vscroll/dist/esm2015/processes/render.js

Virtual scroll engine

import { BaseProcessFactory, CommonProcess, ProcessStatus } from './misc/index';
export default class Render extends BaseProcessFactory(CommonProcess.render) {
  static run(scroller) {
    const { workflow, state: { cycle, render, scroll, fetch }, viewport, routines } = scroller;
    scroller.logger.stat('before new items render');
    if (scroll.positionBeforeAsync === null) {
      scroll.positionBeforeAsync = viewport.scrollPosition;
    }
    render.cancel = routines.render(() => {
      render.cancel = null;
      if (Render.doRender(scroller)) {
        workflow.call({
          process: Render.process,
          status: render.noSize ? ProcessStatus.done : ProcessStatus.next,
          payload: { process: cycle.initiator }
        });
      }
      else {
        workflow.call({
          process: Render.process,
          status: ProcessStatus.error,
          payload: { error: 'Can\'t associate item with element' }
        });
      }
    }, { items: fetch.items.map(i => i.get()) });
  }
  static doRender(scroller) {
    const { state: { fetch, render }, viewport, buffer, logger } = scroller;
    render.positionBefore = viewport.scrollPosition;
    if (!fetch.isCheck) {
      render.sizeBefore = viewport.getScrollableSize();
      if (!fetch.items.every(item => Render.processElement(scroller, item))) {
        return false;
      }
    }
    buffer.checkDefaultSize();
    render.sizeAfter = viewport.getScrollableSize();
    logger.stat('after new items render');
    logger.log(() => render.noSize ? 'viewport size has not been changed' : void 0);
    return true;
  }
  static processElement(scroller, item) {
    const { viewport, buffer } = scroller;
    const element = viewport.findItemElementById(item.nodeId);
    if (!element) {
      return false;
    }
    item.element = element;
    item.makeVisible();
    item.setSize(buffer.getSizeByIndex(item.$index));
    buffer.cacheItem(item);
    return true;
  }
}
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