label - create and manipulate label (text or image) widgets
http://www.purl.org/tcl/home/man/tcl8.4/TkCmd/label.htm
Composite labels: A text label can hold either a constant text or a reference to a textvariable from which it is updated. Occasionally one wants both mixed, for instance to display "Distance from $from to $to: $mi miles", and auto-updated when one of those variables changes. The following code can help:
proc compositelabel {w contents} {
frame $w
set n 0
foreach i $contents {
set w1 [label $w.[incr n]]
if [regexp {^[$](.+)} $i -> varname] {
$w1 configure -textvar ::$varname
} else {
$w1 configure -text $i
}
}
eval pack [winfo children $w] -side left
}
# usage example:
compositelabel .dist {Distance from $from to $to is $m miles}Make sure that the second argument is braced - the dollar signs are not to be seen by the Tcl parser, but rather used to indicate the following is the name of a global variable, not a text constant... (RS)
Among the benefits of Tk is that its programming model encourages "intelligent" displays, and specifically those with modestly dynamic labeling. Run-time context might call for a change in the text of a button (an alternation between "Stop" and "Re-start", for example) or label. The one technical problem that immediately arises with most such improvements is changes in widget size. Bryan Oakley posted a brief explanation of the usual idiom for these situations: "Put it in a frame, and force the frame to a specific height [or width] is one way of doing it. Read up on 'pack propagate', or 'grid propagate' to see how you can keep children from causing their parent[s] to resize."
Incidentally, BLT enjoys a wealth of geometry configurations which help with these tasks.
Tk syntax help - Arts and crafts of Tcl-Tk programming - Category Command