When the user selects a widget the property window changes to
display the properties of the selected object: this is done by the
functions “show_properties
” of
edit_windows.EditBase
and
edit_sizers.SizerBase
, which are called inside
two event handlers for focus and tree selection events.
When the value of a Property is changed, its setter function is
called to update the aspect/layout of the widget the Property belongs
to: such function is obtained from a call to the widget's
“__getitem__
” method, which must
return a 2-tuple (getter, setter) for the Property