The Nemo.Policy QML plugin provides an API for communicating with the
libresource policy manager.

import QtQuick 2.0
import Nemo.Policy

Item {
    id: volumeHandler

    focus: true

    Keys.enabled: permissions.acquired
    Keys.onPressed: {
        if (event.key == Qt.Key_VolumeUp) {
            // increase volume
        } else if (event.key == Qt.Key_VolumeDown) {
            // decrease volume
        }
    }

    Permissions {
        enabled: volumeHandler.activeFocus
        autoRelease: true
        applicationClass: "player"

        Resource {
            type: Resource.ScaleButton
        }
    }
}