bootstrap-italia/dist/plugins/util/scrollbar.js

Bootstrap Italia è un tema Bootstrap 5 per la creazione di applicazioni web nel pieno rispetto delle linee guida di design per i siti internet e i servizi digitali della PA

import SelectorEngine from '../dom/selector-engine.js';
import Manipulator from '../dom/manipulator.js';
import { isElement } from './index.js';

/**
 * --------------------------------------------------------------------------
 * Bootstrap Italia (https://italia.github.io/bootstrap-italia/)
 * Authors: https://github.com/italia/bootstrap-italia/blob/main/AUTHORS
 * Licensed under BSD-3-Clause license (https://github.com/italia/bootstrap-italia/blob/main/LICENSE)
 * This a fork of Bootstrap: Initial license and original file name below
 * Bootstrap (v5.2.3): util/scrollBar.js
 * Licensed under MIT (https://github.com/twbs/bootstrap/blob/main/LICENSE)
 * --------------------------------------------------------------------------
 */


/**
 * Constants
 */

const SELECTOR_FIXED_CONTENT = '.fixed-top, .fixed-bottom, .is-fixed, .sticky-top';
const SELECTOR_STICKY_CONTENT = '.sticky-top';
const PROPERTY_PADDING = 'padding-right';
const PROPERTY_MARGIN = 'margin-right';

/**
 * Class definition
 */

class ScrollBarHelper {
  constructor() {
    this._element = document.body;
  }

  // Public
  getWidth() {
    // https://developer.mozilla.org/en-US/docs/Web/API/Window/innerWidth#usage_notes
    const documentWidth = document.documentElement.clientWidth;
    return Math.abs(window.innerWidth - documentWidth)
  }

  hide() {
    const width = this.getWidth();
    this._disableOverFlow();
    // give padding to element to balance the hidden scrollbar width
    this._setElementAttributes(this._element, PROPERTY_PADDING, (calculatedValue) => calculatedValue + width);
    // trick: We adjust positive paddingRight and negative marginRight to sticky-top elements to keep showing fullwidth
    this._setElementAttributes(SELECTOR_FIXED_CONTENT, PROPERTY_PADDING, (calculatedValue) => calculatedValue + width);
    this._setElementAttributes(SELECTOR_STICKY_CONTENT, PROPERTY_MARGIN, (calculatedValue) => calculatedValue - width);
  }

  reset() {
    this._resetElementAttributes(this._element, 'overflow');
    this._resetElementAttributes(this._element, PROPERTY_PADDING);
    this._resetElementAttributes(SELECTOR_FIXED_CONTENT, PROPERTY_PADDING);
    this._resetElementAttributes(SELECTOR_STICKY_CONTENT, PROPERTY_MARGIN);
  }

  isOverflowing() {
    return this.getWidth() > 0
  }

  // Private
  _disableOverFlow() {
    this._saveInitialAttribute(this._element, 'overflow');
    this._element.style.overflow = 'hidden';
  }

  _setElementAttributes(selector, styleProperty, callback) {
    const scrollbarWidth = this.getWidth();
    const manipulationCallBack = (element) => {
      if (element !== this._element && window.innerWidth > element.clientWidth + scrollbarWidth) {
        return
      }

      this._saveInitialAttribute(element, styleProperty);
      const calculatedValue = window.getComputedStyle(element).getPropertyValue(styleProperty);
      element.style.setProperty(styleProperty, `${callback(Number.parseFloat(calculatedValue))}px`);
    };

    this._applyManipulationCallback(selector, manipulationCallBack);
  }

  _saveInitialAttribute(element, styleProperty) {
    const actualValue = element.style.getPropertyValue(styleProperty);
    if (actualValue) {
      Manipulator.setDataAttribute(element, styleProperty, actualValue);
    }
  }

  _resetElementAttributes(selector, styleProperty) {
    const manipulationCallBack = (element) => {
      const value = Manipulator.getDataAttribute(element, styleProperty);
      // We only want to remove the property if the value is `null`; the value can also be zero
      if (value === null) {
        element.style.removeProperty(styleProperty);
        return
      }

      Manipulator.removeDataAttribute(element, styleProperty);
      element.style.setProperty(styleProperty, value);
    };

    this._applyManipulationCallback(selector, manipulationCallBack);
  }

  _applyManipulationCallback(selector, callBack) {
    if (isElement(selector)) {
      callBack(selector);
      return
    }

    for (const sel of SelectorEngine.find(selector, this._element)) {
      callBack(sel);
    }
  }
}

export { ScrollBarHelper as default };
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