Cranpose Macros

Procedural macros that power the Cranpose declarative syntax.

When to Use

You will rarely interact with this crate directly; it is re-exported by cranpose. Identifying how the #[composable] macro transforms your code is useful for debugging and understanding performance characteristics.

Key Concepts

• #[composable]: This attribute macro transforms a standard Rust function into a Composable function. It injects a hidden Composer parameter and wraps the function body in a uniquely identified group.
• Skipping: The macro generates code to compare current arguments with previous arguments. If they haven't changed, the function body execution is skipped during recomposition, significantly improving performance.

Transformation Example

Conceptual expansion of what #[composable] does:

// Source
#[composable]
fn MyComponent(name: String) {
    Text(name);
}

// Generated (Conceptual)
fn MyComponent(composer: &mut Composer, changed: usize, name: String) {
    composer.start_restart_group(12345); // Unique ID based on location
    
    if changed == 0 && composer.skipping() {
        composer.skip_to_group_end();
    } else {
        Text(composer, changed, name);
    }
    
    composer.end_restart_group(|composer| MyComponent(composer, changed | 1, name));
}