if 0 {[Richard Suchenwirth] 2004-11-14 - Domino is a popular game. In
this weekend fun project, I wanted to have it in [Tcl]/[Tk] too.

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

The real
multiplayer game can't be implemented, as there's no way for one player
to see a piece, while another doesn't - but at least one can use this
for mathematical games with dominoes, as described in Martin Gardner's
"Mathematical Circus". Drag a piece with left mouse button down, rotate
it (counterclockwise 90 degrees) with right-click.
}
 package require Tk
 
 namespace eval domino {
    variable bg black  fg white  size 30
    #-- "Visual" definition of dot patterns - "sugared lists"
    variable pattern
    array set pattern {
        0 {0 0 0
             0
           0 0 0}
        1 {0 0 0
             1
           0 0 0}
        2 {1 0 0
             0
           0 0 1}
        3 {1 0 0
             1
           0 0 1}
        4 {1 0 1
             0
           1 0 1}
        5 {1 0 1
             1
           1 0 1}
        6 {1 1 1
             0
           1 1 1}
    }
    variable points {1 1  1 2  1 3  2 2  3 1  3 2  3 3}
 }
if 0 {This "constructor" creates a domino piece on the [canvas] ''w'',
landscape oriented, with top left corner at ''x''/''y'' and the
specified two point values (0..6). For allowing motion, all canvas items
belonging to a piece with values p|q are tagged with
   * mv (so motion bindings have a common target)
   * d-$p$q for unique identification (assuming no duplicate pieces)
The bd-$p$q tags aren't used yet - in future one might use them for
reverting a piece, i.e. raising or lowering the rectangle.
}
 proc domino::create {w x y val1 val2} {
    variable bg; variable fg; variable size
    set tags [list mv d-$val1$val2]
    set x1 [expr {$x+$size-0.5}]
    set y1 [expr {$y+$size}]
    $w create rect $x $y [expr {$x+2*$size}] $y1 \
        -fill $bg -tags [linsert $tags 0 bd-$val1$val2]
    $w create line $x1 $y $x1 $y1 -fill $fg -tags $tags
    dots $w $x $y $val1 $tags
    dots $w [expr {$x+$size}] $y $