alt SkEvalQuadAt that returns its answer, using Sk2f

BUG=skia:

Review URL: https://codereview.chromium.org/1011493003

4 files changed, 92 insertions, 25 deletions

diff --git a/bench/GeometryBench.cpp b/bench/GeometryBench.cpp
index fd86effc34..1d8575735f 100644
--- a/bench/GeometryBench.cpp
+++ b/bench/GeometryBench.cpp
@@ -129,3 +129,49 @@ DEF_BENCH( return new GeoRectBench_intersect_rect; )
 DEF_BENCH( return new GeoRectBench_Intersects; )
 
 DEF_BENCH( return new GeoRectBench_sort; )
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+class EvalQuadAt0 : public GeometryBench {
+    SkPoint fPts[3];
+public:
+    EvalQuadAt0() : GeometryBench("evalquadat0") {
+        SkRandom rand;
+        for (int i = 0; i < 3; ++i) {
+            fPts[i].set(rand.nextUScalar1(), rand.nextUScalar1());
+        }
+    }
+    
+protected:
+    void onDraw(const int loops, SkCanvas* canvas) SK_OVERRIDE {
+        SkPoint result;
+        for (int outer = 0; outer < loops; ++outer) {
+            for (int i = 0; i < 10000; ++i) {
+                SkEvalQuadAt(fPts, 0.5f, &result);
+            }
+        }
+    }
+};
+DEF_BENCH( return new EvalQuadAt0; )
+
+class EvalQuadAt1 : public GeometryBench {
+    SkPoint fPts[3];
+public:
+    EvalQuadAt1() : GeometryBench("evalquadat1") {
+        SkRandom rand;
+        for (int i = 0; i < 3; ++i) {
+            fPts[i].set(rand.nextUScalar1(), rand.nextUScalar1());
+        }
+    }
+    
+protected:
+    void onDraw(const int loops, SkCanvas* canvas) SK_OVERRIDE {
+        for (int outer = 0; outer < loops; ++outer) {
+            for (int i = 0; i < 10000; ++i) {
+                SkEvalQuadAt(fPts, 0.5f);
+            }
+        }
+    }
+};
+DEF_BENCH( return new EvalQuadAt1; )
+
diff --git a/src/core/SkGeometry.cpp b/src/core/SkGeometry.cpp
index b4d12dbfa4..063c7822b2 100644
--- a/src/core/SkGeometry.cpp
+++ b/src/core/SkGeometry.cpp
@@ -114,17 +114,10 @@ static SkScalar eval_quad_derivative(const SkScalar src[], SkScalar t) {
     return 2 * SkScalarMulAdd(A, t, B);
 }
 
-static SkScalar eval_quad_derivative_at_half(const SkScalar src[]) {
-    SkScalar A = src[4] - 2 * src[2] + src[0];
-    SkScalar B = src[2] - src[0];
-    return A + 2 * B;
-}
-
-void SkEvalQuadAt(const SkPoint src[3], SkScalar t, SkPoint* pt,
-                  SkVector* tangent) {
+void SkEvalQuadAt(const SkPoint src[3], SkScalar t, SkPoint* pt, SkVector* tangent) {
     SkASSERT(src);
     SkASSERT(t >= 0 && t <= SK_Scalar1);
-
+    
     if (pt) {
         pt->set(eval_quad(&src[0].fX, t), eval_quad(&src[0].fY, t));
     }
@@ -134,20 +127,25 @@ void SkEvalQuadAt(const SkPoint src[3], SkScalar t, SkPoint* pt,
     }
 }
 
-void SkEvalQuadAtHalf(const SkPoint src[3], SkPoint* pt, SkVector* tangent) {
+#include "Sk4x.h"
+
+SkPoint SkEvalQuadAt(const SkPoint src[3], SkScalar t) {
     SkASSERT(src);
+    SkASSERT(t >= 0 && t <= SK_Scalar1);
 
