fix bugs found by computing flat clips in 800K skps

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();
@@ skipping 45 matching lines @@
 double SkDLine::exactPoint(const SkDPoint& xy) const {
     if (xy == fPts[0]) {  // do cheapest test first
         return 0;
     }
     if (xy == fPts[1]) {
         return 1;
     }
     return -1;
 }
 
-double SkDLine::nearPoint(const SkDPoint& xy) const {
+double SkDLine::nearPoint(const SkDPoint& xy, bool* unequal) const {
     if (!AlmostBetweenUlps(fPts[0].fX, xy.fX, fPts[1].fX)
             || !AlmostBetweenUlps(fPts[0].fY, xy.fY, fPts[1].fY)) {
         return -1;
     }
     // project a perpendicular ray from the point to the line; find the T on the line
     SkDVector len = fPts[1] - fPts[0]; // the x/y magnitudes of the line
     double denom = len.fX * len.fX + len.fY * len.fY;  // see DLine intersectRay
     SkDVector ab0 = xy - fPts[0];
     double numer = len.fX * ab0.fX + ab0.fY * len.fY;
     if (!between(0, numer, denom)) {
         return -1;
     }
     double t = numer / denom;
     SkDPoint realPt = ptAtT(t);
     double dist = realPt.distance(xy);   // OPTIMIZATION: can we compare against distSq instead ?
     // find the ordinal in the original line with the largest unsigned exponent
     double tiniest = SkTMin(SkTMin(SkTMin(fPts[0].fX, fPts[0].fY), fPts[1].fX), fPts[1].fY);
     double largest = SkTMax(SkTMax(SkTMax(fPts[0].fX, fPts[0].fY), fPts[1].fX), fPts[1].fY);
     largest = SkTMax(largest, -tiniest);
     if (!AlmostEqualUlps(largest, largest + dist)) { // is the dist within ULPS tolerance?
         return -1;
     }
+    if (unequal) {
+        *unequal = (float) largest != (float) (largest + dist);
+    }
     t = SkPinT(t);
     SkASSERT(between(0, t, 1));
     return t;
 }
 
 bool SkDLine::nearRay(const SkDPoint& xy) const {
     // project a perpendicular ray from the point to the line; find the T on the line
     SkDVector len = fPts[1] - fPts[0]; // the x/y magnitudes of the line
     double denom = len.fX * len.fX + len.fY * len.fY;  // see DLine intersectRay
     SkDVector ab0 = xy - fPts[0];
@@ skipping 83 matching lines @@
     double distSq = distU.fX * distU.fX + distU.fY * distU.fY;
     double dist = sqrt(distSq); // OPTIMIZATION: can we compare against distSq instead ?
     double tiniest = SkTMin(SkTMin(x, top), bottom);
     double largest = SkTMax(SkTMax(x, top), bottom);
     largest = SkTMax(largest, -tiniest);
     if (!AlmostEqualUlps(largest, largest + dist)) { // is the dist within ULPS tolerance?
         return -1;
     }
     return t;
 }