Build an android Magisk module that detects volume button long press when the screen is off

Build an android Magisk module that detects volume button long press when the screen is off to control media playback. An exact replica of the xposed module Gravity Box's feature under Media > Volume keys skip track (description: "Skip tracks on volume keys long-press while screen is off") The lack of xposed on Android 9 keeps me from updating because I'd miss that single feature. Making it into a Magisk module would solve that.