalType == 1) {
         fT[0][0] = horizontal_intercept(line, y);
     } else if (horizontalType == 2) {
         fT[0][0] = 0;
         fT[0][1] = 1;
     }
     return fUsed = horizontalType;
 }
 int SkIntersections::horizontal(const SkDLine& line, double left, double right,
                                 double y, bool flipped) {
     fMax = 2;
     // see if end points intersect the opposite line
     double t;
     const SkDPoint leftPt = { left, y };
     if ((t = line.exactPoint(leftPt)) >= 0) {
         insert(t, (double) flipped, leftPt);
     }
     if (left != right) {
         const SkDPoint rightPt = { right, y };
         if ((t = line.exactPoint(rightPt)) >= 0) {
             insert(t, (double) !flipped, rightPt);
         }
         for (int index = 0; index < 2; ++index) {
             if ((t = SkDLine::ExactPointH(line[index], left, right, y)) >= 0) {
                 insert((double) index, flipped ? 1 - t : t, line[index]);
             }
         }
     }
     int result = horizontal_coincident(line, y);
     if (result == 1 && fUsed == 0) {
         fT[0][0] = horizontal_intercept(line, y);
         double xIntercept = line[0].fX + fT[0][0] * (line[1].fX - line[0].fX);
         if (between(left, xIntercept, right)) {
             fT[1][0] = (xIntercept - left) / (right - left);
             if (flipped) {
                 // OPTIMIZATION: ? instead of swapping, pass original line, use [1].fX - [0].fX
                 for (int index = 0; index < result; ++index) {
                     fT[1][index] = 1 - fT[1][index];
                 }
             }
             fPt[0].fX = xIntercept;
             fPt[0].fY = y;
             fUsed = 1;
         }
     }
     if (fAllowNear || result == 2) {
         if ((t = line.nearPoint(leftPt)) >= 0) {
             insert(t, (double) flipped, leftPt);
         }
         if (left != right) {
             const SkDPoint rightPt = { right, y };
             if ((t = line.nearPoint(rightPt)) >= 0) {
                 insert(t, (double) !flipped, rightPt);
             }
             for (int index = 0; index < 2; ++index) {
                 if ((t = SkDLine::NearPointH(line[index], left, right, y)) >= 0) {
                     insert((double) index, flipped ? 1 - t : t, line[index]);
                 }
             }
         }
     }
     cleanUpParallelLines(result == 2);
     return fUsed;
 }
 static int vertical_coincident(const SkDLine& line, double x) {
     double min = line[0].fX;
     double max = line[1].fX;
     if (min > max) {
         SkTSwap(min, max);
     }
     if (!precisely_between(min, x, max)) {
         return 0;
     }
     if (AlmostEqualUlps(min, max)) {
         return 2;
     }
     return 1;
 }
 static double vertical_intercept(const SkDLine& line, double x) {
     return SkPinT((x - line[0].fX) / (line[1].fX - line[0].fX));
 }
 int SkIntersections::vertical(const SkDLine& line, double x) {
     fMax = 2;
     int verticalType = vertical_coincident(line, x);
     if (verticalType == 1) {
         fT[0][0] = vertical_intercept(line, x);
     } else if (verticalType == 2) {
         fT[0][0] = 0;
         fT[0][1] = 1;
     }
     return fUsed = verticalType;
 }
 int SkIntersections::vertical(const SkDLine& line, double top, double bottom,
                               double x, bool flipped) {
     fMax = 2;
     // see if end points intersect the opposite line
     double t;
     SkDPoint topPt = { x, top };
     if ((t = line.exactPoint(topPt)) >= 0) {
         insert(t, (double) flipped, topPt);
     }
     if (top != bottom) {
         SkDPoint bottomPt = { x, bottom };
         if ((t = line.exactPoint(bottomPt)) >= 0) {
             insert(t, (double) !flipped, bottomPt);
         }
         for (int index = 0; index < 2; ++index) {
             if ((t = SkDLine::ExactPointV(line[index], top, bottom, x)) >= 0) {
                 insert((double) index, flipped ? 1 - t : t, line[index]);
             }
         }
     }
     int result = vertical_coincident(line, x);
     if (result == 1 && fUsed == 0) {
         fT[0][0] = vertical_intercept(line, x);
         double yIntercept = line[0].fY + fT[0][0] * (line[1].fY - line[0].fY);
         if (between(top, yIntercept, bottom)) {
             fT[1][0] = (yIntercept - top) / (bottom - top);
             if (flipped) {
                 // OPTIMIZATION: instead of swapping, pass original line, use [1].fY - [0].fY
                 for (int index = 0; index < result; ++index) {
                     fT[1][index] = 1 - fT[1][index];
                 }
             }
             fPt[0].fX = x;
             fPt[0].fY = yIntercept;
             fUsed = 1;
         }
     }
     if (fAllowNear || result == 2) {
         if ((t = line.nearPoint(topPt)) >= 0) {
             insert(t, (double) flipped, topPt);
         }
         if (top != bottom) {
             SkDPoint bottomPt = { x, bottom };
             if ((t = line.nearPoint(bottomPt)) >= 0) {
                 insert(t, (double) !flipped, bottomPt);
             }
             for (int index = 0; index < 2; ++index) {
                 if ((t = SkDLine::NearPointV(line[index], top, bottom, x)) >= 0) {
                     insert((double) index, flipped ? 1 - t : t, line[index]);
                 }
             }
         }
     }
     cleanUpParallelLines(result == 2);
     return fUsed;
 }
 // from http://www.bryceboe.com/wordpress/wp-content/uploads/2006/10/intersect.py
 // 4 subs, 2 muls, 1 cmp
 static bool ccw(const SkDPoint& A, const SkDPoint& B, const SkDPoint& C) {
     return (C.fY - A.fY) * (B.fX - A.fX) > (B.fY - A.fY) * (C.fX - A.fX);
 }
 // 16 subs, 8 muls, 6 cmps
 bool SkIntersections::Test(const SkDLine& a, const SkDLine& b) {
     return ccw(a[0], b[0], b[1]) != ccw(a[1], b[0], b[1])
             && ccw(a[0], a[1], b[0]) != ccw(a[0], a[1], b[1]);
 }

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gfx/skia/trunk/src/pathops/SkDLineIntersection.cpp@6474c204b198 (annotated)

gfx/skia/trunk/src/pathops/SkDLineIntersection.cpp