[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: [WikiDbImage dial.jpg] ====== 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 $(-fg) } trace add variable ::$(-variable) write [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 / 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 . {incr V 5; incr R 120} bind . {incr V -5; incr R -120} ====== ---- **See also** * [A voltmeter-like widget: type 1] * [A simple voltmeter] * [Meter Widget] for a snit::widget that is a 'vertical' meter. * [Another dials widget] for a SGI like slider/roller dial. <> Example | GUI | Widget