text: /*
   * Copyright 2021 Google Inc.
   *
   * Use of this source code is governed by a BSD-style license that can be
   * found in the LICENSE file.
   */
  
  #include "modules/skottie/src/effects/Effects.h"
  
  #include "include/core/SkCanvas.h"
  #include "include/core/SkPictureRecorder.h"
  #include "include/effects/SkRuntimeEffect.h"
  #include "modules/skottie/src/Adapter.h"
  #include "modules/skottie/src/SkottieValue.h"
  #include "modules/sksg/include/SkSGPaint.h"
  #include "modules/sksg/include/SkSGRenderNode.h"
  #include "src/utils/SkJSON.h"
  
  namespace skottie::internal {
  
  #ifdef SK_ENABLE_SKSL
  
  namespace {
  
  static constexpr char gBulgeDisplacementSkSL[] =
      "uniform shader u_layer;"
  
      "uniform float2 u_center;"
      "uniform float2 u_radius;"
      "uniform float  u_h;"
      "uniform float  u_r;"
      "uniform float  u_asinInverseR;"
      "uniform float  u_rcpR;"
      "uniform float  u_rcpAsinInvR;"
      "uniform float  u_selector;"
  
      // AE's bulge effect appears to be a combination of spherical displacement and
      // exponential displacement along the radius.
      // To simplify the math, we pre scale/translate such that the ellipse becomes a
      // circle with radius == 1, centered on origin.
      "float2 displace_sph(float2 v) {"
          "float arc_ratio = asin(length(v)*u_rcpR)*u_rcpAsinInvR;"
          "return normalize(v)*arc_ratio - v;"
      "}"
  
      "float2 displace_exp(float2 v) {"
          "return v*pow(dot(v,v),u_h) - v;"
      "}"
  
      "half2 displace(float2 v) {"
          "float t = dot(v, v);"
          "if (t >= 1) {"
              "return v;"
          "}"
          "float2 d = displace_sph(v) + displace_exp(v);"
          "return v + (d * u_selector);"
      "}"
  
      "half4 main(float2 xy) {"
          "xy = displace(xy);"
          "xy = xy*u_radius + u_center;"
          "return u_layer.eval(xy);"
      "}";
  
  static sk_sp<SkRuntimeEffect> bulge_effect() {
      static const SkRuntimeEffect* effect =
          SkRuntimeEffect::MakeForShader(SkString(gBulgeDisplacementSkSL), {}).effect.release();
      SkASSERT(effect);
  
      return sk_ref_sp(effect);
  }
  
  class BulgeNode final : public sksg::CustomRenderNode {
  public:
      explicit BulgeNode(sk_sp<RenderNode> child, const SkSize& child_size)
          : INHERITED({std::move(child)})
          , fChildSize(child_size) {}
  
      SG_ATTRIBUTE(Center  , SkPoint   , fCenter)
      SG_ATTRIBUTE(Radius  , SkVector  , fRadius)
      SG_ATTRIBUTE(Height  , float     , fHeight)
  
  private:
      sk_sp<SkShader> contentShader() {
          if (!fContentShader || this->hasChildrenInval()) {
              const auto& child = this->children()[0];
              child->revalidate(nullptr, SkMatrix::I());
  
              SkPictureRecorder recorder;
              child->render(recorder.beginRecording(SkRect::MakeSize(fChildSize)));
  
              fContentShader = recorder.finishRecordingAsPicture()
                      ->makeShader(SkTileMode::kRepeat, SkTileMode::kRepeat, SkFilterMode::kLinear,
                                   nullptr, nullptr);
          }
  
          return fContentShader;
      }
  
      sk_sp<SkShader> buildEffectShader() {
          if (fHeight == 0) {
              return nullptr;
          }
  
