fix cubic clip in y

src/core/SkEdgeClipper.cpp

Index: src/core/SkEdgeClipper.cpp
diff --git a/src/core/SkEdgeClipper.cpp b/src/core/SkEdgeClipper.cpp
index 02fb4530fdf375ca866ab7f76f1c2997aa6e3b28..c6a4fb2971312217fa2eb4eb988e9b5594f671b7 100644
--- a/src/core/SkEdgeClipper.cpp
+++ b/src/core/SkEdgeClipper.cpp
@@ -225,63 +225,15 @@ bool SkEdgeClipper::clipQuad(const SkPoint srcPts[3], const SkRect& clip) {
 
 ///////////////////////////////////////////////////////////////////////////////
 
-// Modify pts[] in place so that it is clipped in Y to the clip rect
-static void chop_cubic_in_Y(SkPoint pts[4], const SkRect& clip) {
-
-    // are we partially above
-    if (pts[0].fY < clip.fTop) {
-        SkPoint tmp[7];
-        if (SkChopMonoCubicAtY(pts, clip.fTop, tmp)) {
-            // tmp[3, 4].fY should all be to the below clip.fTop.
-            // Since we can't trust the numerics of
-            // the chopper, we force those conditions now
-            tmp[3].fY = clip.fTop;
-            clamp_ge(tmp[4].fY, clip.fTop);
-
-            pts[0] = tmp[3];
-            pts[1] = tmp[4];
-            pts[2] = tmp[5];
-        } else {
-            // if chopMonoCubicAtY failed, then we may have hit inexact numerics
-            // so we just clamp against the top
-            for (int i = 0; i < 4; i++) {
-                clamp_ge(pts[i].fY, clip.fTop);
-            }
-        }
-    }
-
-    // are we partially below
-    if (pts[3].fY > clip.fBottom) {
-        SkPoint tmp[7];
-        if (SkChopMonoCubicAtY(pts, clip.fBottom, tmp)) {
-            tmp[3].fY = clip.fBottom;
-            clamp_le(tmp[2].fY, clip.fBottom);
-
-            pts[1] = tmp[1];
-            pts[2] = tmp[2];
-            pts[3] = tmp[3];
-        } else {
-            // if chopMonoCubicAtY failed, then we may have hit inexact numerics
-            // so we just clamp against the bottom
-            for (int i = 0; i < 4; i++) {
-                clamp_le(pts[i].fY, clip.fBottom);
-            }
-        }
-    }
-}
-
-static void chop_mono_cubic_at_x(SkPoint pts[4], SkScalar x, SkPoint tmp[7]) {
-    if (SkChopMonoCubicAtX(pts, x, tmp)) {
-        return;
-    }
+static SkScalar mono_cubic_closestT(const SkScalar src[], SkScalar x) {
     SkScalar t = 0.5f;
     SkScalar lastT;
     SkScalar bestT  SK_INIT_TO_AVOID_WARNING;
     SkScalar step = 0.25f;
-    SkScalar D = pts[0].fX;
-    SkScalar A = pts[3].fX + 3*(pts[1].fX - pts[2].fX) - D;
-    SkScalar B = 3*(pts[2].fX - pts[1].fX - pts[1].fX + D);
-    SkScalar C = 3*(pts[1].fX - D);
+    SkScalar D = src[0];
+    SkScalar A = src[6] + 3*(src[2] - src[4]) - D;
+    SkScalar B = 3*(src[4] - src[2] - src[2] + D);
+    SkScalar C = 3*(src[2] - D);
     x -= D;
     SkScalar closest = SK_ScalarMax;
     do {
@@ -295,7 +247,52 @@ static void chop_mono_cubic_at_x(SkPoint pts[4], SkScalar x, SkPoint tmp[7]) {
         t += loc < x ? step : -step;
         step *= 0.5f;
     } while (closest > 0.25f && lastT != t);
-    SkChopCubicAt(pts, tmp, bestT);
+    return bestT;
+}
+
+static void chop_mono_cubic_at_y(SkPoint src[4], SkScalar y, SkPoint dst[7]) {
+    if (SkChopMonoCubicAtY(src, y, dst)) {
+        return;
+    }
+    SkChopCubicAt(src, dst, mono_cubic_closestT(&src->fY, y));
+}
+
+// Modify pts[] in place so that it is clipped in Y to the clip rect
+static void chop_cubic_in_Y(SkPoint pts[4], const SkRect& clip) {
+
+    // are we partially above
+    if (pts[0].fY < clip.fTop) {
+        SkPoint tmp[7];
+        chop_mono_cubic_at_y(pts, clip.fTop, tmp);
+        // tmp[3, 4].fY should all be to the below clip.fTop.
+        // Since we can't trust the numerics of
+        // the chopper, we force those conditions now
+        tmp[3].fY = clip.fTop;
+        clamp_ge(tmp[4].fY, clip.fTop);
+
+        pts[0] = tmp[3];
+        pts[1] = tmp[4];
+        pts[2] = tmp[5];
+    }
+
+    // are we partially below
+    if (pts[3].fY > clip.fBottom) {
+        SkPoint tmp[7];
+        chop_mono_cubic_at_y(pts, clip.fBottom, tmp);
+        tmp[3].fY = clip.fBottom;
+        clamp_le(tmp[2].fY, clip.fBottom);
+
+        pts[1] = tmp[1];
+        pts[2] = tmp[2];
+        pts[3] = tmp[3];
+    }
+}
+
+static void chop_mono_cubic_at_x(SkPoint src[4], SkScalar x, SkPoint dst[7]) {
+    if (SkChopMonoCubicAtX(src, x, dst)) {
+        return;
+    }
+    SkChopCubicAt(src, dst, mono_cubic_closestT(&src->fX, x));
 }
 
 // srcPts[] must be monotonic in X and Y