set_case_sensitive() toggles whether or not GTK searches for
entries in a case sensitive manner. This is used when the Combo
widget is asked to find a value from the list using the current
entry in the text box. This completion can be performed in either a
case sensitive or insensitive manner, depending upon the use of
this function. The Combo widget can also simply complete the
current entry if the user presses the key combination MOD-1 and
"Tab". MOD-1 is often mapped to the "Alt" key, by the xmodmap
utility. Note, however that some window managers also use this key
combination, which will override its use within GTK.