ant-design-vue/components/affix/index.tsx

import { App, CSSProperties, defineComponent, inject } from 'vue';
import PropTypes from '../_util/vue-types';
import classNames from '../_util/classNames';
import omit from 'omit.js';
import ResizeObserver from '../vc-resize-observer';
import BaseMixin from '../_util/BaseMixin';
import throttleByAnimationFrame from '../_util/throttleByAnimationFrame';
import { defaultConfigProvider } from '../config-provider';
import warning from '../_util/warning';
import {
  addObserveTarget,
  removeObserveTarget,
  getTargetRect,
  getFixedTop,
  getFixedBottom,
} from './utils';

function getDefaultTarget() {
  return typeof window !== 'undefined' ? window : null;
}
enum AffixStatus {
  None,
  Prepare,
}
export interface AffixState {
  affixStyle?: CSSProperties;
  placeholderStyle?: CSSProperties;
  status: AffixStatus;
  lastAffix: boolean;
  prevTarget: Window | HTMLElement | null;
}

// Affix
const AffixProps = {
  /**
   * 距离窗口顶部达到指定偏移量后触发
   */
  offsetTop: PropTypes.number,
  offset: PropTypes.number,
  /** 距离窗口底部达到指定偏移量后触发 */
  offsetBottom: PropTypes.number,
  /** 固定状态改变时触发的回调函数 */
  // onChange?: (affixed?: boolean) => void;
  /** 设置 Affix 需要监听其滚动事件的元素，值为一个返回对应 DOM 元素的函数 */
  target: PropTypes.func.def(getDefaultTarget),
  prefixCls: PropTypes.string,
  onChange: PropTypes.func,
  onTestUpdatePosition: PropTypes.func,
};
const Affix = defineComponent({
  name: 'AAffix',
  props: AffixProps,
  mixins: [BaseMixin],
  setup() {
    return {
      configProvider: inject('configProvider', defaultConfigProvider),
    };
  },
  emits: ['change', 'testUpdatePosition'],
  data() {
    return {
      affixStyle: undefined,
      placeholderStyle: undefined,
      status: AffixStatus.None,
      lastAffix: false,
      prevTarget: null,
      timeout: null,
    };
  },
  beforeMount() {
    this.updatePosition = throttleByAnimationFrame(this.updatePosition);
    this.lazyUpdatePosition = throttleByAnimationFrame(this.lazyUpdatePosition);
  },
  mounted() {
    const { target } = this;
    if (target) {
      // [Legacy] Wait for parent component ref has its value.
      // We should use target as directly element instead of function which makes element check hard.
      this.timeout = setTimeout(() => {
        addObserveTarget(target(), this);
        // Mock Event object.
        this.updatePosition();
      });
    }
  },
  updated() {
    this.measure();
  },
  watch: {
    target(val) {
      let newTarget = null;
      if (val) {
        newTarget = val() || null;
      }
      if (this.prevTarget !== newTarget) {
        removeObserveTarget(this);
        if (newTarget) {
          addObserveTarget(newTarget, this);
          // Mock Event object.
          this.updatePosition();
        }
        this.prevTarget = newTarget;
      }
    },
    offsetTop() {
      this.updatePosition();
    },
    offsetBottom() {
      this.updatePosition();
    },
  },
  beforeUnmount() {
    clearTimeout(this.timeout);
    removeObserveTarget(this);
    (this.updatePosition as any).cancel();
    // https://github.com/ant-design/ant-design/issues/22683
    (this.lazyUpdatePosition as any).cancel();
  },
  methods: {
    getOffsetTop() {
      const { offset, offsetBottom } = this;
      let { offsetTop } = this;
      if (typeof offsetTop === 'undefined') {
        offsetTop = offset;
        warning(
          typeof offset === 'undefined',
          'Affix',
          '`offset` is deprecated. Please use `offsetTop` instead.',
        );
      }

      if (offsetBottom === undefined && offsetTop === undefined) {
        offsetTop = 0;
      }
      return offsetTop;
    },

