react-native-vision-camera/ios/Skia Render Layer/DrawableFrameHostObject.mm

//
//  DrawableFrameHostObject.mm
//  VisionCamera
//
//  Created by Marc Rousavy on 20.07.23.
//  Copyright © 2023 mrousavy. All rights reserved.
//

#import "DrawableFrameHostObject.h"
#import "SkCanvas.h"
#import "SkImageHelpers.h"

std::vector<jsi::PropNameID> DrawableFrameHostObject::getPropertyNames(jsi::Runtime& rt) {
  auto result = FrameHostObject::getPropertyNames(rt);
  
  // Skia - Render Frame
  result.push_back(jsi::PropNameID::forUtf8(rt, std::string("render")));

  if (_canvas != nullptr) {
    auto canvasPropNames = _canvas->getPropertyNames(rt);
    for (auto& prop : canvasPropNames) {
      result.push_back(std::move(prop));
    }
  }

  return result;
}

SkRect inscribe(SkSize size, SkRect rect) {
  auto halfWidthDelta = (rect.width() - size.width()) / 2.0;
  auto halfHeightDelta = (rect.height() - size.height()) / 2.0;
  return SkRect::MakeXYWH(rect.x() + halfWidthDelta,
                          rect.y() + halfHeightDelta, size.width(),
                          size.height());
}

jsi::Value DrawableFrameHostObject::get(jsi::Runtime& runtime, const jsi::PropNameID& propName) {
  auto name = propName.utf8(runtime);

  if (name == "render") {
    auto render = JSI_HOST_FUNCTION_LAMBDA {
      if (_canvas == nullptr) {
        throw jsi::JSError(runtime, "Trying to render a Frame without a Skia Canvas! Did you install Skia?");
      }

      // convert CMSampleBuffer to SkImage
      auto context = _canvas->getCanvas()->recordingContext();
      auto image = SkImageHelpers::convertCMSampleBufferToSkImage(context, frame.buffer);

      // draw SkImage
      if (count > 0) {
        // ..with paint/shader
        auto paintHostObject = arguments[0].asObject(runtime).asHostObject<RNSkia::JsiSkPaint>(runtime);
        auto paint = paintHostObject->getObject();
        _canvas->getCanvas()->drawImage(image, 0, 0, SkSamplingOptions(), paint.get());
      } else {
        // ..without paint/shader
        _canvas->getCanvas()->drawImage(image, 0, 0);
      }

      return jsi::Value::undefined();
    };
    return jsi::Function::createFromHostFunction(runtime, jsi::PropNameID::forUtf8(runtime, "render"), 1, render);
  }
  if (name == "isDrawable") {
    return jsi::Value(_canvas != nullptr);
  }

  if (_canvas != nullptr) {
    // If we have a Canvas, try to access the property on there.
    auto result = _canvas->get(runtime, propName);
    if (!result.isUndefined()) {
      return result;
    }
  }

  // fallback to base implementation
  return FrameHostObject::get(runtime, propName);
}

void DrawableFrameHostObject::invalidateCanvas() {
  _canvas = nullptr;
}