fix: Voice and video call buttons missing on Windows due to Linux User-Agent

[jeanroukas]

Description

Hi! According to the README, voice and video calls should be supported. However, the call buttons (phone and camera icons) are missing from the top navigation bar inside the chat window when running the app on Windows.

Cause

In src-tauri/src/window.rs, the hardcoded User-Agent string is strictly forcing a Linux signature:

pub const CHROME_UA: &str =
    "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36";

When running on Windows, WhatsApp Web detects a glaring mismatch between the underlying Windows WebView2 environment and this Linux User-Agent. As a security/anti-bot measure, Meta automatically hides the VoIP call features.

Verification
I cloned the repository, changed CHROME_UA to a standard Windows Chrome string, and compiled it locally using cargo tauri dev. With the Windows User-Agent, the voice and video call buttons instantly appeared.

Suggested Solution

We should adjust CHROME_UA dynamically depending on the target OS using a conditional compilation flag (#[cfg(target_os = ...)]):

#[cfg(windows)]
pub const CHROME_UA: &str =
    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36";

#[cfg(not(windows))]
pub const CHROME_UA: &str =
    "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36";

Thank you for your time and for this great lightweight app!

[jeanroukas]

Important Update after local testing

I have compiled the app locally and changed CHROME_UA to a Windows string. While this successfully makes the call buttons (phone and camera) appear in the UI, they are completely non-functional on Windows.

When clicking either button, WhatsApp Web triggers a modal popup that says: "Make calls with the Windows app - Download WhatsApp for Windows to start making calls."

The root cause:
Meta strictly blocks WebRTC calls on Windows browsers to force users onto their native Microsoft Store app. Even with a modified User-Agent, the underlying WebView2 engine leaks the Windows OS environment (likely via navigator.platform or JS Client Hints), and WhatsApp's scripts instantly block the call.

Conclusion:
Simply spoofing the User-Agent is not enough on Windows. Unless there is a way to deeply inject JS to spoof the platform APIs, the README claiming "Voice messages, voice calls, and video calls -> microphone and camera support" is currently misleading for Windows users.