Attribute Macro tessera

#[tessera]

The #[tessera] attribute macro transforms a regular Rust function into a Tessera UI component.

This macro performs several key transformations:

1. Registers the function as a node in the Tessera component tree
2. Injects measure, state_handler and on_minimize functions into the component scope
3. Manages component tree lifecycle (push/pop operations)
4. Provides error safety by wrapping the original function body

Parameters

• _attr: Attribute arguments (currently unused)
• item: The function to be transformed into a component

Generated Code

The macro generates code that:

• Accesses the Tessera runtime to manage the component tree
• Creates a new component node with the function name
• Provides closures for measure and state_handler functionality
• Executes the original function body within a safe closure
• Cleans up the component tree after execution

Example

use tessera_ui_macros::tessera;

#[tessera]
fn button_component(label: String) {
    // The macro provides access to these functions:
    measure(Box::new(|_| {
        // Custom layout logic
        use tessera_ui::{ComputedData, Px};
        Ok(ComputedData {
            width: Px(100),
            height: Px(50),
        })
    }));
     
    state_handler(Box::new(|_| {
        // Event handling logic
    }));

    on_minimize(Box::new(|minimized| {
        if minimized {
            println!("Window minimized!");
        } else {
            println!("Window restored!");
        }
    }));
}

Error Handling

The macro wraps the original function body in a closure to prevent early returns from breaking the component tree structure. This ensures that the component tree is always properly cleaned up, even if the component function returns early.