skia2/experimental/skottie/SkottieAnimator.cpp

/*
 * Copyright 2017 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "SkottieAnimator.h"

#include "SkCubicMap.h"
#include "SkJSONCPP.h"
#include "SkottieProperties.h"
#include "SkottieParser.h"

#include <memory>

namespace skottie {

namespace {

#define LOG SkDebugf

bool LogFail(const Json::Value& json, const char* msg) {
    const auto dump = json.toStyledString();
    LOG("!! %s: %s", msg, dump.c_str());
    return false;
}

template <typename T>
static inline T lerp(const T&, const T&, float);

template <>
ScalarValue lerp(const ScalarValue& v0, const ScalarValue& v1, float t) {
    SkASSERT(t >= 0 && t <= 1);
    return v0 * (1 - t) + v1 * t;
}

template <>
VectorValue lerp(const VectorValue& v0, const VectorValue& v1, float t) {
    SkASSERT(v0.size() == v1.size());

    VectorValue v;
    v.reserve(v0.size());

    for (size_t i = 0; i < v0.size(); ++i) {
        v.push_back(lerp(v0[i], v1[i], t));
    }

    return v;
}

template <>
ShapeValue lerp(const ShapeValue& v0, const ShapeValue& v1, float t) {
    SkASSERT(t >= 0 && t <= 1);
    SkASSERT(v1.isInterpolatable(v0));

    ShapeValue v;
    SkAssertResult(v1.interpolate(v0, t, &v));
    v.setIsVolatile(true);

    return v;
}

class KeyframeAnimatorBase : public sksg::Animator {
public:
    size_t size() const { return fRecs.size(); }

protected:
    KeyframeAnimatorBase() = default;

    struct KeyframeRec {
        float t0, t1;
        size_t vidx0, vidx1, cmidx;

        bool contains(float t) const { return t0 <= t && t <= t1; }
        bool isConstant() const { return vidx1 == kInvalidIndex; }
        bool isValid() const { return t0 < t1 || this->isConstant(); }
    };

    static constexpr size_t kInvalidIndex = std::numeric_limits<size_t>::max();

    const KeyframeRec& frame(float t) {
        if (!fCachedRec || !fCachedRec->contains(t)) {
            fCachedRec = findFrame(t);
        }
        return *fCachedRec;
    }

    float localT(const KeyframeRec& rec, float t) const {
        SkASSERT(rec.isValid());
        SkASSERT(!rec.isConstant());
        SkASSERT(t > rec.t0 && t < rec.t1);

        auto lt = (t -rec.t0) / (rec.t1 - rec.t0);

        return rec.cmidx != kInvalidIndex
            ? fCubicMaps[rec.cmidx].computeYFromX(lt)
            : lt;
    }

    virtual size_t parseValue(const Json::Value&) = 0;

    void parseKeyFrames(const Json::Value& jframes) {
        if (!jframes.isArray())
            return;

        for (const auto& jframe : jframes) {
            if (!jframe.isObject())
                continue;

            float t0;
            if (!Parse(jframe["t"], &t0)) {
                continue;
            }

            if (!fRecs.empty()) {
                if (fRecs.back().t1 >= t0) {
                    LOG("!! Ignoring out-of-order key frame (t:%f < t:%f)\n", t0, fRecs.back().t1);
                    continue;
                }
                // Back-fill t1 in prev interval.  Note: we do this even if we end up discarding
                // the current interval (to support "t"-only final frames).
                fRecs.back().t1 = t0;
            }

            const auto vidx0 = this->parseValue(jframe["s"]);
            if (vidx0 == kInvalidIndex) {
                continue;
            }

            // Defaults for "hold" frames.
            size_t vidx1 = kInvalidIndex, cmidx = kInvalidIndex;

            if (!ParseDefault(jframe["h"], false)) {
                // Regular frame, requires and end value.
                vidx1 = this->parseValue(jframe["e"]);
                if (vidx1 == kInvalidIndex) {
                    continue;
                }

                // default is linear lerp
                static constexpr SkPoint kDefaultC0 = { 0, 0 },
                                         kDefaultC1 = { 1, 1 };
                const auto c0 = ParseDefault(jframe["i"], kDefaultC0),
                           c1 = ParseDefault(jframe["o"], kDefaultC1);

                if (c0 != kDefaultC0 || c1 != kDefaultC1) {
                    // TODO: is it worth de-duping these?
                    cmidx = fCubicMaps.size();
                    fCubicMaps.emplace_back();
                    // TODO: why do we have to plug these inverted?
                    fCubicMaps.back().setPts(c1, c0);
                }
            }

            fRecs.push_back({t0, t0, vidx0, vidx1, cmidx });
        }

        // If we couldn't determine a t1 for the last frame, discard it.
        if (!fRecs.empty() && !fRecs.back().isValid()) {
            fRecs.pop_back();
        }

