Qt widgets camera examples doesn't handle missing camera input properly. Linux only allows one application to access a camera at a time.

Steps to reproduce:

        Run the camera example.
        Run the camera example again without closing the original application - you should get a warning that the camera is not available

Expected behavior:

The application should not display a camera feed as it is already being used in the already running example.

Buttons should ideally be greyed out/not interactable until camera input is available.

Observed behavior:

All UI elements are still interactable.

Label where the camera playback should show has strange artifacts.

Equipment:

Logitech C920 HD Pro Webcam