Clear the selection and append aString at the end of the
text widget.
replaceSelection: aString
Insert aString in the text widget at the current insertion point,
replacing the currently selected text (if any), and leaving
the text selected.
selectAll
Select the whole contents of the text widget
selectFrom: first to: last
Sets the selection of the text widget to include the characters
starting with the one indexed by first (the very first character in
the widget having index 1) and ending with the one just before
last. If last refers to the same character as first or an earlier
one, then the text widget's selection is cleared.
selection
Answer an empty string if the text widget has no selection, else answer
the currently selected text
selectionRange
Answer nil if the text widget has no selection, else answer
an Interval object whose first item is the index of the
first character in the selection, and whose last item is the
index of the character just after the last one in the
selection.
text: aString
Set the contents of the text widget and select them.