Freeze the camera feed once the scan finishes and "Copy QR code" dialog is showing

[vivekgalatage]

Right now, the app continues with the live feed even after a successful scan and while the "Copy QR code" dialog is still showing up.

Freezing the viewfinder frame upon successful scan would not only help the user analyse the viewfinder frame but also saving the battery power. :)

[gokulkrishh]

@vivekgalatage Good suggestion ;)