The Win32 API is a cornerstone of Windows programming, offering a wide range of functions to interact directly with the Windows operating system. Traditionally accessed through C or C++, the Win32 API can also be harnessed using Rust, a language renowned for its safety, concurrency, and performance. Combining Rust with the Win32 API empowers developers to build robust Windows applications with reduced risk of common bugs such as memory safety issues.
In this post, we’ll walk through how to set up a Rust project that calls the Win32 API, specifically demonstrating how to use the MessageBoxW function to display a Windows message box.
We will use the winapi crate, which provides Rust bindings for the Win32 API.
Step 1: Create a New Rust Project
cargo new –bin api-test
This will create a folder named ‘api-test’ in the directory which will contain main.rs file in the ‘src’ folder and a cargo.toml file which will contain all the dependencies for the project.
Now, let’s add Winapi crate dependency in the project. There’s two ways we can do this first we run a command after navigating to the ‘api-test’ folder.
Step 2: Add the Winapi Dependency
Navigate into the project directory and add the winapi crate with the winuser feature, which contains user interface-related APIs:
cd api-test
cargo add winapi –features winuser
Alternatively, add this manually to your Cargo.toml file:
[dependencies]
winapi = { version = “0.3.9”, features = [“winuser”] }
The MessageBoxW function creates a message box window with customizable text, title, buttons, and icons. Its signature in C looks like this:
To read more about the MessageBoxW api, click here
int MessageBoxW(
[in, optional] HWND hWnd,
[in, optional] LPCWSTR lpText,
[in, optional] LPCWSTR lpCaption,
[in] UINT uType
);
Let’s start with the code:
extern crate winapi;
use winapi::um::winuser::{MessageBoxW, MB_ABORTRETRYIGNORE, MB_ICONQUESTION, IDABORT, IDRETRY, IDIGNORE};
use std::ptr::null_mut;
fn main(){}
loop {}
let title: vec<u16> = “messageboxw\0”.encode_utf16().collect();
let content: vec<u16> = "this is a messageboxw test\0".encode_utf16().collect();
unsafe{}
let reply = messageboxw(null_mut(), content.as_ptr(), title.as_ptr(), MB_ABORTRETRYIGNORE | MB_ICONQUESTION);
match reply {
IDRETRY => {
println!("You pressed Retry");
continue;
},
IDIGNORE => {
println!("You pressed Ignore");
continue;
},
IDABORT => {
println!("Okay.... Aborting now!");
break;
},
_ => {
unreachable!();
}
extern crate winapi;
use winapi::um::winuser::{MessageBoxW, MB_ABORTRETRYIGNORE, MB_ICONQUESTION, IDABORT, IDRETRY, IDIGNORE};
use std::ptr::null_mut;
fn main(){
loop {
let title: Vec<u16> = "MessageBoxW\0".encode_utf16().collect();
let content: Vec<u16> = "This is a MessageBoxW test\0".encode_utf16().collect();
unsafe{
let reply = MessageBoxW(null_mut(), content.as_ptr(), title.as_ptr(), MB_ABORTRETRYIGNORE | MB_ICONQUESTION);
match reply {
IDRETRY => {
println!("You pressed Retry");
continue;
},
IDIGNORE => {
println!("You pressed Ignore");
continue;
},
IDABORT => {
println!("Okay.... Aborting now!");
break;
},
_ => {
unreachable!();
}
}
}
}
}
Combining Rust with the Win32 API lets you build efficient, safe, and native Windows applications. Using the winapi crate, you can easily call Windows functions like MessageBoxW. This tutorial showed how to set up a Rust project, add dependencies, and implement a message box with button handling.
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