@base-ui-components/react/esm/select/scroll-arrow/SelectScrollArrow.js

Base UI is a library of headless ('unstyled') React components and low-level hooks. You gain complete control over your app's CSS and accessibility features.

'use client';

import * as React from 'react';
import PropTypes from 'prop-types';
import { useComponentRenderer } from '../../utils/useComponentRenderer.js';
import { mergeReactProps } from '../../utils/mergeReactProps.js';
import { useSelectRootContext } from '../root/SelectRootContext.js';
import { useSelectPositionerContext } from '../positioner/SelectPositionerContext.js';
import { useTransitionStatus } from '../../utils/useTransitionStatus.js';
import { useForkRef } from '../../utils/useForkRef.js';
import { useAfterExitAnimation } from '../../utils/useAfterExitAnimation.js';

/**
 * @ignore - internal component.
 */
const SelectScrollArrow = /*#__PURE__*/React.forwardRef(function SelectScrollArrow(props, forwardedRef) {
  const {
    render,
    className,
    direction,
    keepMounted = false,
    ...otherProps
  } = props;
  const {
    alignItemToTrigger,
    popupRef,
    scrollUpArrowVisible,
    scrollDownArrowVisible,
    setScrollUpArrowVisible,
    setScrollDownArrowVisible
  } = useSelectRootContext();
  const {
    side
  } = useSelectPositionerContext();
  const visible = direction === 'up' ? scrollUpArrowVisible : scrollDownArrowVisible;
  const frameRef = React.useRef(-1);
  const scrollArrowRef = React.useRef(null);
  const mergedRef = useForkRef(forwardedRef, scrollArrowRef);
  const {
    mounted,
    transitionStatus,
    setMounted
  } = useTransitionStatus(visible);
  useAfterExitAnimation({
    open: visible,
    animatedElementRef: scrollArrowRef,
    onFinished() {
      setMounted(false);
    }
  });
  const state = React.useMemo(() => ({
    direction,
    visible,
    side,
    transitionStatus
  }), [direction, visible, side, transitionStatus]);
  const getScrollArrowProps = React.useCallback((externalProps = {}) => mergeReactProps(externalProps, {
    'aria-hidden': true,
    children: direction === 'down' ? '▼' : '▲',
    style: {
      position: 'absolute'
    },
    onMouseEnter() {
      if (!alignItemToTrigger) {
        return;
      }
      let prevNow = Date.now();
      function handleFrame() {
        const popupElement = popupRef.current;
        if (!popupElement) {
          return;
        }
        const currentNow = Date.now();
        const msElapsed = currentNow - prevNow;
        prevNow = currentNow;
        const pixelsLeftToScroll = direction === 'up' ? popupElement.scrollTop : popupElement.scrollHeight - popupElement.clientHeight - popupElement.scrollTop;
        const pixelsToScroll = Math.min(pixelsLeftToScroll, msElapsed / 2);
        const isScrolledToTop = popupElement.scrollTop === 0;
        const isScrolledToBottom = Math.round(popupElement.scrollTop + popupElement.clientHeight) >= popupElement.scrollHeight;
        if (msElapsed > 0) {
          if (direction === 'up') {
            setScrollUpArrowVisible(!isScrolledToTop);
          } else if (direction === 'down') {
            setScrollDownArrowVisible(!isScrolledToBottom);
          }
          if (direction === 'up' && isScrolledToTop || direction === 'down' && isScrolledToBottom) {
            return;
          }
        }
        const scrollDirection = direction === 'up' ? -1 : 1;
        if (popupRef.current) {
          popupRef.current.scrollTop += scrollDirection * pixelsToScroll;
        }
        frameRef.current = requestAnimationFrame(handleFrame);
      }
      frameRef.current = requestAnimationFrame(handleFrame);
    },
    onMouseLeave() {
      cancelAnimationFrame(frameRef.current);
    }
  }), [direction, alignItemToTrigger, popupRef, setScrollUpArrowVisible, setScrollDownArrowVisible]);
  const {
    renderElement
  } = useComponentRenderer({
    propGetter: getScrollArrowProps,
    ref: mergedRef,
    render: render ?? 'div',
    className,
    state,
    extraProps: {
      hidden: !mounted,
      ...otherProps
    }
  });
  const shouldRender = visible || keepMounted;
  if (!shouldRender) {
    return null;
  }
  return renderElement();
});
process.env.NODE_ENV !== "production" ? SelectScrollArrow.propTypes /* remove-proptypes */ = {
  // ┌────────────────────────────── Warning ──────────────────────────────┐
  // │ These PropTypes are generated from the TypeScript type definitions. │
  // │ To update them, edit the TypeScript types and run `pnpm proptypes`. │
  // └─────────────────────────────────────────────────────────────────────┘
  /**
   * @ignore
   */
  children: PropTypes.node,
  /**
   * CSS class applied to the element, or a function that
   * returns a class based on the component’s state.
   */
  className: PropTypes.oneOfType([PropTypes.func, PropTypes.string]),
  /**
   * @ignore
   */
  direction: PropTypes.oneOf(['down', 'up']).isRequired,
  /**
   * Whether to keep the HTML element in the DOM while the select menu is not scrollable.
   * @default false
   */
  keepMounted: PropTypes.bool,
  /**
   * Allows you to replace the component’s HTML element
   * with a different tag, or compose it with another component.
   *
   * Accepts a `ReactElement` or a function that returns the element to render.
   */
  render: PropTypes.oneOfType([PropTypes.element, PropTypes.func])
} : void 0;
export { SelectScrollArrow };