Application gui disappears for short time when using barcode scanner

[MHermann]

Hello,
on Raspbian Buster I am running my application with Qt5.12.7.
In my application I use a barcode scanner.
Sometimes, not every time, when I scan a barcode with the barcode scanner, my application gui disappears for 1 or 2 seconds.
The barcode is read correctly and the application continues without problems.

Does anybody know this problem and can tell me how I can avoid that the gui of my applications disappears for short time when using barcode scanner?

Kind regards,
MHermann

[SGaist]

Hi,

Likely the monitor gremlin playing with the power switch !

More seriously, you do not give any information about your GUI, what it might be doing when you scan the barcode, what you use for reading barcode, how you get it to your app, etc.

The devil might be in the details.

[MHermann]

The barcode scanner that is used is a hand scanner from Honeywell that is connected by usb.
In the application the barcode scanner is handled like a keyboard. The scanned barcode is read with Keys.onPressed.

[KH-219Design]

What if you bring some other GUI application into the foreground? Perhaps a web browser or a "notepad" type of application. (Something you did not create and something not using Qt.)

If you point the barcode scanner at a barcode and do a scan with any other GUI in the foreground, does this other GUI also disappear for 1 or 2 seconds?