# Listing of doc/example-scripts/tk-horse-race.tcl

A small Horse Race game, originally developed by Richard Suchenwirth in plain Tcl (see http://wiki.tcl.tk/3467). The game was rewritten as a design study in NX by Gustaf Neumann in May 2011.

    package require Tk
    package require nx::trait

     ##############################################################################
     # Trait ListUtils
     #
     # Some list utilities, not part of a package we can require here.
     ##############################################################################

     nx::Trait create ::nx::trait::listUtils {

       :protected method lpick {list} {
         # return a random entry from a given list
         lindex $list [expr {int(rand()*[llength $list])}]
       }
       :protected method lremove {listName what} {
         # remove a list element referenced by the elements value
         :upvar $listName list
         set pos  [lsearch $list $what]
         set list [lreplace $list $pos $pos]
       }
     }

     ##############################################################################
     # Class Horse
     #
     # This class defines the logic, how and where a single horse and
     # jockey are drawn. The painting of the horse happens just at startup
     # time, later the horses are moved via their tags.
     ##############################################################################

     nx::Class create Horse {
       :property name:required      ;# name is the external name of the horse
       :property tag:required       ;# tag is an internal id
       :property canvas:required    ;# the canvas, on which the horse is drawn
       :property n:integer,required ;# the position on the canvas

       :require trait nx::trait::callback
       :require trait nx::trait::listUtils

       :method draw {x y} {
         set hide [:lpick {black brown white gray brown3 brown4}]
         set c1 [:lpick {red yellow blue purple pink green}]
         set c2 [:lpick {red yellow blue purple pink green}]
         ${:canvas} create oval 0 -1 18 4 -fill $hide -outline $hide -tag ${:tag}
         ${:canvas} create line 1 12 3 0 5 12 -fill $hide -tag ${:tag} -width 2
         ${:canvas} create line 15 12 17 0 19 12 -fill $hide -tag ${:tag} -width 2
         ${:canvas} create line 16 0 20 -7 24 -5 -fill $hide -tag ${:tag} -width 3
         # Jockey:
         ${:canvas} create line 9 4 11 1 7 -1 -fill $c1 -width 2 -tag ${:tag}
         ${:canvas} create line 7 -2 10 -6 15 -3 -fill $c2 -width 2 -tag ${:tag}
         ${:canvas} create oval 9 -7 12 -10 -fill orange -outline orange -tag ${:tag}
         ${:canvas} move ${:tag} $x $y
       }

       :method init {} {
         set w [entry ${:canvas}.e${:n} -textvar [:bindvar name] -width 7 -bg green3]
         ${:canvas} create window 5 [expr {${:n}*30+5}] -window $w -anchor nw
         :draw 70 [expr {${:n}*30+14}]
       }
     }

     ##############################################################################
     # Class HorseGame
     #
     # Defines the main canvas of the Game and contains the logic of
     # starting, resetting etc.
     ##############################################################################

     nx::Class create HorseGame {
       :property {bg1 green4}   ;# background color of the canvas
       :property {bg2 green3}   ;# background color of the result label
       :property {width 750}    ;# width of the canvas
       :property {height 330}   ;# height of the canvas
       :property {horses}       ;# a list of horse names participating in the game

       :require trait nx::trait::callback
       :require trait nx::trait::listUtils

       :method init {} {
         #
         # create the canvas
         #
         set :canvas [canvas .c -bg ${:bg1} -width ${:width} -height ${:height}]
         pack ${:canvas}
         #
         # create the Horses
         #
         set n 0
         foreach name ${:horses} {
           set h [::Horse create horse$n -name $name -canvas ${:canvas} -n $n -tag horse$n]
           lappend :tags horse$n
           incr n
         }

         # finish line
         set w [expr {${:width} - 20}]
         ${:canvas} create line $w 0 $w ${:height} -fill white -tag finish

         # start button
         button ${:canvas}.button -text Start -pady 0 -width 0 \
             -command [:callback start ${:tags}]
         ${:canvas} create window 5 [expr {$n*30}] -window ${:canvas}.button -anchor nw

         # label for the results
         label ${:canvas}.winners -textvar [:bindvar winners] -bg ${:bg2} -width 80
         ${:canvas} create window 70 [expr {$n*30}] -window ${:canvas}.winners -anchor nw
       }

       :public method start {running} {
         #
         # When the "Start" button is pressed, we turn this button into a
         # "Reset" button and the horse race starts. We stop, when more
         # than two horses pass the finish line.
         #
         ${:canvas}.button config -text Reset -command [:callback reset]
         set :winners {}
         set finish [expr {[lindex [${:canvas} bbox finish] 2]+10}]
         while {[llength ${:winners}]<3} {
           set this [:lpick $running]
           ${:canvas} move $this [:lpick {0 1 2 3}] 0
           update
           if {[lindex [${:canvas} bbox $this] 2] > $finish} {
             lappend :winners [expr {[llength ${:winners}]+1}]:[$this cget -name]
             :lremove running $this
           }
         }
       }

       :public method reset {} {
         #
         # When the "Reset" button is pressed, we switch back to the start
         # configuration, the horses come back to the start.
         #
         ${:canvas}.button config -text Start -command [:callback start ${:tags}]
         foreach tag ${:tags} {
           set x [lindex [${:canvas} bbox $tag] 0]
           ${:canvas} move $tag [expr {70-$x}] 0
         }
       }
     }

     #
     # everything is defined, create the game
     #
     bind . <space> {exec wish $argv0 &; exit}
     HorseGame new -horses {Blaise NX Animal Ada Alan XOTcl Grace itcl John Linus}