src/librustdoc/html/static/storage.js

   1 /*!
   2  * Copyright 2018 The Rust Project Developers. See the COPYRIGHT
   3  * file at the top-level directory of this distribution and at
   4  * http://rust-lang.org/COPYRIGHT.
   5  *
   6  * Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   7  * http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   8  * <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   9  * option. This file may not be copied, modified, or distributed
  10  * except according to those terms.
  11  */
  12
  13 var currentTheme = document.getElementById("themeStyle");
  14 var mainTheme = document.getElementById("mainThemeStyle");
  15
  16 var savedHref = [];
  17
  18 function onEach(arr, func) {
  19     if (arr && arr.length > 0 && func) {
  20         for (var i = 0; i < arr.length; i++) {
  21             if (func(arr[i]) === true) {
  22                 return true;
  23             }
  24         }
  25     }
  26     return false;
  27 }
  28
  29 function usableLocalStorage() {
  30     // Check if the browser supports localStorage at all:
  31     if (typeof(Storage) === "undefined") {
  32         return false;
  33     }
  34     // Check if we can access it; this access will fail if the browser
  35     // preferences deny access to localStorage, e.g., to prevent storage of
  36     // "cookies" (or cookie-likes, as is the case here).
  37     try {
  38         window.localStorage;
  39     } catch(err) {
  40         // Storage is supported, but browser preferences deny access to it.
  41         return false;
  42     }
  43
  44     return true;
  45 }
  46
  47 function updateLocalStorage(name, value) {
  48     if (usableLocalStorage()) {
  49         localStorage[name] = value;
  50     } else {
  51         // No Web Storage support so we do nothing
  52     }
  53 }
  54
  55 function getCurrentValue(name) {
  56     if (usableLocalStorage() && localStorage[name] !== undefined) {
  57         return localStorage[name];
  58     }
  59     return null;
  60 }
  61
  62 function switchTheme(styleElem, mainStyleElem, newTheme) {
  63     var fullBasicCss = "rustdoc" + resourcesSuffix + ".css";
  64     var fullNewTheme = newTheme + resourcesSuffix + ".css";
  65     var newHref = mainStyleElem.href.replace(fullBasicCss, fullNewTheme);
  66
  67     if (styleElem.href === newHref) {
  68         return;
  69     }
  70
  71     var found = false;
  72     if (savedHref.length === 0) {
  73         onEach(document.getElementsByTagName("link"), function(el) {
  74             savedHref.push(el.href);
  75         });
  76     }
  77     onEach(savedHref, function(el) {
  78         if (el === newHref) {
  79             found = true;
  80             return true;
  81         }
  82     });
  83     if (found === true) {
  84         styleElem.href = newHref;
  85         updateLocalStorage('rustdoc-theme', newTheme);
  86     }
  87 }
  88
  89 switchTheme(currentTheme, mainTheme, getCurrentValue('rustdoc-theme') || 'light');