Merge pull request git#1994 from dscho/reset-dark-mode-preference-when-possible

dark-mode: allow following the system preference again

Author: dscho

assets/js/application.js

@@ -643,7 +643,8 @@ var DarkMode = {
         theme = document.documentElement.dataset.theme === "dark" ? "light" : "dark"
       }
       document.documentElement.dataset.theme = theme
-      localStorage.setItem("theme", theme);
+      if (prefersDarkScheme === (theme === "dark")) localStorage.removeItem("theme");
+      else localStorage.setItem("theme", theme);
       button.attr("src", `${baseURLPrefix}images/${theme === "dark" ? "light" : "dark"}-mode.svg`);
     });
   },

layouts/_default/baseof.html

@@ -49,7 +49,8 @@ <h1>Redirecting&hellip;</h1>
     if (currentTheme) {
       // Check dark mode preference at the OS level
       const prefersDarkScheme = window.matchMedia("(prefers-color-scheme: dark)").matches
-      if ((prefersDarkScheme && currentTheme === "light")
+      if (prefersDarkScheme === (currentTheme === "dark")) localStorage.removeItem("theme")
+      else if ((prefersDarkScheme && currentTheme === "light")
         || (!prefersDarkScheme && currentTheme === "dark")) {
 	document.documentElement.dataset.theme = currentTheme
       }