The best icon format for my application is the rounded square, however, on api 26 and 27 we know that the android uses a predefined adaptive icon (always in circular format) or transforms a non-adaptive icon (circle with space blank and small real icon).
After many tests and searches on the internet, I was convinced that I should produce a circular icon, but luckily I noticed that the facebook icon in these apis maintains its standard (rounded square of normal size).
How can I implement this in my application?
