RFR: 8267546: Add CSS themes as a first-class concept

[Michael Strauß]

On Wed, 9 Nov 2022 22:58:56 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

> This will take a fair bit of discussion regarding how various applications might use such a feature, what the API should look like, etc.
> 

I think there are basically three categories of how applications might use this feature:
1. Extend a built-in theme.
2. Create a new static theme.
3. Create a dynamic theme that responds to OS preferences.

The proposed feature addresses all three categories, with the third option (a dynamic theme) being the most difficult to implement. It requires quite a bit of effort to create such a theme, and a good amount of that effort will be figuring out how OS-level preferences interact with themes (platform independence is a complicating factor).

I've made it an explicit non-goal of this feature to provide an API for higher-level concepts like dark mode, high contrast, etc., since I think APIs for OS design trends should be left to third-party libraries instead.

-------------

PR: https://git.openjdk.org/jfx/pull/511