MOB button - simulate key strokes

[Moo]

My RPi plotter project is nearing completion (well phase one at least). The final thing to get working is the red push button on the top that is pressed to drop a MOB (ideally a long press will drop a normal mark).

I'm running OpenPlotter to tie everything together. The red button is connected to a GPIO on the Pi. When the button is pressed OP can generate a system command.

I had several ideas on how to get the keypress in OCPN
Simulating an ARPA or ARPS target
Simulating a DSC target
Simulating an AIS SART

But these all rely on generating obscure NMEA sentences from Signal K keys some of which, the AIS at least, is not implemented in the OP version of Signal K.

My plan is to use a command line tool to generate a simulated ctrl+space

I found the utility xdotool which seems to fit the bill

I was thinking to use an action to issue a command like

xdotool search --name "OpenCPN 4.6.1" key ctrl+space

which runs without error but doesn't do anything

Somebody else found that

xdotool search "OpenCPN 4.6.1" windowactivate --sync key --clearmodifiers

" works to turn on and off the light in opencpn"

So; anybody any ideas?

Thanks for your time.

[Moo]

Further experimentation has shown that single key shortcuts work such as "M" which turns on the measure tool and "O" toggling chart outlines so the issue is something to do with combinations of keys.