gecko-dev/devtools/client/shared/theme-switching.js

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/* eslint-env browser */
"use strict";
(function() {
  const { require } = ChromeUtils.import("resource://devtools/shared/Loader.jsm", {});
  const Services = require("Services");
  const { gDevTools } = require("devtools/client/framework/devtools");
  const { appendStyleSheet } = require("devtools/client/shared/stylesheet-utils");

  const documentElement = document.documentElement;

  let os;
  const platform = navigator.platform;
  if (platform.startsWith("Win")) {
    os = "win";
  } else if (platform.startsWith("Mac")) {
    os = "mac";
  } else {
    os = "linux";
  }

  documentElement.setAttribute("platform", os);

  // no-theme attributes allows to just est the platform attribute
  // to have per-platform CSS working correctly.
  if (documentElement.getAttribute("no-theme") === "true") {
    return;
  }

  const devtoolsStyleSheets = new WeakMap();
  let gOldTheme = "";

  function forceStyle() {
    const computedStyle = window.getComputedStyle(documentElement);
    if (!computedStyle) {
      // Null when documentElement is not ready. This method is anyways not
      // required then as scrollbars would be in their state without flushing.
      return;
    }
    // Save display value
    const display = computedStyle.display;
    documentElement.style.display = "none";
    // Flush
    window.getComputedStyle(documentElement).display;
    // Restore
    documentElement.style.display = display;
  }

  /*
   * Notify the window that a theme switch finished so tests can check the DOM
   */
  function notifyWindow() {
    window.dispatchEvent(new CustomEvent("theme-switch-complete", {}));
  }

  /*
   * Apply all the sheets from `newTheme` and remove all of the sheets
   * from `oldTheme`
   */
  function switchTheme(newTheme) {
    if (newTheme === gOldTheme) {
      return;
    }
    const oldTheme = gOldTheme;
    gOldTheme = newTheme;

    const oldThemeDef = gDevTools.getThemeDefinition(oldTheme);
    let newThemeDef = gDevTools.getThemeDefinition(newTheme);

    // The theme might not be available anymore (e.g. uninstalled)
    // Use the default one.
    if (!newThemeDef) {
      newThemeDef = gDevTools.getThemeDefinition("light");
    }

    // Store the sheets in a WeakMap for access later when the theme gets
    // unapplied.  It's hard to query for processing instructions so this
    // is an easy way to access them later without storing a property on
    // the window
    devtoolsStyleSheets.set(newThemeDef, []);

    const loadEvents = [];
    for (const url of newThemeDef.stylesheets) {
      const {styleSheet, loadPromise} = appendStyleSheet(document, url);
      devtoolsStyleSheets.get(newThemeDef).push(styleSheet);
      loadEvents.push(loadPromise);
    }

    if (os !== "win" && os !== "mac") {
      // Windows & Mac always use native scrollbars, Linux still uses custom floating
      // scrollbar implementation.
      try {
        const StylesheetUtils = require("devtools/shared/layout/utils");
        const SCROLLBARS_URL = "chrome://devtools/skin/floating-scrollbars-dark-theme.css";
        if (!Services.appShell.hiddenDOMWindow
          .matchMedia("(-moz-overlay-scrollbars)").matches) {
          if (newTheme == "dark") {
            StylesheetUtils.loadSheet(window, SCROLLBARS_URL, "agent");
          } else if (oldTheme == "dark") {
            StylesheetUtils.removeSheet(window, SCROLLBARS_URL, "agent");
          }
          forceStyle();
        }
      } catch (e) {
        console.warn("customize scrollbar styles is only supported in firefox");
      }
    }

    Promise.all(loadEvents).then(() => {
      // Unload all stylesheets and classes from the old theme.
      if (oldThemeDef) {
        for (const name of oldThemeDef.classList) {
          documentElement.classList.remove(name);
        }

        for (const sheet of devtoolsStyleSheets.get(oldThemeDef) || []) {
          sheet.remove();
        }

        if (oldThemeDef.onUnapply) {
          oldThemeDef.onUnapply(window, newTheme);
        }
      }

      // Load all stylesheets and classes from the new theme.
      for (const name of newThemeDef.classList) {
        documentElement.classList.add(name);
      }

      if (newThemeDef.onApply) {
        newThemeDef.onApply(window, oldTheme);
      }

      // Final notification for further theme-switching related logic.
      gDevTools.emit("theme-switched", window, newTheme, oldTheme);
      notifyWindow();
    }, console.error);
  }

  function handlePrefChange() {
    switchTheme(Services.prefs.getCharPref("devtools.theme"));
  }

  if (documentElement.hasAttribute("force-theme")) {
    switchTheme(documentElement.getAttribute("force-theme"));
  } else {
    switchTheme(Services.prefs.getCharPref("devtools.theme"));

    Services.prefs.addObserver("devtools.theme", handlePrefChange);
    window.addEventListener("unload", function() {
      Services.prefs.removeObserver("devtools.theme", handlePrefChange);
    }, { once: true });
  }
})();