feat: add theme setting (Light/Dark/System) with dark mode

Add theme preference (light/dark/system) stored in extension state. System mode follows prefers-color-scheme and listens for changes. Dark mode inverts the monochrome palette (white-on-black). Theme selector added to Display section in settings. Closes #125
2026-02-28 23:22:41 -08:00
parent 834228b572
commit 2bdb547995
6 changed files with 70 additions and 1 deletions
--- a/src/popup/theme.js
+++ b/src/popup/theme.js
@@ -0,0 +1,33 @@
+// Theme management: applies light/dark class to <html> based on preference.
+
+let mediaQuery = null;
+let mediaHandler = null;
+
+function applyTheme(theme) {
+    // Clean up previous system listener
+    if (mediaQuery && mediaHandler) {
+        mediaQuery.removeEventListener("change", mediaHandler);
+        mediaHandler = null;
+    }
+
+    if (theme === "dark") {
+        document.documentElement.classList.add("dark");
+    } else if (theme === "light") {
+        document.documentElement.classList.remove("dark");
+    } else {
+        // system
+        mediaQuery = window.matchMedia("(prefers-color-scheme: dark)");
+        const update = () => {
+            if (mediaQuery.matches) {
+                document.documentElement.classList.add("dark");
+            } else {
+                document.documentElement.classList.remove("dark");
+            }
+        };
+        mediaHandler = update;
+        mediaQuery.addEventListener("change", update);
+        update();
+    }
+}
+
+module.exports = { applyTheme };