The new Gtk3 themes seem to be CSS/SASS based, so the question is: How do I ask the browser for the current theme settings such that I can style buttons or other elements in a webpage to match the system theme?
If there's no universal way, is there a userscript for Chrome or Firefox extension you can recommend that will grab this information from the OS and push it in to the browser in some way that I can access from the web-app side?
I appreciate the response from @gertvdijk, but I more mean how I can grab the style for a particular element and apply it to some random div. If I were building a menu-system from a ul and li elements for example. How do I grab the appropriate style from the theme (fg/bg from non text area) would be a fitting example.