lightningcss

CSS Custom Properties have a cost. If you’re using them as global variables, and don’t need to look them up from JavaScript, or change them according to media queries, it’s good to flatten them out of existence: your bundle will be smaller, your execution faster, and your memory usage reduced. Same with mixins. It would be good if Lightning CSS supported that use case: https://github.com/parcel-bundler/lightningcss/issues/69. Compile-time variables are still a useful feature. CSS Custom Properties get used in a lot of places where compile-time variables would be better.

We tried LightningCSS and it gave buggy output for us because it doesn't keep track of property ordering. I wouldn't use it until that's fixed. https://github.com/parcel-bundler/lightningcss/issues/547 https://github.com/parcel-bundler/lightningcss/issues/572

Libraries for a lot of this stuff exist (albeit in many cases not very mature yet): - https://github.com/pop-os/cosmic-text does text layout (which Taffy explicitly considers out of scope) - https://github.com/AccessKit/accesskit does accessibility - https://github.com/servo/rust-cssparser does value-agnostic CSS parsing (it will parse the general syntax but leaves value parsing up to the user, meaning you can easily add support for whatever properties you what). Libraries like https://github.com/parcel-bundler/lightningcss implement parsing for the standard css properties. - There are crates like https://github.com/BurntSushi/bstr and https://docs.rs/wtf8/latest/wtf8/ for working with non-unicode text We are planning to add a C API to Taffy, but tbh I feel like C is not very good for this kind of modularised approach. You really want to

Hi, author of Parcel CSS here. I have been thinking about implementing the CSS OM spec as the JS API. This is the same API that browsers expose for manipulating stylesheets. The advantage of this is that we don't need to invent something custom. Still thinking through options. https://github.com/parcel-bundler/parcel-css/issues/5 That said, I think I'd want to keep the use cases for JS plugins limited, because it will affect performance significantly. So, if it's something that exists in an official CSS spec somewhere (even if draft), or a really common transformation, it should be implemented in Rust. An example of this is the support for the CSS nesting spec. Ideally, we'd try to keep the amount of custom syntax being invented around CSS to a minimum and stick to standard CSS syntax wherever possible though.