mkdocs-material/src/assets/javascripts/components/Material/Sidebar.js

/*
 * Copyright (c) 2016 Martin Donath <martin.donath@squidfunk.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

/* ----------------------------------------------------------------------------
 * Definition
 * ------------------------------------------------------------------------- */

export default class Sidebar {

  /**
   * Set sidebars to locked state and limit height to parent node
   *
   * @constructor
   * @param {(string|HTMLElement)} el - Selector or HTML element
   */
  constructor(el) {
    this.el_ = (typeof el === "string")
      ? document.querySelector(el)
      : el

    /* Index inner and outer container */
    const inner = this.el_.parentNode
    const outer = this.el_.parentNode.parentNode

    /* Get top and bottom bounds */
    this.offset_ = outer.offsetTop
    this.bounds_ = {
      top: inner.offsetTop,
      bottom: inner.offsetTop + inner.offsetHeight
    }

    /* Initialize current height */
    this.height_ = 0
  }

  /**
   * Update locked state and height
   */
  update() {
    const scroll = window.pageYOffset
    const expand = window.innerHeight

    /* Calculate new bounds */
    const offset = this.bounds_.top - scroll
    const height = expand
                 - Math.max(0, scroll + expand - this.bounds_.bottom)
                 - Math.max(offset, this.offset_)

    /* If height changed, update element */
    if (height !== this.height_)
      this.el_.style.height = `${this.height_ = height}px`

    /* Sidebar should be locked, as we're below parent offset */
    if (offset < this.offset_) {
      if (!this.el_.dataset.mdLocked)
        this.el_.dataset.mdLocked = ""

    /* Sidebar should be unlocked, if locked */
    } else if (typeof this.el_.dataset.mdLocked === "string") {
      delete this.el_.dataset.mdLocked
    }
  }

  /**
   * Reset locked state and height
   */
  reset() {
    delete this.el_.dataset.mdLocked
    this.el_.style.height = ""
    this.height_ = 0
  }
}