Styling Rework

[sleepy-monax]

No description provided.

[pauloamed]

Splitting computed style into compute style and computed value

• relative sizes (eg. em) can live in compute style but not value
• relative font weight (bolder, ligther) can live in compute style but not value
• calc values can live in compute style but not value
• currentColor can live in compute style but not value
• computed value for size could be a union of auto, perc, au
  • able to identify if a Width is a percentage as a computed value

Another points:

• Should border collapse be solved as a computed value? If yes, grid building should also, since it depends on that.

Structure for computed style/props

• A prop can be thought of as tuple key, css value (as in lady bird), which wouldn't enforce types when creating the prop, only when applying. This could affect our performance. Prolly it's better to stick to a specific value type for each prop? However, on the other hand, having a bit Union for all the props hurts compile time.
• In the current design, there is duplication of code and recomputing regarding default values of Props and their initial() methods.

[pauloamed]

Ongoing discussion/refinement with @LuneMercier :

• investigate if transforming Any non-void case from recursive to loop would enhance performance
• suggestion about shifting requires { T::load(parent); } into specific type LoadableStyle, over the cost of adding burden into developer needing to know if the prop they create should be LoadableStyle or not
• benefit from the fact that name() is a one2one relation with a property and use this to optimize the matching T::name() != propName

[pauloamed]

Specs related to this task: https://www.w3.org/TR/css-cascade/#value-stages

Compute:

• values with relative units (em, ex, vh, vw) must be made absolute by multiplying with the appropriate reference size
• certain keywords (e.g., smaller, bolder) must be replaced according to their definitions
• percentages on some properties must be multiplied by a reference value (defined by the property)
• valid relative URLs must be resolved to become absolute.
• The declared value of transparent is "transparent" while the computed and used value is transparent black.

Not compute:

• The currentcolor keyword computes to itself.

[pauloamed]

Another task from this milestone is "Separation build phase and compute phase", to be tackled by @sleepy-monax when adding Stylesheet information in DOM nodes (thus needing to have specified values on stylesheets).

[sleepy-monax]

We should probably closly follow the model described in:

• https://www.w3.org/TR/cssom-1/
• https://drafts.css-houdini.org/css-typed-om