[skotty] Native SkPath interpolation

SkPath supports interpolation, no reason to handle that explicitly in
Skotty.

Change skotty::ShapeValue to convert to SkPaths upfront, when parsing,
and then rely in native interpolation.

TBR=
Change-Id: I32d424ea359e0736909d4e51602ffeb14403feed
Reviewed-on: https://skia-review.googlesource.com/90362
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>

3 files changed, 26 insertions, 56 deletions

diff --git a/experimental/skotty/SkottyAnimator.cpp b/experimental/skotty/SkottyAnimator.cpp
index f08e7088da..51c3d33565 100644
--- a/experimental/skotty/SkottyAnimator.cpp
+++ b/experimental/skotty/SkottyAnimator.cpp
@@ -16,12 +16,6 @@ SkScalar lerp_scalar(SkScalar v0, SkScalar v1, float t) {
     return v0 * (1 - t) + v1 * t;
 }
 
-SkPoint lerp_point(const SkPoint& v0, const SkPoint& v1, float t) {
-    SkASSERT(t >= 0 && t <= 1);
-    return SkPoint::Make(lerp_scalar(v0.x(), v1.x(), t),
-                         lerp_scalar(v0.y(), v1.y(), t));
-}
-
 } // namespace
 
 template <>
@@ -45,18 +39,7 @@ void KeyframeInterval<ShapeValue>::lerp(float t, ShapeValue* v) const {
     SkASSERT(fV0.cardinality() == fV1.cardinality());
     SkASSERT(v->cardinality() == 0);
 
-    v->fVertices.reserve(fV0.cardinality());
-    for (int i = 0; i < fV0.fVertices.count(); ++i) {
-        v->fVertices.push_back(
-            BezierVertex({
-                lerp_point(fV0.fVertices[i].fInPoint , fV1.fVertices[i].fInPoint , t),
-                lerp_point(fV0.fVertices[i].fOutPoint, fV1.fVertices[i].fOutPoint, t),
-                lerp_point(fV0.fVertices[i].fVertex  , fV1.fVertices[i].fVertex  , t)
-            }));
-    }
-
-    // hmm, any meaningful interpolation to consider here?
-    v->fClose = fV0.fClose;
+    SkAssertResult(fV0.fPath.interpolate(fV1.fPath, t, &v->fPath));
 }
 
 } // namespace skotty
diff --git a/experimental/skotty/SkottyProperties.cpp b/experimental/skotty/SkottyProperties.cpp
index 7ee4008975..5d94d73ef6 100644
--- a/experimental/skotty/SkottyProperties.cpp
+++ b/experimental/skotty/SkottyProperties.cpp
@@ -70,9 +70,9 @@ bool VectorValue::Parse(const Json::Value& v, VectorValue* vec) {
 }
 
 bool ShapeValue::Parse(const Json::Value& v, ShapeValue* shape) {
-    PointArray inPts,
-               outPts,
-               verts;
+    PointArray inPts,  // Cubic Bezier "in" control points, relative to vertices.
+               outPts, // Cubic Bezier "out" control points, relative to vertices.
+               verts;  // Cubic Bezier vertices.
 
     // Some files appear to wrap keyframes in arrays for no reason.
     if (v.isArray() && v.size() == 1) {
@@ -89,12 +89,26 @@ bool ShapeValue::Parse(const Json::Value& v, ShapeValue* shape) {
         return false;
     }
 
-    SkASSERT(shape->fVertices.empty());
-    for (int i = 0; i < inPts.count(); ++i) {
-        shape->fVertices.emplace_back(BezierVertex({inPts[i], outPts[i], verts[i]}));
+    SkASSERT(shape->fPath.isEmpty());
+
+    if (!verts.empty()) {
+        shape->fPath.moveTo(verts.front());
+    }
+
+    const auto& addCubic = [&](int from, int to) {
+        shape->fPath.cubicTo(verts[from] + outPts[from],
+                             verts[to]   + inPts[to],
+                             verts[to]);
+    };
+
+    for (int i = 1; i < verts.count(); ++i) {
+        addCubic(i - 1, i);
     }
 
-    shape->fClose = ParseBool(v["c"], false);
+    if (!verts.empty() && ParseBool(v["c"], false)) {
+        addCubic(verts.count() - 1, 0);
+        shape->fPath.close();
+    }
 
     return true;
 }
@@ -141,28 +155,7 @@ std::vector<SkScalar> VectorValue::as<std::vector<SkScalar>>() const {
 
 template <>
 SkPath ShapeValue::as<SkPath>() const {
-    SkPath path;
-
-    if (!fVertices.empty()) {
-        path.moveTo(fVertices.front().fVertex);
-    }
-
-    const auto& addCubic = [](const BezierVertex& from, const BezierVertex& to, SkPath* path) {
-        path->cubicTo(from.fVertex + from.fOutPoint,
-                      to.fVertex   + to.fInPoint,
-                      to.fVertex);
-    };
-
-    for (int i = 1; i < fVertices.count(); ++i) {
-        addCubic(fVertices[i - 1], fVertices[i], &path);
-    }
-
-    if (fClose) {
-        addCubic(fVertices.back(), fVertices.front(), &path);
-        path.close();
-    }
-
-    return path;
+    return fPath;
 }
 
 CompositeRRect::CompositeRRect(sk_sp<sksg::RRect> wrapped_node)
diff --git a/experimental/skotty/SkottyProperties.h b/experimental/skotty/SkottyProperties.h
index e1504747b4..990862f195 100644
--- a/experimental/skotty/SkottyProperties.h
+++ b/experimental/skotty/SkottyProperties.h
@@ -8,6 +8,7 @@
 #ifndef SkottyProperties_DEFINED
 #define SkottyProperties_DEFINED
 
+#include "SkPath.h"
 #include "SkPoint.h"
 #include "SkSize.h"
 #include "SkottyPriv.h"
@@ -27,12 +28,6 @@ class Transform;
 
 namespace  skotty {
 
-struct BezierVertex {
-    SkPoint fInPoint,  // "in" control point, relative to the vertex
-            fOutPoint, // "out" control point, relative to the vertex
-            fVertex;
-};
-
 struct ScalarValue {
     float fVal;
 
@@ -73,8 +68,7 @@ struct VectorValue {
 };
 
 struct ShapeValue {
-    SkTArray<BezierVertex, true> fVertices;
-    bool                         fClose = false;
+    SkPath fPath;
 
     ShapeValue()                              = default;
     ShapeValue(const ShapeValue&)             = delete;
@@ -83,7 +77,7 @@ struct ShapeValue {
 
     static bool Parse(const Json::Value&, ShapeValue*);
 
-    size_t cardinality() const { return SkTo<size_t>(fVertices.count()); }
+    size_t cardinality() const { return SkTo<size_t>(fPath.countVerbs()); }
 
     template <typename T>
     T as() const;