Richard Suchenwirth 2006-10-17 - On the
Thirteenth Annual Tcl/Tk Conference I had only brought my phone, but at a little hackfest in the hotel bar, I just wanted to do another little fun project, so here it is - code for a dial on a
canvas that represent the numeric value of variables:
package require Tk
proc dial {w x0 y0 x1 y1 args} {
array set "" {-from 0 -to 100 -needle red
-bg white -fg black}
array set "" $args
$w create oval $x0 $y0 $x1 $y1 -fill $(-bg)
set xm [expr {($x0+$x1)/2.}]
set ym [expr {($y0+$y1)/2.}]
set id [$w create line $xm $ym $xm [+ $y0 10] -fill $(-needle) -width 3]
$w create oval [- $xm 3] [- $ym 3] [+ $xm 3] [+ $ym 3] -fill $(-fg)
set r [expr {$ym-$y0-15}]
foreach i [dial'steps $(-from) $(-to)] {
set a [dial'angle $(-from) $i $(-to)]
set x [expr {$xm+$r*cos($a)}]
set y [expr {$ym+$r*sin($a)}]
$w create text $x $y -text $i -fill $(-fg)
}
trace var ::$(-variable) w [list dial'set $w $id $(-from) $(-to)]
}
foreach op {+ -} {
proc $op {a b} "expr {\$a $op \$b}"
}
proc dial'steps {min max} {
set step [expr {($max-$min)/50*10}]
set res {}
for {set i $min} {$i<=$max} {incr i $step} {
lappend res $i
}
set res
}
proc dial'angle {min v max} {
expr {(0.5 + double($v-$min)/($max-$min))*acos(-1)*1.5}
}
proc dial'set {w id min max var el op} {
set v [uplevel 1 set $var]
set v [expr {$v<$min? $min: $v>$max? $max: $v}]
foreach {xm ym x1 y1} [$w coords $id] break
set r [expr {hypot($y1-$ym,$x1-$xm)}]
set a [dial'angle $min $v $max]
set x1 [expr {$xm+$r*cos($a)}]
set y1 [expr {$ym+$r*sin($a)}]
$w coords $id $xm $ym $x1 $y1
}
#-------- test & demo - modify the value of two variables with <Up>/<Down> keys
catch {eval destroy [winfo children .]}
catch {unset V R}
pack [canvas .c -takefocus 1]
dial .c 10 10 110 110 -variable V -to 180 -bg yellow
set V 0
dial .c 120 10 220 110 -variable R -to 5000 -fg blue
set R 0
raise .
bind . <Up> {incr V 5; incr R 120}
bind . <Down> {incr V -5; incr R -120}
See also edit
