fn layout_uses_altgr()

in src/platform_impl/windows/event.rs [127:161]

• 27 lines of code
• 5 McCabe index (conditional complexity)

fn layout_uses_altgr() -> bool {
    unsafe {
        static ACTIVE_LAYOUT: AtomicPtr<HKL__> = AtomicPtr::new(ptr::null_mut());
        static USES_ALTGR: AtomicBool = AtomicBool::new(false);

        let hkl = winuser::GetKeyboardLayout(0);
        let old_hkl = ACTIVE_LAYOUT.swap(hkl, Ordering::SeqCst);

        if hkl == old_hkl {
            return USES_ALTGR.load(Ordering::SeqCst);
        }

        let mut keyboard_state_altgr = [0u8; 256];
        // AltGr is an alias for Ctrl+Alt for... some reason. Whatever it is, those are the keypresses
        // we have to emulate to do an AltGr test.
        keyboard_state_altgr[winuser::VK_MENU as usize] = 0x80;
        keyboard_state_altgr[winuser::VK_CONTROL as usize] = 0x80;

        let keyboard_state_empty = [0u8; 256];

        for v_key in 0..=255 {
            let key_noaltgr = get_char(&keyboard_state_empty, v_key, hkl);
            let key_altgr = get_char(&keyboard_state_altgr, v_key, hkl);
            if let (Some(noaltgr), Some(altgr)) = (key_noaltgr, key_altgr) {
                if noaltgr != altgr {
                    USES_ALTGR.store(true, Ordering::SeqCst);
                    return true;
                }
            }
        }

        USES_ALTGR.store(false, Ordering::SeqCst);
        false
    }
}