From 28a5b22e7e12e9f0898f86e609e5c046a3718b3b Mon Sep 17 00:00:00 2001
From: t8y2 <1156263951@qq.com>
Date: Tue, 21 Jul 2026 15:58:04 +0800
Subject: [PATCH] feat(theme): apply saved theme before app startup

---
 apps/desktop/index.html                       | 38 +++++++
 .../lib/__tests__/app/startupTheme.spec.ts    | 99 +++++++++++++++++++
 2 files changed, 137 insertions(+)
 create mode 100644 apps/desktop/src/lib/__tests__/app/startupTheme.spec.ts
diff --git a/apps/desktop/index.html b/apps/desktop/index.html
index a68bf9c53..7a8f9addb 100644
--- a/apps/desktop/index.html
+++ b/apps/desktop/index.html
@@ -5,6 +5,44 @@
     <link rel="icon" type="image/png" href="/favicon.png" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>DBX</title>
+    <style>
+      html,
+      body,
+      #root {
+        background-color: rgb(255 255 255);
+      }
+
+      html.dark,
+      html.dark body,
+      html.dark #root {
+        background-color: rgb(19 20 22);
+      }
+    </style>
+    <script data-dbx-startup-theme>
+      (() => {
+        const root = document.documentElement;
+        let mode = null;
+
+        // localStorage can throw when WebView storage is unavailable; keep the existing light fallback.
+        try {
+          mode = localStorage.getItem("dbx-theme");
+        } catch {}
+
+        const followsSystem = mode === "system" || mode === "soft-system";
+        let dark = mode === "dark" || mode === "soft-dark";
+
+        if (followsSystem) {
+          try {
+            dark = window.matchMedia("(prefers-color-scheme: dark)").matches;
+          } catch {
+            dark = false;
+          }
+        }
+
+        root.classList.toggle("dark", dark);
+        root.style.colorScheme = dark ? "dark" : "light";
+      })();
+    </script>
   </head>
   <body>
     <div id="root">
diff --git a/apps/desktop/src/lib/__tests__/app/startupTheme.spec.ts b/apps/desktop/src/lib/__tests__/app/startupTheme.spec.ts
new file mode 100644
index 000000000..1f90091dd
--- /dev/null
+++ b/apps/desktop/src/lib/__tests__/app/startupTheme.spec.ts
@@ -0,0 +1,99 @@
+import { readFileSync } from "node:fs";
+import { fileURLToPath } from "node:url";
+import { describe, expect, it, vi } from "vitest";
+
+const indexHtml = readFileSync(fileURLToPath(new URL("../../../../index.html", import.meta.url)), "utf8");
+const startupScript = indexHtml.match(/<script data-dbx-startup-theme>([\s\S]*?)<\/script>/)?.[1];
+
+if (!startupScript) throw new Error("Startup theme script not found");
+
+type StartupThemeOptions = {
+  mode?: string | null;
+  prefersDark?: boolean;
+  storageError?: boolean;
+};
+
+function runStartupTheme({ mode = null, prefersDark = false, storageError = false }: StartupThemeOptions = {}) {
+  const toggle = vi.fn();
+  const root = { classList: { toggle }, style: { colorScheme: "" } };
+  const localStorage = {
+    getItem: vi.fn(() => {
+      if (storageError) throw new DOMException("Storage unavailable", "SecurityError");
+      return mode;
+    }),
+  };
+  const matchMedia = vi.fn(() => ({ matches: prefersDark }));
+
+  Function("document", "localStorage", "window", startupScript)({ documentElement: root }, localStorage, { matchMedia });
+
+  return { matchMedia, root, toggle };
+}
+
+describe("startup theme", () => {
+  it("applies dark mode before the application mounts", () => {
+    const { matchMedia, root, toggle } = runStartupTheme({ mode: "dark" });
+
+    expect(toggle).toHaveBeenCalledWith("dark", true);
+    expect(root.style.colorScheme).toBe("dark");
+    expect(matchMedia).not.toHaveBeenCalled();
+  });
+
+  it("keeps explicit light mode light", () => {
+    const { matchMedia, root, toggle } = runStartupTheme({ mode: "light", prefersDark: true });
+
+    expect(toggle).toHaveBeenCalledWith("dark", false);
+    expect(root.style.colorScheme).toBe("light");
+    expect(matchMedia).not.toHaveBeenCalled();
+  });
+
+  it.each([
+    [true, "dark"],
+    [false, "light"],
+  ])("resolves system mode when prefersDark is %s", (prefersDark, appearance) => {
+    const { matchMedia, root, toggle } = runStartupTheme({ mode: "system", prefersDark });
+
+    expect(toggle).toHaveBeenCalledWith("dark", prefersDark);
+    expect(root.style.colorScheme).toBe(appearance);
+    expect(matchMedia).toHaveBeenCalledWith("(prefers-color-scheme: dark)");
+  });
+
+  it("uses the current light default when no preference exists", () => {
+    const { root, toggle } = runStartupTheme();
+
+    expect(toggle).toHaveBeenCalledWith("dark", false);
+    expect(root.style.colorScheme).toBe("light");
+  });
+
+  it("falls back to light when localStorage is unavailable", () => {
+    const { root, toggle } = runStartupTheme({ storageError: true, prefersDark: true });
+
+    expect(toggle).toHaveBeenCalledWith("dark", false);
+    expect(root.style.colorScheme).toBe("light");
+  });
+
+  it("falls back to light for an invalid persisted mode", () => {
+    const { root, toggle } = runStartupTheme({ mode: "invalid", prefersDark: true });
+
+    expect(toggle).toHaveBeenCalledWith("dark", false);
+    expect(root.style.colorScheme).toBe("light");
+  });
+
+  it("falls back to light when system appearance detection is unavailable", () => {
+    const toggle = vi.fn();
+    const root = { classList: { toggle }, style: { colorScheme: "" } };
+
+    Function("document", "localStorage", "window", startupScript)({ documentElement: root }, { getItem: () => "system" }, {});
+
+    expect(toggle).toHaveBeenCalledWith("dark", false);
+    expect(root.style.colorScheme).toBe("light");
+  });
+
+  it.each([
+    ["soft-dark", true],
+    ["soft-light", false],
+  ])("preserves legacy %s mode", (mode, dark) => {
+    const { toggle } = runStartupTheme({ mode });
+
+    expect(toggle).toHaveBeenCalledWith("dark", dark);
+  });
+});
