Add some CSS keywords as static atoms.

[glennw]

r? @kmcallister

[SimonSapin]

Why is this needed? So far we codegen a custom enum (with data for the values) for CSS properties, so we don’t store their name as a string.

[glennw]

The strings are stored here (in python as temps) - https://github.com/servo/servo/blob/master/components/style/properties/mod.rs.mako#L55. I am prototyping getComputedStyle, building on jdm's cssom prototype branch. It has functions like https://github.com/jdm/servo/blob/cssom/components/style/properties/mod.rs.mako#L2421, which can be more efficient if we store the names as static atoms.

Ping me on IRC if you want to discuss more or if there's a better way to achieve this, I'm still finding my way around the DOM / script code.

[SimonSapin]

I am prototyping getComputedStyle, building on jdm's cssom prototype branch. It has functions like https://github.com/jdm/servo/blob/cssom/components/style/properties/mod.rs.mako#L2421, which can be more efficient if we store the names as static atoms.

Ok.

It just seems unfortunate to have a list of CSS properties not just in a different file, but in a different repository. I’m pretty sure we’ll (at least) occasionally fail to update string-cache when adding new properties to Servo. This wouldn’t affect correctness, but still.

I’ve filed #22 about making string-cache generic over the list of static strings. If that happens, Servo could build its list from multiple sources, including the style crate’s codegen.

[glennw]

Actually, once the code lands in master (if it works out the way I'm hoping it will, and if you're happy with the change) that won't be possible. If you declare a static atom that doesn't exist in that table, it's a compile time error due to the way @kmcallister implemented it :)

[SimonSapin]

What does “declare a static atom” mean, and does the style crate do it?

[glennw]

It doesn't currently do that, but I'm hoping it will do in the future, if this stuff works out.

If you write atom!("color") that creates a static atom (which is an integer, created with a perfect hash function) that causes a compile time error if it doesn't exist in the static atoms table.

[SimonSapin]

Ok, that’s good.

[kmcallister]

r+