lightdm-webkit2-greeter/web-greeter/themes/dracula/js/backgrounds.js

class Backgrounds {
  constructor() {
    this._localStorage = window.localStorage;
    this._defaultBackgroundArr = [
      "assets/dracula.png",
      "assets/window-blurred.png",
    ];
    this._sidebar = document.querySelector("#sidebar");
    this._backgroundsList = document.querySelector("#background-selector");
    this._background = document.querySelector("#background");
    this._backgroundImages = null;
    this._backgroundImagesDir = null;
    this._backgroundPath = "";
  }

  _createImage(path) {
    let image = document.createElement("img");
    let button = document.createElement("button");
    let imageName = path.replace(/^.*[\\\/]/, "");
    button.classList.add("image");
    image.src = path;
    image.alt = imageName;
    button.appendChild(image);
    return button;
  }

  async _createBackgroundArray() {
    let images = await this._getImages();
    this._backgroundImages = this._defaultBackgroundArr.concat(images);
    this._setBackgroundImages();
    return new Promise((resolve) => resolve());
  }

  _updateOnStartup() {
    this._backgroundPath =
      this._localStorage.getItem("defaultBackgroundImage") ||
      this._backgroundImages[0];
    this._updateBackgroundImages();
  }

  _updateBackgroundImages() {
    let img = this._background.querySelector("img");
    if (!img) {
      img = document.createElement("img");
      this._background.appendChild(img);
    }
    img.src = this._backgroundPath;
    this._localStorage.setItem(
      "defaultBackgroundImage",
      String(this._backgroundPath)
    );
  }

  _setBackgroundImages() {
    this._backgroundsList.innerHTML = "";
    for (let i = 0; i < this._backgroundImages.length; i++) {
      const path = this._backgroundImages[i];
      let button = this._createImage(path);
      button.addEventListener("click", () => {
        this._backgroundPath = path;
        this._updateBackgroundImages();
      });
      this._backgroundsList.appendChild(button);
    }
  }

  _getImages(path) {
    this._backgroundImagesDir =
      greeter_config.branding.background_images_dir || "/usr/share/backgrounds";
    return new Promise((resolve) => {
      theme_utils.dirlist(
        path ? path : this._backgroundImagesDir,
        true,
        (result) => {
          resolve(result);
        }
      );
    });
  }

  async _init() {
    await this._createBackgroundArray();
    this._updateOnStartup();

    return new Promise((resolve) => resolve());
  }
}