web-dslr/examples/preact/config-utils.js

/*
 * Copyright 2021 Google LLC
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
 */

/** @typedef {import('web-gphoto2').Config} Config */

/**
 * Depth-first lookup of a config node by its gphoto2 name.
 * @param {Config | undefined} config
 * @param {string} name
 * @returns {Config | undefined}
 */
export function findConfig(config, name) {
  if (!config) return undefined;
  if (config.name === name) return config;
  if (config.type !== 'window' && config.type !== 'section') return undefined;
  for (let child of Object.values(config.children)) {
    let found = findConfig(child, name);
    if (found) return found;
  }
  return undefined;
}

/**
 * Read the current value of a config node, if it exists.
 * @param {Config | undefined} config
 * @param {string} name
 */
export function configValue(config, name) {
  let node = findConfig(config, name);
  return node && 'value' in node ? node.value : undefined;
}

/**
 * The read-only summary shown at the bottom of the home screen. These are the
 * names the Canon EOS driver (450D included) exposes; anything missing is
 * simply skipped, so this stays useful on other bodies too.
 * @param {Config | undefined} config
 */
export function statusReadout(config) {
  return [
    ['Mode', 'autoexposuremode'],
    ['Shutter', 'shutterspeed'],
    ['Aperture', 'aperture'],
    ['ISO', 'iso'],
    ['Format', 'imageformat'],
    ['Battery', 'batterylevel'],
    ['Shots left', 'availableshots'],
    ['Target', 'capturetarget']
  ]
    .map(([label, name]) => ({ label, value: configValue(config, name) }))
    .filter(({ value }) => value !== undefined && value !== '');
}

/**
 * Turn a gphoto2 shutter speed string ("1/250", "30", "0.3", "bulb") into
 * seconds. Returns undefined when it can't be parsed.
 * @param {unknown} value
 */
export function shutterSpeedSeconds(value) {
  if (typeof value !== 'string') return undefined;
  let str = value.trim().toLowerCase();
  if (str === 'bulb' || str === '') return undefined;
  let fraction = /^(\d+(?:\.\d+)?)\/(\d+(?:\.\d+)?)$/.exec(str);
  if (fraction) {
    let denominator = Number(fraction[2]);
    return denominator ? Number(fraction[1]) / denominator : undefined;
  }
  let seconds = Number(str.replace(/s$/, ''));
  return Number.isFinite(seconds) ? seconds : undefined;
}

/**
 * How the camera can be held open for a long exposure, if at all.
 *
 * `bulb` is a plain toggle on many bodies; Canon EOS bodies instead drive the
 * shutter through `eosremoterelease`. Returns null when neither is available.
 * @param {Config | undefined} config
 * @returns {{ kind: 'bulb' } | { kind: 'eosremoterelease', press: string, release: string } | null}
 */
export function detectBulbSupport(config) {
  let bulb = findConfig(config, 'bulb');
  if (bulb && bulb.type === 'toggle' && !bulb.readonly) {
    return { kind: 'bulb' };
  }
  let remote = findConfig(config, 'eosremoterelease');
  if (remote && remote.type === 'menu' && !remote.readonly) {
    let press = remote.choices.find(c => /^press full/i.test(c));
    let release = remote.choices.find(c => /^release full/i.test(c));
    if (press && release) {
      return { kind: 'eosremoterelease', press, release };
    }
  }
  return null;
}