Text widgets support the standard X selection.
Selection support is implemented via tags.
If the exportSelection option for the text widget is true
then the sel tag will be associated with the selection:
Whenever characters are tagged with sel the text widget
will claim ownership of the selection.
Attempts to retrieve the
selection will be serviced by the text widget, returning all the
charaters with the sel tag.
If the selection is claimed away by another application or by another
window within this application, then the sel tag will be removed
from all characters in the text.
The sel tag is automatically defined when a text widget is
created, and it may not be deleted with the "pathName :tag delete"
widget command. Furthermore, the selectBackground,
selectBorderWidth, and selectForeground options for
the text widget are tied to the :background,
:borderwidth, and :foreground options for the sel
tag: changes in either will automatically be reflected in the