[Richard Suchenwirth] -- 2000-08-15
Here's a terribly old-fashioned "terminal emulator" looking like UIs of twenty 
years ago - monochrome 24x80, fixed pitch, markup by reverse video, underlining, 
or maybe blinking. Still it might be helpful in porting heritage software where
screen layout was controlled by row/col coordinates.

[http://mini.net/files/retro.jpg]

Interface (procedures):
   terminal -- create such a beefed-up (down?) text widget
   terminal:clear -- clear "screen"
   printat -- at row-col, print text, tags
   tprint -- print text, tags (continue at last position)
   tputs -- print text, tags, newline (scroll if needed)
As the task is so traditional, I didn't bother to wrap it in an OO interface.
Usage examples are at the end. Enjoy ;-)
}
 proc terminal {w args} {
	array set opt [concat {
	-foreground green -background black -font Fixedsys -height 24 -width 80
	} $args]
	eval text $w [array get opt] -wrap none -cursor {{}}
	$w tag configure reverse -foreground [$w cget -background]\
		 -background [$w cget -foreground]
	$w tag configure underlined -underline 1
	$w tag configure [text:blink $w blink]
	terminal:clear $w
	set w
 }
 proc terminal:clear w {
	$w config -state normal
	$w delete 1.0 end
	for {set i 0} {$i<[$w cget -height]} {incr i} {
		if {$i} {$w insert end \n}
		$w insert end [format %[$w cget -width]s ""]
	}
	$w mark set twain 1.0
	$w config -state disabled
 }
 proc text:blink {w tag {t 250}} {
	$w tag configure $tag ;# just to have it at first time
	set bfg [$w tag cget $tag -foreground]
	set fg [$w cget -foreground]
	if {$bfg == $fg} {
		$w tag configure $tag -foreground [$w cget -background]
	} else {
		$w tag configure $tag -foreground $fg
	}
	after $t [list text:blink $w $tag $t]
	update
	set tag
 }
 proc printat {w pos text {tags {}}} {
	set t [split $pos ,]
	$w mark set twain [lindex $t 0].[expr [lindex $t 1]-1]
	if [string length $text] {tprint $w $text $tags}
 }
 proc tprint {w text {tags {}}} {	
	set l [string length $text]
	$w config -state normal
	$w delete twain twain+${l}c
	$w insert twain $text $tags
	$w config -state disabled
 }
 proc tputs {w text {tags {}}} {
	tprint $w $text $tags
	if {[set row [expr int([$w index twain])]]<[$w cget -height]} {
		$w mark set twain [expr $row+1].0
	} else {
		$w config -state normal
		$w delete 1.0 1.end+1c
		$w delete $row.0 $row.end
		$w insert $row.0 [format \n%[$w cget -width]s ""]
		$w config -state disabled
		$w mark set twain $row.0
	}
 }
 ############################ usage examples, little tests
 pack [terminal .t]
 tprint  .t "Hello!"
 printat .t 2,1 "Boldly I say: " bold
 tprint  .t "blinking " {blink bold}
 tprint  .t "has to be underlined" underlined
 tprint  .t " in this reverse world" reverse
 printat .t 4,3 "This should be @4,3"
 printat .t 24,1 "BOTTOM LINE  " reverse
 printat .t 24,78 <E>
 printat .t 1,2 a ;# overwriting a single letter, turn Hello to Hallo
 printat .t 5,5 "Welcome"
 printat .t 7,5 "to the"
 tprint  .t " MACHINE " {reverse underlined}
 tputs   .t ""
 tputs   .t **********************************
 tputs   .t ""
 update
 #after 5000
 for {set i 0} {$i<30} {incr i} {
	tputs .t $i:[clock format [clock seconds]]
	update
	after 100
 }
 tprint  .t "More soon -- stay with us --" {blink reverse}
 printat .t 1,1 "----------- scrolled, but still overwriting -----"
 after 10000 {
	terminal:clear .t 
	tputs .t "A new page in history" {underlined blink}
	printat .t 3,1 "(intentionally left blank)"
	printat .t 24,1 "BOTTOM LINE  " reverse
	printat .t 24,78 <E>
	.t tag configure red -foreground red
	printat .t 5,1 "And yes, this is not monochrome!" red
 }
For matching software, have a look at [Basic in Tcl]...
----
[GPS]: I like what you have done a lot.  I would be interested to see what kind of amazing things you could do to improve [Expect]'s [tkterm] example.
---
[ZLM] : That is sweet. And it's also the first Pink Floyd album that really sucks.