    getOffsetBottom() {
      return this.offsetBottom;
    },
    // =================== Measure ===================
    measure() {
      const { status, lastAffix } = this;
      const { target } = this;
      if (
        status !== AffixStatus.Prepare ||
        !this.$refs.fixedNode ||
        !this.$refs.placeholderNode ||
        !target
      ) {
        return;
      }

      const offsetTop = this.getOffsetTop();
      const offsetBottom = this.getOffsetBottom();

      const targetNode = target();
      if (!targetNode) {
        return;
      }

      const newState = {
        status: AffixStatus.None,
      } as AffixState;
      const targetRect = getTargetRect(targetNode);
      const placeholderReact = getTargetRect(this.$refs.placeholderNode as HTMLElement);
      const fixedTop = getFixedTop(placeholderReact, targetRect, offsetTop);
      const fixedBottom = getFixedBottom(placeholderReact, targetRect, offsetBottom);
      if (fixedTop !== undefined) {
        newState.affixStyle = {
          position: 'fixed',
          top: fixedTop,
          width: placeholderReact.width + 'px',
          height: placeholderReact.height + 'px',
        };
        newState.placeholderStyle = {
          width: placeholderReact.width + 'px',
          height: placeholderReact.height + 'px',
        };
      } else if (fixedBottom !== undefined) {
        newState.affixStyle = {
          position: 'fixed',
          bottom: fixedBottom,
          width: placeholderReact.width + 'px',
          height: placeholderReact.height + 'px',
        };
        newState.placeholderStyle = {
          width: placeholderReact.width + 'px',
          height: placeholderReact.height + 'px',
        };
      }

      newState.lastAffix = !!newState.affixStyle;
      if (lastAffix !== newState.lastAffix) {
        this.$emit('change', newState.lastAffix);
      }

      this.setState(newState);
    },

    prepareMeasure() {
      this.setState({
        status: AffixStatus.Prepare,
        affixStyle: undefined,
        placeholderStyle: undefined,
      });
      this.$forceUpdate();

      // Test if `updatePosition` called
      if (process.env.NODE_ENV === 'test') {
        this.$emit('testUpdatePosition');
      }
    },
    updatePosition() {
      this.prepareMeasure();
    },
    lazyUpdatePosition() {
      const { target } = this;
      const { affixStyle } = this;

      // Check position change before measure to make Safari smooth
      if (target && affixStyle) {
        const offsetTop = this.getOffsetTop();
        const offsetBottom = this.getOffsetBottom();

        const targetNode = target();
        if (targetNode && this.$refs.placeholderNode) {
          const targetRect = getTargetRect(targetNode);
          const placeholderReact = getTargetRect(this.$refs.placeholderNode as HTMLElement);
          const fixedTop = getFixedTop(placeholderReact, targetRect, offsetTop);
          const fixedBottom = getFixedBottom(placeholderReact, targetRect, offsetBottom);

          if (
            (fixedTop !== undefined && affixStyle.top === fixedTop) ||
            (fixedBottom !== undefined && affixStyle.bottom === fixedBottom)
          ) {
            return;
          }
        }
      }
      // Directly call prepare measure since it's already throttled.
      this.prepareMeasure();
    },
  },

  render() {
    const { prefixCls, affixStyle, placeholderStyle, $slots, $props } = this;
    const getPrefixCls = this.configProvider.getPrefixCls;
    const className = classNames({
      [getPrefixCls('affix', prefixCls)]: affixStyle,
    });
    const props = omit($props, ['prefixCls', 'offsetTop', 'offsetBottom', 'target']);
    return (
      <ResizeObserver
        onResize={() => {
          this.updatePosition();
        }}
      >
        <div {...props} style={placeholderStyle} ref="placeholderNode">
          <div class={className} ref="fixedNode" style={affixStyle}>
            {$slots.default && $slots.default()}
          </div>
        </div>
      </ResizeObserver>
    );
  },
});
/* istanbul ignore next */
Affix.install = function(app: App) {
  app.component(Affix.name, Affix);
  return app;
};

export default Affix;