if 0 {[Richard Suchenwirth] 2004-08-25 - Users of [Toy cars] may
appreciate this little utility 
- it makes designing new cars easier (one might even call it poor man's CAD :-). The
Canvas items can be edited in the text widget at bottom. Click the "?"
button to see how it looks, on the canvas above. Moving the cursor in
the canvas shows the x/y coordinates in the window title. Clicking in
the canvas inserts the x/y coordinates into the text widget, at insert
position, so you can sketch out a polygon.
The "<->" mirrors the car in x direction, so you can check how it looks
"on the other side".
The "C" button clears both canvas and text.

[http://mini.net/files/steamroller.gif]

When satisfied, just
copy & paste into an editor that holds your car pool... The example
shows a steamroller which sure looks a bit funny, cruising on the
highway :)
}
 proc render'car {text canvas} {
    $canvas delete all
    $canvas create line -200 0 200 0 -fill lightgrey
    $canvas create line 0 -100 0 100 -fill lightgrey
    foreach line [split [$text get 1.0 end] \n] {
        if {[string trim $line] eq ""} continue
        eval $canvas create $line -tag t
    }
 }
 proc center {w tag} {
    foreach {x0 y0 x1 y1} [$w bbox $tag] break
    list [expr {($x0+$x1)/2.}] [expr {($y0+$y1)/2.}]
 }
 proc int x {expr int($x)}

 pack [canvas .c -height 100] -fill x -expand 1
 .c config -scrollregion {-100 -70 200 30}
 bind .c <Motion> {wm title . [int [%W canvasx %x]],[int [%W canvasy %y]]}
 bind .c <1> {.t insert insert " [int [%W canvasx %x]] [int [%W canvasy %y]]"}
 pack [frame .f -relief sunken -borderwidth 1] -anchor w -fill x
 button .f.? -text ? -width 5 -command {render'car .t .c}
 button .f.<-> -text <-> -width 5 -command {eval .c scale t [center .c t] -1 1}
 button .f.c -text C -width 5 -command {.t delete 1.0 end; .c delete all}
 eval pack [winfo children .f] -side left
 pack [text .t -height 16] -fill both -expand 1
 focus .t

 bind . <Escape> {exec wish $argv0 &; exit}
 bind . <F1> {console show}
 
----
[Arts and crafts of Tcl-Tk programming]