You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: window_backend.rs
    path of file: ./repos/irisia-gui/examples
    
    the code of the file until where you have to start completion: use irisia::{
    element::{Element, ElementUpdate, LayoutElements, PropsUpdateW
    
fn flex_layout(this: &ElModel!(Flex), layouter: LayoutElements) -> Result<()> {
    let (start, end) = this.draw_region();
    let abs = end - start;
    let len = layouter.len();
    let width = abs.0 / len as f32;

    let mut index = 0;
    layouter.layout(|()| {
        if index >= len {
            return None;
        }

        let region = (
            Point(width * index as f32, start.1),
            Point(width * (index + 1) as f32, end.1),
        );
        index += 1;
        Some(region)
    })
}