private static void checkPermission(Context context) {
        String permission = "android.permission.SYSTEM_ALERT_WINDOW";
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (!Settings.canDrawOverlays(context)) {
                throw new IllegalStateException("in order to use Galgo, " +
                        "please add the permission " + permission + " to your AndroidManifest.xml");
            }
        } else {
            int status = context.checkCallingOrSelfPermission(permission);
            if (status == PackageManager.PERMISSION_DENIED) {
                throw new IllegalStateException("in order to use Galgo, " +
                        "please add the permission " + permission + " to your AndroidManifest.xml");
            }
        }
    }
Logs a String message to the screen. This String will be overlayed on top of the
UI elements currently displayed on screen. As a side effect, this message will
also be logged to the standard output via {@link android.util.Log}.

@param message String to be displayed
src/main/java/com/inaka/galgo/Galgo.java