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widget_validator(3tk) widget::validator behaviour widget_validator(3tk) 





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.



  

  
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

  

  

  
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.

  

  

  
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}}
}}}









BUGS, IDEAS, FEEDBACK


This document, and the package it describes, will undoubtedly
    contain bugs and other problems. Please report such in the category
    widget::validator of the Tklib Trackers
    [http://core.tcl.tk/tklib/reportlist]. Please also report any ideas for
    enhancements you may have for either package and/or documentation.






KEYWORDS


invalid, state management, ttk::combobox, ttk::entry, validation,
    widget validation







  

    0.1
    tklib