Calls a named event handler directly. If the function cannot be found or the found handler did not want to handle the event, #f is returned. Otherwise, the return value is the return value of the event handler.
The in and event+ arguments are passed on to the keymap callback procedure if one is found.
If try-chain is not #f, keymaps chained to this one are searched for the function name. If the function is not found and try-chain is #f, an error is also sent to the handler installed with set-error-callback.