compute initial winding from projected rays

src/pathops/SkDQuadLineIntersection.cpp

 /*
  * 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"
 #include "SkPathOpsQuad.h"
 
@@ skipping 77 matching lines @@
 
 class LineQuadraticIntersections {
 public:
     enum PinTPoint {
         kPointUninitialized,
         kPointInitialized
     };
 
     LineQuadraticIntersections(const SkDQuad& q, const SkDLine& l, SkIntersections* i)
         : fQuad(q)
-        , fLine(l)
+        , fLine(&l)
         , fIntersections(i)
         , fAllowNear(true) {
         i->setMax(3);  // allow short partial coincidence plus discrete intersection
     }
 
+    LineQuadraticIntersections(const SkDQuad& q)
+        : fQuad(q) 
+        SkDEBUGPARAMS(fLine(NULL))
+        SkDEBUGPARAMS(fIntersections(NULL))
+        SkDEBUGPARAMS(fAllowNear(false)) {
+    }
+
     void allowNear(bool allow) {
         fAllowNear = allow;
     }
 
     void checkCoincident() {
         int last = fIntersections->used() - 1;
         for (int index = 0; index < last; ) {
             double quadMidT = ((*fIntersections)[0][index] + (*fIntersections)[0][index + 1]) / 2;
             SkDPoint quadMidPt = fQuad.ptAtT(quadMidT);
-            double t = fLine.nearPoint(quadMidPt, NULL);
+            double t = fLine->nearPoint(quadMidPt, NULL);
             if (t < 0) {
                 ++index;
                 continue;
             }
             if (fIntersections->isCoincident(index)) {
                 fIntersections->removeOne(index);
                 --last;
             } else if (fIntersections->isCoincident(index + 1)) {
                 fIntersections->removeOne(index + 1);
                 --last;
@@ skipping 13 matching lines @@
         note that cos(a) = A(djacent) / Hypoteneuse
                   sin(a) = O(pposite) / Hypoteneuse
         since we are computing Ts, we can ignore hypoteneuse, the scale factor:
         |  A     -O    |
         |  O      A    |
         A = line[1].fX - line[0].fX (adjacent side of the right triangle)
         O = line[1].fY - line[0].fY (opposite side of the right triangle)
         for each of the three points (e.g. n = 0 to 2)
         quad[n].fY' = (quad[n].fY - line[0].fY) * A - (quad[n].fX - line[0].fX) * O
     */
-        double adj = fLine[1].fX - fLine[0].fX;
-        double opp = fLine[1].fY - fLine[0].fY;
+        double adj = (*fLine)[1].fX - (*fLine)[0].fX;
+        double opp = (*fLine)[1].fY - (*fLine)[0].fY;
         double r[3];
         for (int n = 0; n < 3; ++n) {
-            r[n] = (fQuad[n].fY - fLine[0].fY) * adj - (fQuad[n].fX - fLine[0].fX) * opp;
+            r[n] = (fQuad[n].fY - (*fLine)[0].fY) * adj - (fQuad[n].fX - (*fLine)[0].fX) * opp;
         }
         double A = r[2];
         double B = r[1];
         double C = r[0];
         A += C - 2 * B;  // A = a - 2*b + c
         B -= C;  // B = -(b - c)
         return SkDQuad::RootsValidT(A, 2 * B, C, roots);
     }
 
     int intersect() {
@@ skipping 100 matching lines @@
             fIntersections->flip();
         }
         checkCoincident();
         return fIntersections->used();
     }
 
 protected:
     // add endpoints first to get zero and one t values exactly
     void addExactEndPoints() {
         for (int qIndex = 0; qIndex < 3; qIndex += 2) {
-            double lineT = fLine.exactPoint(fQuad[qIndex]);
+            double lineT = fLine->exactPoint(fQuad[qIndex]);
             if (lineT < 0) {
                 continue;
             }
             double quadT = (double) (qIndex >> 1);
             fIntersections->insert(quadT, lineT, fQuad[qIndex]);
         }
     }
 
     void addNearEndPoints() {
         for (int qIndex = 0; qIndex < 3; qIndex += 2) {
             double quadT = (double) (qIndex >> 1);
             if (fIntersections->hasT(quadT)) {
                 continue;
             }
-            double lineT = fLine.nearPoint(fQuad[qIndex], NULL);
+            double lineT = fLine->nearPoint(fQuad[qIndex], NULL);
             if (lineT < 0) {
                 continue;
             }
             fIntersections->insert(quadT, lineT, fQuad[qIndex]);
         }
         // FIXME: see if line end is nearly on quad
     }
 