-    if (pt) {
-        SkScalar x01 = SkScalarAve(src[0].fX, src[1].fX);
-        SkScalar y01 = SkScalarAve(src[0].fY, src[1].fY);
-        SkScalar x12 = SkScalarAve(src[1].fX, src[2].fX);
-        SkScalar y12 = SkScalarAve(src[1].fY, src[2].fY);
-        pt->set(SkScalarAve(x01, x12), SkScalarAve(y01, y12));
-    }
-    if (tangent) {
-        tangent->set(eval_quad_derivative_at_half(&src[0].fX),
-                     eval_quad_derivative_at_half(&src[0].fY));
-    }
+    const Sk4f t2(t);
+    const Sk4f two(2);
+    
+    Sk4f P0 = Sk4f::Load2(&src[0].fX);
+    Sk4f P1 = Sk4f::Load2(&src[1].fX);
+    Sk4f P2 = Sk4f::Load2(&src[2].fX);
+    
+    Sk4f A = P2.subtract(P1.multiply(two)).add(P0);
+    Sk4f B = P1.subtract(P0).multiply(two);
+    
+    SkPoint result;
+    A.multiply(t2).add(B).multiply(t2).add(P0).store2(&result.fX);
+    return result;
 }
 
 static void interp_quad_coords(const SkScalar* src, SkScalar* dst, SkScalar t) {
diff --git a/src/core/SkGeometry.h b/src/core/SkGeometry.h
index 4da74f2475..ff863a2294 100644
--- a/src/core/SkGeometry.h
+++ b/src/core/SkGeometry.h
@@ -20,10 +20,8 @@ int SkFindUnitQuadRoots(SkScalar A, SkScalar B, SkScalar C, SkScalar roots[2]);
 /** Set pt to the point on the src quadratic specified by t. t must be
     0 <= t <= 1.0
 */
-void SkEvalQuadAt(const SkPoint src[3], SkScalar t, SkPoint* pt,
-                  SkVector* tangent = NULL);
-void SkEvalQuadAtHalf(const SkPoint src[3], SkPoint* pt,
-                      SkVector* tangent = NULL);
+void SkEvalQuadAt(const SkPoint src[3], SkScalar t, SkPoint* pt, SkVector* tangent = NULL);
+SkPoint SkEvalQuadAt(const SkPoint src[3], SkScalar t);
 
 /** Given a src quadratic bezier, chop it at the specified t value,
     where 0 < t < 1, and return the two new quadratics in dst:
diff --git a/tests/GeometryTest.cpp b/tests/GeometryTest.cpp
index 5151b70805..9be6000a0e 100644
--- a/tests/GeometryTest.cpp
+++ b/tests/GeometryTest.cpp
@@ -7,6 +7,7 @@
 
 #include "SkGeometry.h"
 #include "Test.h"
+#include "SkRandom.h"
 
 static bool nearly_equal(const SkPoint& a, const SkPoint& b) {
     return SkScalarNearlyEqual(a.fX, b.fX) && SkScalarNearlyEqual(a.fY, b.fY);
@@ -33,6 +34,29 @@ static void testChopCubic(skiatest::Reporter* reporter) {
     }
 }
 
+static void test_evalquadat(skiatest::Reporter* reporter) {
+    SkRandom rand;
+    for (int i = 0; i < 1000; ++i) {
+        SkPoint pts[3];
+        for (int j = 0; j < 3; ++j) {
+            pts[j].set(rand.nextSScalar1() * 100, rand.nextSScalar1() * 100);
+        }
+        SkScalar t = 0;
+        const SkScalar dt = SK_Scalar1 / 128;
+        for (int j = 0; j < 128; ++j) {
+            SkPoint r0;
+            SkEvalQuadAt(pts, t, &r0);
+            SkPoint r1 = SkEvalQuadAt(pts, t);
+            bool eq = SkScalarNearlyEqual(r0.fX, r1.fX) && SkScalarNearlyEqual(r0.fY, r1.fY);
+            if (!eq) {
+                SkDebugf("[%d %g] p0 [%10.8f %10.8f] p1 [%10.8f %10.8f]\n", i, t, r0.fX, r0.fY, r1.fX, r1.fY);
+                REPORTER_ASSERT(reporter, eq);
+            }
+            t += dt;
+        }
+    }
+}
+
 DEF_TEST(Geometry, reporter) {
     SkPoint pts[3], dst[5];
 
@@ -58,4 +82,5 @@ DEF_TEST(Geometry, reporter) {
     }
 
     testChopCubic(reporter);
+    test_evalquadat(reporter);
 }