1 files changed, 79 insertions, 0 deletions
diff --git a/chromium/third_party/skia/experimental/Intersection/QuadraticSubDivide.cpp b/chromium/third_party/skia/experimental/Intersection/QuadraticSubDivide.cpp
new file mode 100644
index 00000000000..2ced9e325a7
--- /dev/null
+++ b/chromium/third_party/skia/experimental/Intersection/QuadraticSubDivide.cpp
@@ -0,0 +1,79 @@
+/*
+ * 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 "CurveIntersection.h"
+#include "IntersectionUtilities.h"
+#include "QuadraticUtilities.h"
+
+/*
+Given a quadratic q, t1, and t2, find a small quadratic segment.
+
+The new quadratic is defined by A, B, and C, where
+ A = c[0]*(1 - t1)*(1 - t1) + 2*c[1]*t1*(1 - t1) + c[2]*t1*t1
+ C = c[3]*(1 - t1)*(1 - t1) + 2*c[2]*t1*(1 - t1) + c[1]*t1*t1
+
+To find B, compute the point halfway between t1 and t2:
+
+q(at (t1 + t2)/2) == D
+
+Next, compute where D must be if we know the value of B:
+
+_12 = A/2 + B/2
+12_ = B/2 + C/2
+123 = A/4 + B/2 + C/4
+    = D
+
+Group the known values on one side:
+
+B   = D*2 - A/2 - C/2
+*/
+
+static double interp_quad_coords(const double* src, double t)
+{
+    double ab = interp(src[0], src[2], t);
+    double bc = interp(src[2], src[4], t);
+    double abc = interp(ab, bc, t);
+    return abc;
+}
+
+void sub_divide(const Quadratic& src, double t1, double t2, Quadratic& dst) {
+    double ax = dst[0].x = interp_quad_coords(&src[0].x, t1);
+    double ay = dst[0].y = interp_quad_coords(&src[0].y, t1);
+    double dx = interp_quad_coords(&src[0].x, (t1 + t2) / 2);
+    double dy = interp_quad_coords(&src[0].y, (t1 + t2) / 2);
+    double cx = dst[2].x = interp_quad_coords(&src[0].x, t2);
+    double cy = dst[2].y = interp_quad_coords(&src[0].y, t2);
+    /* bx = */ dst[1].x = 2*dx - (ax + cx)/2;
+    /* by = */ dst[1].y = 2*dy - (ay + cy)/2;
+}
+
+_Point sub_divide(const Quadratic& src, const _Point& a, const _Point& c, double t1, double t2) {
+    _Point b;
+    double dx = interp_quad_coords(&src[0].x, (t1 + t2) / 2);
+    double dy = interp_quad_coords(&src[0].y, (t1 + t2) / 2);
+    b.x = 2 * dx - (a.x + c.x) / 2;
+    b.y = 2 * dy - (a.y + c.y) / 2;
+    return b;
+}
+
+/* classic one t subdivision */
+static void interp_quad_coords(const double* src, double* dst, double t)
+{
+    double ab = interp(src[0], src[2], t);
+    double bc = interp(src[2], src[4], t);
+
+    dst[0] = src[0];
+    dst[2] = ab;
+    dst[4] = interp(ab, bc, t);
+    dst[6] = bc;
+    dst[8] = src[4];
+}
+
+void chop_at(const Quadratic& src, QuadraticPair& dst, double t)
+{
+    interp_quad_coords(&src[0].x, &dst.pts[0].x, t);
+    interp_quad_coords(&src[0].y, &dst.pts[0].y, t);
+}