A function which decides whether the row indicated by iter matches
a given key, and should be displayed as a possible completion for key.
Note that key is normalized and case-folded (see g_utf8_normalize()
and g_utf8_casefold()). If this is not appropriate, match functions
have access to the unmodified key via
gtk_entry_get_text (GTK_ENTRY (gtk_entry_completion_get_entry ())).
A function which decides whether the row indicated by iter matches a given key, and should be displayed as a possible completion for key. Note that key is normalized and case-folded (see g_utf8_normalize() and g_utf8_casefold()). If this is not appropriate, match functions have access to the unmodified key via gtk_entry_get_text (GTK_ENTRY (gtk_entry_completion_get_entry ())).