freifunk · grische · Apr 18, 2026 · Apr 18, 2026 · Apr 18, 2026 · Apr 18, 2026
diff --git a/index.html b/index.html
@@ -30,6 +30,23 @@
     <link rel="mask-icon" href="./mask-icon.svg" color="#FFFFFF" />
     <meta name="theme-color" content="#ffffff" />
 
+    <!-- Keep storage key ("meshviewer.theme") and class name ("theme_night") in sync with lib/theme.ts -->
+    <script>
+      try {
+        var t = localStorage.getItem("meshviewer.theme");
+        if (t === "dark" || (t !== "light" && matchMedia("(prefers-color-scheme: dark)").matches)) {
+          document.documentElement.classList.add("theme_night");
+        }
+      } catch (e) {
+        try {
+          if (matchMedia("(prefers-color-scheme: dark)").matches) {
+            document.documentElement.classList.add("theme_night");
+          }
+        } catch (_) {
+          /* matchMedia unavailable; accept a light paint */
+        }
+      }
+    </script>
     <script src="lib/index.ts" type="module"></script>
   </head>
   <body>

diff --git a/lib/gui.ts b/lib/gui.ts
@@ -18,6 +18,7 @@ import { FilterGui } from "./filters/filtergui.js";
 import { HostnameFilter } from "./filters/hostname.js";
 import * as helper from "./utils/helper.js";
 import { Language } from "./utils/language.js";
+import { cycleTheme, getTheme, initTheme, themeIconSVG } from "./theme.js";
 
 export const Gui = function (language: ReturnType<typeof Language>) {
   const self = {
@@ -78,6 +79,21 @@ export const Gui = function (language: ReturnType<typeof Language>) {
 
   contentDiv.appendChild(buttons);
 
+  initTheme();
+  let buttonTheme = document.createElement("button");
+  buttonTheme.classList.add("theme-toggle");
+  function refreshThemeButton() {
+    let current = getTheme();
+    buttonTheme.innerHTML = themeIconSVG(current);
+    buttonTheme.setAttribute("aria-label", _.t("button.theme." + current));
+  }
+  buttonTheme.onclick = function onclick() {
+    cycleTheme();
+    refreshThemeButton();
+  };
+  refreshThemeButton();
+  buttons.appendChild(buttonTheme);
+
   let buttonToggle = document.createElement("button");
   buttonToggle.classList.add("ion-eye");
   buttonToggle.setAttribute("aria-label", _.t("button.switchView"));

diff --git a/lib/map.ts b/lib/map.ts
@@ -160,19 +160,6 @@ export const Map = function (linkScale: (t: any) => any, sidebar: ReturnType<typ
         map.setZoom(maxZoom);
       }
     }
-
-    let html_tag: Element = document.querySelector("html");
-    let class_list = html_tag.classList;
-    const mode = selectedLayer?.options?.mode;
-    class_list.forEach(function (item) {
-      if (item.startsWith("theme_")) {
-        class_list.remove(item);
-      }
-    });
-    if (html_tag && mode && mode !== "" && !html_tag.classList.contains(mode)) {
-      class_list.add("theme_" + mode);
-      labelLayer.updateLayer();
-    }
   });
 
   map.on("load", function () {

diff --git a/lib/map/labellayer.js b/lib/map/labellayer.js
@@ -165,6 +165,15 @@ export const LabelLayer = L.GridLayer.extend({
     if (this.data) {
       this.prepareLabels();
     }
+    this._onThemeChange = () => this.updateLayer();
+    document.documentElement.addEventListener("themechange", this._onThemeChange);
+  },
+  onRemove: function (map) {
+    if (this._onThemeChange) {
+      document.documentElement.removeEventListener("themechange", this._onThemeChange);
+      this._onThemeChange = null;
+    }
+    L.GridLayer.prototype.onRemove.call(this, map);
   },
   setData: function (data, map, nodeDict, linkDict, linkScale) {
     let config = window.config;

