A few general aspects are discussed in entry validation.
The validation is performed at two levels:
1. Weak validation:
- Allow empty string or sign only - Verify sign
2. Strong validation:
- Strong integer and range check - Change the entry background color to yellow/red on error
The "focusout" validation is optional, it can be removed. Sample code:
proc validInteger {win event X oldX min max} {
# Make sure min<=max
if {$min > $max} {
set tmp $min; set min $max; set max $tmp
}
# Allow valid integers, empty strings, sign without number
# Reject Octal numbers, but allow a single "0"
# Which signes are allowed ?
if {($min <= 0) && ($max >= 0)} { ;# positive & negative sign
set pattern {^[+-]?(()|0|([1-9][0-9]*))$}
} elseif {$max < 0} { ;# negative sign
set pattern {^[-]?(()|0|([1-9][0-9]*))$}
} else { ;# positive sign
set pattern {^[+]?(()|0|([1-9][0-9]*))$}
}
# Weak integer checking: allow empty string, empty sign, reject octals
set weakCheck [regexp $pattern $X]
# if weak check fails, continue with old value
if {! $weakCheck} {set X $oldX}
# Strong integer checking with range
set strongCheck [expr {[string is int -strict $X] && ($X >= $min) && ($X <= $max)}]
switch $event {
key {
$win configure -bg [expr {$strongCheck ? "white" : "yellow"}]
return $weakCheck
}
focusout {
if {! $strongCheck} {$win configure -bg red}
return $strongCheck
}
default {
return 1
}
}
}
proc checkForm {args} {
set err 0
foreach win $args {
switch -- [$win cget -bg] {
red -
yellow {
incr err
}
}
}
if {$err} {
tk_messageBox -type ok -icon error -message "Check $err invalid field(s)"
} else {
tk_messageBox -type ok -message "Changes applied successfully"
}
}
set x1 12; set x2 345; set x3 -678
label .t1 -text "int (10..92)"
entry .e1 -textvariable x1 -validate all -vcmd {validInteger %W %V %P %s +10 +92}
label .t2 -text "int (-256..+1024)"
entry .e2 -textvariable x2 -validate all -vcmd {validInteger %W %V %P %s +1024 -256}
label .t3 -text "int (-768..0)"
entry .e3 -textvariable x3 -validate all -vcmd {validInteger %W %V %P %s -768 0}
button .apply -text "Apply changes" -command {checkForm .e1 .e2 .e3}
grid .t1 .e1 -sticky w
grid .t2 .e2 -sticky w
grid .t3 .e3 -sticky w
grid .apply - -sticky ew
catch {console show}Rolf Schroedter using hints given by Jeffrey Hobbs and DKF