RFR: JDK-8292594: Use CSS custom properties for all fonts and colors

[Jonathan Gibbons]

On Fri, 11 Nov 2022 15:17:23 GMT, Hannes Wallnöfer <hannesw at openjdk.org> wrote:

> Please review a patch to complete the conversion of the javadoc style sheet to use CSS custom properties for all colors and fonts. 
> 
> A few notes for changes that may not be self-explanatory:
> 
>  - I renamed the `--highlight` property prefix used for the active navigation/menu/tab item to `--selected` as the term "highlight" is used for other things such as snippet highlights and active search item targets.
>  - I unified the active color of  copy-to-clipboard buttons to one single value even though they appear on different backgrounds. The value works reasonably well for all uses, and can be changed with a single custom property.
>  - The stylesheet contains a rule for green line numbers in source pages created with the `-linksource` option. This is a very rarely used option so I chose to use a custom property with no defined value but a default value. This means the custom property is not contained in the list of custom property definitions in the style sheet, but it can be defined by a theme if needed.
>  - I removed CSS selectors that are either illegal under HTML 5 such as a[name] or unused.
>  
> This change does not affect the appearance of the generated documentation in the browser. I can provide before/after output including different themes if needed.

It's *really* nice to see those hex constants disappearing from being spread out through the stylesheet.

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Marked as reviewed by jjg (Reviewer).

PR: https://git.openjdk.org/jdk/pull/11109