2004-02-13 [VI]

This isn't a screen saver really.  It just uses the [minimalist curses] package to draw
boxes of various sizes on your screen.  Any keypress exits it.   There's some element
of randomness in how often it draws because every second it picks four coordinates.
But it only draws a rectangle if those coordinates make sense.  Only works on 
terminals that support vt100 like alt character set : true of linux, vt100 and xterm
and derivatives.  Any keypress exits.

 #!/usr/local/tcl/8.4.5/bin/tclsh8.4
 
 package require curses
 
 # Order is nswe
 
 set ldc(nw)   j
 set ldc(ne)   m
 set ldc(se)   l
 set ldc(sw)   k
 set ldc(nswe) n
 set ldc(we)   q
 set ldc(nse)  t
 set ldc(nsw)  u
 set ldc(nwe)  v
 set ldc(swe)  w
 set ldc(ns)   x
 
 
 proc box {row1 col1 row2 col2} {
     global ldc
 
     curses attr on alt
     curses move $row1 $col1
     curses puts $ldc(se)
     curses move $row2 $col1
     curses puts $ldc(ne)
     for {set i [expr $row1 + 1] } {$i < $row2} {incr i} {
 	curses move $i $col1
 	curses puts $ldc(ns)
 	curses move $i $col2
 	curses puts $ldc(ns)
     }
     for {set i [expr $col1 + 1] } {$i < $col2} {incr i} {
 	curses move $row1 $i
 	curses puts $ldc(we)
 	curses move $row2 $i
 	curses puts $ldc(we)
     }
     curses move $row1 $col2
     curses puts $ldc(sw)
     curses move $row2 $col2
     curses puts $ldc(nw)
 }
 
 
 set rows [curses info lines]
 set cols [curses info cols]
 
 expr srand([clock seconds])
 
 curses timeout 0
 
 set i 0
 while {1} {
     incr i
     if {$i % 2 == 0} {
 	curses attr on reverse
     } else {
 	curses attr off reverse
     }
     set row1 [expr int(rand()*$rows)]
     set row2 [expr int(rand()*$rows)]
     set col1 [expr int(rand()*$cols-1)]
     set col2 [expr int(rand()*$cols-1)]
     after 1000
     if {[curses getch] != -1} break
     if {$row2 - $row1 < 2 || $col2 - $col1 < 2} continue
     box $row1 $col1 $row2 $col2
     curses refresh
 }