daggerheart/module/applications/sheets/daggerheart-sheet.mjs

const { HandlebarsApplicationMixin } = foundry.applications.api;

export default function DhpApplicationMixin(Base) {
  return class DhpSheetV2 extends HandlebarsApplicationMixin(Base) {
    constructor(options={}){
      super(options);

      this._dragDrop = this._createDragDropHandlers();
  }

    _attachPartListeners(partId, htmlElement, options) {
      super._attachPartListeners(partId, htmlElement, options);

      this._dragDrop.forEach(d => d.bind(htmlElement));
    }

    static DEFAULT_OPTIONS = {
      position: {
        width: 480,
        height: "auto"
      },
      actions: {
        onEditImage: this._onEditImage
      },
      dragDrop: [],
    };

    async _prepareContext(_options, objectPath='document') {
      const context = await super._prepareContext(_options);
      context.source = this[objectPath].toObject();
      context.fields = this[objectPath].schema.fields;
      context.systemFields = this[objectPath].system ? this[objectPath].system.schema.fields : {};

      return context;
    }

    static _onEditImage(event, target) {
      const attr = target.dataset.edit;
      const current = foundry.utils.getProperty(this.document, attr);
      const { img } = this.document.constructor.getDefaultArtwork?.(this.document.toObject()) ?? {};
      const fp = new FilePicker({
          current,
          type: "image",
          redirectToRoot: img ? [img] : [],
          callback: async path => this._updateImage.bind(this)(path),
          top: this.position.top + 40,
          left: this.position.left + 10
      });
      return fp.browse();
    }

    async _updateImage(path){
      await this.document.update({ "img": path });
    }

    _createDragDropHandlers() {
      return this.options.dragDrop.map(d => {
        // d.permissions = {
        //   dragstart: this._canDragStart.bind(this),
        //   drop: this._canDragDrop.bind(this)
        // };
        d.callbacks = {
          // dragstart: this._onDragStart.bind(this),
          // dragover: this._onDragOver.bind(this),
          drop: this._onDrop.bind(this)
        };
        return new foundry.applications.ux.DragDrop.implementation(d);
      });
    }

    _onDrop(event) {}
  }
}