Add base types for path ops

src/pathops/SkPathOpsLine.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 "SkPathOpsLine.h"
+
+SkDLine SkDLine::subDivide(double t1, double t2) const {
+    SkDVector delta = tangent();
+    SkDLine dst = {{{
+            fPts[0].fX - t1 * delta.fX, fPts[0].fY - t1 * delta.fY}, {
+            fPts[0].fX - t2 * delta.fX, fPts[0].fY - t2 * delta.fY}}};
+    return dst;
+}
+
+// may have this below somewhere else already:
+// copying here because I thought it was clever
+
+// Copyright 2001, softSurfer (www.softsurfer.com)
+// This code may be freely used and modified for any purpose
+// providing that this copyright notice is included with it.
+// SoftSurfer makes no warranty for this code, and cannot be held
+// liable for any real or imagined damage resulting from its use.
+// Users of this code must verify correctness for their application.
+
+// Assume that a class is already given for the object:
+//    Point with coordinates {float x, y;}
+//===================================================================
+
+// isLeft(): tests if a point is Left|On|Right of an infinite line.
+//    Input:  three points P0, P1, and P2
+//    Return: >0 for P2 left of the line through P0 and P1
+//            =0 for P2 on the line
+//            <0 for P2 right of the line
+//    See: the January 2001 Algorithm on Area of Triangles
+//    return (float) ((P1.x - P0.x)*(P2.y - P0.y) - (P2.x - P0.x)*(P1.y - P0.y));
+double SkDLine::isLeft(const SkDPoint& pt) const {
+    SkDVector p0 = fPts[1] - fPts[0];
+    SkDVector p2 = pt - fPts[0];
+    return p0.cross(p2);
+}
+
+SkDPoint SkDLine::xyAtT(double t) const {
+    double one_t = 1 - t;
+    SkDPoint result = { one_t * fPts[0].fX + t * fPts[1].fX, one_t * fPts[0].fY + t * fPts[1].fY };
+    return result;
+}