#!/usr/bin/wish

source color_model

label .l -width 20 -height 10
pack .l
bind .l <Motion> [list OnMotion %x %y]
bind .l <Leave> [list .l configure -bg black]

bind .l <s><h><o><w> ShowOff
focus .l

set pi2 [expr atan2(1, 0) * 4]

#=================================================================

proc OnMotion { x y } {
    global pi2
    set x [expr double($x)/[winfo width .l]*2 - 1]
    set y [expr 1 - double($y)/[winfo height .l]*2]
    set th [expr atan2($y, $x) / $pi2]
    if {$th < 0} { set th [expr $th + 1] }
    set r [expr sqrt($x*$x + $y*$y)]
    if {$r > 1} { set r 1 }
    .l configure -bg [HSBtoSTR $th $r 255]
}

proc ShowOff {} {
    set n 24
    for {set i 0} {$i < $n} {incr i} {
	.l configure -bg [HSBtoSTR [expr double($i)/$n] 1 255]
	update idletasks
	after 50
    }
}