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ConfigSpecs is a list of new and overruled widget-options. The
options can be handled various ways. For derived widgets, the choice is
limited: methods and passive options.
When the value of a METHOD-option is changed by configure or
ConfigSpecs, Tk calls the method (function)
with the corresponding name, passing-on the argument (always a scalar).
A PASSIVE-option just stores the value to be used later.
A cget will call the METHOD-option's function without
extra argument: the function shall return the setting. In this case,
a PASSIVE-method just returns the internally stored value.
Within your own widget, you have to use cget to get your
own passive values to facilitate the future extention of your new widget.
You may write
$obj->values([4,5])as equivalent to
$obj->configure(-values => [4,5])but in former case, the current values are not stored in the internal widget structure. In the latter it will. Also, the latter hides the internal organisation of the object better, providing ways for future improvements of the widgets behaviour.
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Created by Mark Overmeer with PPresenter on 5 august 2001.