XON/XOFF flowcontrol with QextSerialPort

Hello everyboby,
I developed an application in Qt which use the library “qextserialport”.
I use XON/XOFF Flowcontrol and it works correctly ( I use EventDriven mode ), now I need a simple way to know if an XOFF event is occurred and how to report the number of bytes really transmitted to the device at this time ( when XOFF occurred) also is there any way to clear TX data buffer if I want to cancel communication with the device ?

any help is greatly appreciated ! thanks

AFAICT QExtSerialPort does not offer signals to indicate when the receiver is currently suppressing flow (hard or soft) or a method to clear the pending buffer short of closing the port.