        SkASSERT(fRecs.empty() || fRecs.back().isValid());
    }

private:
    const KeyframeRec* findFrame(float t) const {
        SkASSERT(!fRecs.empty());

        auto f0 = &fRecs.front(),
             f1 = &fRecs.back();

        SkASSERT(f0->isValid());
        SkASSERT(f1->isValid());

        if (t < f0->t0) {
            return f0;
        }

        if (t > f1->t1) {
            return f1;
        }

        while (f0 != f1) {
            SkASSERT(f0 < f1);
            SkASSERT(t >= f0->t0 && t <= f1->t1);

            const auto f = f0 + (f1 - f0) / 2;
            SkASSERT(f->isValid());

            if (t > f->t1) {
                f0 = f + 1;
            } else {
                f1 = f;
            }
        }

        SkASSERT(f0 == f1);
        SkASSERT(f0->contains(t));

        return f0;
    }

    std::vector<KeyframeRec> fRecs;
    std::vector<SkCubicMap>  fCubicMaps;
    const KeyframeRec*       fCachedRec = nullptr;

    using INHERITED = sksg::Animator;
};

template <typename T>
class KeyframeAnimator final : public KeyframeAnimatorBase {
public:
    static std::unique_ptr<KeyframeAnimator> Make(const Json::Value& jframes,
                                                  std::function<void(const T&)>&& apply) {
        std::unique_ptr<KeyframeAnimator> animator(new KeyframeAnimator(jframes, std::move(apply)));
        if (!animator->size())
            return nullptr;

        return animator;
    }

protected:
    void onTick(float t) override {
        T val;
        this->eval(this->frame(t), t, &val);

        fApplyFunc(val);
    }

private:
    KeyframeAnimator(const Json::Value& jframes,
                     std::function<void(const T&)>&& apply)
        : fApplyFunc(std::move(apply)) {
        this->parseKeyFrames(jframes);
    }

    size_t parseValue(const Json::Value& jv) override {
        T val;
        if (!Parse(jv, &val) || (!fVs.empty() &&
                ValueTraits<T>::Cardinality(val) != ValueTraits<T>::Cardinality(fVs.back()))) {
            return kInvalidIndex;
        }

        // TODO: full deduping?
        if (fVs.empty() || val != fVs.back()) {
            fVs.push_back(std::move(val));
        }
        return fVs.size() - 1;
    }

    void eval(const KeyframeRec& rec, float t, T* v) const {
        SkASSERT(rec.isValid());
        if (rec.isConstant() || t <= rec.t0) {
            *v = fVs[rec.vidx0];
        } else if (t >= rec.t1) {
            *v = fVs[rec.vidx1];
        } else {
            const auto lt = this->localT(rec, t);
            const auto& v0 = fVs[rec.vidx0];
            const auto& v1 = fVs[rec.vidx1];
            *v = lerp(v0, v1, lt);
        }
    }

    const std::function<void(const T&)> fApplyFunc;
    std::vector<T>                      fVs;


    using INHERITED = KeyframeAnimatorBase;
};

template <typename T>
static inline bool BindPropertyImpl(const Json::Value& jprop,
                                    sksg::Scene::AnimatorList* animators,
                                    std::function<void(const T&)>&& apply,
                                    const T* noop) {
    if (!jprop.isObject())
        return false;

    const auto& jpropA = jprop["a"];
    const auto& jpropK = jprop["k"];

    // Older Json versions don't have an "a" animation marker.
    // For those, we attempt to parse both ways.
    if (!ParseDefault(jpropA, false)) {
        T val;
        if (Parse<T>(jpropK, &val)) {
            // Static property.
            if (noop && val == *noop)
                return false;

            apply(val);
            return true;
        }

        if (!jpropA.isNull()) {
            return LogFail(jprop, "Could not parse (explicit) static property");
        }
    }

    // Keyframe property.
    auto animator = KeyframeAnimator<T>::Make(jpropK, std::move(apply));

    if (!animator) {
        return LogFail(jprop, "Could not parse keyframed property");
    }

    animators->push_back(std::move(animator));

    return true;
}

} // namespace

template <>
bool BindProperty(const Json::Value& jprop,
                  sksg::Scene::AnimatorList* animators,
                  std::function<void(const ScalarValue&)>&& apply,
                  const ScalarValue* noop) {
    return BindPropertyImpl(jprop, animators, std::move(apply), noop);
}

template <>
bool BindProperty(const Json::Value& jprop,
                  sksg::Scene::AnimatorList* animators,
                  std::function<void(const VectorValue&)>&& apply,
                  const VectorValue* noop) {
    return BindPropertyImpl(jprop, animators, std::move(apply), noop);
}

template <>
bool BindProperty(const Json::Value& jprop,
                  sksg::Scene::AnimatorList* animators,
                  std::function<void(const ShapeValue&)>&& apply,
                  const ShapeValue* noop) {
    return BindPropertyImpl(jprop, animators, std::move(apply), noop);
}

} // namespace skottie