Change window color accordingly to theme background

[mqzabin]

Feature description
A feature that makes window decorations color changes accordingly to theme's background.

Reference implementation
Below a screenshot (taken from ChromeOS) with current state on the left and feature examples on the right:

My suggestion to get new window color is: If the background color brightnes (on a HSL perspective) is below some threshold, increase brightness by some fixed (or percentual) value; and decrease if it's above the threshold. Or something like that...

On my example screenshot, I've decreased 5 points on light theme and increased 5 points on dark theme (on a 0-100 brightness scale).

It would be great to see this upstream. It's adds a refined touch to the UI and maybe it's easy to implement.

Thank's for the awesome work!

[williamguilhermesouza]

That would be a really nice feature!!