          SkRuntimeShaderBuilder builder(bulge_effect());
          float adjHeight = std::abs(fHeight)/4;
          float r = (1 + adjHeight)/2/sqrt(adjHeight);
          float h = std::pow(adjHeight, 3)*1.3;
          builder.uniform("u_center")       = fCenter;
          builder.uniform("u_radius")       = fRadius;
          builder.uniform("u_h")            = h;
          builder.uniform("u_r")            = r;
          builder.uniform("u_asinInverseR") = std::asin(1/r);
          builder.uniform("u_rcpR")            = 1.0f/r;
          builder.uniform("u_rcpAsinInvR") = 1.0f/std::asin(1/r);
          builder.uniform("u_selector")     = (fHeight > 0 ? 1.0f : -1.0f);
  
          builder.child("u_layer") = this->contentShader();
  
          const auto lm = SkMatrix::Translate(fCenter.x(), fCenter.y())
                        * SkMatrix::Scale(fRadius.x(), fRadius.y());
          return builder.makeShader(&lm);
      }
  
      SkRect onRevalidate(sksg::InvalidationController* ic, const SkMatrix& ctm) override {
          const auto& child = this->children()[0];
          fEffectShader = buildEffectShader();
          return child->revalidate(ic, ctm);
      }
  
      void onRender(SkCanvas* canvas, const RenderContext* ctx) const override {
          if (fHeight == 0) {
              this->children()[0]->render(canvas, ctx);
              return;
          }
          const auto& bounds = this->bounds();
          const auto local_ctx = ScopedRenderContext(canvas, ctx)
                  .setIsolation(bounds, canvas->getTotalMatrix(), true);
  
          canvas->saveLayer(&bounds, nullptr);
  
          SkPaint effect_paint;
          effect_paint.setShader(fEffectShader);
          effect_paint.setBlendMode(SkBlendMode::kSrcOver);
  
          canvas->drawPaint(effect_paint);
      }
  
      const RenderNode* onNodeAt(const SkPoint&) const override { return nullptr; } // no hit-testing
  
      sk_sp<SkShader> fEffectShader;
      sk_sp<SkShader> fContentShader;
      const SkSize fChildSize;
  
      SkPoint  fCenter = {0,0};
      SkVector fRadius = {0,0};
      float   fHeight = 0;
  
      using INHERITED = sksg::CustomRenderNode;
  };
  
  class BulgeEffectAdapter final : public DiscardableAdapterBase<BulgeEffectAdapter,
                                                               BulgeNode> {
  public:
      BulgeEffectAdapter(const skjson::ArrayValue& jprops,
                        const AnimationBuilder& abuilder,
                        sk_sp<BulgeNode> node)
          : INHERITED(std::move(node))
      {
          enum : size_t {
              kHorizontalRadius_Index = 0,
              kVerticalRadius_Index = 1,
              kBulgeCenter_Index = 2,
              kBulgeHeight_Index = 3,
              // kTaper_Index = 4,
              // kAA_Index = 5,
              // kPinning_Index = 6,
          };
          EffectBinder(jprops, abuilder, this).bind(kHorizontalRadius_Index, fHorizontalRadius)
                                              .bind(kVerticalRadius_Index, fVerticalRadius)
                                              .bind(kBulgeCenter_Index, fCenter)
                                              .bind(kBulgeHeight_Index, fBulgeHeight);
      }
  
  private:
      void onSync() override {
          // pre-shader math
          auto n = this->node();
          n->setCenter({fCenter.x, fCenter.y});
          n->setRadius({fHorizontalRadius, fVerticalRadius});
          n->setHeight(fBulgeHeight);
      }
  
      Vec2Value fCenter;
      ScalarValue fHorizontalRadius,
                  fVerticalRadius,
                  fBulgeHeight;
      using INHERITED = DiscardableAdapterBase<BulgeEffectAdapter, BulgeNode>;
  };
  
  } // namespace
  
  #endif  // SK_ENABLE_SKSL
  
  sk_sp<sksg::RenderNode> EffectBuilder::attachBulgeEffect(const skjson::ArrayValue& jprops,
                                                               sk_sp<sksg::RenderNode> layer) const {
  #ifdef SK_ENABLE_SKSL
      auto shaderNode = sk_make_sp<BulgeNode>(std::move(layer), fLayerSize);
      return fBuilder->attachDiscardableAdapter<BulgeEffectAdapter>(jprops, *fBuilder, std::move(shaderNode));
  #else
      return layer;
  #endif
  }
  
  } // namespace skottie::internal
  