Add 'patternContentUnits' to SVG attributes.

[nullobject]

The patternContentUnits attribute is commonly used when defining a SVG pattern.

This work is part of #1657.

[zpao]

I'm going to take #1548 which has patternUnits, want to update this to just be patternContentUnits (also not in that other PR that there are 2 places that need to be updated). Feel free to also drop the docs change. We haven't been super consistent there so it's going to need a batch update before next release anyway.

[nullobject]

@zpao Sure thing, I'll switch it to the patternContentUnits property only.

[nullobject]

@zpao You mentioned to "also not[e] in that other PR that there are 2 places that need to be updated".

Perhaps my understanding of how DOMAttributeNames is used is totally wrong 😉 but the patternContentUnits attribute is not valid on the <svg> element, so why would I need to define it in the DOMAttributeNames? This could also be incorrect in #1548.

[zpao]

It's not valid on the <svg> element, but it's valid on <pattern>. SVGDOMPropertyConfig isn't about just the <svg> element but all of them. By default React downcases the string specified in Properties (downcased for initial markup and for most HTML attributes). Case actually matters for some of these, so for those we have the DOMAttributeNames escape hatch which allows you to specify the exact string that is valid.

As an example, <linearGradient gradientTransform="rotate(45)"> works but <linearGradient gradienttransform="rotate(45)"> doesn't. Most (all?) SVG attributes seem to be case sensitive, so while there's a bit of duplication in this file, it's necessary for now.

I strongly encourage you to actually create a build of React with your change and then actually use contentPatternUnits in an SVG to ensure everything works. Until we have automated tests here, that's how we've been testing attributes.

[nullobject]

@zpao Thanks for the explanation.

I did indeed try my build in Safari, so I assume it mustn't be too fussy about case on the <pattern> attributes. Anyhow, I've updated my PR to include contentPatternUnits in the DOMAttributeNames. Yay!

[zpao]

Thanks for the quick updates :)

[nullobject]

@zpao My pleasure, thanks for the awesome framework 😉