There was too much code duplication - there still is a bit...
- in some places buttons had text "Read QR code with camera", in others it was "Read QR code from camera"
- 63c224cb53 added a "on_qr_from_file_input_btn"
input method, which was not added everywhere.
- was missing in add_qr_input_combined_button and in editor_contextMenuEvent
5ea614c81a