Example of detouring MessageBoxW in Rust using detour-rs

lib.rs

#[macro_use]
extern crate detour;
extern crate winapi;

// --- std ---
use std::mem;
use std::ffi::CString;
// --- external ---
use kernel32::{GetModuleHandleW, GetProcAddress};
use winapi::{
    ctypes::c_int,
    shared::{
        windef::HWND,
        minwindef::{BOOL, DWORD, HINSTANCE, LPVOID, UINT, TRUE},
    },
    um::{
        winnt::LPCWSTR,
        winuser::MessageBoxW,
    },
};

static_detours! {
  struct DetourMessageBoxW: unsafe extern "system" fn(HWND, LPCWSTR, LPCWSTR, UINT) -> c_int;
}

fn message_boxw_detour(h_wnd: HWND, _: LPCWSTR, lp_caption: LPCWSTR, u_type: UINT) -> c_int {
    // Simply forward the call to the original
    let mut text: Vec<u16> = "Ops, hook by detour-rs.".encode_utf16().collect();
    text.push(0);
    unsafe { DetourMessageBoxW.get().unwrap().call(h_wnd, text.as_ptr() as _, lp_caption, u_type) }
}

type FnMessageBoxW = unsafe extern "system" fn(HWND, LPCWSTR, LPCWSTR, UINT) -> c_int;

#[no_mangle]
#[allow(non_snake_case, unused_variables)]
pub extern "system" fn DllMain(dll_module: HINSTANCE, call_reason: DWORD, reserved: LPVOID) -> BOOL {
    const DLL_PROCESS_ATTACH: DWORD = 1;
    
    if call_reason == DLL_PROCESS_ATTACH {
        // Retrieve an absolute address of `MessageBoxW`
        let address = lookup("user32.dll", "MessageBoxW").unwrap();
        let target: FnMessageBoxW = unsafe { mem::transmute(address) };
        
        let mut hook = unsafe { DetourMessageBoxW.initialize(MessageBoxW, message_boxw_detour).unwrap() };
        unsafe { hook.enable().unwrap() };

        // Omit the drop to persist the hook after the current scope.
        // A better alternative is to define a variable with a longer lifetime.
        mem::forget(hook);
    }

    return TRUE;
}

pub fn lookup(module: &str, symbol: &str) -> Option<usize> {
    let mut module: Vec<u16> = module.encode_utf16().collect();
    module.push(0);
    let symbol = CString::new(symbol).unwrap();
    unsafe {
        let handle = GetModuleHandleW(module.as_ptr());
        match GetProcAddress(handle, symbol.as_ptr()) as usize {
            0 => None,
            n => Some(n),
        }
    }
}

Oh, It seems you update to the version 7.0 and remove get() method.

Yes, the StaticDetour interface has been simplified. You can see a CI-tested example here:
https://github.com/darfink/detour-rs/blob/master/examples/messageboxw_detour.rs

NOTE: It uses 2018 crate edition.