Attribute Macro main

#[main]

A macro to create a main() function with less boilerplate.

When creating applications that support multiple windows, this attribute macro can be used to remove a few lines of code.

The function body is executed during application startup, and the app will continue running until the last window is closed.

This attribute must be attached to a main(&mut PendingApp) or main(&mut App) function. Either form supports a return type or no return type.

&mut PendingApp

When using a PendingApp, the function body is invoked before the app is run. While the example shown below does not require the runtime initialization, some programs do and using the macro means the developer will never forget to add the extra code.

These two example programs are functionally identical:

Without Macro

use cushy::{Open, PendingApp, Run};

fn main() -> cushy::Result {
    let mut app = PendingApp::default();
    let cushy = app.cushy().clone();
    let _guard = cushy.enter_runtime();

    "Hello World".open(&mut app)?;

    app.run()
}

With Macro

use cushy::{Open, PendingApp};

#[cushy::main]
fn main(app: &mut PendingApp) -> cushy::Result {
    "Hello World".open(app)?;
    Ok(())
}

&mut App

When using an App, the function body is invoked after the app’s event loop has begun executing. This is important if the application wants to access monitor information to either position windows precisely or use a full screen video mode.

These two example programs are functionally identical:

Without Macro

use cushy::{App, Open, PendingApp, Run};

fn main() -> cushy::Result {
    let mut app = PendingApp::default();
    app.on_startup(|app| -> cushy::Result {
        "Hello World".open(app)?;
        Ok(())
    });
    app.run()
}

With Macro

use cushy::{App, Open};

#[cushy::main]
fn main(app: &mut App) -> cushy::Result {
    "Hello World".open(app)?;
    Ok(())
}