Zoom in/OUT additional question

[linux multitouch]

Hi
I posted a question about the subject zoom in zoom out.
i am writing X11 input driver.
i looked at the kdb input driver and it use
xf86ProcessActionEvent(ACTION_PREV_MODE, NULL);
xf86ProcessActionEvent(ACTION_NEXT_MODE, NULL);
to emulate zoom in zoom out.Is it the right way.?
Peter Hutterer answer me and told me to use
KEY_ZOOMIN and KEY_ZOOMOUT
But i don't know how to send these events/
thank you
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