RFR: JDK-8289334: Use CSS variables to define fonts and colors

[Jonathan Gibbons]

On Wed, 17 Aug 2022 11:38:18 GMT, Hannes Wallnöfer <hannesw at openjdk.org> wrote:

>> src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/toolkit/resources/stylesheet.css line 959:
>> 
>>> 957: }
>>> 958: div.page-search-info button#page-search-copy:hover {
>>> 959:     background-color: rgba(128, 128, 160, 0.2);
>> 
>> why have the old hex values just been converted to `rgba` values, and not CSS custom properties?
>
> One of my intentions was to keep the number of CSS custom properties as small as possible. I think the hover color of the copy-to-clipboard button (in this case for the search page extra information) is "fringe" enough to not want to define a dedicated property for it.
> 
> Using a `rgba` value with a middle-of-the-road blue-grey color and a low alpha value allows me to generate a semitransparent overlay that works both with light and dark background colors. The only background color this would not work with is if the background was itself a medium grey color, but in this case it could be overridden with a extra CSS rule.

mmmm ... OK, but ...

_Keep everything as simple as possible, but no simpler_

Yes, there is merit it reducing the number of CSS custom properties, but there is equal merit in a simple rule that says that all colors are set via custom properties.   As it stands, we have to explain the (reason for the) exception,

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PR: https://git.openjdk.org/jdk/pull/9839