[bug] `onThemeChanged` doesn't work anymore in latest versions

[ayangweb]

Describe the bug

It worked in the old version, but not in the newest one.

iShot_2025-03-05_15.01.30.mp4

Reproduction

https://github.com/ayangweb/tauri-theme-changed-demo

Expected behavior

No response

Full tauri info output

[✔] Environment
    - OS: Mac OS 14.4.0 arm64 (X64)
    ✔ Xcode Command Line Tools: installed
    ✔ rustc: 1.85.0 (4d91de4e4 2025-02-17)
    ✔ cargo: 1.85.0 (d73d2caf9 2024-12-31)
    ✔ rustup: 1.27.1 (54dd3d00f 2024-04-24)
    ✔ Rust toolchain: stable-aarch64-apple-darwin (default)
    - node: 21.7.1
    - pnpm: 10.5.0
    - yarn: 1.22.22
    - npm: 10.5.0
    - bun: 1.1.29

[-] Packages
    - tauri 🦀: 2.3.1
    - tauri-build 🦀: 2.0.6
    - wry 🦀: 0.50.3
    - tao 🦀: 0.32.7
    - tauri-cli 🦀: 2.0.0-rc.7
    - @tauri-apps/api : 2.3.0
    - @tauri-apps/cli : 2.3.1

[-] Plugins
    - tauri-plugin-opener 🦀: 2.2.6
    - @tauri-apps/plugin-opener : 2.2.6

[-] App
    - build-type: bundle
    - CSP: unset
    - frontendDist: ../dist
    - devUrl: http://localhost:1420/
    - framework: React
    - bundler: Vite

Stack trace

Additional context

tauri info has some extra output that affects viewing

[1111mp]

Getting the system theme via webviewWindow.theme() always returns light. Here is the simplest code example:

 const current = getCurrentWebviewWindow();
  const theme = await current.theme();
  console.log("theme", theme);

  current.onThemeChanged((e) => {
    console.log("payload", e.payload);
  });

I quickly checked the new version of tauri and found the problem. I will issue a PR to help solve this problem.