#!/usr/local/bin/wish
# 30 Jan 1996 Brian Ward bri@blah.math.tu-graz.ac.at

set w .c
canvas $w -height 350 -width 250
scale $w.scale1 -resolution 1 -from 1 -to 100 -variable t -orient horiz \
    -label delay -length 100
scale $w.scale2 -resolution 1 -from 1 -to 60 -variable dist -orient horiz \
    -label extreme -length 100
scale $w.scale3 -resolution 1 -from 1 -to 7 -variable sp -orient horiz \
    -label speed -length 100
button $w.b -text Stop -command "startstop $w.b $w"

pack $w
$w create window 10 200 -window $w.scale1 -anchor nw
$w create window 140 200 -window $w.scale2 -anchor nw
$w create window 10 270 -window $w.scale3 -anchor nw
$w create window 140 300 -window $w.b -anchor nw

# .scale1 .scale2 .scale3

set sign 1
set sp 1
set i 0
set t 17
set dist 35
set stop 0

proc update {w} {
    global sign sp i t dist stop
    if {$stop} { return }
    if {abs($i) > $dist && ($sign * $i) > 0} { set sign [expr $sign * -1] }
    incr i [expr $sign * $sp]
    $w delete segs
    $w create line 50 50  [expr  50 + $i] 20 -tags segs
    $w create line 200 50 [expr 200 - $i] 20 -tags segs
    $w create line 50 50  [expr  50 + $i] 80 -tags segs
    $w create line 200 50 [expr 200 - $i] 80 -tags segs
    $w create line 50 150  [expr  50 - $i] 120 -tags segs
    $w create line 200 150 [expr 200 + $i] 120 -tags segs
    $w create line 50 150  [expr  50 - $i] 180 -tags segs
    $w create line 200 150 [expr 200 + $i] 180 -tags segs
    after $t update $w
}

proc startstop {w ww} {
    # this is kind of childish
    global stop
    if {$stop} {
	set stop 0
	$w config -text Stop
	update $ww
    } else {
	set stop 1
	$w config -text Start
    }
}
$w create line 50 50 200 50
$w create line 50 150 200 150
update $w