Computes the common prefix that is shared by all rows in @completion
that start with @key. If no row matches @key, %NULL will be returned.
Note that a text column must have been set for this function to work,
see gtk_entry_completion_set_text_column() for details.
Computes the common prefix that is shared by all rows in @completion that start with @key. If no row matches @key, %NULL will be returned. Note that a text column must have been set for this function to work, see gtk_entry_completion_set_text_column() for details.