add helper to create fancy underlines

src/pathops/SkPathOpsQuad.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPathOpsQuad_DEFINED
 #define SkPathOpsQuad_DEFINED
 
@@ skipping 44 matching lines @@
     }
 
     const SkDPoint& operator[](int n) const { SkASSERT(n >= 0 && n < kPointCount); return fPts[n]; }
     SkDPoint& operator[](int n) { SkASSERT(n >= 0 && n < kPointCount); return fPts[n]; }
 
     static int AddValidTs(double s[], int realRoots, double* t);
     void align(int endIndex, SkDPoint* dstPt) const;
     SkDQuadPair chopAt(double t) const;
     SkDVector dxdyAtT(double t) const;
     static int FindExtrema(const double src[], double tValue[1]);
+
+    /**
+     *  Return the number of valid roots (0 < root < 1) for this cubic intersecting the
+     *  specified horizontal line.
+     */
+    int horizontalIntersect(double yIntercept, double roots[2]) const;
+
     bool hullIntersects(const SkDQuad& , bool* isLinear) const;
     bool hullIntersects(const SkDConic& , bool* isLinear) const;
     bool hullIntersects(const SkDCubic& , bool* isLinear) const;
     bool isLinear(int startIndex, int endIndex) const;
     bool monotonicInX() const;
     bool monotonicInY() const;
     void otherPts(int oddMan, const SkDPoint* endPt[2]) const;
     SkDPoint ptAtT(double t) const;
     static int RootsReal(double A, double B, double C, double t[2]);
     static int RootsValidT(const double A, const double B, const double C, double s[2]);
     static void SetABC(const double* quad, double* a, double* b, double* c);
     SkDQuad subDivide(double t1, double t2) const;
     static SkDQuad SubDivide(const SkPoint a[kPointCount], double t1, double t2) {
         SkDQuad quad;
         quad.set(a);
         return quad.subDivide(t1, t2);
     }
     SkDPoint subDivide(const SkDPoint& a, const SkDPoint& c, double t1, double t2) const;
     static SkDPoint SubDivide(const SkPoint pts[kPointCount], const SkDPoint& a, const SkDPoint& c,
                               double t1, double t2) {
         SkDQuad quad;
         quad.set(pts);
         return quad.subDivide(a, c, t1, t2);
     }
 
+    /**
+     *  Return the number of valid roots (0 < root < 1) for this cubic intersecting the
+     *  specified vertical line.
+     */
+    int verticalIntersect(double xIntercept, double roots[2]) const;
+
     SkDCubic debugToCubic() const;
     // utilities callable by the user from the debugger when the implementation code is linked in
     void dump() const;
     void dumpID(int id) const;
     void dumpInner() const;
 
 private:
 //  static double Tangent(const double* quadratic, double t);  // uncalled
 };
 
 #endif