vega-lite/src/compile/selection/inputs.ts

Vega-Lite is a concise high-level language for interactive visualization.

import {stringValue} from 'vega-util';
import {disableDirectManipulation, TUPLE, SelectionCompiler} from './index.js';
import {varName} from '../../util.js';
import {assembleInit} from './assemble.js';
import nearest from './nearest.js';
import {TUPLE_FIELDS} from './project.js';
import {isLegendBinding} from '../../selection.js';
import {NewSignal} from 'vega';

const inputBindings: SelectionCompiler<'point'> = {
  defined: (selCmpt) => {
    return (
      selCmpt.type === 'point' &&
      selCmpt.resolve === 'global' &&
      selCmpt.bind &&
      selCmpt.bind !== 'scales' &&
      !isLegendBinding(selCmpt.bind)
    );
  },

  parse: (model, selCmpt, selDef) => disableDirectManipulation(selCmpt, selDef),

  topLevelSignals: (model, selCmpt, signals) => {
    const name = selCmpt.name;
    const proj = selCmpt.project;
    const bind = selCmpt.bind;
    const init = selCmpt.init?.[0]; // Can only exist on single selections (one initial value).
    const datum = nearest.defined(selCmpt) ? '(item().isVoronoi ? datum.datum : datum)' : 'datum';

    proj.items.forEach((p, i) => {
      const sgname = varName(`${name}_${p.field}`);
      const hasSignal = signals.filter((s) => s.name === sgname);

      if (!hasSignal.length) {
        signals.unshift({
          name: sgname,
          ...(init ? {init: assembleInit(init[i])} : {value: null}),
          on: selCmpt.events
            ? [
                {
                  events: selCmpt.events,
                  update: `datum && item().mark.marktype !== 'group' ? ${datum}[${stringValue(p.field)}] : null`,
                },
              ]
            : [],
          bind: (bind as any)[p.field] ?? (bind as any)[p.channel] ?? bind,
        });
      }
    });

    return signals;
  },

  signals: (model, selCmpt, signals) => {
    const name = selCmpt.name;
    const proj = selCmpt.project;
    const signal: NewSignal = signals.find((s) => s.name === name + TUPLE);
    const fields = name + TUPLE_FIELDS;
    const values = proj.items.map((p) => varName(`${name}_${p.field}`));
    const valid = values.map((v) => `${v} !== null`).join(' && ');

    if (values.length) {
      signal.update = `${valid} ? {fields: ${fields}, values: [${values.join(', ')}]} : null`;
    }

    delete signal.value;
    delete signal.on;

    return signals;
  },
};

export default inputBindings;