remove unused SkCubicInterval

src/utils/SkCubicInterval.cpp

-
-/*
- * Copyright 2011 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-#include "SkCubicInterval.h"
-
-static SkScalar eval_cubic(SkScalar c1, SkScalar c2, SkScalar c3,
-                           SkScalar t) {
-    return SkScalarMul(SkScalarMul(SkScalarMul(c3, t) + c2, t) + c1, t);
-}
-
-static SkScalar find_cubic_t(SkScalar c1, SkScalar c2, SkScalar c3,
-                             SkScalar targetX) {
-    SkScalar minT = 0;
-    SkScalar maxT = SK_Scalar1;
-    SkScalar t;
-
-    for (;;) {
-        t = SkScalarAve(minT, maxT);
-        SkScalar x = eval_cubic(c1, c2, c3, t);
-        if (SkScalarNearlyZero(x - targetX)) {
-            break;
-        }
-        // subdivide the range and try again
-        if (x < targetX) {
-            minT = t;
-        } else {
-            maxT = t;
-        }
-    }
-    return t;
-}
-
-/*
-    a(1-t)^3 + 3bt(1-t)^2 + 3ct^2(1-t) + dt^3
-    a: [0, 0]
-    d: [1, 1]
-
-    3bt - 6bt^2 + 3bt^3 + 3ct^2 - 3ct^3 + t^3
-    C1 = t^1: 3b
-    C2 = t^2: 3c - 6b
-    C3 = t^3: 3b - 3c + 1
-
-    ((C3*t + C2)*t + C1)*t
- */
-SkScalar SkEvalCubicInterval(SkScalar x1, SkScalar y1,
-                             SkScalar x2, SkScalar y2,
-                             SkScalar unitX) {
-    x1 = SkScalarPin(x1, 0, SK_Scalar1);
-    x2 = SkScalarPin(x2, 0, SK_Scalar1);
-    unitX = SkScalarPin(unitX, 0, SK_Scalar1);
-
-    // First compute our coefficients in X
-    x1 *= 3;
-    x2 *= 3;
-
-    // now search for t given unitX
-    SkScalar t = find_cubic_t(x1, x2 - 2*x1, x1 - x2 + SK_Scalar1, unitX);
-
-    // now evaluate the cubic in Y
-    y1 *= 3;
-    y2 *= 3;
-    return eval_cubic(y1, y2 - 2*y1, y1 - y2 + SK_Scalar1, t);
-}