Al Marks

Optimize exportparts tree with cache

2

We should be able to cache the exportsparts tree, maybe directly on each node, so that we don't need to walk the same exporting part ancestor more than once.

ShadyParts: noPatch mode support

2

Need to ShadyDOM.wrap where appropriate.

Make ShadyCSS Shadow Parts an optional shim

2

See https://github.com/webcomponents/polyfills/pull/329/files#r430699466 The most important reason to do this could be users who don't want to pay the byte cost of additional shadow parts support.

Shady Parts: move some work to prepareTemplateDom if possible

2

The static parts of a template could be discovered once per template in `prepareTemplateDom`, which could give us a performance improvement. Would still need to account for dynamic DOM insertions,...

Shady Parts: design for build step

2

Investigate whether/how an optional build step could be used to improve performance of shadow parts support in shady css.

Shady Parts: don't call _applyStyleProperties twice

2

Currently, when an instance consumes a ::part rule that consumes a custom property, and native custom properties are not available, `_applyStyleProperties` ends up getting run twice. Once is the normal...

Explainer for Shadow Parts support for native shadow DOM

2

Document how we will support Shadow Parts in browsers that do support native shadow DOM, but don't support ::part (e.g. Safari).