Left control key triggers libdcv error in NICE DCV

Question

When I press the Left Control Key when connecting to an Amazon Linux 2 instance from an Ubuntu 20.04 X11 client, it is ignored, until I release it, at which point the error "libdcv - The keyval was not pressed or it is invalid: FFE3, 25" is printed to stdout on the terminal where I started the DCV script. (FFE3 is the X11 keysym for Control.) I tried two keyboards.

Accepted Answer

It turned out the problem was enabling "Locate Pointer" under "Universal Access" in GNOME settings. (This highlights the mouse pointer when you press and release the left Control key.) Apparently, while it interoperates correctly with other applications, it doesn't play nice with the NICE DCV client. DCV developers might want to look into this.

Technical information: I diagnosed this using `xev`; it was reporting a different, more cryptic message for left control than for right control.

Right control:
```
KeyPress event, serial 37, synthetic NO, window 0x4400001,
    root 0x9f3, subw 0x0, time 71454338, (89,89), root:(2416,2117),
    state 0x0, keycode 105 (keysym 0xffe4, Control_R), same_screen YES,
    XLookupString gives 0 bytes: 
    XmbLookupString gives 0 bytes: 
    XFilterEvent returns: False

KeyRelease event, serial 37, synthetic NO, window 0x4400001,
    root 0x9f3, subw 0x0, time 71454914, (89,89), root:(2416,2117),
    state 0x4, keycode 105 (keysym 0xffe4, Control_R), same_screen YES,
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False
```

Left control:
```
KeymapNotify event, serial 37, synthetic NO, window 0x0,
    keys:  4294967283 0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   
           0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   
```

Left control key triggers libdcv error in NICE DCV

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