parse-srcset 0.1.0

Parse an HTML img srcset attribute into image candidates (url + density/width/height). A faithful port of the WHATWG-based parse-srcset npm package. Zero dependencies, no_std.
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# parse-srcset

[![Crates.io](https://img.shields.io/crates/v/parse-srcset.svg)](https://crates.io/crates/parse-srcset)
[![Documentation](https://docs.rs/parse-srcset/badge.svg)](https://docs.rs/parse-srcset)
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[![License](https://img.shields.io/crates/l/parse-srcset.svg)](#license)

**Parse an HTML `srcset` attribute** into its image candidates — each a URL plus an
optional density (`x`), width (`w`), or height (`h`) descriptor. A faithful Rust
port of the [`parse-srcset`](https://www.npmjs.com/package/parse-srcset) npm package,
which implements the
[WHATWG algorithm](https://html.spec.whatwg.org/multipage/images.html#parsing-a-srcset-attribute).
Zero dependencies and `#![no_std]`.

```rust
use parse_srcset::parse_srcset;

let candidates = parse_srcset("small.jpg 480w, large.jpg 800w, fallback.jpg");
assert_eq!(candidates[0].url, "small.jpg");
assert_eq!(candidates[0].width, Some(480));
assert_eq!(candidates[2].width, None); // bare fallback URL

let dpr = parse_srcset("img.png 1x, img@2x.png 2x");
assert_eq!(dpr[1].density, Some(2.0));
```

## Why parse-srcset?

Responsive-image tooling — build steps, SSR, image CDNs, linters — needs to read
the candidates out of a `srcset` string. The grammar has corners (commas inside
data URLs, descriptor validation, the `w`/`x`/`h` rules) that the canonical JS
parser already nails; this ports it faithfully so Rust tooling matches the browser.

```toml
[dependencies]
parse-srcset = "0.1"
```

## API

| Item | Purpose |
| --- | --- |
| `parse_srcset(input)` | `Vec<ImageCandidate>` |
| `ImageCandidate { url, density, width, height }` | A URL and its optional `x`/`w`/`h` descriptor |

## Behavior

- Candidates are separated by commas; surrounding whitespace is ignored and empty
  candidates are dropped.
- A URL may contain commas (e.g. a `data:` URI); a trailing comma just ends the URL.
- Exactly one of density/width is allowed per candidate (plus an optional height);
  a candidate with conflicting or malformed descriptors is **skipped**, matching the
  reference implementation.
- A `0x` density and `0w`/`0h` are treated as the reference does (density `0` is
  dropped; `0w`/`0h` are errors).

## License

Licensed under either of [Apache-2.0](LICENSE-APACHE) or [MIT](LICENSE-MIT) at
your option.