FLprintk2 — A FLTK opcode that prints a new value every time a control-rate variable changes.
FLprintk2 is similar to FLprintk but shows a k-rate variable's value only when it changes.
idisp -- a handle value that was output from a previous instance of the FLvalue opcode to display the current value of the current valuator in the FLvalue widget itself. If the user doesn't want to use this feature that displays current values, it must be set to a negative number by the user.
kval -- k-rate signal to be displayed.
FLprintk2 is similar to FLprintk, but shows the k-rate variable's value only each time it changes. Useful for monitoring MIDI control changes when using sliders. It should be used for debugging purposes only, since it slows-down performance.