2.2.6 Example Configuration: Initialization

The next option is #:init.

(configure-device
 ...
 #:init (list (lambda ()
                (turn-off-ctls
                 (map control-alsa-ctl
                      (list ak1:left ak1:middle ak1:right ak1:knob)))))
 ...)

This option lets you perform whatever additional initialization of the device you would like to do. It takes as its argument a list of procedures to be run at configuration time. Each procedure is defined using lambda and takes no arguments.

In this example, we define a procedure that turns off all the LEDs. Sometimes, especially if you’re playing around with a configuration and you mess up something, you might end up exiting Librekontrol with some LEDs still on. This procedure returns the device to a clean state.

First, the ALSA hardware-control handle (called a ctl throughout Librekontrol, which tells the program how to find the LED) for each control is retrieved by mapping the control-alsa-ctl procedure onto a list of all the AK1 controls. The resulting list of ctls is then passed to the turn-off-ctls procedure.