@marp-team/marpit/lib/postcss/root/font_size.js

The skinny framework for creating slide deck from Markdown

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.rootFontSizeCustomProp = exports.rootFontSize = exports.default = void 0;
var _postcss_plugin = _interopRequireDefault(require("../../helpers/postcss_plugin"));
function _interopRequireDefault(e) { return e && e.__esModule ? e : { default: e }; }
/** @module */

const rootFontSizeCustomProp = exports.rootFontSizeCustomProp = '--marpit-root-font-size';

/**
 * Marpit PostCSS root font size plugin.
 *
 * Inject CSS variable based on the root slide container `section` for correct
 * calculation of `rem` unit in the context of Marpit.
 *
 * @function rootFontSize
 */
const rootFontSize = exports.rootFontSize = (0, _postcss_plugin.default)('marpit-postcss-root-font-size', () => (css, postcss) => css.walkRules(rule => {
  const injectSelector = new Set();
  for (const selector of rule.selectors) {
    // Detect whether the selector is targeted to section
    const parentSelectors = selector.split(/(\s+|\s*[>~+]\s*)/);
    const targetSelector = parentSelectors.pop();
    const delimiterMatched = targetSelector.match(/[.:#[]/);
    const target = delimiterMatched ? targetSelector.slice(0, delimiterMatched.index) : targetSelector;
    if (target === 'section' || target.endsWith('*') || target === '') {
      // Generate selector for injection
      injectSelector.add([...parentSelectors, target === 'section' ? 'section' : ':marpit-container > :marpit-slide section',
      // Universal selector is targeted to the children `section` of root `section`
      delimiterMatched ? targetSelector.slice(delimiterMatched.index) : ''].join(''));
    }
  }
  if (injectSelector.size === 0) return;

  // Inject CSS variable
  const injectRule = postcss.rule({
    selectors: [...injectSelector.values()]
  });
  rule.walkDecls('font-size', decl => {
    injectRule.append(decl.clone({
      prop: rootFontSizeCustomProp
    }));
  });
  if (injectRule.nodes.length > 0) rule.parent.insertAfter(rule, injectRule);
}));
var _default = exports.default = rootFontSize;