Re: [w3ctag/design-reviews] TAG review for CSS Typed OM (#223)

@slightlyoff  in response to your questions:

> We're starting to review at the London F2F; some stream-of-consciousness questions:
> Is CSSStyleValue really meant to be available in all Worker types? E.g., does it make sense in Service Workers?

Nope, it should be exposed to the Paint API only. Filing an issue on typed om: https://github.com/w3c/css-houdini-drafts/issues/632

> Don't understand how Example 7 works: it looks like the example should work with styleMap, but instead it uses attributeStyleMap, which doesn't seem like it should have values for 'object-position'

The example seems incorrect - it should be checking `computedStyleMap()`. Filed an issue here: https://github.com/w3c/css-houdini-drafts/issues/633

> Should computedStyleMap() be synchronous? It seems to flush style on read...is that right? 

IIUC: when you read values of `computedStyleMap()` it causes a style recalc, so yes it is synchronous.

> And does it need to be a function?

The CSSWG resolved to have it be a function, IIRC. For reasons:

- To mirror getComputedStyle() 
- To reflect that it will return a new `StylePropertyMap` each time. 
@tabatkins 

> ...that gets us to a perhaps bigger question: should the OM be trying to help ensure performant read-back and separation of writes/reads? If this is a chance to go that way, it won't come around again. Has it been discussed?

I don't understand the question here. Could you elaborate?

> @plinss points out that [[tokens]] is a list of strings and not a list of actual tokens. Another way to look at this is that the tokenizer isn't exposed. Should it be?

Exposing a tokenizer was delayed to a Level 2 spec. Context here: https://github.com/w3c/css-houdini-drafts/issues/193

> Are changes to CSSVariableReferenceValues observable without polling?

IIUC. No, the `CSSVariableReferenceValues` objects aren't live, you have to get the new value again, if changed. 

> Are there concrete performance numbers we can point to that show the benefits of the Typed OM approach?

Since there is a lot of discussion about this, I am filing an issue to track the discussion: https://github.com/w3c/css-houdini-drafts/issues/634

> Thanks!

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