# proc to make a button continuously call a function while depressed.

button .b -text "Button"

pack .b

set afterid {}

proc function {} {
    global afterid

    puts "Function."
    set afterid [after 1000 function]
}

bind .b <1> {
    function
}

bind .b <ButtonRelease-1> {
    if {$afterid != {}} {
	after cancel $afterid
	set afterid {}
    }
}