     void addExactHorizontalEndPoints(double left, double right, double y) {
         for (int qIndex = 0; qIndex < 3; qIndex += 2) {
@@ skipping 42 matching lines @@
             if (lineT < 0) {
                 continue;
             }
             fIntersections->insert(quadT, lineT, fQuad[qIndex]);
         }
         // FIXME: see if line end is nearly on quad
     }
 
     double findLineT(double t) {
         SkDPoint xy = fQuad.ptAtT(t);
-        double dx = fLine[1].fX - fLine[0].fX;
-        double dy = fLine[1].fY - fLine[0].fY;
+        double dx = (*fLine)[1].fX - (*fLine)[0].fX;
+        double dy = (*fLine)[1].fY - (*fLine)[0].fY;
         if (fabs(dx) > fabs(dy)) {
-            return (xy.fX - fLine[0].fX) / dx;
+            return (xy.fX - (*fLine)[0].fX) / dx;
         }
-        return (xy.fY - fLine[0].fY) / dy;
+        return (xy.fY - (*fLine)[0].fY) / dy;
     }
 
     bool pinTs(double* quadT, double* lineT, SkDPoint* pt, PinTPoint ptSet) {
         if (!approximately_one_or_less_double(*lineT)) {
             return false;
         }
         if (!approximately_zero_or_more_double(*lineT)) {
             return false;
         }
         double qT = *quadT = SkPinT(*quadT);
         double lT = *lineT = SkPinT(*lineT);
         if (lT == 0 || lT == 1 || (ptSet == kPointUninitialized && qT != 0 && qT != 1)) {
-            *pt = fLine.ptAtT(lT);
+            *pt = (*fLine).ptAtT(lT);
         } else if (ptSet == kPointUninitialized) {
             *pt = fQuad.ptAtT(qT);
         }
         SkPoint gridPt = pt->asSkPoint();
-        if (SkDPoint::ApproximatelyEqual(gridPt, fLine[0].asSkPoint())) {
-            *pt = fLine[0];
+        if (SkDPoint::ApproximatelyEqual(gridPt, (*fLine)[0].asSkPoint())) {
+            *pt = (*fLine)[0];
             *lineT = 0;
-        } else if (SkDPoint::ApproximatelyEqual(gridPt, fLine[1].asSkPoint())) {
-            *pt = fLine[1];
+        } else if (SkDPoint::ApproximatelyEqual(gridPt, (*fLine)[1].asSkPoint())) {
+            *pt = (*fLine)[1];
             *lineT = 1;
         }
         if (fIntersections->used() > 0 && approximately_equal((*fIntersections)[1][0], *lineT)) {
             return false;
         }
         if (gridPt == fQuad[0].asSkPoint()) {
             *pt = fQuad[0];
             *quadT = 0;
         } else if (gridPt == fQuad[2].asSkPoint()) {
             *pt = fQuad[2];
             *quadT = 1;
         }
         return true;
     }
 
 private:
     const SkDQuad& fQuad;
-    const SkDLine& fLine;
+    const SkDLine* fLine;
     SkIntersections* fIntersections;
     bool fAllowNear;
 };
 
 int SkIntersections::horizontal(const SkDQuad& quad, double left, double right, double y,
                                 bool flipped) {
     SkDLine line = {{{ left, y }, { right, y }}};
     LineQuadraticIntersections q(quad, line, this);
     return q.horizontalIntersect(y, left, right, flipped);
 }
@@ skipping 12 matching lines @@
 }
 
 int SkIntersections::intersectRay(const SkDQuad& quad, const SkDLine& line) {
     LineQuadraticIntersections q(quad, line, this);
     fUsed = q.intersectRay(fT[0]);
     for (int index = 0; index < fUsed; ++index) {
         fPt[index] = quad.ptAtT(fT[0][index]);
     }
     return fUsed;
 }
+
+int SkIntersections::HorizontalIntercept(const SkDQuad& quad, SkScalar y, double* roots) {
+    LineQuadraticIntersections q(quad);
+    return q.horizontalIntersect(y, roots);
+}
+
+int SkIntersections::VerticalIntercept(const SkDQuad& quad, SkScalar x, double* roots) {
+    LineQuadraticIntersections q(quad);
+    return q.verticalIntersect(x, roots);
+}