#!/usr/bin/wish -f

# First we create the image. Then we configure the frame which will hold the pieces of
# the image that will form the puzzle. This we pack with a little padding.

set image [image create photo -file picture.gif -width 160 -height 160]

frame .frame -width 120 -height 120 -borderwidth 2 -relief sunken \
-bg grey
pack .frame -side top -pady 1c -padx 1c

# Now we create the individual pieces of the puzzle. This involves fifteen loops
# of the code, which crops portions of the original image to fit on the buttons.

set order {3 1 6 2 5 7 15 13 4 11 8 9 14 10 12}
for {set i 0} {$i < 15} {set i [expr $i+1]} {
    set num [lindex $order $i]
    set xpos($num) [expr ($i%4)*.25]
    set ypos($num) [expr ($i/4)*.25]

    set x [expr $i%4]
    set y [expr $i/4]

    set butImage [image create photo image-${num} -width 40 -height 40]
    $butImage copy  $image  -from [expr round($x*40)] \
                                  [expr round($y*40)] \
                                  [expr round($x*40+40)] \
                                  [expr round($y*40+40)]
    button .frame.$num -relief raised -image $butImage \
                       -command "puzzleSwitch  $num" \
                       -highlightthickness 0 
    place .frame.$num -relx $xpos($num) -rely $ypos($num) \
                      -relwidth .25 -relheight .25
}

# Finally, we have the event handler that deals with the user's input.
# The two global variables are set to show that the initial space in the puzzle is at
# the bottom right-hand corner.

set xpos(space) .75
set ypos(space) .75

proc puzzleSwitch { num} {
    global xpos ypos
    if {(($ypos($num) >= ($ypos(space) - .01))
           && ($ypos($num) <= ($ypos(space) + .01))
           && ($xpos($num) >= ($xpos(space) - .26))
           && ($xpos($num) <= ($xpos(space) + .26)))
           || (($xpos($num) >= ($xpos(space) - .01))
           && ($xpos($num) <= ($xpos(space) + .01))
           && ($ypos($num) >= ($ypos(space) - .26))
           && ($ypos($num) <= ($ypos(space) + .26)))} {
        set tmp $xpos(space)
        set xpos(space) $xpos($num)
        set xpos($num) $tmp
        set tmp $ypos(space)
        set ypos(space) $ypos($num)
        set ypos($num) $tmp
        place .frame.$num -relx $xpos($num) -rely $ypos($num)
    }
}