[bug] After context menus are opened, menu events are no longer received for other menus.

[gulbanana]

Describe the bug

My application has multiple context menus. Once I've popped them each up a couple of times, the handler I've set with on_menu_event() only receives events for the most recent kind of context menu - not others, and not the main menubar.

Reproduction

https://github.com/gulbanana/repro-tauri-contextmenus
To demonstrate the problem:

• npm install
• npm run tauri dev
• Click on the two buttons repeatedly, selecting an item from the menu each time.
• Observe that at first, the text on the screen updates when you select menu items; after a couple of clicks, it stops updating.

Expected behavior

I expect that menu events for existing menus continue to be delivered after using a context menu.

Full tauri info output

[✔] Environment
    - OS: Windows 10.0.19045 X64
    ✔ WebView2: 122.0.2365.66
    ✔ MSVC: Visual Studio Community 2022
    ✔ rustc: 1.76.0 (07dca489a 2024-02-04)
    ✔ cargo: 1.76.0 (c84b36747 2024-01-18)
    ✔ rustup: 1.26.0 (5af9b9484 2023-04-05)
    ✔ Rust toolchain: stable-x86_64-pc-windows-msvc (default)
    - node: 20.11.0
    - pnpm: 8.15.4
    - yarn: 1.22.21
    - npm: 8.5.2

[-] Packages
    - tauri [RUST]: 2.0.0-beta.10
    - tauri-build [RUST]: 2.0.0-beta.8
    - wry [RUST]: 0.37.0
    - tao [RUST]: 0.26.1
    - @tauri-apps/api [NPM]: 2.0.0-beta.4
    - @tauri-apps/cli [NPM]: 2.0.0-beta.8

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

Stack trace

No response

Additional context

No response

[gulbanana]

Here's a brief recording of the bug in action. After menu2 is activated, menu1 no longer functions.

repro-tauri-contextmenus_RgX9HE2SAV.mp4

[gulbanana]

I debugged this a bit and found that muda's platform_impl::windows::menu_subclass_proc is receiving a dwrefdata for the last opened context menu only. I believe this is because all the calls to SetWindowSubclass() in mod.rs use the same HWND - whichever one is most recent will overwrite the refdata.

[gulbanana]

Here's a PR with a hack that seems to work around the issue. Not the right way to fix it long-term, but hopefully having a demo helps.
#159

[gulbanana]

Unfortunately, the fix didn't work. I've updated the original repro (same link) to use tauri beta 12 and muda 0.12.1; the problem still occurs.

I believe this is because, while muda now uses a separate subclass for the context window's event handler, it still shares that subclass between all context menus. So only the last-opened context menu can ever receive events.

[gulbanana]

Thanks for the fix, I'll try the new version soon!