@studiometa/js-toolkit/decorators/withScrolledInView/withScrolledInView.js

A set of useful little bits of JavaScript to boost your project! 🚀

import { withMountWhenInView } from "../withMountWhenInView.js";
import {
  damp,
  clamp,
  clamp01,
  getOffsetSizes,
  isFunction,
  domScheduler as scheduler
} from "../../utils/index.js";
import { normalizeOffset, getEdges } from "./utils.js";
function updateProgress(props, axis, progressKey, currentKey) {
  props[progressKey][axis] = props.start[axis] === props.end[axis] ? 0 : clamp01(
    (props[currentKey][axis] - props.start[axis]) / (props.end[axis] - props.start[axis])
  );
}
function updateProps(props, dampFactor, dampPrecision, axis = "x") {
  props.current[axis] = clamp(
    axis === "x" ? window.scrollX : window.scrollY,
    props.start[axis],
    props.end[axis]
  );
  props.dampedCurrent[axis] = damp(
    props.current[axis],
    props.dampedCurrent[axis],
    dampFactor,
    dampPrecision
  );
  updateProgress(props, axis, "progress", "current");
  updateProgress(props, axis, "dampedProgress", "dampedCurrent");
}
function withScrolledInView(BaseClass, options = {}) {
  class WithScrolledInView extends withMountWhenInView(
    BaseClass,
    options
  ) {
    /**
     * Config.
     */
    static config = {
      ...BaseClass.config,
      emits: ["scrolledInView"],
      options: {
        dampFactor: {
          type: Number,
          default: 0.1
        },
        dampPrecision: {
          type: Number,
          default: 1e-3
        },
        offset: {
          type: String,
          default: "start end / end start"
        }
      }
    };
    __props = {
      start: {
        x: 0,
        y: 0
      },
      end: {
        x: 0,
        y: 0
      },
      current: {
        x: 0,
        y: 0
      },
      dampedCurrent: {
        x: 0,
        y: 0
      },
      progress: {
        x: 0,
        y: 0
      },
      dampedProgress: {
        x: 0,
        y: 0
      }
    };
    shouldEvaluateProps = true;
    get props() {
      if (this.shouldEvaluateProps) {
        this.shouldEvaluateProps = false;
        const targetSizes = options.useOffsetSizes ? getOffsetSizes(this.$el) : this.$el.getBoundingClientRect();
        targetSizes.y += window.scrollY;
        targetSizes.x += window.scrollX;
        const containerSizes = {
          x: 0,
          y: 0,
          height: window.innerHeight,
          width: window.innerWidth
        };
        const offset = normalizeOffset(this.$options.offset);
        const [yStart, yEnd] = getEdges("y", targetSizes, containerSizes, offset);
        const yCurrent = clamp(window.scrollY, yStart, yEnd);
        const yProgress = yStart === yEnd ? 0 : clamp01((yCurrent - yStart) / (yEnd - yStart));
        const [xStart, xEnd] = getEdges("x", targetSizes, containerSizes, offset);
        const xCurrent = clamp(window.scrollX, xStart, xEnd);
        const xProgress = xStart === xEnd ? 0 : clamp01((xCurrent - xStart) / (xEnd - xStart));
        this.__props.start.x = xStart;
        this.__props.start.y = yStart;
        this.__props.end.x = xEnd;
        this.__props.end.y = yEnd;
        this.__props.current.x = xCurrent;
        this.__props.current.y = yCurrent;
        this.__props.dampedCurrent.x = xCurrent;
        this.__props.dampedCurrent.y = yCurrent;
        this.__props.progress.x = xProgress;
        this.__props.progress.y = yProgress;
        this.__props.dampedProgress.x = xProgress;
        this.__props.dampedProgress.y = yProgress;
      }
      return this.__props;
    }
    /**
     * Bind listeners.
     */
    constructor(element) {
      super(element);
      const render = () => {
        scheduler.read(() => {
          const renderFn = this.__callMethod("scrolledInView", this.props);
          if (isFunction(renderFn)) {
            scheduler.write(() => {
              renderFn(this.__props);
            });
          }
        });
      };
      const delegate = {
        handleEvent(event) {
          delegate[event.type](event.detail[0]);
        },
        resized: () => {
          this.shouldEvaluateProps = true;
          render();
        },
        scrolled: (props) => {
          if (props.changed.y || props.changed.x) {
            this.$services.enable("ticked");
          }
        },
        mounted: () => render(),
        ticked: () => {
          const { dampFactor, dampPrecision } = this.$options;
          updateProps(this.__props, dampFactor, dampPrecision, "x");
          updateProps(this.__props, dampFactor, dampPrecision, "y");
          if (this.__props.dampedCurrent.x === this.__props.current.x && this.__props.dampedCurrent.y === this.__props.current.y) {
            this.$services.disable("ticked");
          }
          render();
        }
      };
      this.$on("before-mounted", () => {
        this.$on("mounted", delegate);
        this.$on("resized", delegate);
        this.$on("scrolled", delegate);
        this.$on("ticked", delegate);
      });
      this.$on("destroyed", () => {
        this.$off("mounted", delegate);
        this.$off("resized", delegate);
        this.$off("scrolled", delegate);
        this.$off("ticked", delegate);
        this.__props.dampedCurrent.x = this.__props.current.x;
        this.__props.dampedCurrent.y = this.__props.current.y;
        this.__props.dampedProgress.x = this.__props.progress.x;
        this.__props.dampedProgress.y = this.__props.progress.y;
        render();
      });
    }
  }
  return WithScrolledInView;
}
export {
  withScrolledInView
};
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