path ops -- rewrite angle sort

src/pathops/SkPathOpsCubic.cpp

Index: src/pathops/SkPathOpsCubic.cpp
===================================================================
--- src/pathops/SkPathOpsCubic.cpp	(revision 9425)
+++ src/pathops/SkPathOpsCubic.cpp	(working copy)
@@ -403,11 +403,23 @@
     /* by = */ dst[1].fY = (my * 2 - ny) / 18;
     /* cx = */ dst[2].fX = (nx * 2 - mx) / 18;
     /* cy = */ dst[2].fY = (ny * 2 - my) / 18;
+    // FIXME: call align() ?
     return dst;
 }
 
+void SkDCubic::align(int endIndex, int ctrlIndex, SkDPoint* dstPt) const {  
+    if (fPts[endIndex].fX == fPts[ctrlIndex].fX) {
+        dstPt->fX = fPts[endIndex].fX;
+    }
+    if (fPts[endIndex].fY == fPts[ctrlIndex].fY) {
+        dstPt->fY = fPts[endIndex].fY;
+    }
+}
+
 void SkDCubic::subDivide(const SkDPoint& a, const SkDPoint& d,
                          double t1, double t2, SkDPoint dst[2]) const {
+    SkASSERT(t1 != t2);
+#if 0
     double ex = interp_cubic_coords(&fPts[0].fX, (t1 * 2 + t2) / 3);
     double ey = interp_cubic_coords(&fPts[0].fY, (t1 * 2 + t2) / 3);
     double fx = interp_cubic_coords(&fPts[0].fX, (t1 + t2 * 2) / 3);
@@ -420,6 +432,30 @@
     /* by = */ dst[0].fY = (my * 2 - ny) / 18;
     /* cx = */ dst[1].fX = (nx * 2 - mx) / 18;
     /* cy = */ dst[1].fY = (ny * 2 - my) / 18;
+#else
+    // this approach assumes that the control points computed directly are accurate enough
+    SkDCubic sub = subDivide(t1, t2);
+    dst[0] = sub[1] + (a - sub[0]);
+    dst[1] = sub[2] + (d - sub[3]);
+#endif
+    if (t1 == 0 || t2 == 0) {
+        align(0, 1, t1 == 0 ? &dst[0] : &dst[1]);
+    }
+    if (t1 == 1 || t2 == 1) {
+        align(3, 2, t1 == 1 ? &dst[0] : &dst[1]);
+    }
+    if (precisely_subdivide_equal(dst[0].fX, a.fX)) {
+        dst[0].fX = a.fX;
+    }
+    if (precisely_subdivide_equal(dst[0].fY, a.fY)) {
+        dst[0].fY = a.fY;
+    }
+    if (precisely_subdivide_equal(dst[1].fX, d.fX)) {
+        dst[1].fX = d.fX;
+    }
+    if (precisely_subdivide_equal(dst[1].fY, d.fY)) {
+        dst[1].fY = d.fY;
+    }
 }
 
 /* classic one t subdivision */