ui_layout 0.12.1

A minimal Flexbox-inspired layout engine for Rust GUI
Documentation 
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use std::time::Instant;
use ui_layout::*;

fn make_node(is_flex: bool) -> LayoutNode {
    LayoutNode::new(Style {
        display: if is_flex {
            Display {
                outer: OuterDisplay::Block,
                inner: InnerDisplay::Flex,
            }
        } else {
            Display {
                outer: OuterDisplay::Block,
                inner: InnerDisplay::Flow,
            }
        },
        size: SizeStyle {
            width: LengthOrAuto::Auto,
            height: LengthOrAuto::Auto,
            min_width: LengthOrAuto::Length(Length::Px(0.0)),
            max_width: LengthOrAuto::Length(Length::Px(10_000.0)),
            min_height: LengthOrAuto::Length(Length::Px(0.0)),
            max_height: LengthOrAuto::Length(Length::Px(10_000.0)),
        },
        spacing: Spacing {
            margin_left: LengthOrAuto::Length(Length::Px(2.0)),
            margin_right: LengthOrAuto::Length(Length::Px(2.0)),
            margin_top: LengthOrAuto::Length(Length::Px(1.0)),
            margin_bottom: LengthOrAuto::Length(Length::Px(1.0)),
            padding_left: Length::Px(1.0),
            padding_right: Length::Px(1.0),
            padding_top: Length::Px(1.0),
            padding_bottom: Length::Px(1.0),
            border_left: Length::Px(1.0),
            border_right: Length::Px(1.0),
            border_top: Length::Px(1.0),
            border_bottom: Length::Px(1.0),
        },
        ..Default::default()
    })
}

fn make_tree(depth: usize, max_depth: usize, remaining: &mut usize) -> LayoutNode {
    let is_flex = depth.is_multiple_of(2); // Flex -> Block -> Flex -> ...
    let mut node = make_node(is_flex);

    if depth >= max_depth || *remaining == 0 {
        return node;
    }

    let max_children = if depth < 3 {
        4
    } else if depth < 6 {
        3
    } else if depth < 9 {
        2
    } else {
        1
    };

    let child_count = max_children.min(*remaining);

    let mut children = Vec::with_capacity(child_count);
    for _ in 0..child_count {
        if *remaining == 0 {
            break;
        }
        *remaining -= 1;
        children.push(make_tree(depth + 1, max_depth, remaining));
    }
    node.children = children
        .into_iter()
        .map(|n| LayoutChild::Node(Box::new(n)))
        .collect();
    node
}

fn main() {
    const TOTAL_NODES: usize = 7_000;
    const DEPTH: usize = 16;

    println!("layout performance benchmark");
    println!("TOTAL_NODES = {}", TOTAL_NODES);
    println!("DEPTH       = {}", DEPTH);
    println!("-------------------------");

    let mut remaining = TOTAL_NODES - 1;
    let mut root = make_tree(0, DEPTH, &mut remaining);

    println!("remaining nodes unused = {}", remaining);

    let t1 = {
        let start = Instant::now();
        LayoutEngine::layout(&mut root, 800.0, 600.0);
        start.elapsed()
    };

    println!("1st layout: {:?}", t1);

    let t2 = {
        let start = Instant::now();
        LayoutEngine::layout(&mut root, 800.0, 600.0);
        start.elapsed()
    };

    println!("2nd layout: {:?}", t2);
}