diff --git a/lib/theme.ts b/lib/theme.ts
@@ -0,0 +1,114 @@
+export type Theme = "light" | "dark" | "auto";
+
+// Keep STORAGE_KEY and DARK_CLASS in sync with the pre-paint inline script in index.html.
+const STORAGE_KEY = "meshviewer.theme";
+const DARK_CLASS = "theme_night";
+const THEMES: Theme[] = ["light", "dark", "auto"];
+
+let inMemory: Theme = "auto";
+
+const darkQuery =
+  typeof window !== "undefined" && window.matchMedia ? window.matchMedia("(prefers-color-scheme: dark)") : null;
+
+function isTheme(value: string | null): value is Theme {
+  return value === "light" || value === "dark" || value === "auto";
+}
+
+function read(): Theme {
+  try {
+    let v = localStorage.getItem(STORAGE_KEY);
+    if (isTheme(v)) {
+      return v;
+    }
+  } catch (e) {
+    /* localStorage inaccessible (private mode, sandboxed iframe, file://) */
+  }
+  return inMemory;
+}
+
+function write(value: Theme): void {
+  inMemory = value;
+  try {
+    localStorage.setItem(STORAGE_KEY, value);
+  } catch (e) {
+    /* keep in-memory only */
+  }
+}
+
+export function resolveTheme(): "light" | "dark" {
+  let current = read();
+  if (current === "dark") {
+    return "dark";
+  }
+  if (current === "auto" && darkQuery && darkQuery.matches) {
+    return "dark";
+  }
+  return "light";
+}
+
+function apply(): void {
+  let dark = resolveTheme() === "dark";
+  document.documentElement.classList.toggle(DARK_CLASS, dark);
+  document.documentElement.dispatchEvent(new CustomEvent("themechange"));
+}
+
+export function getTheme(): Theme {
+  return read();
+}
+
+export function cycleTheme(): Theme {
+  let next = THEMES[(THEMES.indexOf(read()) + 1) % THEMES.length];
+  write(next);
+  apply();
+  return next;
+}
+
+export function initTheme(): void {
+  inMemory = read();
+  apply();
+  if (darkQuery) {
+    darkQuery.addEventListener("change", function () {
+      if (read() === "auto") {
+        apply();
+      }
+    });
+  }
+}
+
+const SVG_OPEN = '<svg viewBox="0 0 24 24" fill="currentColor" aria-hidden="true">';
+const SVG_CLOSE = "</svg>";
+
+const SUN_RAYS =
+  '<rect x="11" y="1" width="2" height="3" rx="1"/>' +
+  '<rect x="11" y="20" width="2" height="3" rx="1"/>' +
+  '<rect x="1" y="11" width="3" height="2" rx="1"/>' +
+  '<rect x="20" y="11" width="3" height="2" rx="1"/>';
+
+const SUN =
+  SVG_OPEN +
+  '<circle cx="12" cy="12" r="5"/>' +
+  "<g>" +
+  SUN_RAYS +
+  "</g>" +
+  '<g transform="rotate(45 12 12)">' +
+  SUN_RAYS +
+  "</g>" +
+  SVG_CLOSE;
+
+const MOON = SVG_OPEN + '<path d="M21 12.79A9 9 0 1111.21 3 7 7 0 0021 12.79z"/>' + SVG_CLOSE;
+
+const AUTO =
+  SVG_OPEN +
+  '<path d="M12 4a8 8 0 000 16V4z"/>' +
+  '<circle cx="12" cy="12" r="8" fill="none" stroke="currentColor" stroke-width="1.5"/>' +
+  SVG_CLOSE;
+
+export function themeIconSVG(theme: Theme): string {
+  if (theme === "dark") {
+    return MOON;
+  }
+  if (theme === "auto") {
+    return AUTO;
+  }
+  return SUN;
+}
diff --git a/public/locale/cz.json b/public/locale/cz.json
@@ -63,7 +63,12 @@
   "button": {
     "switchView": "Přepnout zobrazení",
     "location": "Vybrat souřadnice",
-    "tracking": "Lokalizace"
+    "tracking": "Lokalizace",
+    "theme": {
+      "light": "Světlý (další: tmavý)",
+      "dark": "Tmavý (další: auto)",
+      "auto": "Auto (další: světlý)"
+    }
   },
   "momentjs": {
     "calendar": {

diff --git a/public/locale/de.json b/public/locale/de.json
@@ -66,7 +66,12 @@
     "fullscreen": "Vollbildmodus wechseln",
     "tracking": "Lokalisierung",
     "location": "Koordinaten wählen",
-    "ruler": "Lineal"
+    "ruler": "Lineal",
+    "theme": {
+      "light": "Hell (nächstes: dunkel)",
+      "dark": "Dunkel (nächstes: auto)",
+      "auto": "Auto (nächstes: hell)"
+    }
   },
   "momentjs": {
     "calendar": {

diff --git a/public/locale/en.json b/public/locale/en.json
@@ -66,7 +66,12 @@
     "fullscreen": "Toggle fullscreen",
     "tracking": "Localisation",
     "location": "Pick coordinates",
-    "ruler": "Ruler"
+    "ruler": "Ruler",
+    "theme": {
+      "light": "Light (next: dark)",
+      "dark": "Dark (next: auto)",
+      "auto": "Auto (next: light)"
+    }
   },
   "momentjs": {
     "calendar": {

diff --git a/public/locale/fr.json b/public/locale/fr.json
@@ -65,7 +65,12 @@
     "fullscreen": "Vollbildmodus wechseln",
     "tracking": "Localisation",
     "location": "Choisir les coordonnées",
-    "ruler": "Règle"
+    "ruler": "Règle",
+    "theme": {
+      "light": "Clair (suivant : sombre)",
+      "dark": "Sombre (suivant : auto)",
+      "auto": "Auto (suivant : clair)"
+    }
   },
   "momentjs": {
     "calendar": {

diff --git a/public/locale/ru.json b/public/locale/ru.json
@@ -63,7 +63,12 @@
   "button": {
     "switchView": "Переключить вид",
     "location": "Взять координаты",
-    "tracking": "Локализация"
+    "tracking": "Локализация",
+    "theme": {
+      "light": "Светлая (далее: тёмная)",
+      "dark": "Тёмная (далее: авто)",
+      "auto": "Авто (далее: светлая)"
+    }
   },
   "momentjs": {
     "calendar": {

diff --git a/public/locale/tr.json b/public/locale/tr.json
@@ -63,7 +63,12 @@
   "button": {
     "switchView": "Görünümü Değiştir",
     "location": "Koordinatları seç",
-    "tracking": "Yerelleştirme"
+    "tracking": "Yerelleştirme",
+    "theme": {
+      "light": "Açık (sonraki: koyu)",
+      "dark": "Koyu (sonraki: oto)",
+      "auto": "Oto (sonraki: açık)"
+    }
   },
   "momentjs": {
     "calendar": {

diff --git a/scss/modules/_button.scss b/scss/modules/_button.scss
@@ -79,6 +79,13 @@ button {
     margin: variables.$button-distance;
     width: auto;
   }
+
+  &.theme-toggle {
+    svg {
+      height: 1em;
+      width: 1em;
+    }
+  }
 }
 
 // Tooltip