vscroll/dist/esm2015/processes/clip.js

Virtual scroll engine

import { BaseProcessFactory, CommonProcess, ProcessStatus } from './misc/index';
import { Direction } from '../inputs/index';
export default class Clip extends BaseProcessFactory(CommonProcess.clip) {
  static run(scroller) {
    const { workflow } = scroller;
    Clip.doClip(scroller);
    workflow.call({
      process: Clip.process,
      status: ProcessStatus.next
    });
  }
  static doClip(scroller) {
    const { buffer, viewport, state, logger } = scroller;
    const size = { [Direction.backward]: 0, [Direction.forward]: 0 };
    logger.stat(`before clip (${++state.clip.callCount})`);
    const itemsToRemove = buffer.items.filter(item => {
      if (!item.toRemove) {
        return false;
      }
      item.hide();
      size[item.removeDirection] += item.size;
      return true;
    });
    if (itemsToRemove.length) {
      if (size[Direction.backward]) {
        viewport.paddings.byDirection(Direction.backward).size += size[Direction.backward];
      }
      if (size[Direction.forward]) {
        viewport.paddings.byDirection(Direction.forward).size += size[Direction.forward];
      }
      if (scroller.settings.onBeforeClip) {
        scroller.settings.onBeforeClip(itemsToRemove.map(item => item.get()));
      }
    }
    buffer.clip();
    logger.log(() => {
      const list = itemsToRemove.map(({ $index }) => $index);
      return list.length
        ? [
          `clipped ${list.length} item(s) from Buffer` +
            (size.backward ? `, +${size.backward} fwd px` : '') +
            (size.forward ? `, +${size.forward} bwd px` : '') +
            `, range: [${list[0]}..${list[list.length - 1]}]`
        ]
        : 'clipped 0 items from Buffer';
    });
    logger.stat('after clip');
  }
}
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