Question: How does FlatSVGIcon dark mode recoloring work?

When I use a FlatSVGIcon with fill="#6E6E6E" (copied from the icons in the demo), it changes color depending on whether the theme is dark or light (I like that). When I use fill="#000000", it does not. When I download a raw Material icon that doesn’t have a fill specified at all, it is always black. How does it work, what is the underlying mechanism, where is it configured? Is there a documentation for that? Is there a common place where such things are documented (maybe the Demo might be a good spot)?

Thank you.

[DevCharly]

FlatSVGIcon maps only some colours. They are defined in enum FlatIconColors.

The idea is to use only this well defined set of colors in SVG icons and then they are replaced at runtime to dark variants or to other theme colors. Then a single SVG icon (light variant) can be used for dark themes too. IntelliJ Platform uses this mechanism to allow themes to change IntelliJ Platform icons.

The colors are based on IntelliJ Platform Action icons and Noun icons.

You can change/extend the color mapping. Either per icon: see FlatSVGIcon.setColorFilter() Or globally for all icons: see FlatSVGIcon.ColorFilter.getInstance()

[DevCharly]

@howudodat that is a good solution.

is there a preferred property to use to get the highlight color used by the different themes

No. IntelliJ themes are converted from JSON files and do not have such a property. In FlatLaf 2.x core themes there are variables, but they are not accessible via UIManager:

https://github.com/JFormDesigner/FlatLaf/blob/e5956900ea5413fc0e879c0a808272b988cc51c5/flatlaf-core/src/main/resources/com/formdev/flatlaf/FlatLightLaf.properties#L62-L75