bionic (3) widget_validator.3tk.gz
NAME
widget_validator - widget::validator behaviour
SYNOPSIS
package require Tcl 8.5
package require Tk 8.5
package require widget::validator ?0.1?
widget::validator attach w color cmdprefix
widget::validator detach w
widget::validator validate w
_________________________________________________________________
DESCRIPTION
This package provides a unified validation API for ttk's entry and combobox widgets.
Please note that the validation behaviour defined in this package will not reject invalid edits. It will
only highlight the entry containing invalid data and set the proper state flag.
It is the responsibility of the using package or application to decide how and when to actually reject
such invalid content.
widget::validator attach w color cmdprefix
This method adds a validating behaviour to the widget w.
Whenever the content of the widget's entry field changes the specified cmdprefix is invoked and
has to return a boolean value, where true means that content is ok, and false that the content is
invalid. For more information on the command prefix see section Validation. In case of the latter
the background color of the entry field is changed to color to indicate the invalidity.
The system does not support nesting of validators on a widget, nor the attachment of multiple
validators. To change validating conditions detach the current validator first before attaching
the new.
An error is thrown if the widget has already validating behaviour attached to it.
The result of the method is the empty string.
To achieve its aims the package overrides various configuration options of the widget the
behaviour is attached to. These options are restored to their previous values on detach.
If other behaviours are attached the validator may be rendered temporarily (partially) non-
functional. Similarly, if the validator is detached while a different behaviour is also attached
its restoration of configuration settings may render the other non-functional
widget::validator detach w
This method removes the validating behaviour from the widget w and restores it to its original
state.
An error is thrown if the widget has no validating behaviour attached to it.
The result of the method is the empty string.
widget::validator validate w
Invoking this method forces a validation of the widget w, assuming that it has a validator
behaviour attached to it.
The result of the method is the empty string.
VALIDATION
The command prefix for used for validation has to have the following signature:
{*}cmdprefix text
The argument is the text to validate.
The result of the callback has to be a boolean value where true means that text is ok, and false
that text is invalid.
EXAMPLE
package require Tk 8.5
package require widget::validator
set TE {}
set TC {}
ttk::entry .e -textvariable TE
ttk::combobox .c -textvariable TC -values {fruit vegetable corn}
ttk::combobox .n -values {fruit vegetable corn}
ttk::button .x -command ::exit -text Exit
pack .e -expand 1 -fill both -side top
pack .c -expand 1 -fill both -side top
pack .n -expand 1 -fill both -side top
pack .x -expand 1 -fill both -side top
widget::validator attach .e lightblue {apply {text {
expr {$text ne {}}
}}}
widget::validator attach .c yellow {apply {text {
expr {$text ni {{} hello world}}
}}}
widget::validator attach .n pink {apply {text {
expr {$text ni {{} blub}}
}}}
KEYWORDS
invalid, state management, ttk::combobox, ttk::entry, validation, widget validation