Normalization of a CSS z-index value to a 32-bit floating-point number

Note

This project is a work in progress, so please watch for a new release and ensure to use the latest version.

Origin

I struggled to map CSS z-index values to 32-bit floating-point numbers between 0.0 and 1.0 because dividing a large number by another large number, such as 2_147_483_646.0 / 2_147_483_647.0, does not yield precise results.

To illustrate the issue, here are some examples (see playground):

2_147_483_646.0 / 2_147_483_647.0 = 1.0
2_147_483_645.0 / 2_147_483_647.0 = 1.0
2_147_483_644.0 / 2_147_483_647.0 = 1.0
2_147_483_643.0 / 2_147_483_647.0 = 1.0
2_147_483_642.0 / 2_147_483_647.0 = 1.0
2_147_483_641.0 / 2_147_483_647.0 = 1.0
2_147_483_640.0 / 2_147_483_647.0 = 1.0
2_147_483_639.0 / 2_147_483_647.0 = 1.0
2_147_483_638.0 / 2_147_483_647.0 = 1.0
2_147_483_637.0 / 2_147_483_647.0 = 1.0

I spent some time experimenting to figure out a reasonable approach to this challenge, and I may have finally found a way to manage the headache of mapping CSS z-index values.

Usage

Run the following Cargo command in your project directory:

cargo add normalize-css-z

Or add the following line to your Cargo.toml:

[dependencies]
normalize-css-z = "0.7"

And in your Rust file:

use normalize_css_z::normalize;

fn main() {
    let z_ = 2_147_483_647;
    if let Some(z) = normalize(z_) {
        // Do something with `z`.
    } else {
        // Handle unsupported z-index.
    }
}

Custom lower, middle, and upper ranges are now available under the 'custom' feature flag as of version 0.6

NOTE: This version has not been thoroughly tested yet.

To use, add the following line to your Cargo.toml:

[dependencies]
normalize-css-z = { version = "0.7", features = ["custom"] }

And in your Rust file:

use normalize_css_z::{
    normalizer::Normalizer,
    ranges::RangesBuilder,
};

fn main() {
    let builder = RangesBuilder::default()
        .with_lower(0..=100)
        .with_middle(101..=200)
        .with_upper(201..=300);
    let normalizer = Normalizer::new(builder.build());

    if let Some(z) = normalizer.calc(0) {
        // Do something with `z`.
    } else {
        // Handle unsupported z-index.
    }
}

Supported ranges of z-indexes

Total number of supported z-indexes (as of 1/16/2024)

8,388,608 * 3 + 1 = 25,165,825

License

Licensed under either of

• Apache License, Version 2.0
• MIT license

at your option.