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themeswap.js
42 lines (42 loc) · 2.17 KB
/
themeswap.js
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// Small function to quickly swap out themes. Gets put into the <head> tag..
function set_theme_from_local_storage() {
// Browser does not support Web Storage, bail early.
if(typeof(window.localStorage) === "undefined") return;
// Get the user-picked theme from localStorage. May be `null`, which means the default
// theme.
var theme = window.localStorage.getItem("documenter-theme");
// Initialize a few variables for the loop:
//
// - active: will contain the index of the theme that should be active. Note that there
// is no guarantee that localStorage contains sane values. If `active` stays `null`
// we either could not find the theme or it is the default (primary) theme anyway.
// Either way, we then need to stick to the primary theme.
//
// - disabled: style sheets that should be disabled (i.e. all the theme style sheets
// that are not the currently active theme)
var active = null; var disabled = [];
for (var i = 0; i < document.styleSheets.length; i++) {
var ss = document.styleSheets[i];
// The <link> tag of each style sheet is expected to have a data-theme-name attribute
// which must contain the name of the theme. The names in localStorage much match this.
var themename = ss.ownerNode.getAttribute("data-theme-name");
// attribute not set => non-theme stylesheet => ignore
if(themename === null) continue;
// To distinguish the default (primary) theme, it needs to have the data-theme-primary
// attribute set.
var isprimary = (ss.ownerNode.getAttribute("data-theme-primary") !== null);
// If we find a matching theme (and it's not the default), we'll set active to non-null
if(!isprimary && themename === theme) active = i;
// Store the style sheets of inactive themes so that we could disable them
if(themename !== theme) disabled.push(ss);
}
if(active !== null) {
// If we did find an active theme, we'll (1) add the theme--$(theme) class to <html>
document.getElementsByTagName('html')[0].className = "theme--" + theme;
// and (2) disable all the other theme stylesheets
disabled.forEach(function(ss){
ss.disabled = true;
});
}
}
set_theme_from_local_storage();