Solution: Compability with react-custom-scrollbars

[5angel]

After a long discussion in #143 I also took a shot at this problem and arrived to the following solution:

import React, { Component } from 'react';
import { Scrollbars } from 'react-custom-scrollbars';
import { List } from 'react-virtualized';

const SCROLL_DIRECTION_BACKWARD = -1;
const SCROLL_DIRECTION_FORWARD = 1;
const SCROLL_POSITION_CHANGE_REASON_OBSERVED = 'observed';

const listStyle = {
  overflowX: false,
  overflowY: false,
};

export default class SmartList extends Component {
  _getScrollDirection(scrollTop) {
    const {
      scrollTop: oldScrollTop,
      scrollDirectionVertical,
    } = this.List.Grid.state;

    if (scrollTop !== oldScrollTop) {
      return scrollTop > oldScrollTop ?
        SCROLL_DIRECTION_FORWARD :
        SCROLL_DIRECTION_BACKWARD;
    }

    return scrollDirectionVertical;
  }

  handleScroll = ({ target }) => {
    const {
      scrollTop,
      scrollLeft,
    } = target;

    const { Grid: grid } = this.List;

    grid._debounceScrollEnded();

    const scrollDirectionVertical = this._getScrollDirection(scrollTop);
    const totalColumnsWidth = grid._columnSizeAndPositionManager.getTotalSize();
    const totalRowsHeight = grid._rowSizeAndPositionManager.getTotalSize();

    grid.setState({
      isScrolling: true,
      scrollDirectionVertical,
      scrollTop,
      scrollPositionChangeReason: SCROLL_POSITION_CHANGE_REASON_OBSERVED,
    });

    grid._invokeOnScrollMemoizer({ scrollLeft, scrollTop, totalColumnsWidth, totalRowsHeight });
  };

  List = null;

  render() {
    const { width, height } = this.props;

    return (
      <Scrollbars
        autoHide
        style={{ width, height }}
        onScroll={this.handleScroll}
      >
        <List
          {...this.props}
          ref={instance => (this.List = instance)}
          style={listStyle}
        />
      </Scrollbars>
    );
  }
}

You can see that I've pretty much rewritten the _onScroll method in https://github.com/bvaughn/react-virtualized/blob/master/source/Grid/Grid.js#L1110

The simplest way to make this work will be to add a way to bypass the container node check in _onScroll.

@bvaughn what do you think?

[bvaughn]

I don't understand this comment on #143:

@bvaughn can you maybe add a second parameter to _onScroll that let you pass event from another container?

_onScroll (and _invokeOnScrollMemoizer) are private- not intended to be called by external code.

I guess Grid could be refactored to add a new handleScroll({ scrollLeft, scrollTop }) method that _onScroll calls internally but could also be called externally. This would avoid the node-check.

[bvaughn]

If you'd like to submit a PR I'll review it.

[5angel]

@bvaughn ah, yes, you're right about that one. brb 👍

[5angel]

@bvaughn I'm a bit concerned that test don't pass even without my changes 🤔

[bvaughn]

https://circleci.com/gh/bvaughn/react-virtualized

[bvaughn]

Did you yarn install or npm install ?

[5angel]

This is a fresh system, so I installed latest node an run npm install. And it failed too, yeah. Should I try yarn?

[bvaughn]

Use yarn install

[5angel]

@bvaughn 👌 Yup, it works now, thanks.

[bvaughn]

😅 Glad to hear

[alexpyzhianov]

For anyone who struggles with handleScrollEvent and doesn't understand how it is related to the code snippet above, here how it all looks with the new method. @5angel tons of 👍 to you

import React, { Component } from 'react';
import { Scrollbars } from 'react-custom-scrollbars';
import { List } from 'react-virtualized';

const listStyle = {
  overflowX: false,
  overflowY: false,
};

export default class SmartList extends Component {
  handleScroll = ({ target }) => {
    const { scrollTop, scrollLeft } = target;

    const { Grid: grid } = this.List;

    grid.handleScrollEvent({ scrollTop, scrollLeft });
  }

  List = null;

  render() {
    const { width, height } = this.props;

    return (
      <Scrollbars
        autoHide
        style={{ width, height }}
        onScroll={this.handleScroll}
      >
        <List
          {...this.props}
          ref={instance => (this.List = instance)}
          style={listStyle}
        />
      </Scrollbars>
    );
  }
}

[evercool]

Hi, may I ask for help with solution from @alexpyzhianov? The method handleScrollEvent when fires and updates Grid component causes lags on scrolling. The method handleScrollEvent was bombed by scrolling events so I tried to reduce them by calling it only for scrolls of certain height. It wasnt so laggy, but still each call cause lag on scroll. Next step I tried was to call it in setTimeout to force run it in a new thread (I was desperated) - same result. Any ideas?

[vbrvk]

@evercool have you found solution?

[Justin-ZS]

Maybe another solution, it works for me:

import React from 'react';
import { Scrollbars } from 'react-custom-scrollbars';
import { List, AutoSizer } from 'react-virtualized';

export class DemoList extends React.Component {
  handleScroll = (e) => {
    this.list.Grid._onScroll(e);
  }
  componentDidMount = () => {
    this.list.Grid._scrollingContainer = this.scroll.view;
  }
  render() {
    return (
        <AutoSizer>
          {({ height, width }) => (
            <Scrollbars ref={node => this.scroll = node} onScroll={this.handleScroll} style={{ height, width }}>
              <List
                {...this.props}
                style={{ overflowX: 'visible', overflowY: 'visible' }}
                ref={node => this.list = node}
                height={height}
              />
            </Scrollbars>
          )}
        </AutoSizer>
    );
  }
}

[anstosa]

@evercool @borovik96 I'm having a similar problem. Trying to use react-custom-scrollbars instead of ScrollSync to avoid lag problem but the onScroll callback is called for API updates as well so on scroll, the natural event fires, which I use to call scrollTop(y) on the partner Scrollbars instance, but then it triggers onScroll on the other instance and fires it back, etc etc. react-custom-scrollbars does not differentiate API events from user events unfortunately... Any ideas?

[serle]

Can this technique be used with the table and would it let the headers be fixed and only scroll the data?